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Based on kernel version 4.0. Page generated on 2015-04-14 21:23 EST.

1	<?xml version="1.0" encoding="UTF-8"?>
2	<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
3		"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
4	
5	<book id="drmDevelopersGuide">
6	  <bookinfo>
7	    <title>Linux DRM Developer's Guide</title>
8	
9	    <authorgroup>
10	      <author>
11		<firstname>Jesse</firstname>
12		<surname>Barnes</surname>
13		<contrib>Initial version</contrib>
14		<affiliation>
15		  <orgname>Intel Corporation</orgname>
16		  <address>
17		    <email>jesse.barnes@intel.com</email>
18		  </address>
19		</affiliation>
20	      </author>
21	      <author>
22		<firstname>Laurent</firstname>
23		<surname>Pinchart</surname>
24		<contrib>Driver internals</contrib>
25		<affiliation>
26		  <orgname>Ideas on board SPRL</orgname>
27		  <address>
28		    <email>laurent.pinchart@ideasonboard.com</email>
29		  </address>
30		</affiliation>
31	      </author>
32	      <author>
33		<firstname>Daniel</firstname>
34		<surname>Vetter</surname>
35		<contrib>Contributions all over the place</contrib>
36		<affiliation>
37		  <orgname>Intel Corporation</orgname>
38		  <address>
39		    <email>daniel.vetter@ffwll.ch</email>
40		  </address>
41		</affiliation>
42	      </author>
43	    </authorgroup>
44	
45	    <copyright>
46	      <year>2008-2009</year>
47	      <year>2013-2014</year>
48	      <holder>Intel Corporation</holder>
49	    </copyright>
50	    <copyright>
51	      <year>2012</year>
52	      <holder>Laurent Pinchart</holder>
53	    </copyright>
54	
55	    <legalnotice>
56	      <para>
57		The contents of this file may be used under the terms of the GNU
58		General Public License version 2 (the "GPL") as distributed in
59		the kernel source COPYING file.
60	      </para>
61	    </legalnotice>
62	
63	    <revhistory>
64	      <!-- Put document revisions here, newest first. -->
65	      <revision>
66		<revnumber>1.0</revnumber>
67		<date>2012-07-13</date>
68		<authorinitials>LP</authorinitials>
69		<revremark>Added extensive documentation about driver internals.
70		</revremark>
71	      </revision>
72	    </revhistory>
73	  </bookinfo>
74	
75	<toc></toc>
76	
77	<part id="drmCore">
78	  <title>DRM Core</title>
79	  <partintro>
80	    <para>
81	      This first part of the DRM Developer's Guide documents core DRM code,
82	      helper libraries for writing drivers and generic userspace interfaces
83	      exposed by DRM drivers.
84	    </para>
85	  </partintro>
86	
87	  <chapter id="drmIntroduction">
88	    <title>Introduction</title>
89	    <para>
90	      The Linux DRM layer contains code intended to support the needs
91	      of complex graphics devices, usually containing programmable
92	      pipelines well suited to 3D graphics acceleration.  Graphics
93	      drivers in the kernel may make use of DRM functions to make
94	      tasks like memory management, interrupt handling and DMA easier,
95	      and provide a uniform interface to applications.
96	    </para>
97	    <para>
98	      A note on versions: this guide covers features found in the DRM
99	      tree, including the TTM memory manager, output configuration and
100	      mode setting, and the new vblank internals, in addition to all
101	      the regular features found in current kernels.
102	    </para>
103	    <para>
104	      [Insert diagram of typical DRM stack here]
105	    </para>
106	  </chapter>
107	
108	  <!-- Internals -->
109	
110	  <chapter id="drmInternals">
111	    <title>DRM Internals</title>
112	    <para>
113	      This chapter documents DRM internals relevant to driver authors
114	      and developers working to add support for the latest features to
115	      existing drivers.
116	    </para>
117	    <para>
118	      First, we go over some typical driver initialization
119	      requirements, like setting up command buffers, creating an
120	      initial output configuration, and initializing core services.
121	      Subsequent sections cover core internals in more detail,
122	      providing implementation notes and examples.
123	    </para>
124	    <para>
125	      The DRM layer provides several services to graphics drivers,
126	      many of them driven by the application interfaces it provides
127	      through libdrm, the library that wraps most of the DRM ioctls.
128	      These include vblank event handling, memory
129	      management, output management, framebuffer management, command
130	      submission &amp; fencing, suspend/resume support, and DMA
131	      services.
132	    </para>
133	
134	  <!-- Internals: driver init -->
135	
136	  <sect1>
137	    <title>Driver Initialization</title>
138	    <para>
139	      At the core of every DRM driver is a <structname>drm_driver</structname>
140	      structure. Drivers typically statically initialize a drm_driver structure,
141	      and then pass it to one of the <function>drm_*_init()</function> functions
142	      to register it with the DRM subsystem.
143	    </para>
144	    <para>
145	      Newer drivers that no longer require a <structname>drm_bus</structname>
146	      structure can alternatively use the low-level device initialization and
147	      registration functions such as <function>drm_dev_alloc()</function> and
148	      <function>drm_dev_register()</function> directly.
149	    </para>
150	    <para>
151	      The <structname>drm_driver</structname> structure contains static
152	      information that describes the driver and features it supports, and
153	      pointers to methods that the DRM core will call to implement the DRM API.
154	      We will first go through the <structname>drm_driver</structname> static
155	      information fields, and will then describe individual operations in
156	      details as they get used in later sections.
157	    </para>
158	    <sect2>
159	      <title>Driver Information</title>
160	      <sect3>
161	        <title>Driver Features</title>
162	        <para>
163	          Drivers inform the DRM core about their requirements and supported
164	          features by setting appropriate flags in the
165	          <structfield>driver_features</structfield> field. Since those flags
166	          influence the DRM core behaviour since registration time, most of them
167	          must be set to registering the <structname>drm_driver</structname>
168	          instance.
169	        </para>
170	        <synopsis>u32 driver_features;</synopsis>
171	        <variablelist>
172	          <title>Driver Feature Flags</title>
173	          <varlistentry>
174	            <term>DRIVER_USE_AGP</term>
175	            <listitem><para>
176	              Driver uses AGP interface, the DRM core will manage AGP resources.
177	            </para></listitem>
178	          </varlistentry>
179	          <varlistentry>
180	            <term>DRIVER_REQUIRE_AGP</term>
181	            <listitem><para>
182	              Driver needs AGP interface to function. AGP initialization failure
183	              will become a fatal error.
184	            </para></listitem>
185	          </varlistentry>
186	          <varlistentry>
187	            <term>DRIVER_PCI_DMA</term>
188	            <listitem><para>
189	              Driver is capable of PCI DMA, mapping of PCI DMA buffers to
190	              userspace will be enabled. Deprecated.
191	            </para></listitem>
192	          </varlistentry>
193	          <varlistentry>
194	            <term>DRIVER_SG</term>
195	            <listitem><para>
196	              Driver can perform scatter/gather DMA, allocation and mapping of
197	              scatter/gather buffers will be enabled. Deprecated.
198	            </para></listitem>
199	          </varlistentry>
200	          <varlistentry>
201	            <term>DRIVER_HAVE_DMA</term>
202	            <listitem><para>
203	              Driver supports DMA, the userspace DMA API will be supported.
204	              Deprecated.
205	            </para></listitem>
206	          </varlistentry>
207	          <varlistentry>
208	            <term>DRIVER_HAVE_IRQ</term><term>DRIVER_IRQ_SHARED</term>
209	            <listitem><para>
210	              DRIVER_HAVE_IRQ indicates whether the driver has an IRQ handler
211	              managed by the DRM Core. The core will support simple IRQ handler
212	              installation when the flag is set. The installation process is
213	              described in <xref linkend="drm-irq-registration"/>.</para>
214	              <para>DRIVER_IRQ_SHARED indicates whether the device &amp; handler
215	              support shared IRQs (note that this is required of PCI  drivers).
216	            </para></listitem>
217	          </varlistentry>
218	          <varlistentry>
219	            <term>DRIVER_GEM</term>
220	            <listitem><para>
221	              Driver use the GEM memory manager.
222	            </para></listitem>
223	          </varlistentry>
224	          <varlistentry>
225	            <term>DRIVER_MODESET</term>
226	            <listitem><para>
227	              Driver supports mode setting interfaces (KMS).
228	            </para></listitem>
229	          </varlistentry>
230	          <varlistentry>
231	            <term>DRIVER_PRIME</term>
232	            <listitem><para>
233	              Driver implements DRM PRIME buffer sharing.
234	            </para></listitem>
235	          </varlistentry>
236	          <varlistentry>
237	            <term>DRIVER_RENDER</term>
238	            <listitem><para>
239	              Driver supports dedicated render nodes.
240	            </para></listitem>
241	          </varlistentry>
242	          <varlistentry>
243	            <term>DRIVER_ATOMIC</term>
244	            <listitem><para>
245	              Driver supports atomic properties.  In this case the driver
246	              must implement appropriate obj->atomic_get_property() vfuncs
247	              for any modeset objects with driver specific properties.
248	            </para></listitem>
249	          </varlistentry>
250	        </variablelist>
251	      </sect3>
252	      <sect3>
253	        <title>Major, Minor and Patchlevel</title>
254	        <synopsis>int major;
255	int minor;
256	int patchlevel;</synopsis>
257	        <para>
258	          The DRM core identifies driver versions by a major, minor and patch
259	          level triplet. The information is printed to the kernel log at
260	          initialization time and passed to userspace through the
261	          DRM_IOCTL_VERSION ioctl.
262	        </para>
263	        <para>
264	          The major and minor numbers are also used to verify the requested driver
265	          API version passed to DRM_IOCTL_SET_VERSION. When the driver API changes
266	          between minor versions, applications can call DRM_IOCTL_SET_VERSION to
267	          select a specific version of the API. If the requested major isn't equal
268	          to the driver major, or the requested minor is larger than the driver
269	          minor, the DRM_IOCTL_SET_VERSION call will return an error. Otherwise
270	          the driver's set_version() method will be called with the requested
271	          version.
272	        </para>
273	      </sect3>
274	      <sect3>
275	        <title>Name, Description and Date</title>
276	        <synopsis>char *name;
277	char *desc;
278	char *date;</synopsis>
279	        <para>
280	          The driver name is printed to the kernel log at initialization time,
281	          used for IRQ registration and passed to userspace through
282	          DRM_IOCTL_VERSION.
283	        </para>
284	        <para>
285	          The driver description is a purely informative string passed to
286	          userspace through the DRM_IOCTL_VERSION ioctl and otherwise unused by
287	          the kernel.
288	        </para>
289	        <para>
290	          The driver date, formatted as YYYYMMDD, is meant to identify the date of
291	          the latest modification to the driver. However, as most drivers fail to
292	          update it, its value is mostly useless. The DRM core prints it to the
293	          kernel log at initialization time and passes it to userspace through the
294	          DRM_IOCTL_VERSION ioctl.
295	        </para>
296	      </sect3>
297	    </sect2>
298	    <sect2>
299	      <title>Device Registration</title>
300	      <para>
301	        A number of functions are provided to help with device registration.
302	        The functions deal with PCI and platform devices, respectively.
303	      </para>
304	!Edrivers/gpu/drm/drm_pci.c
305	!Edrivers/gpu/drm/drm_platform.c
306	      <para>
307	        New drivers that no longer rely on the services provided by the
308	        <structname>drm_bus</structname> structure can call the low-level
309	        device registration functions directly. The
310	        <function>drm_dev_alloc()</function> function can be used to allocate
311	        and initialize a new <structname>drm_device</structname> structure.
312	        Drivers will typically want to perform some additional setup on this
313	        structure, such as allocating driver-specific data and storing a
314	        pointer to it in the DRM device's <structfield>dev_private</structfield>
315	        field. Drivers should also set the device's unique name using the
316	        <function>drm_dev_set_unique()</function> function. After it has been
317	        set up a device can be registered with the DRM subsystem by calling
318	        <function>drm_dev_register()</function>. This will cause the device to
319	        be exposed to userspace and will call the driver's
320	        <structfield>.load()</structfield> implementation. When a device is
321	        removed, the DRM device can safely be unregistered and freed by calling
322	        <function>drm_dev_unregister()</function> followed by a call to
323	        <function>drm_dev_unref()</function>.
324	      </para>
325	!Edrivers/gpu/drm/drm_drv.c
326	    </sect2>
327	    <sect2>
328	      <title>Driver Load</title>
329	      <para>
330	        The <methodname>load</methodname> method is the driver and device
331	        initialization entry point. The method is responsible for allocating and
332		initializing driver private data, performing resource allocation and
333		mapping (e.g. acquiring
334	        clocks, mapping registers or allocating command buffers), initializing
335	        the memory manager (<xref linkend="drm-memory-management"/>), installing
336	        the IRQ handler (<xref linkend="drm-irq-registration"/>), setting up
337	        vertical blanking handling (<xref linkend="drm-vertical-blank"/>), mode
338		setting (<xref linkend="drm-mode-setting"/>) and initial output
339		configuration (<xref linkend="drm-kms-init"/>).
340	      </para>
341	      <note><para>
342	        If compatibility is a concern (e.g. with drivers converted over from
343	        User Mode Setting to Kernel Mode Setting), care must be taken to prevent
344	        device initialization and control that is incompatible with currently
345	        active userspace drivers. For instance, if user level mode setting
346	        drivers are in use, it would be problematic to perform output discovery
347	        &amp; configuration at load time. Likewise, if user-level drivers
348	        unaware of memory management are in use, memory management and command
349	        buffer setup may need to be omitted. These requirements are
350	        driver-specific, and care needs to be taken to keep both old and new
351	        applications and libraries working.
352	      </para></note>
353	      <synopsis>int (*load) (struct drm_device *, unsigned long flags);</synopsis>
354	      <para>
355	        The method takes two arguments, a pointer to the newly created
356		<structname>drm_device</structname> and flags. The flags are used to
357		pass the <structfield>driver_data</structfield> field of the device id
358		corresponding to the device passed to <function>drm_*_init()</function>.
359		Only PCI devices currently use this, USB and platform DRM drivers have
360		their <methodname>load</methodname> method called with flags to 0.
361	      </para>
362	      <sect3>
363	        <title>Driver Private Data</title>
364	        <para>
365	          The driver private hangs off the main
366	          <structname>drm_device</structname> structure and can be used for
367	          tracking various device-specific bits of information, like register
368	          offsets, command buffer status, register state for suspend/resume, etc.
369	          At load time, a driver may simply allocate one and set
370	          <structname>drm_device</structname>.<structfield>dev_priv</structfield>
371	          appropriately; it should be freed and
372	          <structname>drm_device</structname>.<structfield>dev_priv</structfield>
373	          set to NULL when the driver is unloaded.
374	        </para>
375	      </sect3>
376	      <sect3 id="drm-irq-registration">
377	        <title>IRQ Registration</title>
378	        <para>
379	          The DRM core tries to facilitate IRQ handler registration and
380	          unregistration by providing <function>drm_irq_install</function> and
381	          <function>drm_irq_uninstall</function> functions. Those functions only
382	          support a single interrupt per device, devices that use more than one
383	          IRQs need to be handled manually.
384	        </para>
385	        <sect4>
386	          <title>Managed IRQ Registration</title>
387	          <para>
388	            <function>drm_irq_install</function> starts by calling the
389	            <methodname>irq_preinstall</methodname> driver operation. The operation
390	            is optional and must make sure that the interrupt will not get fired by
391	            clearing all pending interrupt flags or disabling the interrupt.
392	          </para>
393	          <para>
394	            The passed-in IRQ will then be requested by a call to
395	            <function>request_irq</function>. If the DRIVER_IRQ_SHARED driver
396	            feature flag is set, a shared (IRQF_SHARED) IRQ handler will be
397	            requested.
398	          </para>
399	          <para>
400	            The IRQ handler function must be provided as the mandatory irq_handler
401	            driver operation. It will get passed directly to
402	            <function>request_irq</function> and thus has the same prototype as all
403	            IRQ handlers. It will get called with a pointer to the DRM device as the
404	            second argument.
405	          </para>
406	          <para>
407	            Finally the function calls the optional
408	            <methodname>irq_postinstall</methodname> driver operation. The operation
409	            usually enables interrupts (excluding the vblank interrupt, which is
410	            enabled separately), but drivers may choose to enable/disable interrupts
411	            at a different time.
412	          </para>
413	          <para>
414	            <function>drm_irq_uninstall</function> is similarly used to uninstall an
415	            IRQ handler. It starts by waking up all processes waiting on a vblank
416	            interrupt to make sure they don't hang, and then calls the optional
417	            <methodname>irq_uninstall</methodname> driver operation. The operation
418	            must disable all hardware interrupts. Finally the function frees the IRQ
419	            by calling <function>free_irq</function>.
420	          </para>
421	        </sect4>
422	        <sect4>
423	          <title>Manual IRQ Registration</title>
424	          <para>
425	            Drivers that require multiple interrupt handlers can't use the managed
426	            IRQ registration functions. In that case IRQs must be registered and
427	            unregistered manually (usually with the <function>request_irq</function>
428	            and <function>free_irq</function> functions, or their devm_* equivalent).
429	          </para>
430	          <para>
431	            When manually registering IRQs, drivers must not set the DRIVER_HAVE_IRQ
432	            driver feature flag, and must not provide the
433		    <methodname>irq_handler</methodname> driver operation. They must set the
434		    <structname>drm_device</structname> <structfield>irq_enabled</structfield>
435		    field to 1 upon registration of the IRQs, and clear it to 0 after
436		    unregistering the IRQs.
437	          </para>
438	        </sect4>
439	      </sect3>
440	      <sect3>
441	        <title>Memory Manager Initialization</title>
442	        <para>
443	          Every DRM driver requires a memory manager which must be initialized at
444	          load time. DRM currently contains two memory managers, the Translation
445	          Table Manager (TTM) and the Graphics Execution Manager (GEM).
446	          This document describes the use of the GEM memory manager only. See
447	          <xref linkend="drm-memory-management"/> for details.
448	        </para>
449	      </sect3>
450	      <sect3>
451	        <title>Miscellaneous Device Configuration</title>
452	        <para>
453	          Another task that may be necessary for PCI devices during configuration
454	          is mapping the video BIOS. On many devices, the VBIOS describes device
455	          configuration, LCD panel timings (if any), and contains flags indicating
456	          device state. Mapping the BIOS can be done using the pci_map_rom() call,
457	          a convenience function that takes care of mapping the actual ROM,
458	          whether it has been shadowed into memory (typically at address 0xc0000)
459	          or exists on the PCI device in the ROM BAR. Note that after the ROM has
460	          been mapped and any necessary information has been extracted, it should
461	          be unmapped; on many devices, the ROM address decoder is shared with
462	          other BARs, so leaving it mapped could cause undesired behaviour like
463	          hangs or memory corruption.
464	  <!--!Fdrivers/pci/rom.c pci_map_rom-->
465	        </para>
466	      </sect3>
467	    </sect2>
468	  </sect1>
469	
470	  <!-- Internals: memory management -->
471	
472	  <sect1 id="drm-memory-management">
473	    <title>Memory management</title>
474	    <para>
475	      Modern Linux systems require large amount of graphics memory to store
476	      frame buffers, textures, vertices and other graphics-related data. Given
477	      the very dynamic nature of many of that data, managing graphics memory
478	      efficiently is thus crucial for the graphics stack and plays a central
479	      role in the DRM infrastructure.
480	    </para>
481	    <para>
482	      The DRM core includes two memory managers, namely Translation Table Maps
483	      (TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory
484	      manager to be developed and tried to be a one-size-fits-them all
485	      solution. It provides a single userspace API to accommodate the need of
486	      all hardware, supporting both Unified Memory Architecture (UMA) devices
487	      and devices with dedicated video RAM (i.e. most discrete video cards).
488	      This resulted in a large, complex piece of code that turned out to be
489	      hard to use for driver development.
490	    </para>
491	    <para>
492	      GEM started as an Intel-sponsored project in reaction to TTM's
493	      complexity. Its design philosophy is completely different: instead of
494	      providing a solution to every graphics memory-related problems, GEM
495	      identified common code between drivers and created a support library to
496	      share it. GEM has simpler initialization and execution requirements than
497	      TTM, but has no video RAM management capabilities and is thus limited to
498	      UMA devices.
499	    </para>
500	    <sect2>
501	      <title>The Translation Table Manager (TTM)</title>
502	      <para>
503	        TTM design background and information belongs here.
504	      </para>
505	      <sect3>
506	        <title>TTM initialization</title>
507	        <warning><para>This section is outdated.</para></warning>
508	        <para>
509	          Drivers wishing to support TTM must fill out a drm_bo_driver
510	          structure. The structure contains several fields with function
511	          pointers for initializing the TTM, allocating and freeing memory,
512	          waiting for command completion and fence synchronization, and memory
513	          migration. See the radeon_ttm.c file for an example of usage.
514	        </para>
515	        <para>
516	          The ttm_global_reference structure is made up of several fields:
517	        </para>
518	        <programlisting>
519	          struct ttm_global_reference {
520	                  enum ttm_global_types global_type;
521	                  size_t size;
522	                  void *object;
523	                  int (*init) (struct ttm_global_reference *);
524	                  void (*release) (struct ttm_global_reference *);
525	          };
526	        </programlisting>
527	        <para>
528	          There should be one global reference structure for your memory
529	          manager as a whole, and there will be others for each object
530	          created by the memory manager at runtime.  Your global TTM should
531	          have a type of TTM_GLOBAL_TTM_MEM.  The size field for the global
532	          object should be sizeof(struct ttm_mem_global), and the init and
533	          release hooks should point at your driver-specific init and
534	          release routines, which probably eventually call
535	          ttm_mem_global_init and ttm_mem_global_release, respectively.
536	        </para>
537	        <para>
538	          Once your global TTM accounting structure is set up and initialized
539	          by calling ttm_global_item_ref() on it,
540	          you need to create a buffer object TTM to
541	          provide a pool for buffer object allocation by clients and the
542	          kernel itself.  The type of this object should be TTM_GLOBAL_TTM_BO,
543	          and its size should be sizeof(struct ttm_bo_global).  Again,
544	          driver-specific init and release functions may be provided,
545	          likely eventually calling ttm_bo_global_init() and
546	          ttm_bo_global_release(), respectively.  Also, like the previous
547	          object, ttm_global_item_ref() is used to create an initial reference
548	          count for the TTM, which will call your initialization function.
549	        </para>
550	      </sect3>
551	    </sect2>
552	    <sect2 id="drm-gem">
553	      <title>The Graphics Execution Manager (GEM)</title>
554	      <para>
555	        The GEM design approach has resulted in a memory manager that doesn't
556	        provide full coverage of all (or even all common) use cases in its
557	        userspace or kernel API. GEM exposes a set of standard memory-related
558	        operations to userspace and a set of helper functions to drivers, and let
559	        drivers implement hardware-specific operations with their own private API.
560	      </para>
561	      <para>
562	        The GEM userspace API is described in the
563	        <ulink url="http://lwn.net/Articles/283798/"><citetitle>GEM - the Graphics
564	        Execution Manager</citetitle></ulink> article on LWN. While slightly
565	        outdated, the document provides a good overview of the GEM API principles.
566	        Buffer allocation and read and write operations, described as part of the
567	        common GEM API, are currently implemented using driver-specific ioctls.
568	      </para>
569	      <para>
570	        GEM is data-agnostic. It manages abstract buffer objects without knowing
571	        what individual buffers contain. APIs that require knowledge of buffer
572	        contents or purpose, such as buffer allocation or synchronization
573	        primitives, are thus outside of the scope of GEM and must be implemented
574	        using driver-specific ioctls.
575	      </para>
576	      <para>
577	        On a fundamental level, GEM involves several operations:
578	        <itemizedlist>
579	          <listitem>Memory allocation and freeing</listitem>
580	          <listitem>Command execution</listitem>
581	          <listitem>Aperture management at command execution time</listitem>
582	        </itemizedlist>
583	        Buffer object allocation is relatively straightforward and largely
584	        provided by Linux's shmem layer, which provides memory to back each
585	        object.
586	      </para>
587	      <para>
588	        Device-specific operations, such as command execution, pinning, buffer
589	        read &amp; write, mapping, and domain ownership transfers are left to
590	        driver-specific ioctls.
591	      </para>
592	      <sect3>
593	        <title>GEM Initialization</title>
594	        <para>
595	          Drivers that use GEM must set the DRIVER_GEM bit in the struct
596	          <structname>drm_driver</structname>
597	          <structfield>driver_features</structfield> field. The DRM core will
598	          then automatically initialize the GEM core before calling the
599	          <methodname>load</methodname> operation. Behind the scene, this will
600	          create a DRM Memory Manager object which provides an address space
601	          pool for object allocation.
602	        </para>
603	        <para>
604	          In a KMS configuration, drivers need to allocate and initialize a
605	          command ring buffer following core GEM initialization if required by
606	          the hardware. UMA devices usually have what is called a "stolen"
607	          memory region, which provides space for the initial framebuffer and
608	          large, contiguous memory regions required by the device. This space is
609	          typically not managed by GEM, and must be initialized separately into
610	          its own DRM MM object.
611	        </para>
612	      </sect3>
613	      <sect3>
614	        <title>GEM Objects Creation</title>
615	        <para>
616	          GEM splits creation of GEM objects and allocation of the memory that
617	          backs them in two distinct operations.
618	        </para>
619	        <para>
620	          GEM objects are represented by an instance of struct
621	          <structname>drm_gem_object</structname>. Drivers usually need to extend
622	          GEM objects with private information and thus create a driver-specific
623	          GEM object structure type that embeds an instance of struct
624	          <structname>drm_gem_object</structname>.
625	        </para>
626	        <para>
627	          To create a GEM object, a driver allocates memory for an instance of its
628	          specific GEM object type and initializes the embedded struct
629	          <structname>drm_gem_object</structname> with a call to
630	          <function>drm_gem_object_init</function>. The function takes a pointer to
631	          the DRM device, a pointer to the GEM object and the buffer object size
632	          in bytes.
633	        </para>
634	        <para>
635	          GEM uses shmem to allocate anonymous pageable memory.
636	          <function>drm_gem_object_init</function> will create an shmfs file of
637	          the requested size and store it into the struct
638	          <structname>drm_gem_object</structname> <structfield>filp</structfield>
639	          field. The memory is used as either main storage for the object when the
640	          graphics hardware uses system memory directly or as a backing store
641	          otherwise.
642	        </para>
643	        <para>
644	          Drivers are responsible for the actual physical pages allocation by
645	          calling <function>shmem_read_mapping_page_gfp</function> for each page.
646	          Note that they can decide to allocate pages when initializing the GEM
647	          object, or to delay allocation until the memory is needed (for instance
648	          when a page fault occurs as a result of a userspace memory access or
649	          when the driver needs to start a DMA transfer involving the memory).
650	        </para>
651	        <para>
652	          Anonymous pageable memory allocation is not always desired, for instance
653	          when the hardware requires physically contiguous system memory as is
654	          often the case in embedded devices. Drivers can create GEM objects with
655	          no shmfs backing (called private GEM objects) by initializing them with
656	          a call to <function>drm_gem_private_object_init</function> instead of
657	          <function>drm_gem_object_init</function>. Storage for private GEM
658	          objects must be managed by drivers.
659	        </para>
660	        <para>
661	          Drivers that do not need to extend GEM objects with private information
662	          can call the <function>drm_gem_object_alloc</function> function to
663	          allocate and initialize a struct <structname>drm_gem_object</structname>
664	          instance. The GEM core will call the optional driver
665	          <methodname>gem_init_object</methodname> operation after initializing
666	          the GEM object with <function>drm_gem_object_init</function>.
667	          <synopsis>int (*gem_init_object) (struct drm_gem_object *obj);</synopsis>
668	        </para>
669	        <para>
670	          No alloc-and-init function exists for private GEM objects.
671	        </para>
672	      </sect3>
673	      <sect3>
674	        <title>GEM Objects Lifetime</title>
675	        <para>
676	          All GEM objects are reference-counted by the GEM core. References can be
677	          acquired and release by <function>calling drm_gem_object_reference</function>
678	          and <function>drm_gem_object_unreference</function> respectively. The
679	          caller must hold the <structname>drm_device</structname>
680	          <structfield>struct_mutex</structfield> lock. As a convenience, GEM
681	          provides the <function>drm_gem_object_reference_unlocked</function> and
682	          <function>drm_gem_object_unreference_unlocked</function> functions that
683	          can be called without holding the lock.
684	        </para>
685	        <para>
686	          When the last reference to a GEM object is released the GEM core calls
687	          the <structname>drm_driver</structname>
688	          <methodname>gem_free_object</methodname> operation. That operation is
689	          mandatory for GEM-enabled drivers and must free the GEM object and all
690	          associated resources.
691	        </para>
692	        <para>
693	          <synopsis>void (*gem_free_object) (struct drm_gem_object *obj);</synopsis>
694	          Drivers are responsible for freeing all GEM object resources, including
695	          the resources created by the GEM core. If an mmap offset has been
696	          created for the object (in which case
697	          <structname>drm_gem_object</structname>::<structfield>map_list</structfield>::<structfield>map</structfield>
698	          is not NULL) it must be freed by a call to
699	          <function>drm_gem_free_mmap_offset</function>. The shmfs backing store
700	          must be released by calling <function>drm_gem_object_release</function>
701	          (that function can safely be called if no shmfs backing store has been
702	          created).
703	        </para>
704	      </sect3>
705	      <sect3>
706	        <title>GEM Objects Naming</title>
707	        <para>
708	          Communication between userspace and the kernel refers to GEM objects
709	          using local handles, global names or, more recently, file descriptors.
710	          All of those are 32-bit integer values; the usual Linux kernel limits
711	          apply to the file descriptors.
712	        </para>
713	        <para>
714	          GEM handles are local to a DRM file. Applications get a handle to a GEM
715	          object through a driver-specific ioctl, and can use that handle to refer
716	          to the GEM object in other standard or driver-specific ioctls. Closing a
717	          DRM file handle frees all its GEM handles and dereferences the
718	          associated GEM objects.
719	        </para>
720	        <para>
721	          To create a handle for a GEM object drivers call
722	          <function>drm_gem_handle_create</function>. The function takes a pointer
723	          to the DRM file and the GEM object and returns a locally unique handle.
724	          When the handle is no longer needed drivers delete it with a call to
725	          <function>drm_gem_handle_delete</function>. Finally the GEM object
726	          associated with a handle can be retrieved by a call to
727	          <function>drm_gem_object_lookup</function>.
728	        </para>
729	        <para>
730	          Handles don't take ownership of GEM objects, they only take a reference
731	          to the object that will be dropped when the handle is destroyed. To
732	          avoid leaking GEM objects, drivers must make sure they drop the
733	          reference(s) they own (such as the initial reference taken at object
734	          creation time) as appropriate, without any special consideration for the
735	          handle. For example, in the particular case of combined GEM object and
736	          handle creation in the implementation of the
737	          <methodname>dumb_create</methodname> operation, drivers must drop the
738	          initial reference to the GEM object before returning the handle.
739	        </para>
740	        <para>
741	          GEM names are similar in purpose to handles but are not local to DRM
742	          files. They can be passed between processes to reference a GEM object
743	          globally. Names can't be used directly to refer to objects in the DRM
744	          API, applications must convert handles to names and names to handles
745	          using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls
746	          respectively. The conversion is handled by the DRM core without any
747	          driver-specific support.
748	        </para>
749	        <para>
750	          GEM also supports buffer sharing with dma-buf file descriptors through
751	          PRIME. GEM-based drivers must use the provided helpers functions to
752	          implement the exporting and importing correctly. See <xref linkend="drm-prime-support" />.
753	          Since sharing file descriptors is inherently more secure than the
754	          easily guessable and global GEM names it is the preferred buffer
755	          sharing mechanism. Sharing buffers through GEM names is only supported
756	          for legacy userspace. Furthermore PRIME also allows cross-device
757	          buffer sharing since it is based on dma-bufs.
758	        </para>
759	      </sect3>
760	      <sect3 id="drm-gem-objects-mapping">
761	        <title>GEM Objects Mapping</title>
762	        <para>
763	          Because mapping operations are fairly heavyweight GEM favours
764	          read/write-like access to buffers, implemented through driver-specific
765	          ioctls, over mapping buffers to userspace. However, when random access
766	          to the buffer is needed (to perform software rendering for instance),
767	          direct access to the object can be more efficient.
768	        </para>
769	        <para>
770	          The mmap system call can't be used directly to map GEM objects, as they
771	          don't have their own file handle. Two alternative methods currently
772	          co-exist to map GEM objects to userspace. The first method uses a
773	          driver-specific ioctl to perform the mapping operation, calling
774	          <function>do_mmap</function> under the hood. This is often considered
775	          dubious, seems to be discouraged for new GEM-enabled drivers, and will
776	          thus not be described here.
777	        </para>
778	        <para>
779	          The second method uses the mmap system call on the DRM file handle.
780	          <synopsis>void *mmap(void *addr, size_t length, int prot, int flags, int fd,
781	             off_t offset);</synopsis>
782	          DRM identifies the GEM object to be mapped by a fake offset passed
783	          through the mmap offset argument. Prior to being mapped, a GEM object
784	          must thus be associated with a fake offset. To do so, drivers must call
785	          <function>drm_gem_create_mmap_offset</function> on the object. The
786	          function allocates a fake offset range from a pool and stores the
787	          offset divided by PAGE_SIZE in
788	          <literal>obj-&gt;map_list.hash.key</literal>. Care must be taken not to
789	          call <function>drm_gem_create_mmap_offset</function> if a fake offset
790	          has already been allocated for the object. This can be tested by
791	          <literal>obj-&gt;map_list.map</literal> being non-NULL.
792	        </para>
793	        <para>
794	          Once allocated, the fake offset value
795	          (<literal>obj-&gt;map_list.hash.key &lt;&lt; PAGE_SHIFT</literal>)
796	          must be passed to the application in a driver-specific way and can then
797	          be used as the mmap offset argument.
798	        </para>
799	        <para>
800	          The GEM core provides a helper method <function>drm_gem_mmap</function>
801	          to handle object mapping. The method can be set directly as the mmap
802	          file operation handler. It will look up the GEM object based on the
803	          offset value and set the VMA operations to the
804	          <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
805	          field. Note that <function>drm_gem_mmap</function> doesn't map memory to
806	          userspace, but relies on the driver-provided fault handler to map pages
807	          individually.
808	        </para>
809	        <para>
810	          To use <function>drm_gem_mmap</function>, drivers must fill the struct
811	          <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
812	          field with a pointer to VM operations.
813	        </para>
814	        <para>
815	          <synopsis>struct vm_operations_struct *gem_vm_ops
816	
817	  struct vm_operations_struct {
818	          void (*open)(struct vm_area_struct * area);
819	          void (*close)(struct vm_area_struct * area);
820	          int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf);
821	  };</synopsis>
822	        </para>
823	        <para>
824	          The <methodname>open</methodname> and <methodname>close</methodname>
825	          operations must update the GEM object reference count. Drivers can use
826	          the <function>drm_gem_vm_open</function> and
827	          <function>drm_gem_vm_close</function> helper functions directly as open
828	          and close handlers.
829	        </para>
830	        <para>
831	          The fault operation handler is responsible for mapping individual pages
832	          to userspace when a page fault occurs. Depending on the memory
833	          allocation scheme, drivers can allocate pages at fault time, or can
834	          decide to allocate memory for the GEM object at the time the object is
835	          created.
836	        </para>
837	        <para>
838	          Drivers that want to map the GEM object upfront instead of handling page
839	          faults can implement their own mmap file operation handler.
840	        </para>
841	      </sect3>
842	      <sect3>
843	        <title>Memory Coherency</title>
844	        <para>
845	          When mapped to the device or used in a command buffer, backing pages
846	          for an object are flushed to memory and marked write combined so as to
847	          be coherent with the GPU. Likewise, if the CPU accesses an object
848	          after the GPU has finished rendering to the object, then the object
849	          must be made coherent with the CPU's view of memory, usually involving
850	          GPU cache flushing of various kinds. This core CPU&lt;-&gt;GPU
851	          coherency management is provided by a device-specific ioctl, which
852	          evaluates an object's current domain and performs any necessary
853	          flushing or synchronization to put the object into the desired
854	          coherency domain (note that the object may be busy, i.e. an active
855	          render target; in that case, setting the domain blocks the client and
856	          waits for rendering to complete before performing any necessary
857	          flushing operations).
858	        </para>
859	      </sect3>
860	      <sect3>
861	        <title>Command Execution</title>
862	        <para>
863	          Perhaps the most important GEM function for GPU devices is providing a
864	          command execution interface to clients. Client programs construct
865	          command buffers containing references to previously allocated memory
866	          objects, and then submit them to GEM. At that point, GEM takes care to
867	          bind all the objects into the GTT, execute the buffer, and provide
868	          necessary synchronization between clients accessing the same buffers.
869	          This often involves evicting some objects from the GTT and re-binding
870	          others (a fairly expensive operation), and providing relocation
871	          support which hides fixed GTT offsets from clients. Clients must take
872	          care not to submit command buffers that reference more objects than
873	          can fit in the GTT; otherwise, GEM will reject them and no rendering
874	          will occur. Similarly, if several objects in the buffer require fence
875	          registers to be allocated for correct rendering (e.g. 2D blits on
876	          pre-965 chips), care must be taken not to require more fence registers
877	          than are available to the client. Such resource management should be
878	          abstracted from the client in libdrm.
879	        </para>
880	      </sect3>
881	      <sect3>
882	        <title>GEM Function Reference</title>
883	!Edrivers/gpu/drm/drm_gem.c
884	      </sect3>
885	    </sect2>
886	    <sect2>
887	      <title>VMA Offset Manager</title>
888	!Pdrivers/gpu/drm/drm_vma_manager.c vma offset manager
889	!Edrivers/gpu/drm/drm_vma_manager.c
890	!Iinclude/drm/drm_vma_manager.h
891	    </sect2>
892	    <sect2 id="drm-prime-support">
893	      <title>PRIME Buffer Sharing</title>
894	      <para>
895	        PRIME is the cross device buffer sharing framework in drm, originally
896	        created for the OPTIMUS range of multi-gpu platforms. To userspace
897	        PRIME buffers are dma-buf based file descriptors.
898	      </para>
899	      <sect3>
900	        <title>Overview and Driver Interface</title>
901	        <para>
902	          Similar to GEM global names, PRIME file descriptors are
903	          also used to share buffer objects across processes. They offer
904	          additional security: as file descriptors must be explicitly sent over
905	          UNIX domain sockets to be shared between applications, they can't be
906	          guessed like the globally unique GEM names.
907	        </para>
908	        <para>
909	          Drivers that support the PRIME
910	          API must set the DRIVER_PRIME bit in the struct
911	          <structname>drm_driver</structname>
912	          <structfield>driver_features</structfield> field, and implement the
913	          <methodname>prime_handle_to_fd</methodname> and
914	          <methodname>prime_fd_to_handle</methodname> operations.
915	        </para>
916	        <para>
917	          <synopsis>int (*prime_handle_to_fd)(struct drm_device *dev,
918	                          struct drm_file *file_priv, uint32_t handle,
919	                          uint32_t flags, int *prime_fd);
920	int (*prime_fd_to_handle)(struct drm_device *dev,
921	                          struct drm_file *file_priv, int prime_fd,
922	                          uint32_t *handle);</synopsis>
923	            Those two operations convert a handle to a PRIME file descriptor and
924	            vice versa. Drivers must use the kernel dma-buf buffer sharing framework
925	            to manage the PRIME file descriptors. Similar to the mode setting
926	            API PRIME is agnostic to the underlying buffer object manager, as
927	            long as handles are 32bit unsigned integers.
928	          </para>
929	          <para>
930	            While non-GEM drivers must implement the operations themselves, GEM
931	            drivers must use the <function>drm_gem_prime_handle_to_fd</function>
932	            and <function>drm_gem_prime_fd_to_handle</function> helper functions.
933	            Those helpers rely on the driver
934	            <methodname>gem_prime_export</methodname> and
935	            <methodname>gem_prime_import</methodname> operations to create a dma-buf
936	            instance from a GEM object (dma-buf exporter role) and to create a GEM
937	            object from a dma-buf instance (dma-buf importer role).
938	          </para>
939	          <para>
940	            <synopsis>struct dma_buf * (*gem_prime_export)(struct drm_device *dev,
941	                             struct drm_gem_object *obj,
942	                             int flags);
943	struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev,
944	                                            struct dma_buf *dma_buf);</synopsis>
945	            These two operations are mandatory for GEM drivers that support
946	            PRIME.
947	          </para>
948	        </sect3>
949	      <sect3>
950	        <title>PRIME Helper Functions</title>
951	!Pdrivers/gpu/drm/drm_prime.c PRIME Helpers
952	      </sect3>
953	    </sect2>
954	    <sect2>
955	      <title>PRIME Function References</title>
956	!Edrivers/gpu/drm/drm_prime.c
957	    </sect2>
958	    <sect2>
959	      <title>DRM MM Range Allocator</title>
960	      <sect3>
961	        <title>Overview</title>
962	!Pdrivers/gpu/drm/drm_mm.c Overview
963	      </sect3>
964	      <sect3>
965	        <title>LRU Scan/Eviction Support</title>
966	!Pdrivers/gpu/drm/drm_mm.c lru scan roaster
967	      </sect3>
968	      </sect2>
969	    <sect2>
970	      <title>DRM MM Range Allocator Function References</title>
971	!Edrivers/gpu/drm/drm_mm.c
972	!Iinclude/drm/drm_mm.h
973	    </sect2>
974	    <sect2>
975	      <title>CMA Helper Functions Reference</title>
976	!Pdrivers/gpu/drm/drm_gem_cma_helper.c cma helpers
977	!Edrivers/gpu/drm/drm_gem_cma_helper.c
978	!Iinclude/drm/drm_gem_cma_helper.h
979	    </sect2>
980	  </sect1>
981	
982	  <!-- Internals: mode setting -->
983	
984	  <sect1 id="drm-mode-setting">
985	    <title>Mode Setting</title>
986	    <para>
987	      Drivers must initialize the mode setting core by calling
988	      <function>drm_mode_config_init</function> on the DRM device. The function
989	      initializes the <structname>drm_device</structname>
990	      <structfield>mode_config</structfield> field and never fails. Once done,
991	      mode configuration must be setup by initializing the following fields.
992	    </para>
993	    <itemizedlist>
994	      <listitem>
995	        <synopsis>int min_width, min_height;
996	int max_width, max_height;</synopsis>
997	        <para>
998		  Minimum and maximum width and height of the frame buffers in pixel
999		  units.
1000		</para>
1001	      </listitem>
1002	      <listitem>
1003	        <synopsis>struct drm_mode_config_funcs *funcs;</synopsis>
1004		<para>Mode setting functions.</para>
1005	      </listitem>
1006	    </itemizedlist>
1007	    <sect2>
1008	      <title>Display Modes Function Reference</title>
1009	!Iinclude/drm/drm_modes.h
1010	!Edrivers/gpu/drm/drm_modes.c
1011	    </sect2>
1012	    <sect2>
1013	      <title>Atomic Mode Setting Function Reference</title>
1014	!Edrivers/gpu/drm/drm_atomic.c
1015	    </sect2>
1016	    <sect2>
1017	      <title>Frame Buffer Creation</title>
1018	      <synopsis>struct drm_framebuffer *(*fb_create)(struct drm_device *dev,
1019					     struct drm_file *file_priv,
1020					     struct drm_mode_fb_cmd2 *mode_cmd);</synopsis>
1021	      <para>
1022	        Frame buffers are abstract memory objects that provide a source of
1023	        pixels to scanout to a CRTC. Applications explicitly request the
1024	        creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls and
1025	        receive an opaque handle that can be passed to the KMS CRTC control,
1026	        plane configuration and page flip functions.
1027	      </para>
1028	      <para>
1029	        Frame buffers rely on the underneath memory manager for low-level memory
1030	        operations. When creating a frame buffer applications pass a memory
1031	        handle (or a list of memory handles for multi-planar formats) through
1032		the <parameter>drm_mode_fb_cmd2</parameter> argument. For drivers using
1033		GEM as their userspace buffer management interface this would be a GEM
1034		handle.  Drivers are however free to use their own backing storage object
1035		handles, e.g. vmwgfx directly exposes special TTM handles to userspace
1036		and so expects TTM handles in the create ioctl and not GEM handles.
1037	      </para>
1038	      <para>
1039	        Drivers must first validate the requested frame buffer parameters passed
1040	        through the mode_cmd argument. In particular this is where invalid
1041	        sizes, pixel formats or pitches can be caught.
1042	      </para>
1043	      <para>
1044	        If the parameters are deemed valid, drivers then create, initialize and
1045	        return an instance of struct <structname>drm_framebuffer</structname>.
1046	        If desired the instance can be embedded in a larger driver-specific
1047		structure. Drivers must fill its <structfield>width</structfield>,
1048		<structfield>height</structfield>, <structfield>pitches</structfield>,
1049	        <structfield>offsets</structfield>, <structfield>depth</structfield>,
1050	        <structfield>bits_per_pixel</structfield> and
1051	        <structfield>pixel_format</structfield> fields from the values passed
1052	        through the <parameter>drm_mode_fb_cmd2</parameter> argument. They
1053	        should call the <function>drm_helper_mode_fill_fb_struct</function>
1054	        helper function to do so.
1055	      </para>
1056	
1057	      <para>
1058		The initialization of the new framebuffer instance is finalized with a
1059		call to <function>drm_framebuffer_init</function> which takes a pointer
1060		to DRM frame buffer operations (struct
1061		<structname>drm_framebuffer_funcs</structname>). Note that this function
1062		publishes the framebuffer and so from this point on it can be accessed
1063		concurrently from other threads. Hence it must be the last step in the
1064		driver's framebuffer initialization sequence. Frame buffer operations
1065		are
1066	        <itemizedlist>
1067	          <listitem>
1068	            <synopsis>int (*create_handle)(struct drm_framebuffer *fb,
1069			     struct drm_file *file_priv, unsigned int *handle);</synopsis>
1070	            <para>
1071	              Create a handle to the frame buffer underlying memory object. If
1072	              the frame buffer uses a multi-plane format, the handle will
1073	              reference the memory object associated with the first plane.
1074	            </para>
1075	            <para>
1076	              Drivers call <function>drm_gem_handle_create</function> to create
1077	              the handle.
1078	            </para>
1079	          </listitem>
1080	          <listitem>
1081	            <synopsis>void (*destroy)(struct drm_framebuffer *framebuffer);</synopsis>
1082	            <para>
1083	              Destroy the frame buffer object and frees all associated
1084	              resources. Drivers must call
1085	              <function>drm_framebuffer_cleanup</function> to free resources
1086	              allocated by the DRM core for the frame buffer object, and must
1087	              make sure to unreference all memory objects associated with the
1088	              frame buffer. Handles created by the
1089	              <methodname>create_handle</methodname> operation are released by
1090	              the DRM core.
1091	            </para>
1092	          </listitem>
1093	          <listitem>
1094	            <synopsis>int (*dirty)(struct drm_framebuffer *framebuffer,
1095		     struct drm_file *file_priv, unsigned flags, unsigned color,
1096		     struct drm_clip_rect *clips, unsigned num_clips);</synopsis>
1097	            <para>
1098	              This optional operation notifies the driver that a region of the
1099	              frame buffer has changed in response to a DRM_IOCTL_MODE_DIRTYFB
1100	              ioctl call.
1101	            </para>
1102	          </listitem>
1103	        </itemizedlist>
1104	      </para>
1105	      <para>
1106		The lifetime of a drm framebuffer is controlled with a reference count,
1107		drivers can grab additional references with
1108		<function>drm_framebuffer_reference</function>and drop them
1109		again with <function>drm_framebuffer_unreference</function>. For
1110		driver-private framebuffers for which the last reference is never
1111		dropped (e.g. for the fbdev framebuffer when the struct
1112		<structname>drm_framebuffer</structname> is embedded into the fbdev
1113		helper struct) drivers can manually clean up a framebuffer at module
1114		unload time with
1115		<function>drm_framebuffer_unregister_private</function>.
1116	      </para>
1117	    </sect2>
1118	    <sect2>
1119	      <title>Dumb Buffer Objects</title>
1120	      <para>
1121		The KMS API doesn't standardize backing storage object creation and
1122		leaves it to driver-specific ioctls. Furthermore actually creating a
1123		buffer object even for GEM-based drivers is done through a
1124		driver-specific ioctl - GEM only has a common userspace interface for
1125		sharing and destroying objects. While not an issue for full-fledged
1126		graphics stacks that include device-specific userspace components (in
1127		libdrm for instance), this limit makes DRM-based early boot graphics
1128		unnecessarily complex.
1129	      </para>
1130	      <para>
1131	        Dumb objects partly alleviate the problem by providing a standard
1132	        API to create dumb buffers suitable for scanout, which can then be used
1133	        to create KMS frame buffers.
1134	      </para>
1135	      <para>
1136	        To support dumb objects drivers must implement the
1137	        <methodname>dumb_create</methodname>,
1138	        <methodname>dumb_destroy</methodname> and
1139	        <methodname>dumb_map_offset</methodname> operations.
1140	      </para>
1141	      <itemizedlist>
1142	        <listitem>
1143	          <synopsis>int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev,
1144	                   struct drm_mode_create_dumb *args);</synopsis>
1145	          <para>
1146	            The <methodname>dumb_create</methodname> operation creates a driver
1147		    object (GEM or TTM handle) suitable for scanout based on the
1148		    width, height and depth from the struct
1149		    <structname>drm_mode_create_dumb</structname> argument. It fills the
1150		    argument's <structfield>handle</structfield>,
1151		    <structfield>pitch</structfield> and <structfield>size</structfield>
1152		    fields with a handle for the newly created object and its line
1153	            pitch and size in bytes.
1154	          </para>
1155	        </listitem>
1156	        <listitem>
1157	          <synopsis>int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev,
1158	                    uint32_t handle);</synopsis>
1159	          <para>
1160	            The <methodname>dumb_destroy</methodname> operation destroys a dumb
1161	            object created by <methodname>dumb_create</methodname>.
1162	          </para>
1163	        </listitem>
1164	        <listitem>
1165	          <synopsis>int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev,
1166	                       uint32_t handle, uint64_t *offset);</synopsis>
1167	          <para>
1168	            The <methodname>dumb_map_offset</methodname> operation associates an
1169	            mmap fake offset with the object given by the handle and returns
1170	            it. Drivers must use the
1171	            <function>drm_gem_create_mmap_offset</function> function to
1172	            associate the fake offset as described in
1173	            <xref linkend="drm-gem-objects-mapping"/>.
1174	          </para>
1175	        </listitem>
1176	      </itemizedlist>
1177	      <para>
1178	        Note that dumb objects may not be used for gpu acceleration, as has been
1179		attempted on some ARM embedded platforms. Such drivers really must have
1180		a hardware-specific ioctl to allocate suitable buffer objects.
1181	      </para>
1182	    </sect2>
1183	    <sect2>
1184	      <title>Output Polling</title>
1185	      <synopsis>void (*output_poll_changed)(struct drm_device *dev);</synopsis>
1186	      <para>
1187	        This operation notifies the driver that the status of one or more
1188	        connectors has changed. Drivers that use the fb helper can just call the
1189	        <function>drm_fb_helper_hotplug_event</function> function to handle this
1190	        operation.
1191	      </para>
1192	    </sect2>
1193	    <sect2>
1194	      <title>Locking</title>
1195	      <para>
1196	        Beside some lookup structures with their own locking (which is hidden
1197		behind the interface functions) most of the modeset state is protected
1198		by the <code>dev-&lt;mode_config.lock</code> mutex and additionally
1199		per-crtc locks to allow cursor updates, pageflips and similar operations
1200		to occur concurrently with background tasks like output detection.
1201		Operations which cross domains like a full modeset always grab all
1202		locks. Drivers there need to protect resources shared between crtcs with
1203		additional locking. They also need to be careful to always grab the
1204		relevant crtc locks if a modset functions touches crtc state, e.g. for
1205		load detection (which does only grab the <code>mode_config.lock</code>
1206		to allow concurrent screen updates on live crtcs).
1207	      </para>
1208	    </sect2>
1209	  </sect1>
1210	
1211	  <!-- Internals: kms initialization and cleanup -->
1212	
1213	  <sect1 id="drm-kms-init">
1214	    <title>KMS Initialization and Cleanup</title>
1215	    <para>
1216	      A KMS device is abstracted and exposed as a set of planes, CRTCs, encoders
1217	      and connectors. KMS drivers must thus create and initialize all those
1218	      objects at load time after initializing mode setting.
1219	    </para>
1220	    <sect2>
1221	      <title>CRTCs (struct <structname>drm_crtc</structname>)</title>
1222	      <para>
1223	        A CRTC is an abstraction representing a part of the chip that contains a
1224		pointer to a scanout buffer. Therefore, the number of CRTCs available
1225		determines how many independent scanout buffers can be active at any
1226		given time. The CRTC structure contains several fields to support this:
1227		a pointer to some video memory (abstracted as a frame buffer object), a
1228		display mode, and an (x, y) offset into the video memory to support
1229		panning or configurations where one piece of video memory spans multiple
1230		CRTCs.
1231	      </para>
1232	      <sect3>
1233	        <title>CRTC Initialization</title>
1234	        <para>
1235	          A KMS device must create and register at least one struct
1236	          <structname>drm_crtc</structname> instance. The instance is allocated
1237	          and zeroed by the driver, possibly as part of a larger structure, and
1238	          registered with a call to <function>drm_crtc_init</function> with a
1239	          pointer to CRTC functions.
1240	        </para>
1241	      </sect3>
1242	      <sect3 id="drm-kms-crtcops">
1243	        <title>CRTC Operations</title>
1244	        <sect4>
1245	          <title>Set Configuration</title>
1246	          <synopsis>int (*set_config)(struct drm_mode_set *set);</synopsis>
1247	          <para>
1248	            Apply a new CRTC configuration to the device. The configuration
1249	            specifies a CRTC, a frame buffer to scan out from, a (x,y) position in
1250	            the frame buffer, a display mode and an array of connectors to drive
1251	            with the CRTC if possible.
1252	          </para>
1253	          <para>
1254	            If the frame buffer specified in the configuration is NULL, the driver
1255	            must detach all encoders connected to the CRTC and all connectors
1256	            attached to those encoders and disable them.
1257	          </para>
1258	          <para>
1259	            This operation is called with the mode config lock held.
1260	          </para>
1261	          <note><para>
1262		    Note that the drm core has no notion of restoring the mode setting
1263		    state after resume, since all resume handling is in the full
1264		    responsibility of the driver. The common mode setting helper library
1265		    though provides a helper which can be used for this:
1266		    <function>drm_helper_resume_force_mode</function>.
1267	          </para></note>
1268	        </sect4>
1269	        <sect4>
1270	          <title>Page Flipping</title>
1271	          <synopsis>int (*page_flip)(struct drm_crtc *crtc, struct drm_framebuffer *fb,
1272	                   struct drm_pending_vblank_event *event);</synopsis>
1273	          <para>
1274	            Schedule a page flip to the given frame buffer for the CRTC. This
1275	            operation is called with the mode config mutex held.
1276	          </para>
1277	          <para>
1278	            Page flipping is a synchronization mechanism that replaces the frame
1279	            buffer being scanned out by the CRTC with a new frame buffer during
1280	            vertical blanking, avoiding tearing. When an application requests a page
1281	            flip the DRM core verifies that the new frame buffer is large enough to
1282	            be scanned out by  the CRTC in the currently configured mode and then
1283	            calls the CRTC <methodname>page_flip</methodname> operation with a
1284	            pointer to the new frame buffer.
1285	          </para>
1286	          <para>
1287	            The <methodname>page_flip</methodname> operation schedules a page flip.
1288	            Once any pending rendering targeting the new frame buffer has
1289	            completed, the CRTC will be reprogrammed to display that frame buffer
1290	            after the next vertical refresh. The operation must return immediately
1291	            without waiting for rendering or page flip to complete and must block
1292	            any new rendering to the frame buffer until the page flip completes.
1293	          </para>
1294	          <para>
1295	            If a page flip can be successfully scheduled the driver must set the
1296	            <code>drm_crtc-&lt;fb</code> field to the new framebuffer pointed to
1297	            by <code>fb</code>. This is important so that the reference counting
1298	            on framebuffers stays balanced.
1299	          </para>
1300	          <para>
1301	            If a page flip is already pending, the
1302	            <methodname>page_flip</methodname> operation must return
1303	            -<errorname>EBUSY</errorname>.
1304	          </para>
1305	          <para>
1306	            To synchronize page flip to vertical blanking the driver will likely
1307	            need to enable vertical blanking interrupts. It should call
1308	            <function>drm_vblank_get</function> for that purpose, and call
1309	            <function>drm_vblank_put</function> after the page flip completes.
1310	          </para>
1311	          <para>
1312	            If the application has requested to be notified when page flip completes
1313	            the <methodname>page_flip</methodname> operation will be called with a
1314	            non-NULL <parameter>event</parameter> argument pointing to a
1315	            <structname>drm_pending_vblank_event</structname> instance. Upon page
1316	            flip completion the driver must call <methodname>drm_send_vblank_event</methodname>
1317	            to fill in the event and send to wake up any waiting processes.
1318	            This can be performed with
1319	            <programlisting><![CDATA[
1320	            spin_lock_irqsave(&dev->event_lock, flags);
1321	            ...
1322	            drm_send_vblank_event(dev, pipe, event);
1323	            spin_unlock_irqrestore(&dev->event_lock, flags);
1324	            ]]></programlisting>
1325	          </para>
1326	          <note><para>
1327	            FIXME: Could drivers that don't need to wait for rendering to complete
1328	            just add the event to <literal>dev-&gt;vblank_event_list</literal> and
1329	            let the DRM core handle everything, as for "normal" vertical blanking
1330	            events?
1331	          </para></note>
1332	          <para>
1333	            While waiting for the page flip to complete, the
1334	            <literal>event-&gt;base.link</literal> list head can be used freely by
1335	            the driver to store the pending event in a driver-specific list.
1336	          </para>
1337	          <para>
1338	            If the file handle is closed before the event is signaled, drivers must
1339	            take care to destroy the event in their
1340	            <methodname>preclose</methodname> operation (and, if needed, call
1341	            <function>drm_vblank_put</function>).
1342	          </para>
1343	        </sect4>
1344	        <sect4>
1345	          <title>Miscellaneous</title>
1346	          <itemizedlist>
1347	            <listitem>
1348	              <synopsis>void (*set_property)(struct drm_crtc *crtc,
1349	                     struct drm_property *property, uint64_t value);</synopsis>
1350	              <para>
1351	                Set the value of the given CRTC property to
1352	                <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1353	                for more information about properties.
1354	              </para>
1355	            </listitem>
1356	            <listitem>
1357	              <synopsis>void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b,
1358	                        uint32_t start, uint32_t size);</synopsis>
1359	              <para>
1360	                Apply a gamma table to the device. The operation is optional.
1361	              </para>
1362	            </listitem>
1363	            <listitem>
1364	              <synopsis>void (*destroy)(struct drm_crtc *crtc);</synopsis>
1365	              <para>
1366	                Destroy the CRTC when not needed anymore. See
1367	                <xref linkend="drm-kms-init"/>.
1368	              </para>
1369	            </listitem>
1370	          </itemizedlist>
1371	        </sect4>
1372	      </sect3>
1373	    </sect2>
1374	    <sect2>
1375	      <title>Planes (struct <structname>drm_plane</structname>)</title>
1376	      <para>
1377	        A plane represents an image source that can be blended with or overlayed
1378		on top of a CRTC during the scanout process. Planes are associated with
1379		a frame buffer to crop a portion of the image memory (source) and
1380		optionally scale it to a destination size. The result is then blended
1381		with or overlayed on top of a CRTC.
1382	      </para>
1383	      <para>
1384	      The DRM core recognizes three types of planes:
1385	      <itemizedlist>
1386	        <listitem>
1387	        DRM_PLANE_TYPE_PRIMARY represents a "main" plane for a CRTC.  Primary
1388	        planes are the planes operated upon by CRTC modesetting and flipping
1389	        operations described in <xref linkend="drm-kms-crtcops"/>.
1390	        </listitem>
1391	        <listitem>
1392	        DRM_PLANE_TYPE_CURSOR represents a "cursor" plane for a CRTC.  Cursor
1393	        planes are the planes operated upon by the DRM_IOCTL_MODE_CURSOR and
1394	        DRM_IOCTL_MODE_CURSOR2 ioctls.
1395	        </listitem>
1396	        <listitem>
1397	        DRM_PLANE_TYPE_OVERLAY represents all non-primary, non-cursor planes.
1398	        Some drivers refer to these types of planes as "sprites" internally.
1399	        </listitem>
1400	      </itemizedlist>
1401	      For compatibility with legacy userspace, only overlay planes are made
1402	      available to userspace by default.  Userspace clients may set the
1403	      DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate that
1404	      they wish to receive a universal plane list containing all plane types.
1405	      </para>
1406	      <sect3>
1407	        <title>Plane Initialization</title>
1408	        <para>
1409	          To create a plane, a KMS drivers allocates and
1410	          zeroes an instances of struct <structname>drm_plane</structname>
1411	          (possibly as part of a larger structure) and registers it with a call
1412	          to <function>drm_universal_plane_init</function>. The function takes a bitmask
1413	          of the CRTCs that can be associated with the plane, a pointer to the
1414	          plane functions, a list of format supported formats, and the type of
1415	          plane (primary, cursor, or overlay) being initialized.
1416	        </para>
1417	        <para>
1418	          Cursor and overlay planes are optional.  All drivers should provide
1419	          one primary plane per CRTC (although this requirement may change in
1420	          the future); drivers that do not wish to provide special handling for
1421	          primary planes may make use of the helper functions described in
1422	          <xref linkend="drm-kms-planehelpers"/> to create and register a
1423	          primary plane with standard capabilities.
1424	        </para>
1425	      </sect3>
1426	      <sect3>
1427	        <title>Plane Operations</title>
1428	        <itemizedlist>
1429	          <listitem>
1430	            <synopsis>int (*update_plane)(struct drm_plane *plane, struct drm_crtc *crtc,
1431	                        struct drm_framebuffer *fb, int crtc_x, int crtc_y,
1432	                        unsigned int crtc_w, unsigned int crtc_h,
1433	                        uint32_t src_x, uint32_t src_y,
1434	                        uint32_t src_w, uint32_t src_h);</synopsis>
1435	            <para>
1436	              Enable and configure the plane to use the given CRTC and frame buffer.
1437	            </para>
1438	            <para>
1439	              The source rectangle in frame buffer memory coordinates is given by
1440	              the <parameter>src_x</parameter>, <parameter>src_y</parameter>,
1441	              <parameter>src_w</parameter> and <parameter>src_h</parameter>
1442	              parameters (as 16.16 fixed point values). Devices that don't support
1443	              subpixel plane coordinates can ignore the fractional part.
1444	            </para>
1445	            <para>
1446	              The destination rectangle in CRTC coordinates is given by the
1447	              <parameter>crtc_x</parameter>, <parameter>crtc_y</parameter>,
1448	              <parameter>crtc_w</parameter> and <parameter>crtc_h</parameter>
1449	              parameters (as integer values). Devices scale the source rectangle to
1450	              the destination rectangle. If scaling is not supported, and the source
1451	              rectangle size doesn't match the destination rectangle size, the
1452	              driver must return a -<errorname>EINVAL</errorname> error.
1453	            </para>
1454	          </listitem>
1455	          <listitem>
1456	            <synopsis>int (*disable_plane)(struct drm_plane *plane);</synopsis>
1457	            <para>
1458	              Disable the plane. The DRM core calls this method in response to a
1459	              DRM_IOCTL_MODE_SETPLANE ioctl call with the frame buffer ID set to 0.
1460	              Disabled planes must not be processed by the CRTC.
1461	            </para>
1462	          </listitem>
1463	          <listitem>
1464	            <synopsis>void (*destroy)(struct drm_plane *plane);</synopsis>
1465	            <para>
1466	              Destroy the plane when not needed anymore. See
1467	              <xref linkend="drm-kms-init"/>.
1468	            </para>
1469	          </listitem>
1470	        </itemizedlist>
1471	      </sect3>
1472	    </sect2>
1473	    <sect2>
1474	      <title>Encoders (struct <structname>drm_encoder</structname>)</title>
1475	      <para>
1476	        An encoder takes pixel data from a CRTC and converts it to a format
1477		suitable for any attached connectors. On some devices, it may be
1478		possible to have a CRTC send data to more than one encoder. In that
1479		case, both encoders would receive data from the same scanout buffer,
1480		resulting in a "cloned" display configuration across the connectors
1481		attached to each encoder.
1482	      </para>
1483	      <sect3>
1484	        <title>Encoder Initialization</title>
1485	        <para>
1486	          As for CRTCs, a KMS driver must create, initialize and register at
1487	          least one struct <structname>drm_encoder</structname> instance. The
1488	          instance is allocated and zeroed by the driver, possibly as part of a
1489	          larger structure.
1490	        </para>
1491	        <para>
1492	          Drivers must initialize the struct <structname>drm_encoder</structname>
1493	          <structfield>possible_crtcs</structfield> and
1494	          <structfield>possible_clones</structfield> fields before registering the
1495	          encoder. Both fields are bitmasks of respectively the CRTCs that the
1496	          encoder can be connected to, and sibling encoders candidate for cloning.
1497	        </para>
1498	        <para>
1499	          After being initialized, the encoder must be registered with a call to
1500	          <function>drm_encoder_init</function>. The function takes a pointer to
1501	          the encoder functions and an encoder type. Supported types are
1502	          <itemizedlist>
1503	            <listitem>
1504	              DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A
1505	              </listitem>
1506	            <listitem>
1507	              DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort
1508	            </listitem>
1509	            <listitem>
1510	              DRM_MODE_ENCODER_LVDS for display panels
1511	            </listitem>
1512	            <listitem>
1513	              DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, Component,
1514	              SCART)
1515	            </listitem>
1516	            <listitem>
1517	              DRM_MODE_ENCODER_VIRTUAL for virtual machine displays
1518	            </listitem>
1519	          </itemizedlist>
1520	        </para>
1521	        <para>
1522	          Encoders must be attached to a CRTC to be used. DRM drivers leave
1523	          encoders unattached at initialization time. Applications (or the fbdev
1524	          compatibility layer when implemented) are responsible for attaching the
1525	          encoders they want to use to a CRTC.
1526	        </para>
1527	      </sect3>
1528	      <sect3>
1529	        <title>Encoder Operations</title>
1530	        <itemizedlist>
1531	          <listitem>
1532	            <synopsis>void (*destroy)(struct drm_encoder *encoder);</synopsis>
1533	            <para>
1534	              Called to destroy the encoder when not needed anymore. See
1535	              <xref linkend="drm-kms-init"/>.
1536	            </para>
1537	          </listitem>
1538	          <listitem>
1539	            <synopsis>void (*set_property)(struct drm_plane *plane,
1540	                     struct drm_property *property, uint64_t value);</synopsis>
1541	            <para>
1542	              Set the value of the given plane property to
1543	              <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1544	              for more information about properties.
1545	            </para>
1546	          </listitem>
1547	        </itemizedlist>
1548	      </sect3>
1549	    </sect2>
1550	    <sect2>
1551	      <title>Connectors (struct <structname>drm_connector</structname>)</title>
1552	      <para>
1553	        A connector is the final destination for pixel data on a device, and
1554		usually connects directly to an external display device like a monitor
1555		or laptop panel. A connector can only be attached to one encoder at a
1556		time. The connector is also the structure where information about the
1557		attached display is kept, so it contains fields for display data, EDID
1558		data, DPMS &amp; connection status, and information about modes
1559		supported on the attached displays.
1560	      </para>
1561	      <sect3>
1562	        <title>Connector Initialization</title>
1563	        <para>
1564	          Finally a KMS driver must create, initialize, register and attach at
1565	          least one struct <structname>drm_connector</structname> instance. The
1566	          instance is created as other KMS objects and initialized by setting the
1567	          following fields.
1568	        </para>
1569	        <variablelist>
1570	          <varlistentry>
1571	            <term><structfield>interlace_allowed</structfield></term>
1572	            <listitem><para>
1573	              Whether the connector can handle interlaced modes.
1574	            </para></listitem>
1575	          </varlistentry>
1576	          <varlistentry>
1577	            <term><structfield>doublescan_allowed</structfield></term>
1578	            <listitem><para>
1579	              Whether the connector can handle doublescan.
1580	            </para></listitem>
1581	          </varlistentry>
1582	          <varlistentry>
1583	            <term><structfield>display_info
1584	            </structfield></term>
1585	            <listitem><para>
1586	              Display information is filled from EDID information when a display
1587	              is detected. For non hot-pluggable displays such as flat panels in
1588	              embedded systems, the driver should initialize the
1589	              <structfield>display_info</structfield>.<structfield>width_mm</structfield>
1590	              and
1591	              <structfield>display_info</structfield>.<structfield>height_mm</structfield>
1592	              fields with the physical size of the display.
1593	            </para></listitem>
1594	          </varlistentry>
1595	          <varlistentry>
1596	            <term id="drm-kms-connector-polled"><structfield>polled</structfield></term>
1597	            <listitem><para>
1598	              Connector polling mode, a combination of
1599	              <variablelist>
1600	                <varlistentry>
1601	                  <term>DRM_CONNECTOR_POLL_HPD</term>
1602	                  <listitem><para>
1603	                    The connector generates hotplug events and doesn't need to be
1604	                    periodically polled. The CONNECT and DISCONNECT flags must not
1605	                    be set together with the HPD flag.
1606	                  </para></listitem>
1607	                </varlistentry>
1608	                <varlistentry>
1609	                  <term>DRM_CONNECTOR_POLL_CONNECT</term>
1610	                  <listitem><para>
1611	                    Periodically poll the connector for connection.
1612	                  </para></listitem>
1613	                </varlistentry>
1614	                <varlistentry>
1615	                  <term>DRM_CONNECTOR_POLL_DISCONNECT</term>
1616	                  <listitem><para>
1617	                    Periodically poll the connector for disconnection.
1618	                  </para></listitem>
1619	                </varlistentry>
1620	              </variablelist>
1621	              Set to 0 for connectors that don't support connection status
1622	              discovery.
1623	            </para></listitem>
1624	          </varlistentry>
1625	        </variablelist>
1626	        <para>
1627	          The connector is then registered with a call to
1628	          <function>drm_connector_init</function> with a pointer to the connector
1629	          functions and a connector type, and exposed through sysfs with a call to
1630	          <function>drm_connector_register</function>.
1631	        </para>
1632	        <para>
1633	          Supported connector types are
1634	          <itemizedlist>
1635	            <listitem>DRM_MODE_CONNECTOR_VGA</listitem>
1636	            <listitem>DRM_MODE_CONNECTOR_DVII</listitem>
1637	            <listitem>DRM_MODE_CONNECTOR_DVID</listitem>
1638	            <listitem>DRM_MODE_CONNECTOR_DVIA</listitem>
1639	            <listitem>DRM_MODE_CONNECTOR_Composite</listitem>
1640	            <listitem>DRM_MODE_CONNECTOR_SVIDEO</listitem>
1641	            <listitem>DRM_MODE_CONNECTOR_LVDS</listitem>
1642	            <listitem>DRM_MODE_CONNECTOR_Component</listitem>
1643	            <listitem>DRM_MODE_CONNECTOR_9PinDIN</listitem>
1644	            <listitem>DRM_MODE_CONNECTOR_DisplayPort</listitem>
1645	            <listitem>DRM_MODE_CONNECTOR_HDMIA</listitem>
1646	            <listitem>DRM_MODE_CONNECTOR_HDMIB</listitem>
1647	            <listitem>DRM_MODE_CONNECTOR_TV</listitem>
1648	            <listitem>DRM_MODE_CONNECTOR_eDP</listitem>
1649	            <listitem>DRM_MODE_CONNECTOR_VIRTUAL</listitem>
1650	          </itemizedlist>
1651	        </para>
1652	        <para>
1653	          Connectors must be attached to an encoder to be used. For devices that
1654	          map connectors to encoders 1:1, the connector should be attached at
1655	          initialization time with a call to
1656	          <function>drm_mode_connector_attach_encoder</function>. The driver must
1657	          also set the <structname>drm_connector</structname>
1658	          <structfield>encoder</structfield> field to point to the attached
1659	          encoder.
1660	        </para>
1661	        <para>
1662	          Finally, drivers must initialize the connectors state change detection
1663	          with a call to <function>drm_kms_helper_poll_init</function>. If at
1664	          least one connector is pollable but can't generate hotplug interrupts
1665	          (indicated by the DRM_CONNECTOR_POLL_CONNECT and
1666	          DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will
1667	          automatically be queued to periodically poll for changes. Connectors
1668	          that can generate hotplug interrupts must be marked with the
1669	          DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must
1670	          call <function>drm_helper_hpd_irq_event</function>. The function will
1671	          queue a delayed work to check the state of all connectors, but no
1672	          periodic polling will be done.
1673	        </para>
1674	      </sect3>
1675	      <sect3>
1676	        <title>Connector Operations</title>
1677	        <note><para>
1678	          Unless otherwise state, all operations are mandatory.
1679	        </para></note>
1680	        <sect4>
1681	          <title>DPMS</title>
1682	          <synopsis>void (*dpms)(struct drm_connector *connector, int mode);</synopsis>
1683	          <para>
1684	            The DPMS operation sets the power state of a connector. The mode
1685	            argument is one of
1686	            <itemizedlist>
1687	              <listitem><para>DRM_MODE_DPMS_ON</para></listitem>
1688	              <listitem><para>DRM_MODE_DPMS_STANDBY</para></listitem>
1689	              <listitem><para>DRM_MODE_DPMS_SUSPEND</para></listitem>
1690	              <listitem><para>DRM_MODE_DPMS_OFF</para></listitem>
1691	            </itemizedlist>
1692	          </para>
1693	          <para>
1694	            In all but DPMS_ON mode the encoder to which the connector is attached
1695	            should put the display in low-power mode by driving its signals
1696	            appropriately. If more than one connector is attached to the encoder
1697	            care should be taken not to change the power state of other displays as
1698	            a side effect. Low-power mode should be propagated to the encoders and
1699	            CRTCs when all related connectors are put in low-power mode.
1700	          </para>
1701	        </sect4>
1702	        <sect4>
1703	          <title>Modes</title>
1704	          <synopsis>int (*fill_modes)(struct drm_connector *connector, uint32_t max_width,
1705	                      uint32_t max_height);</synopsis>
1706	          <para>
1707	            Fill the mode list with all supported modes for the connector. If the
1708	            <parameter>max_width</parameter> and <parameter>max_height</parameter>
1709	            arguments are non-zero, the implementation must ignore all modes wider
1710	            than <parameter>max_width</parameter> or higher than
1711	            <parameter>max_height</parameter>.
1712	          </para>
1713	          <para>
1714	            The connector must also fill in this operation its
1715	            <structfield>display_info</structfield>
1716	            <structfield>width_mm</structfield> and
1717	            <structfield>height_mm</structfield> fields with the connected display
1718	            physical size in millimeters. The fields should be set to 0 if the value
1719	            isn't known or is not applicable (for instance for projector devices).
1720	          </para>
1721	        </sect4>
1722	        <sect4>
1723	          <title>Connection Status</title>
1724	          <para>
1725	            The connection status is updated through polling or hotplug events when
1726	            supported (see <xref linkend="drm-kms-connector-polled"/>). The status
1727	            value is reported to userspace through ioctls and must not be used
1728	            inside the driver, as it only gets initialized by a call to
1729	            <function>drm_mode_getconnector</function> from userspace.
1730	          </para>
1731	          <synopsis>enum drm_connector_status (*detect)(struct drm_connector *connector,
1732	                                        bool force);</synopsis>
1733	          <para>
1734	            Check to see if anything is attached to the connector. The
1735	            <parameter>force</parameter> parameter is set to false whilst polling or
1736	            to true when checking the connector due to user request.
1737	            <parameter>force</parameter> can be used by the driver to avoid
1738	            expensive, destructive operations during automated probing.
1739	          </para>
1740	          <para>
1741	            Return connector_status_connected if something is connected to the
1742	            connector, connector_status_disconnected if nothing is connected and
1743	            connector_status_unknown if the connection state isn't known.
1744	          </para>
1745	          <para>
1746	            Drivers should only return connector_status_connected if the connection
1747	            status has really been probed as connected. Connectors that can't detect
1748	            the connection status, or failed connection status probes, should return
1749	            connector_status_unknown.
1750	          </para>
1751	        </sect4>
1752	        <sect4>
1753	          <title>Miscellaneous</title>
1754	          <itemizedlist>
1755	            <listitem>
1756	              <synopsis>void (*set_property)(struct drm_connector *connector,
1757	                     struct drm_property *property, uint64_t value);</synopsis>
1758	              <para>
1759	                Set the value of the given connector property to
1760	                <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1761	                for more information about properties.
1762	              </para>
1763	            </listitem>
1764	            <listitem>
1765	              <synopsis>void (*destroy)(struct drm_connector *connector);</synopsis>
1766	              <para>
1767	                Destroy the connector when not needed anymore. See
1768	                <xref linkend="drm-kms-init"/>.
1769	              </para>
1770	            </listitem>
1771	          </itemizedlist>
1772	        </sect4>
1773	      </sect3>
1774	    </sect2>
1775	    <sect2>
1776	      <title>Cleanup</title>
1777	      <para>
1778	        The DRM core manages its objects' lifetime. When an object is not needed
1779		anymore the core calls its destroy function, which must clean up and
1780		free every resource allocated for the object. Every
1781		<function>drm_*_init</function> call must be matched with a
1782		corresponding <function>drm_*_cleanup</function> call to cleanup CRTCs
1783		(<function>drm_crtc_cleanup</function>), planes
1784		(<function>drm_plane_cleanup</function>), encoders
1785		(<function>drm_encoder_cleanup</function>) and connectors
1786		(<function>drm_connector_cleanup</function>). Furthermore, connectors
1787		that have been added to sysfs must be removed by a call to
1788		<function>drm_connector_unregister</function> before calling
1789		<function>drm_connector_cleanup</function>.
1790	      </para>
1791	      <para>
1792	        Connectors state change detection must be cleanup up with a call to
1793		<function>drm_kms_helper_poll_fini</function>.
1794	      </para>
1795	    </sect2>
1796	    <sect2>
1797	      <title>Output discovery and initialization example</title>
1798	      <programlisting><![CDATA[
1799	void intel_crt_init(struct drm_device *dev)
1800	{
1801		struct drm_connector *connector;
1802		struct intel_output *intel_output;
1803	
1804		intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL);
1805		if (!intel_output)
1806			return;
1807	
1808		connector = &intel_output->base;
1809		drm_connector_init(dev, &intel_output->base,
1810				   &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA);
1811	
1812		drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs,
1813				 DRM_MODE_ENCODER_DAC);
1814	
1815		drm_mode_connector_attach_encoder(&intel_output->base,
1816						  &intel_output->enc);
1817	
1818		/* Set up the DDC bus. */
1819		intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A");
1820		if (!intel_output->ddc_bus) {
1821			dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration "
1822				   "failed.\n");
1823			return;
1824		}
1825	
1826		intel_output->type = INTEL_OUTPUT_ANALOG;
1827		connector->interlace_allowed = 0;
1828		connector->doublescan_allowed = 0;
1829	
1830		drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs);
1831		drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs);
1832	
1833		drm_connector_register(connector);
1834	}]]></programlisting>
1835	      <para>
1836	        In the example above (taken from the i915 driver), a CRTC, connector and
1837	        encoder combination is created. A device-specific i2c bus is also
1838	        created for fetching EDID data and performing monitor detection. Once
1839	        the process is complete, the new connector is registered with sysfs to
1840	        make its properties available to applications.
1841	      </para>
1842	    </sect2>
1843	    <sect2>
1844	      <title>KMS API Functions</title>
1845	!Edrivers/gpu/drm/drm_crtc.c
1846	    </sect2>
1847	    <sect2>
1848	      <title>KMS Data Structures</title>
1849	!Iinclude/drm/drm_crtc.h
1850	    </sect2>
1851	    <sect2>
1852	      <title>KMS Locking</title>
1853	!Pdrivers/gpu/drm/drm_modeset_lock.c kms locking
1854	!Iinclude/drm/drm_modeset_lock.h
1855	!Edrivers/gpu/drm/drm_modeset_lock.c
1856	    </sect2>
1857	  </sect1>
1858	
1859	  <!-- Internals: kms helper functions -->
1860	
1861	  <sect1>
1862	    <title>Mode Setting Helper Functions</title>
1863	    <para>
1864	      The plane, CRTC, encoder and connector functions provided by the drivers
1865	      implement the DRM API. They're called by the DRM core and ioctl handlers
1866	      to handle device state changes and configuration request. As implementing
1867	      those functions often requires logic not specific to drivers, mid-layer
1868	      helper functions are available to avoid duplicating boilerplate code.
1869	    </para>
1870	    <para>
1871	      The DRM core contains one mid-layer implementation. The mid-layer provides
1872	      implementations of several plane, CRTC, encoder and connector functions
1873	      (called from the top of the mid-layer) that pre-process requests and call
1874	      lower-level functions provided by the driver (at the bottom of the
1875	      mid-layer). For instance, the
1876	      <function>drm_crtc_helper_set_config</function> function can be used to
1877	      fill the struct <structname>drm_crtc_funcs</structname>
1878	      <structfield>set_config</structfield> field. When called, it will split
1879	      the <methodname>set_config</methodname> operation in smaller, simpler
1880	      operations and call the driver to handle them.
1881	    </para>
1882	    <para>
1883	      To use the mid-layer, drivers call <function>drm_crtc_helper_add</function>,
1884	      <function>drm_encoder_helper_add</function> and
1885	      <function>drm_connector_helper_add</function> functions to install their
1886	      mid-layer bottom operations handlers, and fill the
1887	      <structname>drm_crtc_funcs</structname>,
1888	      <structname>drm_encoder_funcs</structname> and
1889	      <structname>drm_connector_funcs</structname> structures with pointers to
1890	      the mid-layer top API functions. Installing the mid-layer bottom operation
1891	      handlers is best done right after registering the corresponding KMS object.
1892	    </para>
1893	    <para>
1894	      The mid-layer is not split between CRTC, encoder and connector operations.
1895	      To use it, a driver must provide bottom functions for all of the three KMS
1896	      entities.
1897	    </para>
1898	    <sect2>
1899	      <title>Helper Functions</title>
1900	      <itemizedlist>
1901	        <listitem>
1902	          <synopsis>int drm_crtc_helper_set_config(struct drm_mode_set *set);</synopsis>
1903	          <para>
1904	            The <function>drm_crtc_helper_set_config</function> helper function
1905	            is a CRTC <methodname>set_config</methodname> implementation. It
1906	            first tries to locate the best encoder for each connector by calling
1907	            the connector <methodname>best_encoder</methodname> helper
1908	            operation.
1909	          </para>
1910	          <para>
1911	            After locating the appropriate encoders, the helper function will
1912	            call the <methodname>mode_fixup</methodname> encoder and CRTC helper
1913	            operations to adjust the requested mode, or reject it completely in
1914	            which case an error will be returned to the application. If the new
1915	            configuration after mode adjustment is identical to the current
1916	            configuration the helper function will return without performing any
1917	            other operation.
1918	          </para>
1919	          <para>
1920	            If the adjusted mode is identical to the current mode but changes to
1921	            the frame buffer need to be applied, the
1922	            <function>drm_crtc_helper_set_config</function> function will call
1923	            the CRTC <methodname>mode_set_base</methodname> helper operation. If
1924	            the adjusted mode differs from the current mode, or if the
1925	            <methodname>mode_set_base</methodname> helper operation is not
1926	            provided, the helper function performs a full mode set sequence by
1927	            calling the <methodname>prepare</methodname>,
1928	            <methodname>mode_set</methodname> and
1929	            <methodname>commit</methodname> CRTC and encoder helper operations,
1930	            in that order.
1931	          </para>
1932	        </listitem>
1933	        <listitem>
1934	          <synopsis>void drm_helper_connector_dpms(struct drm_connector *connector, int mode);</synopsis>
1935	          <para>
1936	            The <function>drm_helper_connector_dpms</function> helper function
1937	            is a connector <methodname>dpms</methodname> implementation that
1938	            tracks power state of connectors. To use the function, drivers must
1939	            provide <methodname>dpms</methodname> helper operations for CRTCs
1940	            and encoders to apply the DPMS state to the device.
1941	          </para>
1942	          <para>
1943	            The mid-layer doesn't track the power state of CRTCs and encoders.
1944	            The <methodname>dpms</methodname> helper operations can thus be
1945	            called with a mode identical to the currently active mode.
1946	          </para>
1947	        </listitem>
1948	        <listitem>
1949	          <synopsis>int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
1950	                                            uint32_t maxX, uint32_t maxY);</synopsis>
1951	          <para>
1952	            The <function>drm_helper_probe_single_connector_modes</function> helper
1953	            function is a connector <methodname>fill_modes</methodname>
1954	            implementation that updates the connection status for the connector
1955	            and then retrieves a list of modes by calling the connector
1956	            <methodname>get_modes</methodname> helper operation.
1957	          </para>
1958	         <para>
1959	            If the helper operation returns no mode, and if the connector status
1960	            is connector_status_connected, standard VESA DMT modes up to
1961	            1024x768 are automatically added to the modes list by a call to
1962	            <function>drm_add_modes_noedid</function>.
1963	          </para>
1964	          <para>
1965	            The function then filters out modes larger than
1966	            <parameter>max_width</parameter> and <parameter>max_height</parameter>
1967	            if specified. It finally calls the optional connector
1968	            <methodname>mode_valid</methodname> helper operation for each mode in
1969	            the probed list to check whether the mode is valid for the connector.
1970	          </para>
1971	        </listitem>
1972	      </itemizedlist>
1973	    </sect2>
1974	    <sect2>
1975	      <title>CRTC Helper Operations</title>
1976	      <itemizedlist>
1977	        <listitem id="drm-helper-crtc-mode-fixup">
1978	          <synopsis>bool (*mode_fixup)(struct drm_crtc *crtc,
1979	                       const struct drm_display_mode *mode,
1980	                       struct drm_display_mode *adjusted_mode);</synopsis>
1981	          <para>
1982	            Let CRTCs adjust the requested mode or reject it completely. This
1983	            operation returns true if the mode is accepted (possibly after being
1984	            adjusted) or false if it is rejected.
1985	          </para>
1986	          <para>
1987	            The <methodname>mode_fixup</methodname> operation should reject the
1988	            mode if it can't reasonably use it. The definition of "reasonable"
1989	            is currently fuzzy in this context. One possible behaviour would be
1990	            to set the adjusted mode to the panel timings when a fixed-mode
1991	            panel is used with hardware capable of scaling. Another behaviour
1992	            would be to accept any input mode and adjust it to the closest mode
1993	            supported by the hardware (FIXME: This needs to be clarified).
1994	          </para>
1995	        </listitem>
1996	        <listitem>
1997	          <synopsis>int (*mode_set_base)(struct drm_crtc *crtc, int x, int y,
1998	                     struct drm_framebuffer *old_fb)</synopsis>
1999	          <para>
2000	            Move the CRTC on the current frame buffer (stored in
2001	            <literal>crtc-&gt;fb</literal>) to position (x,y). Any of the frame
2002	            buffer, x position or y position may have been modified.
2003	          </para>
2004	          <para>
2005	            This helper operation is optional. If not provided, the
2006	            <function>drm_crtc_helper_set_config</function> function will fall
2007	            back to the <methodname>mode_set</methodname> helper operation.
2008	          </para>
2009	          <note><para>
2010	            FIXME: Why are x and y passed as arguments, as they can be accessed
2011	            through <literal>crtc-&gt;x</literal> and
2012	            <literal>crtc-&gt;y</literal>?
2013	          </para></note>
2014	        </listitem>
2015	        <listitem>
2016	          <synopsis>void (*prepare)(struct drm_crtc *crtc);</synopsis>
2017	          <para>
2018	            Prepare the CRTC for mode setting. This operation is called after
2019	            validating the requested mode. Drivers use it to perform
2020	            device-specific operations required before setting the new mode.
2021	          </para>
2022	        </listitem>
2023	        <listitem>
2024	          <synopsis>int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,
2025	                struct drm_display_mode *adjusted_mode, int x, int y,
2026	                struct drm_framebuffer *old_fb);</synopsis>
2027	          <para>
2028	            Set a new mode, position and frame buffer. Depending on the device
2029	            requirements, the mode can be stored internally by the driver and
2030	            applied in the <methodname>commit</methodname> operation, or
2031	            programmed to the hardware immediately.
2032	          </para>
2033	          <para>
2034	            The <methodname>mode_set</methodname> operation returns 0 on success
2035		    or a negative error code if an error occurs.
2036	          </para>
2037	        </listitem>
2038	        <listitem>
2039	          <synopsis>void (*commit)(struct drm_crtc *crtc);</synopsis>
2040	          <para>
2041	            Commit a mode. This operation is called after setting the new mode.
2042	            Upon return the device must use the new mode and be fully
2043	            operational.
2044	          </para>
2045	        </listitem>
2046	      </itemizedlist>
2047	    </sect2>
2048	    <sect2>
2049	      <title>Encoder Helper Operations</title>
2050	      <itemizedlist>
2051	        <listitem>
2052	          <synopsis>bool (*mode_fixup)(struct drm_encoder *encoder,
2053	                       const struct drm_display_mode *mode,
2054	                       struct drm_display_mode *adjusted_mode);</synopsis>
2055	          <para>
2056	            Let encoders adjust the requested mode or reject it completely. This
2057	            operation returns true if the mode is accepted (possibly after being
2058	            adjusted) or false if it is rejected. See the
2059	            <link linkend="drm-helper-crtc-mode-fixup">mode_fixup CRTC helper
2060	            operation</link> for an explanation of the allowed adjustments.
2061	          </para>
2062	        </listitem>
2063	        <listitem>
2064	          <synopsis>void (*prepare)(struct drm_encoder *encoder);</synopsis>
2065	          <para>
2066	            Prepare the encoder for mode setting. This operation is called after
2067	            validating the requested mode. Drivers use it to perform
2068	            device-specific operations required before setting the new mode.
2069	          </para>
2070	        </listitem>
2071	        <listitem>
2072	          <synopsis>void (*mode_set)(struct drm_encoder *encoder,
2073	                 struct drm_display_mode *mode,
2074	                 struct drm_display_mode *adjusted_mode);</synopsis>
2075	          <para>
2076	            Set a new mode. Depending on the device requirements, the mode can
2077	            be stored internally by the driver and applied in the
2078	            <methodname>commit</methodname> operation, or programmed to the
2079	            hardware immediately.
2080	          </para>
2081	        </listitem>
2082	        <listitem>
2083	          <synopsis>void (*commit)(struct drm_encoder *encoder);</synopsis>
2084	          <para>
2085	            Commit a mode. This operation is called after setting the new mode.
2086	            Upon return the device must use the new mode and be fully
2087	            operational.
2088	          </para>
2089	        </listitem>
2090	      </itemizedlist>
2091	    </sect2>
2092	    <sect2>
2093	      <title>Connector Helper Operations</title>
2094	      <itemizedlist>
2095	        <listitem>
2096	          <synopsis>struct drm_encoder *(*best_encoder)(struct drm_connector *connector);</synopsis>
2097	          <para>
2098	            Return a pointer to the best encoder for the connecter. Device that
2099	            map connectors to encoders 1:1 simply return the pointer to the
2100	            associated encoder. This operation is mandatory.
2101	          </para>
2102	        </listitem>
2103	        <listitem>
2104	          <synopsis>int (*get_modes)(struct drm_connector *connector);</synopsis>
2105	          <para>
2106	            Fill the connector's <structfield>probed_modes</structfield> list
2107	            by parsing EDID data with <function>drm_add_edid_modes</function>,
2108	            adding standard VESA DMT modes with <function>drm_add_modes_noedid</function>,
2109	            or calling <function>drm_mode_probed_add</function> directly for every
2110	            supported mode and return the number of modes it has detected. This
2111	            operation is mandatory.
2112	          </para>
2113	          <para>
2114	            Note that the caller function will automatically add standard VESA
2115	            DMT modes up to 1024x768 if the <methodname>get_modes</methodname>
2116	            helper operation returns no mode and if the connector status is
2117	            connector_status_connected. There is no need to call
2118	            <function>drm_add_edid_modes</function> manually in that case.
2119	          </para>
2120	          <para>
2121	            When adding modes manually the driver creates each mode with a call to
2122	            <function>drm_mode_create</function> and must fill the following fields.
2123	            <itemizedlist>
2124	              <listitem>
2125	                <synopsis>__u32 type;</synopsis>
2126	                <para>
2127	                  Mode type bitmask, a combination of
2128	                  <variablelist>
2129	                    <varlistentry>
2130	                      <term>DRM_MODE_TYPE_BUILTIN</term>
2131	                      <listitem><para>not used?</para></listitem>
2132	                    </varlistentry>
2133	                    <varlistentry>
2134	                      <term>DRM_MODE_TYPE_CLOCK_C</term>
2135	                      <listitem><para>not used?</para></listitem>
2136	                    </varlistentry>
2137	                    <varlistentry>
2138	                      <term>DRM_MODE_TYPE_CRTC_C</term>
2139	                      <listitem><para>not used?</para></listitem>
2140	                    </varlistentry>
2141	                    <varlistentry>
2142	                      <term>
2143	        DRM_MODE_TYPE_PREFERRED - The preferred mode for the connector
2144	                      </term>
2145	                      <listitem>
2146	                        <para>not used?</para>
2147	                      </listitem>
2148	                    </varlistentry>
2149	                    <varlistentry>
2150	                      <term>DRM_MODE_TYPE_DEFAULT</term>
2151	                      <listitem><para>not used?</para></listitem>
2152	                    </varlistentry>
2153	                    <varlistentry>
2154	                      <term>DRM_MODE_TYPE_USERDEF</term>
2155	                      <listitem><para>not used?</para></listitem>
2156	                    </varlistentry>
2157	                    <varlistentry>
2158	                      <term>DRM_MODE_TYPE_DRIVER</term>
2159	                      <listitem>
2160	                        <para>
2161	                          The mode has been created by the driver (as opposed to
2162	                          to user-created modes).
2163	                        </para>
2164	                      </listitem>
2165	                    </varlistentry>
2166	                  </variablelist>
2167	                  Drivers must set the DRM_MODE_TYPE_DRIVER bit for all modes they
2168	                  create, and set the DRM_MODE_TYPE_PREFERRED bit for the preferred
2169	                  mode.
2170	                </para>
2171	              </listitem>
2172	              <listitem>
2173	                <synopsis>__u32 clock;</synopsis>
2174	                <para>Pixel clock frequency in kHz unit</para>
2175	              </listitem>
2176	              <listitem>
2177	                <synopsis>__u16 hdisplay, hsync_start, hsync_end, htotal;
2178	    __u16 vdisplay, vsync_start, vsync_end, vtotal;</synopsis>
2179	                <para>Horizontal and vertical timing information</para>
2180	                <screen><![CDATA[
2181	             Active                 Front           Sync           Back
2182	             Region                 Porch                          Porch
2183	    <-----------------------><----------------><-------------><-------------->
2184	
2185	      //////////////////////|
2186	     ////////////////////// |
2187	    //////////////////////  |..................               ................
2188	                                               _______________
2189	
2190	    <----- [hv]display ----->
2191	    <------------- [hv]sync_start ------------>
2192	    <--------------------- [hv]sync_end --------------------->
2193	    <-------------------------------- [hv]total ----------------------------->
2194	]]></screen>
2195	              </listitem>
2196	              <listitem>
2197	                <synopsis>__u16 hskew;
2198	    __u16 vscan;</synopsis>
2199	                <para>Unknown</para>
2200	              </listitem>
2201	              <listitem>
2202	                <synopsis>__u32 flags;</synopsis>
2203	                <para>
2204	                  Mode flags, a combination of
2205	                  <variablelist>
2206	                    <varlistentry>
2207	                      <term>DRM_MODE_FLAG_PHSYNC</term>
2208	                      <listitem><para>
2209	                        Horizontal sync is active high
2210	                      </para></listitem>
2211	                    </varlistentry>
2212	                    <varlistentry>
2213	                      <term>DRM_MODE_FLAG_NHSYNC</term>
2214	                      <listitem><para>
2215	                        Horizontal sync is active low
2216	                      </para></listitem>
2217	                    </varlistentry>
2218	                    <varlistentry>
2219	                      <term>DRM_MODE_FLAG_PVSYNC</term>
2220	                      <listitem><para>
2221	                        Vertical sync is active high
2222	                      </para></listitem>
2223	                    </varlistentry>
2224	                    <varlistentry>
2225	                      <term>DRM_MODE_FLAG_NVSYNC</term>
2226	                      <listitem><para>
2227	                        Vertical sync is active low
2228	                      </para></listitem>
2229	                    </varlistentry>
2230	                    <varlistentry>
2231	                      <term>DRM_MODE_FLAG_INTERLACE</term>
2232	                      <listitem><para>
2233	                        Mode is interlaced
2234	                      </para></listitem>
2235	                    </varlistentry>
2236	                    <varlistentry>
2237	                      <term>DRM_MODE_FLAG_DBLSCAN</term>
2238	                      <listitem><para>
2239	                        Mode uses doublescan
2240	                      </para></listitem>
2241	                    </varlistentry>
2242	                    <varlistentry>
2243	                      <term>DRM_MODE_FLAG_CSYNC</term>
2244	                      <listitem><para>
2245	                        Mode uses composite sync
2246	                      </para></listitem>
2247	                    </varlistentry>
2248	                    <varlistentry>
2249	                      <term>DRM_MODE_FLAG_PCSYNC</term>
2250	                      <listitem><para>
2251	                        Composite sync is active high
2252	                      </para></listitem>
2253	                    </varlistentry>
2254	                    <varlistentry>
2255	                      <term>DRM_MODE_FLAG_NCSYNC</term>
2256	                      <listitem><para>
2257	                        Composite sync is active low
2258	                      </para></listitem>
2259	                    </varlistentry>
2260	                    <varlistentry>
2261	                      <term>DRM_MODE_FLAG_HSKEW</term>
2262	                      <listitem><para>
2263	                        hskew provided (not used?)
2264	                      </para></listitem>
2265	                    </varlistentry>
2266	                    <varlistentry>
2267	                      <term>DRM_MODE_FLAG_BCAST</term>
2268	                      <listitem><para>
2269	                        not used?
2270	                      </para></listitem>
2271	                    </varlistentry>
2272	                    <varlistentry>
2273	                      <term>DRM_MODE_FLAG_PIXMUX</term>
2274	                      <listitem><para>
2275	                        not used?
2276	                      </para></listitem>
2277	                    </varlistentry>
2278	                    <varlistentry>
2279	                      <term>DRM_MODE_FLAG_DBLCLK</term>
2280	                      <listitem><para>
2281	                        not used?
2282	                      </para></listitem>
2283	                    </varlistentry>
2284	                    <varlistentry>
2285	                      <term>DRM_MODE_FLAG_CLKDIV2</term>
2286	                      <listitem><para>
2287	                        ?
2288	                      </para></listitem>
2289	                    </varlistentry>
2290	                  </variablelist>
2291	                </para>
2292	                <para>
2293	                  Note that modes marked with the INTERLACE or DBLSCAN flags will be
2294	                  filtered out by
2295	                  <function>drm_helper_probe_single_connector_modes</function> if
2296	                  the connector's <structfield>interlace_allowed</structfield> or
2297	                  <structfield>doublescan_allowed</structfield> field is set to 0.
2298	                </para>
2299	              </listitem>
2300	              <listitem>
2301	                <synopsis>char name[DRM_DISPLAY_MODE_LEN];</synopsis>
2302	                <para>
2303	                  Mode name. The driver must call
2304	                  <function>drm_mode_set_name</function> to fill the mode name from
2305	                  <structfield>hdisplay</structfield>,
2306	                  <structfield>vdisplay</structfield> and interlace flag after
2307	                  filling the corresponding fields.
2308	                </para>
2309	              </listitem>
2310	            </itemizedlist>
2311	          </para>
2312	          <para>
2313	            The <structfield>vrefresh</structfield> value is computed by
2314	            <function>drm_helper_probe_single_connector_modes</function>.
2315	          </para>
2316	          <para>
2317	            When parsing EDID data, <function>drm_add_edid_modes</function> fills the
2318	            connector <structfield>display_info</structfield>
2319	            <structfield>width_mm</structfield> and
2320	            <structfield>height_mm</structfield> fields. When creating modes
2321	            manually the <methodname>get_modes</methodname> helper operation must
2322	            set the <structfield>display_info</structfield>
2323	            <structfield>width_mm</structfield> and
2324	            <structfield>height_mm</structfield> fields if they haven't been set
2325	            already (for instance at initialization time when a fixed-size panel is
2326	            attached to the connector). The mode <structfield>width_mm</structfield>
2327	            and <structfield>height_mm</structfield> fields are only used internally
2328	            during EDID parsing and should not be set when creating modes manually.
2329	          </para>
2330	        </listitem>
2331	        <listitem>
2332	          <synopsis>int (*mode_valid)(struct drm_connector *connector,
2333			  struct drm_display_mode *mode);</synopsis>
2334	          <para>
2335	            Verify whether a mode is valid for the connector. Return MODE_OK for
2336	            supported modes and one of the enum drm_mode_status values (MODE_*)
2337	            for unsupported modes. This operation is optional.
2338	          </para>
2339	          <para>
2340	            As the mode rejection reason is currently not used beside for
2341	            immediately removing the unsupported mode, an implementation can
2342	            return MODE_BAD regardless of the exact reason why the mode is not
2343	            valid.
2344	          </para>
2345	          <note><para>
2346	            Note that the <methodname>mode_valid</methodname> helper operation is
2347	            only called for modes detected by the device, and
2348	            <emphasis>not</emphasis> for modes set by the user through the CRTC
2349	            <methodname>set_config</methodname> operation.
2350	          </para></note>
2351	        </listitem>
2352	      </itemizedlist>
2353	    </sect2>
2354	    <sect2>
2355	      <title>Atomic Modeset Helper Functions Reference</title>
2356	      <sect3>
2357		<title>Overview</title>
2358	!Pdrivers/gpu/drm/drm_atomic_helper.c overview
2359	      </sect3>
2360	      <sect3>
2361		<title>Implementing Asynchronous Atomic Commit</title>
2362	!Pdrivers/gpu/drm/drm_atomic_helper.c implementing async commit
2363	      </sect3>
2364	      <sect3>
2365		<title>Atomic State Reset and Initialization</title>
2366	!Pdrivers/gpu/drm/drm_atomic_helper.c atomic state reset and initialization
2367	      </sect3>
2368	!Iinclude/drm/drm_atomic_helper.h
2369	!Edrivers/gpu/drm/drm_atomic_helper.c
2370	    </sect2>
2371	    <sect2>
2372	      <title>Modeset Helper Functions Reference</title>
2373	!Iinclude/drm/drm_crtc_helper.h
2374	!Edrivers/gpu/drm/drm_crtc_helper.c
2375	!Pdrivers/gpu/drm/drm_crtc_helper.c overview
2376	    </sect2>
2377	    <sect2>
2378	      <title>Output Probing Helper Functions Reference</title>
2379	!Pdrivers/gpu/drm/drm_probe_helper.c output probing helper overview
2380	!Edrivers/gpu/drm/drm_probe_helper.c
2381	    </sect2>
2382	    <sect2>
2383	      <title>fbdev Helper Functions Reference</title>
2384	!Pdrivers/gpu/drm/drm_fb_helper.c fbdev helpers
2385	!Edrivers/gpu/drm/drm_fb_helper.c
2386	!Iinclude/drm/drm_fb_helper.h
2387	    </sect2>
2388	    <sect2>
2389	      <title>Display Port Helper Functions Reference</title>
2390	!Pdrivers/gpu/drm/drm_dp_helper.c dp helpers
2391	!Iinclude/drm/drm_dp_helper.h
2392	!Edrivers/gpu/drm/drm_dp_helper.c
2393	    </sect2>
2394	    <sect2>
2395	      <title>Display Port MST Helper Functions Reference</title>
2396	!Pdrivers/gpu/drm/drm_dp_mst_topology.c dp mst helper
2397	!Iinclude/drm/drm_dp_mst_helper.h
2398	!Edrivers/gpu/drm/drm_dp_mst_topology.c
2399	    </sect2>
2400	    <sect2>
2401	      <title>MIPI DSI Helper Functions Reference</title>
2402	!Pdrivers/gpu/drm/drm_mipi_dsi.c dsi helpers
2403	!Iinclude/drm/drm_mipi_dsi.h
2404	!Edrivers/gpu/drm/drm_mipi_dsi.c
2405	    </sect2>
2406	    <sect2>
2407	      <title>EDID Helper Functions Reference</title>
2408	!Edrivers/gpu/drm/drm_edid.c
2409	    </sect2>
2410	    <sect2>
2411	      <title>Rectangle Utilities Reference</title>
2412	!Pinclude/drm/drm_rect.h rect utils
2413	!Iinclude/drm/drm_rect.h
2414	!Edrivers/gpu/drm/drm_rect.c
2415	    </sect2>
2416	    <sect2>
2417	      <title>Flip-work Helper Reference</title>
2418	!Pinclude/drm/drm_flip_work.h flip utils
2419	!Iinclude/drm/drm_flip_work.h
2420	!Edrivers/gpu/drm/drm_flip_work.c
2421	    </sect2>
2422	    <sect2>
2423	      <title>HDMI Infoframes Helper Reference</title>
2424	      <para>
2425		Strictly speaking this is not a DRM helper library but generally useable
2426		by any driver interfacing with HDMI outputs like v4l or alsa drivers.
2427		But it nicely fits into the overall topic of mode setting helper
2428		libraries and hence is also included here.
2429	      </para>
2430	!Iinclude/linux/hdmi.h
2431	!Edrivers/video/hdmi.c
2432	    </sect2>
2433	    <sect2>
2434	      <title id="drm-kms-planehelpers">Plane Helper Reference</title>
2435	!Edrivers/gpu/drm/drm_plane_helper.c
2436	!Pdrivers/gpu/drm/drm_plane_helper.c overview
2437	    </sect2>
2438	    <sect2>
2439		  <title>Tile group</title>
2440	!Pdrivers/gpu/drm/drm_crtc.c Tile group
2441	    </sect2>
2442	  </sect1>
2443	
2444	  <!-- Internals: kms properties -->
2445	
2446	  <sect1 id="drm-kms-properties">
2447	    <title>KMS Properties</title>
2448	    <para>
2449	      Drivers may need to expose additional parameters to applications than
2450	      those described in the previous sections. KMS supports attaching
2451	      properties to CRTCs, connectors and planes and offers a userspace API to
2452	      list, get and set the property values.
2453	    </para>
2454	    <para>
2455	      Properties are identified by a name that uniquely defines the property
2456	      purpose, and store an associated value. For all property types except blob
2457	      properties the value is a 64-bit unsigned integer.
2458	    </para>
2459	    <para>
2460	      KMS differentiates between properties and property instances. Drivers
2461	      first create properties and then create and associate individual instances
2462	      of those properties to objects. A property can be instantiated multiple
2463	      times and associated with different objects. Values are stored in property
2464	      instances, and all other property information are stored in the property
2465	      and shared between all instances of the property.
2466	    </para>
2467	    <para>
2468	      Every property is created with a type that influences how the KMS core
2469	      handles the property. Supported property types are
2470	      <variablelist>
2471	        <varlistentry>
2472	          <term>DRM_MODE_PROP_RANGE</term>
2473	          <listitem><para>Range properties report their minimum and maximum
2474	            admissible values. The KMS core verifies that values set by
2475	            application fit in that range.</para></listitem>
2476	        </varlistentry>
2477	        <varlistentry>
2478	          <term>DRM_MODE_PROP_ENUM</term>
2479	          <listitem><para>Enumerated properties take a numerical value that
2480	            ranges from 0 to the number of enumerated values defined by the
2481	            property minus one, and associate a free-formed string name to each
2482	            value. Applications can retrieve the list of defined value-name pairs
2483	            and use the numerical value to get and set property instance values.
2484	            </para></listitem>
2485	        </varlistentry>
2486	        <varlistentry>
2487	          <term>DRM_MODE_PROP_BITMASK</term>
2488	          <listitem><para>Bitmask properties are enumeration properties that
2489	            additionally restrict all enumerated values to the 0..63 range.
2490	            Bitmask property instance values combine one or more of the
2491	            enumerated bits defined by the property.</para></listitem>
2492	        </varlistentry>
2493	        <varlistentry>
2494	          <term>DRM_MODE_PROP_BLOB</term>
2495	          <listitem><para>Blob properties store a binary blob without any format
2496	            restriction. The binary blobs are created as KMS standalone objects,
2497	            and blob property instance values store the ID of their associated
2498	            blob object.</para>
2499		    <para>Blob properties are only used for the connector EDID property
2500		    and cannot be created by drivers.</para></listitem>
2501	        </varlistentry>
2502	      </variablelist>
2503	    </para>
2504	    <para>
2505	      To create a property drivers call one of the following functions depending
2506	      on the property type. All property creation functions take property flags
2507	      and name, as well as type-specific arguments.
2508	      <itemizedlist>
2509	        <listitem>
2510	          <synopsis>struct drm_property *drm_property_create_range(struct drm_device *dev, int flags,
2511	                                               const char *name,
2512	                                               uint64_t min, uint64_t max);</synopsis>
2513	          <para>Create a range property with the given minimum and maximum
2514	            values.</para>
2515	        </listitem>
2516	        <listitem>
2517	          <synopsis>struct drm_property *drm_property_create_enum(struct drm_device *dev, int flags,
2518	                                              const char *name,
2519	                                              const struct drm_prop_enum_list *props,
2520	                                              int num_values);</synopsis>
2521	          <para>Create an enumerated property. The <parameter>props</parameter>
2522	            argument points to an array of <parameter>num_values</parameter>
2523	            value-name pairs.</para>
2524	        </listitem>
2525	        <listitem>
2526	          <synopsis>struct drm_property *drm_property_create_bitmask(struct drm_device *dev,
2527	                                                 int flags, const char *name,
2528	                                                 const struct drm_prop_enum_list *props,
2529	                                                 int num_values);</synopsis>
2530	          <para>Create a bitmask property. The <parameter>props</parameter>
2531	            argument points to an array of <parameter>num_values</parameter>
2532	            value-name pairs.</para>
2533	        </listitem>
2534	      </itemizedlist>
2535	    </para>
2536	    <para>
2537	      Properties can additionally be created as immutable, in which case they
2538	      will be read-only for applications but can be modified by the driver. To
2539	      create an immutable property drivers must set the DRM_MODE_PROP_IMMUTABLE
2540	      flag at property creation time.
2541	    </para>
2542	    <para>
2543	      When no array of value-name pairs is readily available at property
2544	      creation time for enumerated or range properties, drivers can create
2545	      the property using the <function>drm_property_create</function> function
2546	      and manually add enumeration value-name pairs by calling the
2547	      <function>drm_property_add_enum</function> function. Care must be taken to
2548	      properly specify the property type through the <parameter>flags</parameter>
2549	      argument.
2550	    </para>
2551	    <para>
2552	      After creating properties drivers can attach property instances to CRTC,
2553	      connector and plane objects by calling the
2554	      <function>drm_object_attach_property</function>. The function takes a
2555	      pointer to the target object, a pointer to the previously created property
2556	      and an initial instance value.
2557	    </para>
2558	    <sect2>
2559		<title>Existing KMS Properties</title>
2560		<para>
2561		The following table gives description of drm properties exposed by various
2562		modules/drivers.
2563		</para>
2564		<table border="1" cellpadding="0" cellspacing="0">
2565		<tbody>
2566		<tr style="font-weight: bold;">
2567		<td valign="top" >Owner Module/Drivers</td>
2568		<td valign="top" >Group</td>
2569		<td valign="top" >Property Name</td>
2570		<td valign="top" >Type</td>
2571		<td valign="top" >Property Values</td>
2572		<td valign="top" >Object attached</td>
2573		<td valign="top" >Description/Restrictions</td>
2574		</tr>
2575		<tr>
2576		<td rowspan="36" valign="top" >DRM</td>
2577		<td rowspan="5" valign="top" >Connector</td>
2578		<td valign="top" >“EDID”</td>
2579		<td valign="top" >BLOB | IMMUTABLE</td>
2580		<td valign="top" >0</td>
2581		<td valign="top" >Connector</td>
2582		<td valign="top" >Contains id of edid blob ptr object.</td>
2583		</tr>
2584		<tr>
2585		<td valign="top" >“DPMS”</td>
2586		<td valign="top" >ENUM</td>
2587		<td valign="top" >{ “On”, “Standby”, “Suspend”, “Off” }</td>
2588		<td valign="top" >Connector</td>
2589		<td valign="top" >Contains DPMS operation mode value.</td>
2590		</tr>
2591		<tr>
2592		<td valign="top" >“PATH”</td>
2593		<td valign="top" >BLOB | IMMUTABLE</td>
2594		<td valign="top" >0</td>
2595		<td valign="top" >Connector</td>
2596		<td valign="top" >Contains topology path to a connector.</td>
2597		</tr>
2598		<tr>
2599		<td valign="top" >“TILE”</td>
2600		<td valign="top" >BLOB | IMMUTABLE</td>
2601		<td valign="top" >0</td>
2602		<td valign="top" >Connector</td>
2603		<td valign="top" >Contains tiling information for a connector.</td>
2604		</tr>
2605		<tr>
2606		<td valign="top" >“CRTC_ID”</td>
2607		<td valign="top" >OBJECT</td>
2608		<td valign="top" >DRM_MODE_OBJECT_CRTC</td>
2609		<td valign="top" >Connector</td>
2610		<td valign="top" >CRTC that connector is attached to (atomic)</td>
2611		</tr>
2612		<tr>
2613		<td rowspan="11" valign="top" >Plane</td>
2614		<td valign="top" >“type”</td>
2615		<td valign="top" >ENUM | IMMUTABLE</td>
2616		<td valign="top" >{ "Overlay", "Primary", "Cursor" }</td>
2617		<td valign="top" >Plane</td>
2618		<td valign="top" >Plane type</td>
2619		</tr>
2620		<tr>
2621		<td valign="top" >“SRC_X”</td>
2622		<td valign="top" >RANGE</td>
2623		<td valign="top" >Min=0, Max=UINT_MAX</td>
2624		<td valign="top" >Plane</td>
2625		<td valign="top" >Scanout source x coordinate in 16.16 fixed point (atomic)</td>
2626		</tr>
2627		<tr>
2628		<td valign="top" >“SRC_Y”</td>
2629		<td valign="top" >RANGE</td>
2630		<td valign="top" >Min=0, Max=UINT_MAX</td>
2631		<td valign="top" >Plane</td>
2632		<td valign="top" >Scanout source y coordinate in 16.16 fixed point (atomic)</td>
2633		</tr>
2634		<tr>
2635		<td valign="top" >“SRC_W”</td>
2636		<td valign="top" >RANGE</td>
2637		<td valign="top" >Min=0, Max=UINT_MAX</td>
2638		<td valign="top" >Plane</td>
2639		<td valign="top" >Scanout source width in 16.16 fixed point (atomic)</td>
2640		</tr>
2641		<tr>
2642		<td valign="top" >“SRC_H”</td>
2643		<td valign="top" >RANGE</td>
2644		<td valign="top" >Min=0, Max=UINT_MAX</td>
2645		<td valign="top" >Plane</td>
2646		<td valign="top" >Scanout source height in 16.16 fixed point (atomic)</td>
2647		</tr>
2648		<tr>
2649		<td valign="top" >“CRTC_X”</td>
2650		<td valign="top" >SIGNED_RANGE</td>
2651		<td valign="top" >Min=INT_MIN, Max=INT_MAX</td>
2652		<td valign="top" >Plane</td>
2653		<td valign="top" >Scanout CRTC (destination) x coordinate (atomic)</td>
2654		</tr>
2655		<tr>
2656		<td valign="top" >“CRTC_Y”</td>
2657		<td valign="top" >SIGNED_RANGE</td>
2658		<td valign="top" >Min=INT_MIN, Max=INT_MAX</td>
2659		<td valign="top" >Plane</td>
2660		<td valign="top" >Scanout CRTC (destination) y coordinate (atomic)</td>
2661		</tr>
2662		<tr>
2663		<td valign="top" >“CRTC_W”</td>
2664		<td valign="top" >RANGE</td>
2665		<td valign="top" >Min=0, Max=UINT_MAX</td>
2666		<td valign="top" >Plane</td>
2667		<td valign="top" >Scanout CRTC (destination) width (atomic)</td>
2668		</tr>
2669		<tr>
2670		<td valign="top" >“CRTC_H”</td>
2671		<td valign="top" >RANGE</td>
2672		<td valign="top" >Min=0, Max=UINT_MAX</td>
2673		<td valign="top" >Plane</td>
2674		<td valign="top" >Scanout CRTC (destination) height (atomic)</td>
2675		</tr>
2676		<tr>
2677		<td valign="top" >“FB_ID”</td>
2678		<td valign="top" >OBJECT</td>
2679		<td valign="top" >DRM_MODE_OBJECT_FB</td>
2680		<td valign="top" >Plane</td>
2681		<td valign="top" >Scanout framebuffer (atomic)</td>
2682		</tr>
2683		<tr>
2684		<td valign="top" >“CRTC_ID”</td>
2685		<td valign="top" >OBJECT</td>
2686		<td valign="top" >DRM_MODE_OBJECT_CRTC</td>
2687		<td valign="top" >Plane</td>
2688		<td valign="top" >CRTC that plane is attached to (atomic)</td>
2689		</tr>
2690		<tr>
2691		<td rowspan="2" valign="top" >DVI-I</td>
2692		<td valign="top" >“subconnector”</td>
2693		<td valign="top" >ENUM</td>
2694		<td valign="top" >{ “Unknown”, “DVI-D”, “DVI-A” }</td>
2695		<td valign="top" >Connector</td>
2696		<td valign="top" >TBD</td>
2697		</tr>
2698		<tr>
2699		<td valign="top" >“select subconnector”</td>
2700		<td valign="top" >ENUM</td>
2701		<td valign="top" >{ “Automatic”, “DVI-D”, “DVI-A” }</td>
2702		<td valign="top" >Connector</td>
2703		<td valign="top" >TBD</td>
2704		</tr>
2705		<tr>
2706		<td rowspan="13" valign="top" >TV</td>
2707		<td valign="top" >“subconnector”</td>
2708		<td valign="top" >ENUM</td>
2709		<td valign="top" >{ "Unknown", "Composite", "SVIDEO", "Component", "SCART" }</td>
2710		<td valign="top" >Connector</td>
2711		<td valign="top" >TBD</td>
2712		</tr>
2713		<tr>
2714		<td valign="top" >“select subconnector”</td>
2715		<td valign="top" >ENUM</td>
2716		<td valign="top" >{ "Automatic", "Composite", "SVIDEO", "Component", "SCART" }</td>
2717		<td valign="top" >Connector</td>
2718		<td valign="top" >TBD</td>
2719		</tr>
2720		<tr>
2721		<td valign="top" >“mode”</td>
2722		<td valign="top" >ENUM</td>
2723		<td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2724		<td valign="top" >Connector</td>
2725		<td valign="top" >TBD</td>
2726		</tr>
2727		<tr>
2728		<td valign="top" >“left margin”</td>
2729		<td valign="top" >RANGE</td>
2730		<td valign="top" >Min=0, Max=100</td>
2731		<td valign="top" >Connector</td>
2732		<td valign="top" >TBD</td>
2733		</tr>
2734		<tr>
2735		<td valign="top" >“right margin”</td>
2736		<td valign="top" >RANGE</td>
2737		<td valign="top" >Min=0, Max=100</td>
2738		<td valign="top" >Connector</td>
2739		<td valign="top" >TBD</td>
2740		</tr>
2741		<tr>
2742		<td valign="top" >“top margin”</td>
2743		<td valign="top" >RANGE</td>
2744		<td valign="top" >Min=0, Max=100</td>
2745		<td valign="top" >Connector</td>
2746		<td valign="top" >TBD</td>
2747		</tr>
2748		<tr>
2749		<td valign="top" >“bottom margin”</td>
2750		<td valign="top" >RANGE</td>
2751		<td valign="top" >Min=0, Max=100</td>
2752		<td valign="top" >Connector</td>
2753		<td valign="top" >TBD</td>
2754		</tr>
2755		<tr>
2756		<td valign="top" >“brightness”</td>
2757		<td valign="top" >RANGE</td>
2758		<td valign="top" >Min=0, Max=100</td>
2759		<td valign="top" >Connector</td>
2760		<td valign="top" >TBD</td>
2761		</tr>
2762		<tr>
2763		<td valign="top" >“contrast”</td>
2764		<td valign="top" >RANGE</td>
2765		<td valign="top" >Min=0, Max=100</td>
2766		<td valign="top" >Connector</td>
2767		<td valign="top" >TBD</td>
2768		</tr>
2769		<tr>
2770		<td valign="top" >“flicker reduction”</td>
2771		<td valign="top" >RANGE</td>
2772		<td valign="top" >Min=0, Max=100</td>
2773		<td valign="top" >Connector</td>
2774		<td valign="top" >TBD</td>
2775		</tr>
2776		<tr>
2777		<td valign="top" >“overscan”</td>
2778		<td valign="top" >RANGE</td>
2779		<td valign="top" >Min=0, Max=100</td>
2780		<td valign="top" >Connector</td>
2781		<td valign="top" >TBD</td>
2782		</tr>
2783		<tr>
2784		<td valign="top" >“saturation”</td>
2785		<td valign="top" >RANGE</td>
2786		<td valign="top" >Min=0, Max=100</td>
2787		<td valign="top" >Connector</td>
2788		<td valign="top" >TBD</td>
2789		</tr>
2790		<tr>
2791		<td valign="top" >“hue”</td>
2792		<td valign="top" >RANGE</td>
2793		<td valign="top" >Min=0, Max=100</td>
2794		<td valign="top" >Connector</td>
2795		<td valign="top" >TBD</td>
2796		</tr>
2797		<tr>
2798		<td rowspan="2" valign="top" >Virtual GPU</td>
2799		<td valign="top" >“suggested X”</td>
2800		<td valign="top" >RANGE</td>
2801		<td valign="top" >Min=0, Max=0xffffffff</td>
2802		<td valign="top" >Connector</td>
2803		<td valign="top" >property to suggest an X offset for a connector</td>
2804		</tr>
2805		<tr>
2806		<td valign="top" >“suggested Y”</td>
2807		<td valign="top" >RANGE</td>
2808		<td valign="top" >Min=0, Max=0xffffffff</td>
2809		<td valign="top" >Connector</td>
2810		<td valign="top" >property to suggest an Y offset for a connector</td>
2811		</tr>
2812		<tr>
2813		<td rowspan="3" valign="top" >Optional</td>
2814		<td valign="top" >“scaling mode”</td>
2815		<td valign="top" >ENUM</td>
2816		<td valign="top" >{ "None", "Full", "Center", "Full aspect" }</td>
2817		<td valign="top" >Connector</td>
2818		<td valign="top" >TBD</td>
2819		</tr>
2820		<tr>
2821		<td valign="top" >"aspect ratio"</td>
2822		<td valign="top" >ENUM</td>
2823		<td valign="top" >{ "None", "4:3", "16:9" }</td>
2824		<td valign="top" >Connector</td>
2825		<td valign="top" >DRM property to set aspect ratio from user space app.
2826			This enum is made generic to allow addition of custom aspect
2827			ratios.</td>
2828		</tr>
2829		<tr>
2830		<td valign="top" >“dirty”</td>
2831		<td valign="top" >ENUM | IMMUTABLE</td>
2832		<td valign="top" >{ "Off", "On", "Annotate" }</td>
2833		<td valign="top" >Connector</td>
2834		<td valign="top" >TBD</td>
2835		</tr>
2836		<tr>
2837		<td rowspan="21" valign="top" >i915</td>
2838		<td rowspan="2" valign="top" >Generic</td>
2839		<td valign="top" >"Broadcast RGB"</td>
2840		<td valign="top" >ENUM</td>
2841		<td valign="top" >{ "Automatic", "Full", "Limited 16:235" }</td>
2842		<td valign="top" >Connector</td>
2843		<td valign="top" >TBD</td>
2844		</tr>
2845		<tr>
2846		<td valign="top" >“audio”</td>
2847		<td valign="top" >ENUM</td>
2848		<td valign="top" >{ "force-dvi", "off", "auto", "on" }</td>
2849		<td valign="top" >Connector</td>
2850		<td valign="top" >TBD</td>
2851		</tr>
2852		<tr>
2853		<td rowspan="1" valign="top" >Plane</td>
2854		<td valign="top" >“rotation”</td>
2855		<td valign="top" >BITMASK</td>
2856		<td valign="top" >{ 0, "rotate-0" }, { 2, "rotate-180" }</td>
2857		<td valign="top" >Plane</td>
2858		<td valign="top" >TBD</td>
2859		</tr>
2860		<tr>
2861		<td rowspan="17" valign="top" >SDVO-TV</td>
2862		<td valign="top" >“mode”</td>
2863		<td valign="top" >ENUM</td>
2864		<td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2865		<td valign="top" >Connector</td>
2866		<td valign="top" >TBD</td>
2867		</tr>
2868		<tr>
2869		<td valign="top" >"left_margin"</td>
2870		<td valign="top" >RANGE</td>
2871		<td valign="top" >Min=0, Max= SDVO dependent</td>
2872		<td valign="top" >Connector</td>
2873		<td valign="top" >TBD</td>
2874		</tr>
2875		<tr>
2876		<td valign="top" >"right_margin"</td>
2877		<td valign="top" >RANGE</td>
2878		<td valign="top" >Min=0, Max= SDVO dependent</td>
2879		<td valign="top" >Connector</td>
2880		<td valign="top" >TBD</td>
2881		</tr>
2882		<tr>
2883		<td valign="top" >"top_margin"</td>
2884		<td valign="top" >RANGE</td>
2885		<td valign="top" >Min=0, Max= SDVO dependent</td>
2886		<td valign="top" >Connector</td>
2887		<td valign="top" >TBD</td>
2888		</tr>
2889		<tr>
2890		<td valign="top" >"bottom_margin"</td>
2891		<td valign="top" >RANGE</td>
2892		<td valign="top" >Min=0, Max= SDVO dependent</td>
2893		<td valign="top" >Connector</td>
2894		<td valign="top" >TBD</td>
2895		</tr>
2896		<tr>
2897		<td valign="top" >“hpos”</td>
2898		<td valign="top" >RANGE</td>
2899		<td valign="top" >Min=0, Max= SDVO dependent</td>
2900		<td valign="top" >Connector</td>
2901		<td valign="top" >TBD</td>
2902		</tr>
2903		<tr>
2904		<td valign="top" >“vpos”</td>
2905		<td valign="top" >RANGE</td>
2906		<td valign="top" >Min=0, Max= SDVO dependent</td>
2907		<td valign="top" >Connector</td>
2908		<td valign="top" >TBD</td>
2909		</tr>
2910		<tr>
2911		<td valign="top" >“contrast”</td>
2912		<td valign="top" >RANGE</td>
2913		<td valign="top" >Min=0, Max= SDVO dependent</td>
2914		<td valign="top" >Connector</td>
2915		<td valign="top" >TBD</td>
2916		</tr>
2917		<tr>
2918		<td valign="top" >“saturation”</td>
2919		<td valign="top" >RANGE</td>
2920		<td valign="top" >Min=0, Max= SDVO dependent</td>
2921		<td valign="top" >Connector</td>
2922		<td valign="top" >TBD</td>
2923		</tr>
2924		<tr>
2925		<td valign="top" >“hue”</td>
2926		<td valign="top" >RANGE</td>
2927		<td valign="top" >Min=0, Max= SDVO dependent</td>
2928		<td valign="top" >Connector</td>
2929		<td valign="top" >TBD</td>
2930		</tr>
2931		<tr>
2932		<td valign="top" >“sharpness”</td>
2933		<td valign="top" >RANGE</td>
2934		<td valign="top" >Min=0, Max= SDVO dependent</td>
2935		<td valign="top" >Connector</td>
2936		<td valign="top" >TBD</td>
2937		</tr>
2938		<tr>
2939		<td valign="top" >“flicker_filter”</td>
2940		<td valign="top" >RANGE</td>
2941		<td valign="top" >Min=0, Max= SDVO dependent</td>
2942		<td valign="top" >Connector</td>
2943		<td valign="top" >TBD</td>
2944		</tr>
2945		<tr>
2946		<td valign="top" >“flicker_filter_adaptive”</td>
2947		<td valign="top" >RANGE</td>
2948		<td valign="top" >Min=0, Max= SDVO dependent</td>
2949		<td valign="top" >Connector</td>
2950		<td valign="top" >TBD</td>
2951		</tr>
2952		<tr>
2953		<td valign="top" >“flicker_filter_2d”</td>
2954		<td valign="top" >RANGE</td>
2955		<td valign="top" >Min=0, Max= SDVO dependent</td>
2956		<td valign="top" >Connector</td>
2957		<td valign="top" >TBD</td>
2958		</tr>
2959		<tr>
2960		<td valign="top" >“tv_chroma_filter”</td>
2961		<td valign="top" >RANGE</td>
2962		<td valign="top" >Min=0, Max= SDVO dependent</td>
2963		<td valign="top" >Connector</td>
2964		<td valign="top" >TBD</td>
2965		</tr>
2966		<tr>
2967		<td valign="top" >“tv_luma_filter”</td>
2968		<td valign="top" >RANGE</td>
2969		<td valign="top" >Min=0, Max= SDVO dependent</td>
2970		<td valign="top" >Connector</td>
2971		<td valign="top" >TBD</td>
2972		</tr>
2973		<tr>
2974		<td valign="top" >“dot_crawl”</td>
2975		<td valign="top" >RANGE</td>
2976		<td valign="top" >Min=0, Max=1</td>
2977		<td valign="top" >Connector</td>
2978		<td valign="top" >TBD</td>
2979		</tr>
2980		<tr>
2981		<td valign="top" >SDVO-TV/LVDS</td>
2982		<td valign="top" >“brightness”</td>
2983		<td valign="top" >RANGE</td>
2984		<td valign="top" >Min=0, Max= SDVO dependent</td>
2985		<td valign="top" >Connector</td>
2986		<td valign="top" >TBD</td>
2987		</tr>
2988		<tr>
2989		<td rowspan="2" valign="top" >CDV gma-500</td>
2990		<td rowspan="2" valign="top" >Generic</td>
2991		<td valign="top" >"Broadcast RGB"</td>
2992		<td valign="top" >ENUM</td>
2993		<td valign="top" >{ “Full”, “Limited 16:235” }</td>
2994		<td valign="top" >Connector</td>
2995		<td valign="top" >TBD</td>
2996		</tr>
2997		<tr>
2998		<td valign="top" >"Broadcast RGB"</td>
2999		<td valign="top" >ENUM</td>
3000		<td valign="top" >{ “off”, “auto”, “on” }</td>
3001		<td valign="top" >Connector</td>
3002		<td valign="top" >TBD</td>
3003		</tr>
3004		<tr>
3005		<td rowspan="19" valign="top" >Poulsbo</td>
3006		<td rowspan="1" valign="top" >Generic</td>
3007		<td valign="top" >“backlight”</td>
3008		<td valign="top" >RANGE</td>
3009		<td valign="top" >Min=0, Max=100</td>
3010		<td valign="top" >Connector</td>
3011		<td valign="top" >TBD</td>
3012		</tr>
3013		<tr>
3014		<td rowspan="17" valign="top" >SDVO-TV</td>
3015		<td valign="top" >“mode”</td>
3016		<td valign="top" >ENUM</td>
3017		<td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
3018		<td valign="top" >Connector</td>
3019		<td valign="top" >TBD</td>
3020		</tr>
3021		<tr>
3022		<td valign="top" >"left_margin"</td>
3023		<td valign="top" >RANGE</td>
3024		<td valign="top" >Min=0, Max= SDVO dependent</td>
3025		<td valign="top" >Connector</td>
3026		<td valign="top" >TBD</td>
3027		</tr>
3028		<tr>
3029		<td valign="top" >"right_margin"</td>
3030		<td valign="top" >RANGE</td>
3031		<td valign="top" >Min=0, Max= SDVO dependent</td>
3032		<td valign="top" >Connector</td>
3033		<td valign="top" >TBD</td>
3034		</tr>
3035		<tr>
3036		<td valign="top" >"top_margin"</td>
3037		<td valign="top" >RANGE</td>
3038		<td valign="top" >Min=0, Max= SDVO dependent</td>
3039		<td valign="top" >Connector</td>
3040		<td valign="top" >TBD</td>
3041		</tr>
3042		<tr>
3043		<td valign="top" >"bottom_margin"</td>
3044		<td valign="top" >RANGE</td>
3045		<td valign="top" >Min=0, Max= SDVO dependent</td>
3046		<td valign="top" >Connector</td>
3047		<td valign="top" >TBD</td>
3048		</tr>
3049		<tr>
3050		<td valign="top" >“hpos”</td>
3051		<td valign="top" >RANGE</td>
3052		<td valign="top" >Min=0, Max= SDVO dependent</td>
3053		<td valign="top" >Connector</td>
3054		<td valign="top" >TBD</td>
3055		</tr>
3056		<tr>
3057		<td valign="top" >“vpos”</td>
3058		<td valign="top" >RANGE</td>
3059		<td valign="top" >Min=0, Max= SDVO dependent</td>
3060		<td valign="top" >Connector</td>
3061		<td valign="top" >TBD</td>
3062		</tr>
3063		<tr>
3064		<td valign="top" >“contrast”</td>
3065		<td valign="top" >RANGE</td>
3066		<td valign="top" >Min=0, Max= SDVO dependent</td>
3067		<td valign="top" >Connector</td>
3068		<td valign="top" >TBD</td>
3069		</tr>
3070		<tr>
3071		<td valign="top" >“saturation”</td>
3072		<td valign="top" >RANGE</td>
3073		<td valign="top" >Min=0, Max= SDVO dependent</td>
3074		<td valign="top" >Connector</td>
3075		<td valign="top" >TBD</td>
3076		</tr>
3077		<tr>
3078		<td valign="top" >“hue”</td>
3079		<td valign="top" >RANGE</td>
3080		<td valign="top" >Min=0, Max= SDVO dependent</td>
3081		<td valign="top" >Connector</td>
3082		<td valign="top" >TBD</td>
3083		</tr>
3084		<tr>
3085		<td valign="top" >“sharpness”</td>
3086		<td valign="top" >RANGE</td>
3087		<td valign="top" >Min=0, Max= SDVO dependent</td>
3088		<td valign="top" >Connector</td>
3089		<td valign="top" >TBD</td>
3090		</tr>
3091		<tr>
3092		<td valign="top" >“flicker_filter”</td>
3093		<td valign="top" >RANGE</td>
3094		<td valign="top" >Min=0, Max= SDVO dependent</td>
3095		<td valign="top" >Connector</td>
3096		<td valign="top" >TBD</td>
3097		</tr>
3098		<tr>
3099		<td valign="top" >“flicker_filter_adaptive”</td>
3100		<td valign="top" >RANGE</td>
3101		<td valign="top" >Min=0, Max= SDVO dependent</td>
3102		<td valign="top" >Connector</td>
3103		<td valign="top" >TBD</td>
3104		</tr>
3105		<tr>
3106		<td valign="top" >“flicker_filter_2d”</td>
3107		<td valign="top" >RANGE</td>
3108		<td valign="top" >Min=0, Max= SDVO dependent</td>
3109		<td valign="top" >Connector</td>
3110		<td valign="top" >TBD</td>
3111		</tr>
3112		<tr>
3113		<td valign="top" >“tv_chroma_filter”</td>
3114		<td valign="top" >RANGE</td>
3115		<td valign="top" >Min=0, Max= SDVO dependent</td>
3116		<td valign="top" >Connector</td>
3117		<td valign="top" >TBD</td>
3118		</tr>
3119		<tr>
3120		<td valign="top" >“tv_luma_filter”</td>
3121		<td valign="top" >RANGE</td>
3122		<td valign="top" >Min=0, Max= SDVO dependent</td>
3123		<td valign="top" >Connector</td>
3124		<td valign="top" >TBD</td>
3125		</tr>
3126		<tr>
3127		<td valign="top" >“dot_crawl”</td>
3128		<td valign="top" >RANGE</td>
3129		<td valign="top" >Min=0, Max=1</td>
3130		<td valign="top" >Connector</td>
3131		<td valign="top" >TBD</td>
3132		</tr>
3133		<tr>
3134		<td valign="top" >SDVO-TV/LVDS</td>
3135		<td valign="top" >“brightness”</td>
3136		<td valign="top" >RANGE</td>
3137		<td valign="top" >Min=0, Max= SDVO dependent</td>
3138		<td valign="top" >Connector</td>
3139		<td valign="top" >TBD</td>
3140		</tr>
3141		<tr>
3142		<td rowspan="11" valign="top" >armada</td>
3143		<td rowspan="2" valign="top" >CRTC</td>
3144		<td valign="top" >"CSC_YUV"</td>
3145		<td valign="top" >ENUM</td>
3146		<td valign="top" >{ "Auto" , "CCIR601", "CCIR709" }</td>
3147		<td valign="top" >CRTC</td>
3148		<td valign="top" >TBD</td>
3149		</tr>
3150		<tr>
3151		<td valign="top" >"CSC_RGB"</td>
3152		<td valign="top" >ENUM</td>
3153		<td valign="top" >{ "Auto", "Computer system", "Studio" }</td>
3154		<td valign="top" >CRTC</td>
3155		<td valign="top" >TBD</td>
3156		</tr>
3157		<tr>
3158		<td rowspan="9" valign="top" >Overlay</td>
3159		<td valign="top" >"colorkey"</td>
3160		<td valign="top" >RANGE</td>
3161		<td valign="top" >Min=0, Max=0xffffff</td>
3162		<td valign="top" >Plane</td>
3163		<td valign="top" >TBD</td>
3164		</tr>
3165		<tr>
3166		<td valign="top" >"colorkey_min"</td>
3167		<td valign="top" >RANGE</td>
3168		<td valign="top" >Min=0, Max=0xffffff</td>
3169		<td valign="top" >Plane</td>
3170		<td valign="top" >TBD</td>
3171		</tr>
3172		<tr>
3173		<td valign="top" >"colorkey_max"</td>
3174		<td valign="top" >RANGE</td>
3175		<td valign="top" >Min=0, Max=0xffffff</td>
3176		<td valign="top" >Plane</td>
3177		<td valign="top" >TBD</td>
3178		</tr>
3179		<tr>
3180		<td valign="top" >"colorkey_val"</td>
3181		<td valign="top" >RANGE</td>
3182		<td valign="top" >Min=0, Max=0xffffff</td>
3183		<td valign="top" >Plane</td>
3184		<td valign="top" >TBD</td>
3185		</tr>
3186		<tr>
3187		<td valign="top" >"colorkey_alpha"</td>
3188		<td valign="top" >RANGE</td>
3189		<td valign="top" >Min=0, Max=0xffffff</td>
3190		<td valign="top" >Plane</td>
3191		<td valign="top" >TBD</td>
3192		</tr>
3193		<tr>
3194		<td valign="top" >"colorkey_mode"</td>
3195		<td valign="top" >ENUM</td>
3196		<td valign="top" >{ "disabled", "Y component", "U component"
3197		, "V component", "RGB", “R component", "G component", "B component" }</td>
3198		<td valign="top" >Plane</td>
3199		<td valign="top" >TBD</td>
3200		</tr>
3201		<tr>
3202		<td valign="top" >"brightness"</td>
3203		<td valign="top" >RANGE</td>
3204		<td valign="top" >Min=0, Max=256 + 255</td>
3205		<td valign="top" >Plane</td>
3206		<td valign="top" >TBD</td>
3207		</tr>
3208		<tr>
3209		<td valign="top" >"contrast"</td>
3210		<td valign="top" >RANGE</td>
3211		<td valign="top" >Min=0, Max=0x7fff</td>
3212		<td valign="top" >Plane</td>
3213		<td valign="top" >TBD</td>
3214		</tr>
3215		<tr>
3216		<td valign="top" >"saturation"</td>
3217		<td valign="top" >RANGE</td>
3218		<td valign="top" >Min=0, Max=0x7fff</td>
3219		<td valign="top" >Plane</td>
3220		<td valign="top" >TBD</td>
3221		</tr>
3222		<tr>
3223		<td rowspan="2" valign="top" >exynos</td>
3224		<td valign="top" >CRTC</td>
3225		<td valign="top" >“mode”</td>
3226		<td valign="top" >ENUM</td>
3227		<td valign="top" >{ "normal", "blank" }</td>
3228		<td valign="top" >CRTC</td>
3229		<td valign="top" >TBD</td>
3230		</tr>
3231		<tr>
3232		<td valign="top" >Overlay</td>
3233		<td valign="top" >“zpos”</td>
3234		<td valign="top" >RANGE</td>
3235		<td valign="top" >Min=0, Max=MAX_PLANE-1</td>
3236		<td valign="top" >Plane</td>
3237		<td valign="top" >TBD</td>
3238		</tr>
3239		<tr>
3240		<td rowspan="2" valign="top" >i2c/ch7006_drv</td>
3241		<td valign="top" >Generic</td>
3242		<td valign="top" >“scale”</td>
3243		<td valign="top" >RANGE</td>
3244		<td valign="top" >Min=0, Max=2</td>
3245		<td valign="top" >Connector</td>
3246		<td valign="top" >TBD</td>
3247		</tr>
3248		<tr>
3249		<td rowspan="1" valign="top" >TV</td>
3250		<td valign="top" >“mode”</td>
3251		<td valign="top" >ENUM</td>
3252		<td valign="top" >{ "PAL", "PAL-M","PAL-N"}, ”PAL-Nc"
3253		, "PAL-60", "NTSC-M", "NTSC-J" }</td>
3254		<td valign="top" >Connector</td>
3255		<td valign="top" >TBD</td>
3256		</tr>
3257		<tr>
3258		<td rowspan="15" valign="top" >nouveau</td>
3259		<td rowspan="6" valign="top" >NV10 Overlay</td>
3260		<td valign="top" >"colorkey"</td>
3261		<td valign="top" >RANGE</td>
3262		<td valign="top" >Min=0, Max=0x01ffffff</td>
3263		<td valign="top" >Plane</td>
3264		<td valign="top" >TBD</td>
3265		</tr>
3266		<tr>
3267		<td valign="top" >“contrast”</td>
3268		<td valign="top" >RANGE</td>
3269		<td valign="top" >Min=0, Max=8192-1</td>
3270		<td valign="top" >Plane</td>
3271		<td valign="top" >TBD</td>
3272		</tr>
3273		<tr>
3274		<td valign="top" >“brightness”</td>
3275		<td valign="top" >RANGE</td>
3276		<td valign="top" >Min=0, Max=1024</td>
3277		<td valign="top" >Plane</td>
3278		<td valign="top" >TBD</td>
3279		</tr>
3280		<tr>
3281		<td valign="top" >“hue”</td>
3282		<td valign="top" >RANGE</td>
3283		<td valign="top" >Min=0, Max=359</td>
3284		<td valign="top" >Plane</td>
3285		<td valign="top" >TBD</td>
3286		</tr>
3287		<tr>
3288		<td valign="top" >“saturation”</td>
3289		<td valign="top" >RANGE</td>
3290		<td valign="top" >Min=0, Max=8192-1</td>
3291		<td valign="top" >Plane</td>
3292		<td valign="top" >TBD</td>
3293		</tr>
3294		<tr>
3295		<td valign="top" >“iturbt_709”</td>
3296		<td valign="top" >RANGE</td>
3297		<td valign="top" >Min=0, Max=1</td>
3298		<td valign="top" >Plane</td>
3299		<td valign="top" >TBD</td>
3300		</tr>
3301		<tr>
3302		<td rowspan="2" valign="top" >Nv04 Overlay</td>
3303		<td valign="top" >“colorkey”</td>
3304		<td valign="top" >RANGE</td>
3305		<td valign="top" >Min=0, Max=0x01ffffff</td>
3306		<td valign="top" >Plane</td>
3307		<td valign="top" >TBD</td>
3308		</tr>
3309		<tr>
3310		<td valign="top" >“brightness”</td>
3311		<td valign="top" >RANGE</td>
3312		<td valign="top" >Min=0, Max=1024</td>
3313		<td valign="top" >Plane</td>
3314		<td valign="top" >TBD</td>
3315		</tr>
3316		<tr>
3317		<td rowspan="7" valign="top" >Display</td>
3318		<td valign="top" >“dithering mode”</td>
3319		<td valign="top" >ENUM</td>
3320		<td valign="top" >{ "auto", "off", "on" }</td>
3321		<td valign="top" >Connector</td>
3322		<td valign="top" >TBD</td>
3323		</tr>
3324		<tr>
3325		<td valign="top" >“dithering depth”</td>
3326		<td valign="top" >ENUM</td>
3327		<td valign="top" >{ "auto", "off", "on", "static 2x2", "dynamic 2x2", "temporal" }</td>
3328		<td valign="top" >Connector</td>
3329		<td valign="top" >TBD</td>
3330		</tr>
3331		<tr>
3332		<td valign="top" >“underscan”</td>
3333		<td valign="top" >ENUM</td>
3334		<td valign="top" >{ "auto", "6 bpc", "8 bpc" }</td>
3335		<td valign="top" >Connector</td>
3336		<td valign="top" >TBD</td>
3337		</tr>
3338		<tr>
3339		<td valign="top" >“underscan hborder”</td>
3340		<td valign="top" >RANGE</td>
3341		<td valign="top" >Min=0, Max=128</td>
3342		<td valign="top" >Connector</td>
3343		<td valign="top" >TBD</td>
3344		</tr>
3345		<tr>
3346		<td valign="top" >“underscan vborder”</td>
3347		<td valign="top" >RANGE</td>
3348		<td valign="top" >Min=0, Max=128</td>
3349		<td valign="top" >Connector</td>
3350		<td valign="top" >TBD</td>
3351		</tr>
3352		<tr>
3353		<td valign="top" >“vibrant hue”</td>
3354		<td valign="top" >RANGE</td>
3355		<td valign="top" >Min=0, Max=180</td>
3356		<td valign="top" >Connector</td>
3357		<td valign="top" >TBD</td>
3358		</tr>
3359		<tr>
3360		<td valign="top" >“color vibrance”</td>
3361		<td valign="top" >RANGE</td>
3362		<td valign="top" >Min=0, Max=200</td>
3363		<td valign="top" >Connector</td>
3364		<td valign="top" >TBD</td>
3365		</tr>
3366		<tr>
3367		<td rowspan="2" valign="top" >omap</td>
3368		<td rowspan="2" valign="top" >Generic</td>
3369		<td valign="top" >“rotation”</td>
3370		<td valign="top" >BITMASK</td>
3371		<td valign="top" >{ 0, "rotate-0" },
3372		{ 1, "rotate-90" },
3373		{ 2, "rotate-180" },
3374		{ 3, "rotate-270" },
3375		{ 4, "reflect-x" },
3376		{ 5, "reflect-y" }</td>
3377		<td valign="top" >CRTC, Plane</td>
3378		<td valign="top" >TBD</td>
3379		</tr>
3380		<tr>
3381		<td valign="top" >“zorder”</td>
3382		<td valign="top" >RANGE</td>
3383		<td valign="top" >Min=0, Max=3</td>
3384		<td valign="top" >CRTC, Plane</td>
3385		<td valign="top" >TBD</td>
3386		</tr>
3387		<tr>
3388		<td valign="top" >qxl</td>
3389		<td valign="top" >Generic</td>
3390		<td valign="top" >“hotplug_mode_update"</td>
3391		<td valign="top" >RANGE</td>
3392		<td valign="top" >Min=0, Max=1</td>
3393		<td valign="top" >Connector</td>
3394		<td valign="top" >TBD</td>
3395		</tr>
3396		<tr>
3397		<td rowspan="9" valign="top" >radeon</td>
3398		<td valign="top" >DVI-I</td>
3399		<td valign="top" >“coherent”</td>
3400		<td valign="top" >RANGE</td>
3401		<td valign="top" >Min=0, Max=1</td>
3402		<td valign="top" >Connector</td>
3403		<td valign="top" >TBD</td>
3404		</tr>
3405		<tr>
3406		<td valign="top" >DAC enable load detect</td>
3407		<td valign="top" >“load detection”</td>
3408		<td valign="top" >RANGE</td>
3409		<td valign="top" >Min=0, Max=1</td>
3410		<td valign="top" >Connector</td>
3411		<td valign="top" >TBD</td>
3412		</tr>
3413		<tr>
3414		<td valign="top" >TV Standard</td>
3415		<td valign="top" >"tv standard"</td>
3416		<td valign="top" >ENUM</td>
3417		<td valign="top" >{ "ntsc", "pal", "pal-m", "pal-60", "ntsc-j"
3418		, "scart-pal", "pal-cn", "secam" }</td>
3419		<td valign="top" >Connector</td>
3420		<td valign="top" >TBD</td>
3421		</tr>
3422		<tr>
3423		<td valign="top" >legacy TMDS PLL detect</td>
3424		<td valign="top" >"tmds_pll"</td>
3425		<td valign="top" >ENUM</td>
3426		<td valign="top" >{ "driver", "bios" }</td>
3427		<td valign="top" >-</td>
3428		<td valign="top" >TBD</td>
3429		</tr>
3430		<tr>
3431		<td rowspan="3" valign="top" >Underscan</td>
3432		<td valign="top" >"underscan"</td>
3433		<td valign="top" >ENUM</td>
3434		<td valign="top" >{ "off", "on", "auto" }</td>
3435		<td valign="top" >Connector</td>
3436		<td valign="top" >TBD</td>
3437		</tr>
3438		<tr>
3439		<td valign="top" >"underscan hborder"</td>
3440		<td valign="top" >RANGE</td>
3441		<td valign="top" >Min=0, Max=128</td>
3442		<td valign="top" >Connector</td>
3443		<td valign="top" >TBD</td>
3444		</tr>
3445		<tr>
3446		<td valign="top" >"underscan vborder"</td>
3447		<td valign="top" >RANGE</td>
3448		<td valign="top" >Min=0, Max=128</td>
3449		<td valign="top" >Connector</td>
3450		<td valign="top" >TBD</td>
3451		</tr>
3452		<tr>
3453		<td valign="top" >Audio</td>
3454		<td valign="top" >“audio”</td>
3455		<td valign="top" >ENUM</td>
3456		<td valign="top" >{ "off", "on", "auto" }</td>
3457		<td valign="top" >Connector</td>
3458		<td valign="top" >TBD</td>
3459		</tr>
3460		<tr>
3461		<td valign="top" >FMT Dithering</td>
3462		<td valign="top" >“dither”</td>
3463		<td valign="top" >ENUM</td>
3464		<td valign="top" >{ "off", "on" }</td>
3465		<td valign="top" >Connector</td>
3466		<td valign="top" >TBD</td>
3467		</tr>
3468		<tr>
3469		<td rowspan="3" valign="top" >rcar-du</td>
3470		<td rowspan="3" valign="top" >Generic</td>
3471		<td valign="top" >"alpha"</td>
3472		<td valign="top" >RANGE</td>
3473		<td valign="top" >Min=0, Max=255</td>
3474		<td valign="top" >Plane</td>
3475		<td valign="top" >TBD</td>
3476		</tr>
3477		<tr>
3478		<td valign="top" >"colorkey"</td>
3479		<td valign="top" >RANGE</td>
3480		<td valign="top" >Min=0, Max=0x01ffffff</td>
3481		<td valign="top" >Plane</td>
3482		<td valign="top" >TBD</td>
3483		</tr>
3484		<tr>
3485		<td valign="top" >"zpos"</td>
3486		<td valign="top" >RANGE</td>
3487		<td valign="top" >Min=1, Max=7</td>
3488		<td valign="top" >Plane</td>
3489		<td valign="top" >TBD</td>
3490		</tr>
3491		</tbody>
3492		</table>
3493	    </sect2>
3494	  </sect1>
3495	
3496	  <!-- Internals: vertical blanking -->
3497	
3498	  <sect1 id="drm-vertical-blank">
3499	    <title>Vertical Blanking</title>
3500	    <para>
3501	      Vertical blanking plays a major role in graphics rendering. To achieve
3502	      tear-free display, users must synchronize page flips and/or rendering to
3503	      vertical blanking. The DRM API offers ioctls to perform page flips
3504	      synchronized to vertical blanking and wait for vertical blanking.
3505	    </para>
3506	    <para>
3507	      The DRM core handles most of the vertical blanking management logic, which
3508	      involves filtering out spurious interrupts, keeping race-free blanking
3509	      counters, coping with counter wrap-around and resets and keeping use
3510	      counts. It relies on the driver to generate vertical blanking interrupts
3511	      and optionally provide a hardware vertical blanking counter. Drivers must
3512	      implement the following operations.
3513	    </para>
3514	    <itemizedlist>
3515	      <listitem>
3516	        <synopsis>int (*enable_vblank) (struct drm_device *dev, int crtc);
3517	void (*disable_vblank) (struct drm_device *dev, int crtc);</synopsis>
3518	        <para>
3519		  Enable or disable vertical blanking interrupts for the given CRTC.
3520		</para>
3521	      </listitem>
3522	      <listitem>
3523	        <synopsis>u32 (*get_vblank_counter) (struct drm_device *dev, int crtc);</synopsis>
3524	        <para>
3525		  Retrieve the value of the vertical blanking counter for the given
3526		  CRTC. If the hardware maintains a vertical blanking counter its value
3527		  should be returned. Otherwise drivers can use the
3528		  <function>drm_vblank_count</function> helper function to handle this
3529		  operation.
3530		</para>
3531	      </listitem>
3532	    </itemizedlist>
3533	    <para>
3534	      Drivers must initialize the vertical blanking handling core with a call to
3535	      <function>drm_vblank_init</function> in their
3536	      <methodname>load</methodname> operation. The function will set the struct
3537	      <structname>drm_device</structname>
3538	      <structfield>vblank_disable_allowed</structfield> field to 0. This will
3539	      keep vertical blanking interrupts enabled permanently until the first mode
3540	      set operation, where <structfield>vblank_disable_allowed</structfield> is
3541	      set to 1. The reason behind this is not clear. Drivers can set the field
3542	      to 1 after <function>calling drm_vblank_init</function> to make vertical
3543	      blanking interrupts dynamically managed from the beginning.
3544	    </para>
3545	    <para>
3546	      Vertical blanking interrupts can be enabled by the DRM core or by drivers
3547	      themselves (for instance to handle page flipping operations). The DRM core
3548	      maintains a vertical blanking use count to ensure that the interrupts are
3549	      not disabled while a user still needs them. To increment the use count,
3550	      drivers call <function>drm_vblank_get</function>. Upon return vertical
3551	      blanking interrupts are guaranteed to be enabled.
3552	    </para>
3553	    <para>
3554	      To decrement the use count drivers call
3555	      <function>drm_vblank_put</function>. Only when the use count drops to zero
3556	      will the DRM core disable the vertical blanking interrupts after a delay
3557	      by scheduling a timer. The delay is accessible through the vblankoffdelay
3558	      module parameter or the <varname>drm_vblank_offdelay</varname> global
3559	      variable and expressed in milliseconds. Its default value is 5000 ms.
3560	      Zero means never disable, and a negative value means disable immediately.
3561	      Drivers may override the behaviour by setting the
3562	      <structname>drm_device</structname>
3563	      <structfield>vblank_disable_immediate</structfield> flag, which when set
3564	      causes vblank interrupts to be disabled immediately regardless of the
3565	      drm_vblank_offdelay value. The flag should only be set if there's a
3566	      properly working hardware vblank counter present.
3567	    </para>
3568	    <para>
3569	      When a vertical blanking interrupt occurs drivers only need to call the
3570	      <function>drm_handle_vblank</function> function to account for the
3571	      interrupt.
3572	    </para>
3573	    <para>
3574	      Resources allocated by <function>drm_vblank_init</function> must be freed
3575	      with a call to <function>drm_vblank_cleanup</function> in the driver
3576	      <methodname>unload</methodname> operation handler.
3577	    </para>
3578	    <sect2>
3579	      <title>Vertical Blanking and Interrupt Handling Functions Reference</title>
3580	!Edrivers/gpu/drm/drm_irq.c
3581	!Finclude/drm/drmP.h drm_crtc_vblank_waitqueue
3582	    </sect2>
3583	  </sect1>
3584	
3585	  <!-- Internals: open/close, file operations and ioctls -->
3586	
3587	  <sect1>
3588	    <title>Open/Close, File Operations and IOCTLs</title>
3589	    <sect2>
3590	      <title>Open and Close</title>
3591	      <synopsis>int (*firstopen) (struct drm_device *);
3592	void (*lastclose) (struct drm_device *);
3593	int (*open) (struct drm_device *, struct drm_file *);
3594	void (*preclose) (struct drm_device *, struct drm_file *);
3595	void (*postclose) (struct drm_device *, struct drm_file *);</synopsis>
3596	      <abstract>Open and close handlers. None of those methods are mandatory.
3597	      </abstract>
3598	      <para>
3599	        The <methodname>firstopen</methodname> method is called by the DRM core
3600		for legacy UMS (User Mode Setting) drivers only when an application
3601		opens a device that has no other opened file handle. UMS drivers can
3602		implement it to acquire device resources. KMS drivers can't use the
3603		method and must acquire resources in the <methodname>load</methodname>
3604		method instead.
3605	      </para>
3606	      <para>
3607		Similarly the <methodname>lastclose</methodname> method is called when
3608		the last application holding a file handle opened on the device closes
3609		it, for both UMS and KMS drivers. Additionally, the method is also
3610		called at module unload time or, for hot-pluggable devices, when the
3611		device is unplugged. The <methodname>firstopen</methodname> and
3612		<methodname>lastclose</methodname> calls can thus be unbalanced.
3613	      </para>
3614	      <para>
3615	        The <methodname>open</methodname> method is called every time the device
3616		is opened by an application. Drivers can allocate per-file private data
3617		in this method and store them in the struct
3618		<structname>drm_file</structname> <structfield>driver_priv</structfield>
3619		field. Note that the <methodname>open</methodname> method is called
3620		before <methodname>firstopen</methodname>.
3621	      </para>
3622	      <para>
3623	        The close operation is split into <methodname>preclose</methodname> and
3624		<methodname>postclose</methodname> methods. Drivers must stop and
3625		cleanup all per-file operations in the <methodname>preclose</methodname>
3626		method. For instance pending vertical blanking and page flip events must
3627		be cancelled. No per-file operation is allowed on the file handle after
3628		returning from the <methodname>preclose</methodname> method.
3629	      </para>
3630	      <para>
3631	        Finally the <methodname>postclose</methodname> method is called as the
3632		last step of the close operation, right before calling the
3633		<methodname>lastclose</methodname> method if no other open file handle
3634		exists for the device. Drivers that have allocated per-file private data
3635		in the <methodname>open</methodname> method should free it here.
3636	      </para>
3637	      <para>
3638	        The <methodname>lastclose</methodname> method should restore CRTC and
3639		plane properties to default value, so that a subsequent open of the
3640		device will not inherit state from the previous user. It can also be
3641		used to execute delayed power switching state changes, e.g. in
3642		conjunction with the vga-switcheroo infrastructure. Beyond that KMS
3643		drivers should not do any further cleanup. Only legacy UMS drivers might
3644		need to clean up device state so that the vga console or an independent
3645		fbdev driver could take over.
3646	      </para>
3647	    </sect2>
3648	    <sect2>
3649	      <title>File Operations</title>
3650	      <synopsis>const struct file_operations *fops</synopsis>
3651	      <abstract>File operations for the DRM device node.</abstract>
3652	      <para>
3653	        Drivers must define the file operations structure that forms the DRM
3654		userspace API entry point, even though most of those operations are
3655		implemented in the DRM core. The <methodname>open</methodname>,
3656		<methodname>release</methodname> and <methodname>ioctl</methodname>
3657		operations are handled by
3658		<programlisting>
3659		.owner = THIS_MODULE,
3660		.open = drm_open,
3661		.release = drm_release,
3662		.unlocked_ioctl = drm_ioctl,
3663	  #ifdef CONFIG_COMPAT
3664		.compat_ioctl = drm_compat_ioctl,
3665	  #endif
3666	        </programlisting>
3667	      </para>
3668	      <para>
3669	        Drivers that implement private ioctls that requires 32/64bit
3670		compatibility support must provide their own
3671		<methodname>compat_ioctl</methodname> handler that processes private
3672		ioctls and calls <function>drm_compat_ioctl</function> for core ioctls.
3673	      </para>
3674	      <para>
3675	        The <methodname>read</methodname> and <methodname>poll</methodname>
3676		operations provide support for reading DRM events and polling them. They
3677		are implemented by
3678		<programlisting>
3679		.poll = drm_poll,
3680		.read = drm_read,
3681		.llseek = no_llseek,
3682		</programlisting>
3683	      </para>
3684	      <para>
3685	        The memory mapping implementation varies depending on how the driver
3686		manages memory. Pre-GEM drivers will use <function>drm_mmap</function>,
3687		while GEM-aware drivers will use <function>drm_gem_mmap</function>. See
3688		<xref linkend="drm-gem"/>.
3689		<programlisting>
3690		.mmap = drm_gem_mmap,
3691		</programlisting>
3692	      </para>
3693	      <para>
3694	        No other file operation is supported by the DRM API.
3695	      </para>
3696	    </sect2>
3697	    <sect2>
3698	      <title>IOCTLs</title>
3699	      <synopsis>struct drm_ioctl_desc *ioctls;
3700	int num_ioctls;</synopsis>
3701	      <abstract>Driver-specific ioctls descriptors table.</abstract>
3702	      <para>
3703	        Driver-specific ioctls numbers start at DRM_COMMAND_BASE. The ioctls
3704		descriptors table is indexed by the ioctl number offset from the base
3705		value. Drivers can use the DRM_IOCTL_DEF_DRV() macro to initialize the
3706		table entries.
3707	      </para>
3708	      <para>
3709	        <programlisting>DRM_IOCTL_DEF_DRV(ioctl, func, flags)</programlisting>
3710		<para>
3711		  <parameter>ioctl</parameter> is the ioctl name. Drivers must define
3712		  the DRM_##ioctl and DRM_IOCTL_##ioctl macros to the ioctl number
3713		  offset from DRM_COMMAND_BASE and the ioctl number respectively. The
3714		  first macro is private to the device while the second must be exposed
3715		  to userspace in a public header.
3716		</para>
3717		<para>
3718		  <parameter>func</parameter> is a pointer to the ioctl handler function
3719		  compatible with the <type>drm_ioctl_t</type> type.
3720		  <programlisting>typedef int drm_ioctl_t(struct drm_device *dev, void *data,
3721			struct drm_file *file_priv);</programlisting>
3722		</para>
3723		<para>
3724		  <parameter>flags</parameter> is a bitmask combination of the following
3725		  values. It restricts how the ioctl is allowed to be called.
3726		  <itemizedlist>
3727		    <listitem><para>
3728		      DRM_AUTH - Only authenticated callers allowed
3729		    </para></listitem>
3730		    <listitem><para>
3731		      DRM_MASTER - The ioctl can only be called on the master file
3732		      handle
3733		    </para></listitem>
3734	            <listitem><para>
3735		      DRM_ROOT_ONLY - Only callers with the SYSADMIN capability allowed
3736		    </para></listitem>
3737	            <listitem><para>
3738		      DRM_CONTROL_ALLOW - The ioctl can only be called on a control
3739		      device
3740		    </para></listitem>
3741	            <listitem><para>
3742		      DRM_UNLOCKED - The ioctl handler will be called without locking
3743		      the DRM global mutex
3744		    </para></listitem>
3745		  </itemizedlist>
3746		</para>
3747	      </para>
3748	    </sect2>
3749	  </sect1>
3750	  <sect1>
3751	    <title>Legacy Support Code</title>
3752	    <para>
3753	      The section very briefly covers some of the old legacy support code which
3754	      is only used by old DRM drivers which have done a so-called shadow-attach
3755	      to the underlying device instead of registering as a real driver. This
3756	      also includes some of the old generic buffer management and command
3757	      submission code. Do not use any of this in new and modern drivers.
3758	    </para>
3759	
3760	    <sect2>
3761	      <title>Legacy Suspend/Resume</title>
3762	      <para>
3763		The DRM core provides some suspend/resume code, but drivers wanting full
3764		suspend/resume support should provide save() and restore() functions.
3765		These are called at suspend, hibernate, or resume time, and should perform
3766		any state save or restore required by your device across suspend or
3767		hibernate states.
3768	      </para>
3769	      <synopsis>int (*suspend) (struct drm_device *, pm_message_t state);
3770	  int (*resume) (struct drm_device *);</synopsis>
3771	      <para>
3772		Those are legacy suspend and resume methods which
3773		<emphasis>only</emphasis> work with the legacy shadow-attach driver
3774		registration functions. New driver should use the power management
3775		interface provided by their bus type (usually through
3776		the struct <structname>device_driver</structname> dev_pm_ops) and set
3777		these methods to NULL.
3778	      </para>
3779	    </sect2>
3780	
3781	    <sect2>
3782	      <title>Legacy DMA Services</title>
3783	      <para>
3784		This should cover how DMA mapping etc. is supported by the core.
3785		These functions are deprecated and should not be used.
3786	      </para>
3787	    </sect2>
3788	  </sect1>
3789	  </chapter>
3790	
3791	<!-- TODO
3792	
3793	- Add a glossary
3794	- Document the struct_mutex catch-all lock
3795	- Document connector properties
3796	
3797	- Why is the load method optional?
3798	- What are drivers supposed to set the initial display state to, and how?
3799	  Connector's DPMS states are not initialized and are thus equal to
3800	  DRM_MODE_DPMS_ON. The fbcon compatibility layer calls
3801	  drm_helper_disable_unused_functions(), which disables unused encoders and
3802	  CRTCs, but doesn't touch the connectors' DPMS state, and
3803	  drm_helper_connector_dpms() in reaction to fbdev blanking events. Do drivers
3804	  that don't implement (or just don't use) fbcon compatibility need to call
3805	  those functions themselves?
3806	- KMS drivers must call drm_vblank_pre_modeset() and drm_vblank_post_modeset()
3807	  around mode setting. Should this be done in the DRM core?
3808	- vblank_disable_allowed is set to 1 in the first drm_vblank_post_modeset()
3809	  call and never set back to 0. It seems to be safe to permanently set it to 1
3810	  in drm_vblank_init() for KMS driver, and it might be safe for UMS drivers as
3811	  well. This should be investigated.
3812	- crtc and connector .save and .restore operations are only used internally in
3813	  drivers, should they be removed from the core?
3814	- encoder mid-layer .save and .restore operations are only used internally in
3815	  drivers, should they be removed from the core?
3816	- encoder mid-layer .detect operation is only used internally in drivers,
3817	  should it be removed from the core?
3818	-->
3819	
3820	  <!-- External interfaces -->
3821	
3822	  <chapter id="drmExternals">
3823	    <title>Userland interfaces</title>
3824	    <para>
3825	      The DRM core exports several interfaces to applications,
3826	      generally intended to be used through corresponding libdrm
3827	      wrapper functions.  In addition, drivers export device-specific
3828	      interfaces for use by userspace drivers &amp; device-aware
3829	      applications through ioctls and sysfs files.
3830	    </para>
3831	    <para>
3832	      External interfaces include: memory mapping, context management,
3833	      DMA operations, AGP management, vblank control, fence
3834	      management, memory management, and output management.
3835	    </para>
3836	    <para>
3837	      Cover generic ioctls and sysfs layout here.  We only need high-level
3838	      info, since man pages should cover the rest.
3839	    </para>
3840	
3841	  <!-- External: render nodes -->
3842	
3843	    <sect1>
3844	      <title>Render nodes</title>
3845	      <para>
3846	        DRM core provides multiple character-devices for user-space to use.
3847	        Depending on which device is opened, user-space can perform a different
3848	        set of operations (mainly ioctls). The primary node is always created
3849	        and called card&lt;num&gt;. Additionally, a currently
3850	        unused control node, called controlD&lt;num&gt; is also
3851	        created. The primary node provides all legacy operations and
3852	        historically was the only interface used by userspace. With KMS, the
3853	        control node was introduced. However, the planned KMS control interface
3854	        has never been written and so the control node stays unused to date.
3855	      </para>
3856	      <para>
3857	        With the increased use of offscreen renderers and GPGPU applications,
3858	        clients no longer require running compositors or graphics servers to
3859	        make use of a GPU. But the DRM API required unprivileged clients to
3860	        authenticate to a DRM-Master prior to getting GPU access. To avoid this
3861	        step and to grant clients GPU access without authenticating, render
3862	        nodes were introduced. Render nodes solely serve render clients, that
3863	        is, no modesetting or privileged ioctls can be issued on render nodes.
3864	        Only non-global rendering commands are allowed. If a driver supports
3865	        render nodes, it must advertise it via the DRIVER_RENDER
3866	        DRM driver capability. If not supported, the primary node must be used
3867	        for render clients together with the legacy drmAuth authentication
3868	        procedure.
3869	      </para>
3870	      <para>
3871	        If a driver advertises render node support, DRM core will create a
3872	        separate render node called renderD&lt;num&gt;. There will
3873	        be one render node per device. No ioctls except  PRIME-related ioctls
3874	        will be allowed on this node. Especially GEM_OPEN will be
3875	        explicitly prohibited. Render nodes are designed to avoid the
3876	        buffer-leaks, which occur if clients guess the flink names or mmap
3877	        offsets on the legacy interface. Additionally to this basic interface,
3878	        drivers must mark their driver-dependent render-only ioctls as
3879	        DRM_RENDER_ALLOW so render clients can use them. Driver
3880	        authors must be careful not to allow any privileged ioctls on render
3881	        nodes.
3882	      </para>
3883	      <para>
3884	        With render nodes, user-space can now control access to the render node
3885	        via basic file-system access-modes. A running graphics server which
3886	        authenticates clients on the privileged primary/legacy node is no longer
3887	        required. Instead, a client can open the render node and is immediately
3888	        granted GPU access. Communication between clients (or servers) is done
3889	        via PRIME. FLINK from render node to legacy node is not supported. New
3890	        clients must not use the insecure FLINK interface.
3891	      </para>
3892	      <para>
3893	        Besides dropping all modeset/global ioctls, render nodes also drop the
3894	        DRM-Master concept. There is no reason to associate render clients with
3895	        a DRM-Master as they are independent of any graphics server. Besides,
3896	        they must work without any running master, anyway.
3897	        Drivers must be able to run without a master object if they support
3898	        render nodes. If, on the other hand, a driver requires shared state
3899	        between clients which is visible to user-space and accessible beyond
3900	        open-file boundaries, they cannot support render nodes.
3901	      </para>
3902	    </sect1>
3903	
3904	  <!-- External: vblank handling -->
3905	
3906	    <sect1>
3907	      <title>VBlank event handling</title>
3908	      <para>
3909	        The DRM core exposes two vertical blank related ioctls:
3910	        <variablelist>
3911	          <varlistentry>
3912	            <term>DRM_IOCTL_WAIT_VBLANK</term>
3913	            <listitem>
3914	              <para>
3915	                This takes a struct drm_wait_vblank structure as its argument,
3916	                and it is used to block or request a signal when a specified
3917	                vblank event occurs.
3918	              </para>
3919	            </listitem>
3920	          </varlistentry>
3921	          <varlistentry>
3922	            <term>DRM_IOCTL_MODESET_CTL</term>
3923	            <listitem>
3924	              <para>
3925			This was only used for user-mode-settind drivers around
3926			modesetting changes to allow the kernel to update the vblank
3927			interrupt after mode setting, since on many devices the vertical
3928			blank counter is reset to 0 at some point during modeset. Modern
3929			drivers should not call this any more since with kernel mode
3930			setting it is a no-op.
3931	              </para>
3932	            </listitem>
3933	          </varlistentry>
3934	        </variablelist>
3935	      </para>
3936	    </sect1>
3937	
3938	  </chapter>
3939	</part>
3940	<part id="drmDrivers">
3941	  <title>DRM Drivers</title>
3942	
3943	  <partintro>
3944	    <para>
3945	      This second part of the DRM Developer's Guide documents driver code,
3946	      implementation details and also all the driver-specific userspace
3947	      interfaces. Especially since all hardware-acceleration interfaces to
3948	      userspace are driver specific for efficiency and other reasons these
3949	      interfaces can be rather substantial. Hence every driver has its own
3950	      chapter.
3951	    </para>
3952	  </partintro>
3953	
3954	  <chapter id="drmI915">
3955	    <title>drm/i915 Intel GFX Driver</title>
3956	    <para>
3957	      The drm/i915 driver supports all (with the exception of some very early
3958	      models) integrated GFX chipsets with both Intel display and rendering
3959	      blocks. This excludes a set of SoC platforms with an SGX rendering unit,
3960	      those have basic support through the gma500 drm driver.
3961	    </para>
3962	    <sect1>
3963	      <title>Core Driver Infrastructure</title>
3964	      <para>
3965		This section covers core driver infrastructure used by both the display
3966		and the GEM parts of the driver.
3967	      </para>
3968	      <sect2>
3969	        <title>Runtime Power Management</title>
3970	!Pdrivers/gpu/drm/i915/intel_runtime_pm.c runtime pm
3971	!Idrivers/gpu/drm/i915/intel_runtime_pm.c
3972	!Idrivers/gpu/drm/i915/intel_uncore.c
3973	      </sect2>
3974	      <sect2>
3975	        <title>Interrupt Handling</title>
3976	!Pdrivers/gpu/drm/i915/i915_irq.c interrupt handling
3977	!Fdrivers/gpu/drm/i915/i915_irq.c intel_irq_init intel_irq_init_hw intel_hpd_init
3978	!Fdrivers/gpu/drm/i915/i915_irq.c intel_irq_fini
3979	!Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_disable_interrupts
3980	!Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_enable_interrupts
3981	      </sect2>
3982	    </sect1>
3983	    <sect1>
3984	      <title>Display Hardware Handling</title>
3985	      <para>
3986	        This section covers everything related to the display hardware including
3987	        the mode setting infrastructure, plane, sprite and cursor handling and
3988	        display, output probing and related topics.
3989	      </para>
3990	      <sect2>
3991	        <title>Mode Setting Infrastructure</title>
3992	        <para>
3993	          The i915 driver is thus far the only DRM driver which doesn't use the
3994	          common DRM helper code to implement mode setting sequences. Thus it
3995	          has its own tailor-made infrastructure for executing a display
3996	          configuration change.
3997	        </para>
3998	      </sect2>
3999	      <sect2>
4000	        <title>Frontbuffer Tracking</title>
4001	!Pdrivers/gpu/drm/i915/intel_frontbuffer.c frontbuffer tracking
4002	!Idrivers/gpu/drm/i915/intel_frontbuffer.c
4003	!Fdrivers/gpu/drm/i915/intel_drv.h intel_frontbuffer_flip
4004	!Fdrivers/gpu/drm/i915/i915_gem.c i915_gem_track_fb
4005	      </sect2>
4006	      <sect2>
4007	        <title>Display FIFO Underrun Reporting</title>
4008	!Pdrivers/gpu/drm/i915/intel_fifo_underrun.c fifo underrun handling
4009	!Idrivers/gpu/drm/i915/intel_fifo_underrun.c
4010	      </sect2>
4011	      <sect2>
4012	        <title>Plane Configuration</title>
4013	        <para>
4014		  This section covers plane configuration and composition with the
4015		  primary plane, sprites, cursors and overlays. This includes the
4016		  infrastructure to do atomic vsync'ed updates of all this state and
4017		  also tightly coupled topics like watermark setup and computation,
4018		  framebuffer compression and panel self refresh.
4019	        </para>
4020	      </sect2>
4021	      <sect2>
4022	        <title>Atomic Plane Helpers</title>
4023	!Pdrivers/gpu/drm/i915/intel_atomic_plane.c atomic plane helpers
4024	!Idrivers/gpu/drm/i915/intel_atomic_plane.c
4025	      </sect2>
4026	      <sect2>
4027	        <title>Output Probing</title>
4028	        <para>
4029		  This section covers output probing and related infrastructure like the
4030		  hotplug interrupt storm detection and mitigation code. Note that the
4031		  i915 driver still uses most of the common DRM helper code for output
4032		  probing, so those sections fully apply.
4033	        </para>
4034	      </sect2>
4035	      <sect2>
4036		<title>High Definition Audio</title>
4037	!Pdrivers/gpu/drm/i915/intel_audio.c High Definition Audio over HDMI and Display Port
4038	!Idrivers/gpu/drm/i915/intel_audio.c
4039	      </sect2>
4040	      <sect2>
4041		<title>Panel Self Refresh PSR (PSR/SRD)</title>
4042	!Pdrivers/gpu/drm/i915/intel_psr.c Panel Self Refresh (PSR/SRD)
4043	!Idrivers/gpu/drm/i915/intel_psr.c
4044	      </sect2>
4045	      <sect2>
4046		<title>Frame Buffer Compression (FBC)</title>
4047	!Pdrivers/gpu/drm/i915/intel_fbc.c Frame Buffer Compression (FBC)
4048	!Idrivers/gpu/drm/i915/intel_fbc.c
4049	      </sect2>
4050	      <sect2>
4051	        <title>DPIO</title>
4052	!Pdrivers/gpu/drm/i915/i915_reg.h DPIO
4053		<table id="dpiox2">
4054		  <title>Dual channel PHY (VLV/CHV)</title>
4055		  <tgroup cols="8">
4056		    <colspec colname="c0" />
4057		    <colspec colname="c1" />
4058		    <colspec colname="c2" />
4059		    <colspec colname="c3" />
4060		    <colspec colname="c4" />
4061		    <colspec colname="c5" />
4062		    <colspec colname="c6" />
4063		    <colspec colname="c7" />
4064		    <spanspec spanname="ch0" namest="c0" nameend="c3" />
4065		    <spanspec spanname="ch1" namest="c4" nameend="c7" />
4066		    <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
4067		    <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
4068		    <spanspec spanname="ch1pcs01" namest="c4" nameend="c5" />
4069		    <spanspec spanname="ch1pcs23" namest="c6" nameend="c7" />
4070		    <thead>
4071		      <row>
4072			<entry spanname="ch0">CH0</entry>
4073			<entry spanname="ch1">CH1</entry>
4074		      </row>
4075		    </thead>
4076		    <tbody valign="top" align="center">
4077		      <row>
4078			<entry spanname="ch0">CMN/PLL/REF</entry>
4079			<entry spanname="ch1">CMN/PLL/REF</entry>
4080		      </row>
4081		      <row>
4082			<entry spanname="ch0pcs01">PCS01</entry>
4083			<entry spanname="ch0pcs23">PCS23</entry>
4084			<entry spanname="ch1pcs01">PCS01</entry>
4085			<entry spanname="ch1pcs23">PCS23</entry>
4086		      </row>
4087		      <row>
4088			<entry>TX0</entry>
4089			<entry>TX1</entry>
4090			<entry>TX2</entry>
4091			<entry>TX3</entry>
4092			<entry>TX0</entry>
4093			<entry>TX1</entry>
4094			<entry>TX2</entry>
4095			<entry>TX3</entry>
4096		      </row>
4097		      <row>
4098			<entry spanname="ch0">DDI0</entry>
4099			<entry spanname="ch1">DDI1</entry>
4100		      </row>
4101		    </tbody>
4102		  </tgroup>
4103		</table>
4104		<table id="dpiox1">
4105		  <title>Single channel PHY (CHV)</title>
4106		  <tgroup cols="4">
4107		    <colspec colname="c0" />
4108		    <colspec colname="c1" />
4109		    <colspec colname="c2" />
4110		    <colspec colname="c3" />
4111		    <spanspec spanname="ch0" namest="c0" nameend="c3" />
4112		    <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
4113		    <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
4114		    <thead>
4115		      <row>
4116			<entry spanname="ch0">CH0</entry>
4117		      </row>
4118		    </thead>
4119		    <tbody valign="top" align="center">
4120		      <row>
4121			<entry spanname="ch0">CMN/PLL/REF</entry>
4122		      </row>
4123		      <row>
4124			<entry spanname="ch0pcs01">PCS01</entry>
4125			<entry spanname="ch0pcs23">PCS23</entry>
4126		      </row>
4127		      <row>
4128			<entry>TX0</entry>
4129			<entry>TX1</entry>
4130			<entry>TX2</entry>
4131			<entry>TX3</entry>
4132		      </row>
4133		      <row>
4134			<entry spanname="ch0">DDI2</entry>
4135		      </row>
4136		    </tbody>
4137		  </tgroup>
4138		</table>
4139	      </sect2>
4140	    </sect1>
4141	
4142	    <sect1>
4143	      <title>Memory Management and Command Submission</title>
4144	      <para>
4145		This sections covers all things related to the GEM implementation in the
4146		i915 driver.
4147	      </para>
4148	      <sect2>
4149	        <title>Batchbuffer Parsing</title>
4150	!Pdrivers/gpu/drm/i915/i915_cmd_parser.c batch buffer command parser
4151	!Idrivers/gpu/drm/i915/i915_cmd_parser.c
4152	      </sect2>
4153	      <sect2>
4154	        <title>Batchbuffer Pools</title>
4155	!Pdrivers/gpu/drm/i915/i915_gem_batch_pool.c batch pool
4156	!Idrivers/gpu/drm/i915/i915_gem_batch_pool.c
4157	      </sect2>
4158	      <sect2>
4159	        <title>Logical Rings, Logical Ring Contexts and Execlists</title>
4160	!Pdrivers/gpu/drm/i915/intel_lrc.c Logical Rings, Logical Ring Contexts and Execlists
4161	!Idrivers/gpu/drm/i915/intel_lrc.c
4162	      </sect2>
4163	      <sect2>
4164	        <title>Global GTT views</title>
4165	!Pdrivers/gpu/drm/i915/i915_gem_gtt.c Global GTT views
4166	!Idrivers/gpu/drm/i915/i915_gem_gtt.c
4167	      </sect2>
4168	      <sect2>
4169	        <title>Buffer Object Eviction</title>
4170		<para>
4171		  This section documents the interface function for evicting buffer
4172		  objects to make space available in the virtual gpu address spaces.
4173		  Note that this is mostly orthogonal to shrinking buffer objects
4174		  caches, which has the goal to make main memory (shared with the gpu
4175		  through the unified memory architecture) available.
4176		</para>
4177	!Idrivers/gpu/drm/i915/i915_gem_evict.c
4178	      </sect2>
4179	    </sect1>
4180	
4181	    <sect1>
4182	      <title> Tracing </title>
4183	      <para>
4184	    This sections covers all things related to the tracepoints implemented in
4185	    the i915 driver.
4186	      </para>
4187	      <sect2>
4188	        <title> i915_ppgtt_create and i915_ppgtt_release </title>
4189	!Pdrivers/gpu/drm/i915/i915_trace.h i915_ppgtt_create and i915_ppgtt_release tracepoints
4190	      </sect2>
4191	      <sect2>
4192	        <title> i915_context_create and i915_context_free </title>
4193	!Pdrivers/gpu/drm/i915/i915_trace.h i915_context_create and i915_context_free tracepoints
4194	      </sect2>
4195	      <sect2>
4196	        <title> switch_mm </title>
4197	!Pdrivers/gpu/drm/i915/i915_trace.h switch_mm tracepoint
4198	      </sect2>
4199	    </sect1>
4200	
4201	  </chapter>
4202	!Cdrivers/gpu/drm/i915/i915_irq.c
4203	</part>
4204	</book>
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