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Based on kernel version 3.19. Page generated on 2015-02-13 21:20 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	        </variablelist>
243	      </sect3>
244	      <sect3>
245	        <title>Major, Minor and Patchlevel</title>
246	        <synopsis>int major;
247	int minor;
248	int patchlevel;</synopsis>
249	        <para>
250	          The DRM core identifies driver versions by a major, minor and patch
251	          level triplet. The information is printed to the kernel log at
252	          initialization time and passed to userspace through the
253	          DRM_IOCTL_VERSION ioctl.
254	        </para>
255	        <para>
256	          The major and minor numbers are also used to verify the requested driver
257	          API version passed to DRM_IOCTL_SET_VERSION. When the driver API changes
258	          between minor versions, applications can call DRM_IOCTL_SET_VERSION to
259	          select a specific version of the API. If the requested major isn't equal
260	          to the driver major, or the requested minor is larger than the driver
261	          minor, the DRM_IOCTL_SET_VERSION call will return an error. Otherwise
262	          the driver's set_version() method will be called with the requested
263	          version.
264	        </para>
265	      </sect3>
266	      <sect3>
267	        <title>Name, Description and Date</title>
268	        <synopsis>char *name;
269	char *desc;
270	char *date;</synopsis>
271	        <para>
272	          The driver name is printed to the kernel log at initialization time,
273	          used for IRQ registration and passed to userspace through
274	          DRM_IOCTL_VERSION.
275	        </para>
276	        <para>
277	          The driver description is a purely informative string passed to
278	          userspace through the DRM_IOCTL_VERSION ioctl and otherwise unused by
279	          the kernel.
280	        </para>
281	        <para>
282	          The driver date, formatted as YYYYMMDD, is meant to identify the date of
283	          the latest modification to the driver. However, as most drivers fail to
284	          update it, its value is mostly useless. The DRM core prints it to the
285	          kernel log at initialization time and passes it to userspace through the
286	          DRM_IOCTL_VERSION ioctl.
287	        </para>
288	      </sect3>
289	    </sect2>
290	    <sect2>
291	      <title>Device Registration</title>
292	      <para>
293	        A number of functions are provided to help with device registration.
294	        The functions deal with PCI and platform devices, respectively.
295	      </para>
296	!Edrivers/gpu/drm/drm_pci.c
297	!Edrivers/gpu/drm/drm_platform.c
298	      <para>
299	        New drivers that no longer rely on the services provided by the
300	        <structname>drm_bus</structname> structure can call the low-level
301	        device registration functions directly. The
302	        <function>drm_dev_alloc()</function> function can be used to allocate
303	        and initialize a new <structname>drm_device</structname> structure.
304	        Drivers will typically want to perform some additional setup on this
305	        structure, such as allocating driver-specific data and storing a
306	        pointer to it in the DRM device's <structfield>dev_private</structfield>
307	        field. Drivers should also set the device's unique name using the
308	        <function>drm_dev_set_unique()</function> function. After it has been
309	        set up a device can be registered with the DRM subsystem by calling
310	        <function>drm_dev_register()</function>. This will cause the device to
311	        be exposed to userspace and will call the driver's
312	        <structfield>.load()</structfield> implementation. When a device is
313	        removed, the DRM device can safely be unregistered and freed by calling
314	        <function>drm_dev_unregister()</function> followed by a call to
315	        <function>drm_dev_unref()</function>.
316	      </para>
317	!Edrivers/gpu/drm/drm_drv.c
318	    </sect2>
319	    <sect2>
320	      <title>Driver Load</title>
321	      <para>
322	        The <methodname>load</methodname> method is the driver and device
323	        initialization entry point. The method is responsible for allocating and
324		initializing driver private data, performing resource allocation and
325		mapping (e.g. acquiring
326	        clocks, mapping registers or allocating command buffers), initializing
327	        the memory manager (<xref linkend="drm-memory-management"/>), installing
328	        the IRQ handler (<xref linkend="drm-irq-registration"/>), setting up
329	        vertical blanking handling (<xref linkend="drm-vertical-blank"/>), mode
330		setting (<xref linkend="drm-mode-setting"/>) and initial output
331		configuration (<xref linkend="drm-kms-init"/>).
332	      </para>
333	      <note><para>
334	        If compatibility is a concern (e.g. with drivers converted over from
335	        User Mode Setting to Kernel Mode Setting), care must be taken to prevent
336	        device initialization and control that is incompatible with currently
337	        active userspace drivers. For instance, if user level mode setting
338	        drivers are in use, it would be problematic to perform output discovery
339	        &amp; configuration at load time. Likewise, if user-level drivers
340	        unaware of memory management are in use, memory management and command
341	        buffer setup may need to be omitted. These requirements are
342	        driver-specific, and care needs to be taken to keep both old and new
343	        applications and libraries working.
344	      </para></note>
345	      <synopsis>int (*load) (struct drm_device *, unsigned long flags);</synopsis>
346	      <para>
347	        The method takes two arguments, a pointer to the newly created
348		<structname>drm_device</structname> and flags. The flags are used to
349		pass the <structfield>driver_data</structfield> field of the device id
350		corresponding to the device passed to <function>drm_*_init()</function>.
351		Only PCI devices currently use this, USB and platform DRM drivers have
352		their <methodname>load</methodname> method called with flags to 0.
353	      </para>
354	      <sect3>
355	        <title>Driver Private Data</title>
356	        <para>
357	          The driver private hangs off the main
358	          <structname>drm_device</structname> structure and can be used for
359	          tracking various device-specific bits of information, like register
360	          offsets, command buffer status, register state for suspend/resume, etc.
361	          At load time, a driver may simply allocate one and set
362	          <structname>drm_device</structname>.<structfield>dev_priv</structfield>
363	          appropriately; it should be freed and
364	          <structname>drm_device</structname>.<structfield>dev_priv</structfield>
365	          set to NULL when the driver is unloaded.
366	        </para>
367	      </sect3>
368	      <sect3 id="drm-irq-registration">
369	        <title>IRQ Registration</title>
370	        <para>
371	          The DRM core tries to facilitate IRQ handler registration and
372	          unregistration by providing <function>drm_irq_install</function> and
373	          <function>drm_irq_uninstall</function> functions. Those functions only
374	          support a single interrupt per device, devices that use more than one
375	          IRQs need to be handled manually.
376	        </para>
377	        <sect4>
378	          <title>Managed IRQ Registration</title>
379	          <para>
380	            <function>drm_irq_install</function> starts by calling the
381	            <methodname>irq_preinstall</methodname> driver operation. The operation
382	            is optional and must make sure that the interrupt will not get fired by
383	            clearing all pending interrupt flags or disabling the interrupt.
384	          </para>
385	          <para>
386	            The passed-in IRQ will then be requested by a call to
387	            <function>request_irq</function>. If the DRIVER_IRQ_SHARED driver
388	            feature flag is set, a shared (IRQF_SHARED) IRQ handler will be
389	            requested.
390	          </para>
391	          <para>
392	            The IRQ handler function must be provided as the mandatory irq_handler
393	            driver operation. It will get passed directly to
394	            <function>request_irq</function> and thus has the same prototype as all
395	            IRQ handlers. It will get called with a pointer to the DRM device as the
396	            second argument.
397	          </para>
398	          <para>
399	            Finally the function calls the optional
400	            <methodname>irq_postinstall</methodname> driver operation. The operation
401	            usually enables interrupts (excluding the vblank interrupt, which is
402	            enabled separately), but drivers may choose to enable/disable interrupts
403	            at a different time.
404	          </para>
405	          <para>
406	            <function>drm_irq_uninstall</function> is similarly used to uninstall an
407	            IRQ handler. It starts by waking up all processes waiting on a vblank
408	            interrupt to make sure they don't hang, and then calls the optional
409	            <methodname>irq_uninstall</methodname> driver operation. The operation
410	            must disable all hardware interrupts. Finally the function frees the IRQ
411	            by calling <function>free_irq</function>.
412	          </para>
413	        </sect4>
414	        <sect4>
415	          <title>Manual IRQ Registration</title>
416	          <para>
417	            Drivers that require multiple interrupt handlers can't use the managed
418	            IRQ registration functions. In that case IRQs must be registered and
419	            unregistered manually (usually with the <function>request_irq</function>
420	            and <function>free_irq</function> functions, or their devm_* equivalent).
421	          </para>
422	          <para>
423	            When manually registering IRQs, drivers must not set the DRIVER_HAVE_IRQ
424	            driver feature flag, and must not provide the
425		    <methodname>irq_handler</methodname> driver operation. They must set the
426		    <structname>drm_device</structname> <structfield>irq_enabled</structfield>
427		    field to 1 upon registration of the IRQs, and clear it to 0 after
428		    unregistering the IRQs.
429	          </para>
430	        </sect4>
431	      </sect3>
432	      <sect3>
433	        <title>Memory Manager Initialization</title>
434	        <para>
435	          Every DRM driver requires a memory manager which must be initialized at
436	          load time. DRM currently contains two memory managers, the Translation
437	          Table Manager (TTM) and the Graphics Execution Manager (GEM).
438	          This document describes the use of the GEM memory manager only. See
439	          <xref linkend="drm-memory-management"/> for details.
440	        </para>
441	      </sect3>
442	      <sect3>
443	        <title>Miscellaneous Device Configuration</title>
444	        <para>
445	          Another task that may be necessary for PCI devices during configuration
446	          is mapping the video BIOS. On many devices, the VBIOS describes device
447	          configuration, LCD panel timings (if any), and contains flags indicating
448	          device state. Mapping the BIOS can be done using the pci_map_rom() call,
449	          a convenience function that takes care of mapping the actual ROM,
450	          whether it has been shadowed into memory (typically at address 0xc0000)
451	          or exists on the PCI device in the ROM BAR. Note that after the ROM has
452	          been mapped and any necessary information has been extracted, it should
453	          be unmapped; on many devices, the ROM address decoder is shared with
454	          other BARs, so leaving it mapped could cause undesired behaviour like
455	          hangs or memory corruption.
456	  <!--!Fdrivers/pci/rom.c pci_map_rom-->
457	        </para>
458	      </sect3>
459	    </sect2>
460	  </sect1>
461	
462	  <!-- Internals: memory management -->
463	
464	  <sect1 id="drm-memory-management">
465	    <title>Memory management</title>
466	    <para>
467	      Modern Linux systems require large amount of graphics memory to store
468	      frame buffers, textures, vertices and other graphics-related data. Given
469	      the very dynamic nature of many of that data, managing graphics memory
470	      efficiently is thus crucial for the graphics stack and plays a central
471	      role in the DRM infrastructure.
472	    </para>
473	    <para>
474	      The DRM core includes two memory managers, namely Translation Table Maps
475	      (TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory
476	      manager to be developed and tried to be a one-size-fits-them all
477	      solution. It provides a single userspace API to accommodate the need of
478	      all hardware, supporting both Unified Memory Architecture (UMA) devices
479	      and devices with dedicated video RAM (i.e. most discrete video cards).
480	      This resulted in a large, complex piece of code that turned out to be
481	      hard to use for driver development.
482	    </para>
483	    <para>
484	      GEM started as an Intel-sponsored project in reaction to TTM's
485	      complexity. Its design philosophy is completely different: instead of
486	      providing a solution to every graphics memory-related problems, GEM
487	      identified common code between drivers and created a support library to
488	      share it. GEM has simpler initialization and execution requirements than
489	      TTM, but has no video RAM management capabilities and is thus limited to
490	      UMA devices.
491	    </para>
492	    <sect2>
493	      <title>The Translation Table Manager (TTM)</title>
494	      <para>
495	        TTM design background and information belongs here.
496	      </para>
497	      <sect3>
498	        <title>TTM initialization</title>
499	        <warning><para>This section is outdated.</para></warning>
500	        <para>
501	          Drivers wishing to support TTM must fill out a drm_bo_driver
502	          structure. The structure contains several fields with function
503	          pointers for initializing the TTM, allocating and freeing memory,
504	          waiting for command completion and fence synchronization, and memory
505	          migration. See the radeon_ttm.c file for an example of usage.
506	        </para>
507	        <para>
508	          The ttm_global_reference structure is made up of several fields:
509	        </para>
510	        <programlisting>
511	          struct ttm_global_reference {
512	                  enum ttm_global_types global_type;
513	                  size_t size;
514	                  void *object;
515	                  int (*init) (struct ttm_global_reference *);
516	                  void (*release) (struct ttm_global_reference *);
517	          };
518	        </programlisting>
519	        <para>
520	          There should be one global reference structure for your memory
521	          manager as a whole, and there will be others for each object
522	          created by the memory manager at runtime.  Your global TTM should
523	          have a type of TTM_GLOBAL_TTM_MEM.  The size field for the global
524	          object should be sizeof(struct ttm_mem_global), and the init and
525	          release hooks should point at your driver-specific init and
526	          release routines, which probably eventually call
527	          ttm_mem_global_init and ttm_mem_global_release, respectively.
528	        </para>
529	        <para>
530	          Once your global TTM accounting structure is set up and initialized
531	          by calling ttm_global_item_ref() on it,
532	          you need to create a buffer object TTM to
533	          provide a pool for buffer object allocation by clients and the
534	          kernel itself.  The type of this object should be TTM_GLOBAL_TTM_BO,
535	          and its size should be sizeof(struct ttm_bo_global).  Again,
536	          driver-specific init and release functions may be provided,
537	          likely eventually calling ttm_bo_global_init() and
538	          ttm_bo_global_release(), respectively.  Also, like the previous
539	          object, ttm_global_item_ref() is used to create an initial reference
540	          count for the TTM, which will call your initialization function.
541	        </para>
542	      </sect3>
543	    </sect2>
544	    <sect2 id="drm-gem">
545	      <title>The Graphics Execution Manager (GEM)</title>
546	      <para>
547	        The GEM design approach has resulted in a memory manager that doesn't
548	        provide full coverage of all (or even all common) use cases in its
549	        userspace or kernel API. GEM exposes a set of standard memory-related
550	        operations to userspace and a set of helper functions to drivers, and let
551	        drivers implement hardware-specific operations with their own private API.
552	      </para>
553	      <para>
554	        The GEM userspace API is described in the
555	        <ulink url="http://lwn.net/Articles/283798/"><citetitle>GEM - the Graphics
556	        Execution Manager</citetitle></ulink> article on LWN. While slightly
557	        outdated, the document provides a good overview of the GEM API principles.
558	        Buffer allocation and read and write operations, described as part of the
559	        common GEM API, are currently implemented using driver-specific ioctls.
560	      </para>
561	      <para>
562	        GEM is data-agnostic. It manages abstract buffer objects without knowing
563	        what individual buffers contain. APIs that require knowledge of buffer
564	        contents or purpose, such as buffer allocation or synchronization
565	        primitives, are thus outside of the scope of GEM and must be implemented
566	        using driver-specific ioctls.
567	      </para>
568	      <para>
569	        On a fundamental level, GEM involves several operations:
570	        <itemizedlist>
571	          <listitem>Memory allocation and freeing</listitem>
572	          <listitem>Command execution</listitem>
573	          <listitem>Aperture management at command execution time</listitem>
574	        </itemizedlist>
575	        Buffer object allocation is relatively straightforward and largely
576	        provided by Linux's shmem layer, which provides memory to back each
577	        object.
578	      </para>
579	      <para>
580	        Device-specific operations, such as command execution, pinning, buffer
581	        read &amp; write, mapping, and domain ownership transfers are left to
582	        driver-specific ioctls.
583	      </para>
584	      <sect3>
585	        <title>GEM Initialization</title>
586	        <para>
587	          Drivers that use GEM must set the DRIVER_GEM bit in the struct
588	          <structname>drm_driver</structname>
589	          <structfield>driver_features</structfield> field. The DRM core will
590	          then automatically initialize the GEM core before calling the
591	          <methodname>load</methodname> operation. Behind the scene, this will
592	          create a DRM Memory Manager object which provides an address space
593	          pool for object allocation.
594	        </para>
595	        <para>
596	          In a KMS configuration, drivers need to allocate and initialize a
597	          command ring buffer following core GEM initialization if required by
598	          the hardware. UMA devices usually have what is called a "stolen"
599	          memory region, which provides space for the initial framebuffer and
600	          large, contiguous memory regions required by the device. This space is
601	          typically not managed by GEM, and must be initialized separately into
602	          its own DRM MM object.
603	        </para>
604	      </sect3>
605	      <sect3>
606	        <title>GEM Objects Creation</title>
607	        <para>
608	          GEM splits creation of GEM objects and allocation of the memory that
609	          backs them in two distinct operations.
610	        </para>
611	        <para>
612	          GEM objects are represented by an instance of struct
613	          <structname>drm_gem_object</structname>. Drivers usually need to extend
614	          GEM objects with private information and thus create a driver-specific
615	          GEM object structure type that embeds an instance of struct
616	          <structname>drm_gem_object</structname>.
617	        </para>
618	        <para>
619	          To create a GEM object, a driver allocates memory for an instance of its
620	          specific GEM object type and initializes the embedded struct
621	          <structname>drm_gem_object</structname> with a call to
622	          <function>drm_gem_object_init</function>. The function takes a pointer to
623	          the DRM device, a pointer to the GEM object and the buffer object size
624	          in bytes.
625	        </para>
626	        <para>
627	          GEM uses shmem to allocate anonymous pageable memory.
628	          <function>drm_gem_object_init</function> will create an shmfs file of
629	          the requested size and store it into the struct
630	          <structname>drm_gem_object</structname> <structfield>filp</structfield>
631	          field. The memory is used as either main storage for the object when the
632	          graphics hardware uses system memory directly or as a backing store
633	          otherwise.
634	        </para>
635	        <para>
636	          Drivers are responsible for the actual physical pages allocation by
637	          calling <function>shmem_read_mapping_page_gfp</function> for each page.
638	          Note that they can decide to allocate pages when initializing the GEM
639	          object, or to delay allocation until the memory is needed (for instance
640	          when a page fault occurs as a result of a userspace memory access or
641	          when the driver needs to start a DMA transfer involving the memory).
642	        </para>
643	        <para>
644	          Anonymous pageable memory allocation is not always desired, for instance
645	          when the hardware requires physically contiguous system memory as is
646	          often the case in embedded devices. Drivers can create GEM objects with
647	          no shmfs backing (called private GEM objects) by initializing them with
648	          a call to <function>drm_gem_private_object_init</function> instead of
649	          <function>drm_gem_object_init</function>. Storage for private GEM
650	          objects must be managed by drivers.
651	        </para>
652	        <para>
653	          Drivers that do not need to extend GEM objects with private information
654	          can call the <function>drm_gem_object_alloc</function> function to
655	          allocate and initialize a struct <structname>drm_gem_object</structname>
656	          instance. The GEM core will call the optional driver
657	          <methodname>gem_init_object</methodname> operation after initializing
658	          the GEM object with <function>drm_gem_object_init</function>.
659	          <synopsis>int (*gem_init_object) (struct drm_gem_object *obj);</synopsis>
660	        </para>
661	        <para>
662	          No alloc-and-init function exists for private GEM objects.
663	        </para>
664	      </sect3>
665	      <sect3>
666	        <title>GEM Objects Lifetime</title>
667	        <para>
668	          All GEM objects are reference-counted by the GEM core. References can be
669	          acquired and release by <function>calling drm_gem_object_reference</function>
670	          and <function>drm_gem_object_unreference</function> respectively. The
671	          caller must hold the <structname>drm_device</structname>
672	          <structfield>struct_mutex</structfield> lock. As a convenience, GEM
673	          provides the <function>drm_gem_object_reference_unlocked</function> and
674	          <function>drm_gem_object_unreference_unlocked</function> functions that
675	          can be called without holding the lock.
676	        </para>
677	        <para>
678	          When the last reference to a GEM object is released the GEM core calls
679	          the <structname>drm_driver</structname>
680	          <methodname>gem_free_object</methodname> operation. That operation is
681	          mandatory for GEM-enabled drivers and must free the GEM object and all
682	          associated resources.
683	        </para>
684	        <para>
685	          <synopsis>void (*gem_free_object) (struct drm_gem_object *obj);</synopsis>
686	          Drivers are responsible for freeing all GEM object resources, including
687	          the resources created by the GEM core. If an mmap offset has been
688	          created for the object (in which case
689	          <structname>drm_gem_object</structname>::<structfield>map_list</structfield>::<structfield>map</structfield>
690	          is not NULL) it must be freed by a call to
691	          <function>drm_gem_free_mmap_offset</function>. The shmfs backing store
692	          must be released by calling <function>drm_gem_object_release</function>
693	          (that function can safely be called if no shmfs backing store has been
694	          created).
695	        </para>
696	      </sect3>
697	      <sect3>
698	        <title>GEM Objects Naming</title>
699	        <para>
700	          Communication between userspace and the kernel refers to GEM objects
701	          using local handles, global names or, more recently, file descriptors.
702	          All of those are 32-bit integer values; the usual Linux kernel limits
703	          apply to the file descriptors.
704	        </para>
705	        <para>
706	          GEM handles are local to a DRM file. Applications get a handle to a GEM
707	          object through a driver-specific ioctl, and can use that handle to refer
708	          to the GEM object in other standard or driver-specific ioctls. Closing a
709	          DRM file handle frees all its GEM handles and dereferences the
710	          associated GEM objects.
711	        </para>
712	        <para>
713	          To create a handle for a GEM object drivers call
714	          <function>drm_gem_handle_create</function>. The function takes a pointer
715	          to the DRM file and the GEM object and returns a locally unique handle.
716	          When the handle is no longer needed drivers delete it with a call to
717	          <function>drm_gem_handle_delete</function>. Finally the GEM object
718	          associated with a handle can be retrieved by a call to
719	          <function>drm_gem_object_lookup</function>.
720	        </para>
721	        <para>
722	          Handles don't take ownership of GEM objects, they only take a reference
723	          to the object that will be dropped when the handle is destroyed. To
724	          avoid leaking GEM objects, drivers must make sure they drop the
725	          reference(s) they own (such as the initial reference taken at object
726	          creation time) as appropriate, without any special consideration for the
727	          handle. For example, in the particular case of combined GEM object and
728	          handle creation in the implementation of the
729	          <methodname>dumb_create</methodname> operation, drivers must drop the
730	          initial reference to the GEM object before returning the handle.
731	        </para>
732	        <para>
733	          GEM names are similar in purpose to handles but are not local to DRM
734	          files. They can be passed between processes to reference a GEM object
735	          globally. Names can't be used directly to refer to objects in the DRM
736	          API, applications must convert handles to names and names to handles
737	          using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls
738	          respectively. The conversion is handled by the DRM core without any
739	          driver-specific support.
740	        </para>
741	        <para>
742	          GEM also supports buffer sharing with dma-buf file descriptors through
743	          PRIME. GEM-based drivers must use the provided helpers functions to
744	          implement the exporting and importing correctly. See <xref linkend="drm-prime-support" />.
745	          Since sharing file descriptors is inherently more secure than the
746	          easily guessable and global GEM names it is the preferred buffer
747	          sharing mechanism. Sharing buffers through GEM names is only supported
748	          for legacy userspace. Furthermore PRIME also allows cross-device
749	          buffer sharing since it is based on dma-bufs.
750	        </para>
751	      </sect3>
752	      <sect3 id="drm-gem-objects-mapping">
753	        <title>GEM Objects Mapping</title>
754	        <para>
755	          Because mapping operations are fairly heavyweight GEM favours
756	          read/write-like access to buffers, implemented through driver-specific
757	          ioctls, over mapping buffers to userspace. However, when random access
758	          to the buffer is needed (to perform software rendering for instance),
759	          direct access to the object can be more efficient.
760	        </para>
761	        <para>
762	          The mmap system call can't be used directly to map GEM objects, as they
763	          don't have their own file handle. Two alternative methods currently
764	          co-exist to map GEM objects to userspace. The first method uses a
765	          driver-specific ioctl to perform the mapping operation, calling
766	          <function>do_mmap</function> under the hood. This is often considered
767	          dubious, seems to be discouraged for new GEM-enabled drivers, and will
768	          thus not be described here.
769	        </para>
770	        <para>
771	          The second method uses the mmap system call on the DRM file handle.
772	          <synopsis>void *mmap(void *addr, size_t length, int prot, int flags, int fd,
773	             off_t offset);</synopsis>
774	          DRM identifies the GEM object to be mapped by a fake offset passed
775	          through the mmap offset argument. Prior to being mapped, a GEM object
776	          must thus be associated with a fake offset. To do so, drivers must call
777	          <function>drm_gem_create_mmap_offset</function> on the object. The
778	          function allocates a fake offset range from a pool and stores the
779	          offset divided by PAGE_SIZE in
780	          <literal>obj-&gt;map_list.hash.key</literal>. Care must be taken not to
781	          call <function>drm_gem_create_mmap_offset</function> if a fake offset
782	          has already been allocated for the object. This can be tested by
783	          <literal>obj-&gt;map_list.map</literal> being non-NULL.
784	        </para>
785	        <para>
786	          Once allocated, the fake offset value
787	          (<literal>obj-&gt;map_list.hash.key &lt;&lt; PAGE_SHIFT</literal>)
788	          must be passed to the application in a driver-specific way and can then
789	          be used as the mmap offset argument.
790	        </para>
791	        <para>
792	          The GEM core provides a helper method <function>drm_gem_mmap</function>
793	          to handle object mapping. The method can be set directly as the mmap
794	          file operation handler. It will look up the GEM object based on the
795	          offset value and set the VMA operations to the
796	          <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
797	          field. Note that <function>drm_gem_mmap</function> doesn't map memory to
798	          userspace, but relies on the driver-provided fault handler to map pages
799	          individually.
800	        </para>
801	        <para>
802	          To use <function>drm_gem_mmap</function>, drivers must fill the struct
803	          <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
804	          field with a pointer to VM operations.
805	        </para>
806	        <para>
807	          <synopsis>struct vm_operations_struct *gem_vm_ops
808	
809	  struct vm_operations_struct {
810	          void (*open)(struct vm_area_struct * area);
811	          void (*close)(struct vm_area_struct * area);
812	          int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf);
813	  };</synopsis>
814	        </para>
815	        <para>
816	          The <methodname>open</methodname> and <methodname>close</methodname>
817	          operations must update the GEM object reference count. Drivers can use
818	          the <function>drm_gem_vm_open</function> and
819	          <function>drm_gem_vm_close</function> helper functions directly as open
820	          and close handlers.
821	        </para>
822	        <para>
823	          The fault operation handler is responsible for mapping individual pages
824	          to userspace when a page fault occurs. Depending on the memory
825	          allocation scheme, drivers can allocate pages at fault time, or can
826	          decide to allocate memory for the GEM object at the time the object is
827	          created.
828	        </para>
829	        <para>
830	          Drivers that want to map the GEM object upfront instead of handling page
831	          faults can implement their own mmap file operation handler.
832	        </para>
833	      </sect3>
834	      <sect3>
835	        <title>Memory Coherency</title>
836	        <para>
837	          When mapped to the device or used in a command buffer, backing pages
838	          for an object are flushed to memory and marked write combined so as to
839	          be coherent with the GPU. Likewise, if the CPU accesses an object
840	          after the GPU has finished rendering to the object, then the object
841	          must be made coherent with the CPU's view of memory, usually involving
842	          GPU cache flushing of various kinds. This core CPU&lt;-&gt;GPU
843	          coherency management is provided by a device-specific ioctl, which
844	          evaluates an object's current domain and performs any necessary
845	          flushing or synchronization to put the object into the desired
846	          coherency domain (note that the object may be busy, i.e. an active
847	          render target; in that case, setting the domain blocks the client and
848	          waits for rendering to complete before performing any necessary
849	          flushing operations).
850	        </para>
851	      </sect3>
852	      <sect3>
853	        <title>Command Execution</title>
854	        <para>
855	          Perhaps the most important GEM function for GPU devices is providing a
856	          command execution interface to clients. Client programs construct
857	          command buffers containing references to previously allocated memory
858	          objects, and then submit them to GEM. At that point, GEM takes care to
859	          bind all the objects into the GTT, execute the buffer, and provide
860	          necessary synchronization between clients accessing the same buffers.
861	          This often involves evicting some objects from the GTT and re-binding
862	          others (a fairly expensive operation), and providing relocation
863	          support which hides fixed GTT offsets from clients. Clients must take
864	          care not to submit command buffers that reference more objects than
865	          can fit in the GTT; otherwise, GEM will reject them and no rendering
866	          will occur. Similarly, if several objects in the buffer require fence
867	          registers to be allocated for correct rendering (e.g. 2D blits on
868	          pre-965 chips), care must be taken not to require more fence registers
869	          than are available to the client. Such resource management should be
870	          abstracted from the client in libdrm.
871	        </para>
872	      </sect3>
873	      <sect3>
874	        <title>GEM Function Reference</title>
875	!Edrivers/gpu/drm/drm_gem.c
876	      </sect3>
877	    </sect2>
878	    <sect2>
879	      <title>VMA Offset Manager</title>
880	!Pdrivers/gpu/drm/drm_vma_manager.c vma offset manager
881	!Edrivers/gpu/drm/drm_vma_manager.c
882	!Iinclude/drm/drm_vma_manager.h
883	    </sect2>
884	    <sect2 id="drm-prime-support">
885	      <title>PRIME Buffer Sharing</title>
886	      <para>
887	        PRIME is the cross device buffer sharing framework in drm, originally
888	        created for the OPTIMUS range of multi-gpu platforms. To userspace
889	        PRIME buffers are dma-buf based file descriptors.
890	      </para>
891	      <sect3>
892	        <title>Overview and Driver Interface</title>
893	        <para>
894	          Similar to GEM global names, PRIME file descriptors are
895	          also used to share buffer objects across processes. They offer
896	          additional security: as file descriptors must be explicitly sent over
897	          UNIX domain sockets to be shared between applications, they can't be
898	          guessed like the globally unique GEM names.
899	        </para>
900	        <para>
901	          Drivers that support the PRIME
902	          API must set the DRIVER_PRIME bit in the struct
903	          <structname>drm_driver</structname>
904	          <structfield>driver_features</structfield> field, and implement the
905	          <methodname>prime_handle_to_fd</methodname> and
906	          <methodname>prime_fd_to_handle</methodname> operations.
907	        </para>
908	        <para>
909	          <synopsis>int (*prime_handle_to_fd)(struct drm_device *dev,
910	                          struct drm_file *file_priv, uint32_t handle,
911	                          uint32_t flags, int *prime_fd);
912	int (*prime_fd_to_handle)(struct drm_device *dev,
913	                          struct drm_file *file_priv, int prime_fd,
914	                          uint32_t *handle);</synopsis>
915	            Those two operations convert a handle to a PRIME file descriptor and
916	            vice versa. Drivers must use the kernel dma-buf buffer sharing framework
917	            to manage the PRIME file descriptors. Similar to the mode setting
918	            API PRIME is agnostic to the underlying buffer object manager, as
919	            long as handles are 32bit unsigned integers.
920	          </para>
921	          <para>
922	            While non-GEM drivers must implement the operations themselves, GEM
923	            drivers must use the <function>drm_gem_prime_handle_to_fd</function>
924	            and <function>drm_gem_prime_fd_to_handle</function> helper functions.
925	            Those helpers rely on the driver
926	            <methodname>gem_prime_export</methodname> and
927	            <methodname>gem_prime_import</methodname> operations to create a dma-buf
928	            instance from a GEM object (dma-buf exporter role) and to create a GEM
929	            object from a dma-buf instance (dma-buf importer role).
930	          </para>
931	          <para>
932	            <synopsis>struct dma_buf * (*gem_prime_export)(struct drm_device *dev,
933	                             struct drm_gem_object *obj,
934	                             int flags);
935	struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev,
936	                                            struct dma_buf *dma_buf);</synopsis>
937	            These two operations are mandatory for GEM drivers that support
938	            PRIME.
939	          </para>
940	        </sect3>
941	      <sect3>
942	        <title>PRIME Helper Functions</title>
943	!Pdrivers/gpu/drm/drm_prime.c PRIME Helpers
944	      </sect3>
945	    </sect2>
946	    <sect2>
947	      <title>PRIME Function References</title>
948	!Edrivers/gpu/drm/drm_prime.c
949	    </sect2>
950	    <sect2>
951	      <title>DRM MM Range Allocator</title>
952	      <sect3>
953	        <title>Overview</title>
954	!Pdrivers/gpu/drm/drm_mm.c Overview
955	      </sect3>
956	      <sect3>
957	        <title>LRU Scan/Eviction Support</title>
958	!Pdrivers/gpu/drm/drm_mm.c lru scan roaster
959	      </sect3>
960	      </sect2>
961	    <sect2>
962	      <title>DRM MM Range Allocator Function References</title>
963	!Edrivers/gpu/drm/drm_mm.c
964	!Iinclude/drm/drm_mm.h
965	    </sect2>
966	    <sect2>
967	      <title>CMA Helper Functions Reference</title>
968	!Pdrivers/gpu/drm/drm_gem_cma_helper.c cma helpers
969	!Edrivers/gpu/drm/drm_gem_cma_helper.c
970	!Iinclude/drm/drm_gem_cma_helper.h
971	    </sect2>
972	  </sect1>
973	
974	  <!-- Internals: mode setting -->
975	
976	  <sect1 id="drm-mode-setting">
977	    <title>Mode Setting</title>
978	    <para>
979	      Drivers must initialize the mode setting core by calling
980	      <function>drm_mode_config_init</function> on the DRM device. The function
981	      initializes the <structname>drm_device</structname>
982	      <structfield>mode_config</structfield> field and never fails. Once done,
983	      mode configuration must be setup by initializing the following fields.
984	    </para>
985	    <itemizedlist>
986	      <listitem>
987	        <synopsis>int min_width, min_height;
988	int max_width, max_height;</synopsis>
989	        <para>
990		  Minimum and maximum width and height of the frame buffers in pixel
991		  units.
992		</para>
993	      </listitem>
994	      <listitem>
995	        <synopsis>struct drm_mode_config_funcs *funcs;</synopsis>
996		<para>Mode setting functions.</para>
997	      </listitem>
998	    </itemizedlist>
999	    <sect2>
1000	      <title>Display Modes Function Reference</title>
1001	!Iinclude/drm/drm_modes.h
1002	!Edrivers/gpu/drm/drm_modes.c
1003	    </sect2>
1004	    <sect2>
1005	      <title>Atomic Mode Setting Function Reference</title>
1006	!Edrivers/gpu/drm/drm_atomic.c
1007	    </sect2>
1008	    <sect2>
1009	      <title>Frame Buffer Creation</title>
1010	      <synopsis>struct drm_framebuffer *(*fb_create)(struct drm_device *dev,
1011					     struct drm_file *file_priv,
1012					     struct drm_mode_fb_cmd2 *mode_cmd);</synopsis>
1013	      <para>
1014	        Frame buffers are abstract memory objects that provide a source of
1015	        pixels to scanout to a CRTC. Applications explicitly request the
1016	        creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls and
1017	        receive an opaque handle that can be passed to the KMS CRTC control,
1018	        plane configuration and page flip functions.
1019	      </para>
1020	      <para>
1021	        Frame buffers rely on the underneath memory manager for low-level memory
1022	        operations. When creating a frame buffer applications pass a memory
1023	        handle (or a list of memory handles for multi-planar formats) through
1024		the <parameter>drm_mode_fb_cmd2</parameter> argument. For drivers using
1025		GEM as their userspace buffer management interface this would be a GEM
1026		handle.  Drivers are however free to use their own backing storage object
1027		handles, e.g. vmwgfx directly exposes special TTM handles to userspace
1028		and so expects TTM handles in the create ioctl and not GEM handles.
1029	      </para>
1030	      <para>
1031	        Drivers must first validate the requested frame buffer parameters passed
1032	        through the mode_cmd argument. In particular this is where invalid
1033	        sizes, pixel formats or pitches can be caught.
1034	      </para>
1035	      <para>
1036	        If the parameters are deemed valid, drivers then create, initialize and
1037	        return an instance of struct <structname>drm_framebuffer</structname>.
1038	        If desired the instance can be embedded in a larger driver-specific
1039		structure. Drivers must fill its <structfield>width</structfield>,
1040		<structfield>height</structfield>, <structfield>pitches</structfield>,
1041	        <structfield>offsets</structfield>, <structfield>depth</structfield>,
1042	        <structfield>bits_per_pixel</structfield> and
1043	        <structfield>pixel_format</structfield> fields from the values passed
1044	        through the <parameter>drm_mode_fb_cmd2</parameter> argument. They
1045	        should call the <function>drm_helper_mode_fill_fb_struct</function>
1046	        helper function to do so.
1047	      </para>
1048	
1049	      <para>
1050		The initialization of the new framebuffer instance is finalized with a
1051		call to <function>drm_framebuffer_init</function> which takes a pointer
1052		to DRM frame buffer operations (struct
1053		<structname>drm_framebuffer_funcs</structname>). Note that this function
1054		publishes the framebuffer and so from this point on it can be accessed
1055		concurrently from other threads. Hence it must be the last step in the
1056		driver's framebuffer initialization sequence. Frame buffer operations
1057		are
1058	        <itemizedlist>
1059	          <listitem>
1060	            <synopsis>int (*create_handle)(struct drm_framebuffer *fb,
1061			     struct drm_file *file_priv, unsigned int *handle);</synopsis>
1062	            <para>
1063	              Create a handle to the frame buffer underlying memory object. If
1064	              the frame buffer uses a multi-plane format, the handle will
1065	              reference the memory object associated with the first plane.
1066	            </para>
1067	            <para>
1068	              Drivers call <function>drm_gem_handle_create</function> to create
1069	              the handle.
1070	            </para>
1071	          </listitem>
1072	          <listitem>
1073	            <synopsis>void (*destroy)(struct drm_framebuffer *framebuffer);</synopsis>
1074	            <para>
1075	              Destroy the frame buffer object and frees all associated
1076	              resources. Drivers must call
1077	              <function>drm_framebuffer_cleanup</function> to free resources
1078	              allocated by the DRM core for the frame buffer object, and must
1079	              make sure to unreference all memory objects associated with the
1080	              frame buffer. Handles created by the
1081	              <methodname>create_handle</methodname> operation are released by
1082	              the DRM core.
1083	            </para>
1084	          </listitem>
1085	          <listitem>
1086	            <synopsis>int (*dirty)(struct drm_framebuffer *framebuffer,
1087		     struct drm_file *file_priv, unsigned flags, unsigned color,
1088		     struct drm_clip_rect *clips, unsigned num_clips);</synopsis>
1089	            <para>
1090	              This optional operation notifies the driver that a region of the
1091	              frame buffer has changed in response to a DRM_IOCTL_MODE_DIRTYFB
1092	              ioctl call.
1093	            </para>
1094	          </listitem>
1095	        </itemizedlist>
1096	      </para>
1097	      <para>
1098		The lifetime of a drm framebuffer is controlled with a reference count,
1099		drivers can grab additional references with
1100		<function>drm_framebuffer_reference</function>and drop them
1101		again with <function>drm_framebuffer_unreference</function>. For
1102		driver-private framebuffers for which the last reference is never
1103		dropped (e.g. for the fbdev framebuffer when the struct
1104		<structname>drm_framebuffer</structname> is embedded into the fbdev
1105		helper struct) drivers can manually clean up a framebuffer at module
1106		unload time with
1107		<function>drm_framebuffer_unregister_private</function>.
1108	      </para>
1109	    </sect2>
1110	    <sect2>
1111	      <title>Dumb Buffer Objects</title>
1112	      <para>
1113		The KMS API doesn't standardize backing storage object creation and
1114		leaves it to driver-specific ioctls. Furthermore actually creating a
1115		buffer object even for GEM-based drivers is done through a
1116		driver-specific ioctl - GEM only has a common userspace interface for
1117		sharing and destroying objects. While not an issue for full-fledged
1118		graphics stacks that include device-specific userspace components (in
1119		libdrm for instance), this limit makes DRM-based early boot graphics
1120		unnecessarily complex.
1121	      </para>
1122	      <para>
1123	        Dumb objects partly alleviate the problem by providing a standard
1124	        API to create dumb buffers suitable for scanout, which can then be used
1125	        to create KMS frame buffers.
1126	      </para>
1127	      <para>
1128	        To support dumb objects drivers must implement the
1129	        <methodname>dumb_create</methodname>,
1130	        <methodname>dumb_destroy</methodname> and
1131	        <methodname>dumb_map_offset</methodname> operations.
1132	      </para>
1133	      <itemizedlist>
1134	        <listitem>
1135	          <synopsis>int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev,
1136	                   struct drm_mode_create_dumb *args);</synopsis>
1137	          <para>
1138	            The <methodname>dumb_create</methodname> operation creates a driver
1139		    object (GEM or TTM handle) suitable for scanout based on the
1140		    width, height and depth from the struct
1141		    <structname>drm_mode_create_dumb</structname> argument. It fills the
1142		    argument's <structfield>handle</structfield>,
1143		    <structfield>pitch</structfield> and <structfield>size</structfield>
1144		    fields with a handle for the newly created object and its line
1145	            pitch and size in bytes.
1146	          </para>
1147	        </listitem>
1148	        <listitem>
1149	          <synopsis>int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev,
1150	                    uint32_t handle);</synopsis>
1151	          <para>
1152	            The <methodname>dumb_destroy</methodname> operation destroys a dumb
1153	            object created by <methodname>dumb_create</methodname>.
1154	          </para>
1155	        </listitem>
1156	        <listitem>
1157	          <synopsis>int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev,
1158	                       uint32_t handle, uint64_t *offset);</synopsis>
1159	          <para>
1160	            The <methodname>dumb_map_offset</methodname> operation associates an
1161	            mmap fake offset with the object given by the handle and returns
1162	            it. Drivers must use the
1163	            <function>drm_gem_create_mmap_offset</function> function to
1164	            associate the fake offset as described in
1165	            <xref linkend="drm-gem-objects-mapping"/>.
1166	          </para>
1167	        </listitem>
1168	      </itemizedlist>
1169	      <para>
1170	        Note that dumb objects may not be used for gpu acceleration, as has been
1171		attempted on some ARM embedded platforms. Such drivers really must have
1172		a hardware-specific ioctl to allocate suitable buffer objects.
1173	      </para>
1174	    </sect2>
1175	    <sect2>
1176	      <title>Output Polling</title>
1177	      <synopsis>void (*output_poll_changed)(struct drm_device *dev);</synopsis>
1178	      <para>
1179	        This operation notifies the driver that the status of one or more
1180	        connectors has changed. Drivers that use the fb helper can just call the
1181	        <function>drm_fb_helper_hotplug_event</function> function to handle this
1182	        operation.
1183	      </para>
1184	    </sect2>
1185	    <sect2>
1186	      <title>Locking</title>
1187	      <para>
1188	        Beside some lookup structures with their own locking (which is hidden
1189		behind the interface functions) most of the modeset state is protected
1190		by the <code>dev-&lt;mode_config.lock</code> mutex and additionally
1191		per-crtc locks to allow cursor updates, pageflips and similar operations
1192		to occur concurrently with background tasks like output detection.
1193		Operations which cross domains like a full modeset always grab all
1194		locks. Drivers there need to protect resources shared between crtcs with
1195		additional locking. They also need to be careful to always grab the
1196		relevant crtc locks if a modset functions touches crtc state, e.g. for
1197		load detection (which does only grab the <code>mode_config.lock</code>
1198		to allow concurrent screen updates on live crtcs).
1199	      </para>
1200	    </sect2>
1201	  </sect1>
1202	
1203	  <!-- Internals: kms initialization and cleanup -->
1204	
1205	  <sect1 id="drm-kms-init">
1206	    <title>KMS Initialization and Cleanup</title>
1207	    <para>
1208	      A KMS device is abstracted and exposed as a set of planes, CRTCs, encoders
1209	      and connectors. KMS drivers must thus create and initialize all those
1210	      objects at load time after initializing mode setting.
1211	    </para>
1212	    <sect2>
1213	      <title>CRTCs (struct <structname>drm_crtc</structname>)</title>
1214	      <para>
1215	        A CRTC is an abstraction representing a part of the chip that contains a
1216		pointer to a scanout buffer. Therefore, the number of CRTCs available
1217		determines how many independent scanout buffers can be active at any
1218		given time. The CRTC structure contains several fields to support this:
1219		a pointer to some video memory (abstracted as a frame buffer object), a
1220		display mode, and an (x, y) offset into the video memory to support
1221		panning or configurations where one piece of video memory spans multiple
1222		CRTCs.
1223	      </para>
1224	      <sect3>
1225	        <title>CRTC Initialization</title>
1226	        <para>
1227	          A KMS device must create and register at least one struct
1228	          <structname>drm_crtc</structname> instance. The instance is allocated
1229	          and zeroed by the driver, possibly as part of a larger structure, and
1230	          registered with a call to <function>drm_crtc_init</function> with a
1231	          pointer to CRTC functions.
1232	        </para>
1233	      </sect3>
1234	      <sect3 id="drm-kms-crtcops">
1235	        <title>CRTC Operations</title>
1236	        <sect4>
1237	          <title>Set Configuration</title>
1238	          <synopsis>int (*set_config)(struct drm_mode_set *set);</synopsis>
1239	          <para>
1240	            Apply a new CRTC configuration to the device. The configuration
1241	            specifies a CRTC, a frame buffer to scan out from, a (x,y) position in
1242	            the frame buffer, a display mode and an array of connectors to drive
1243	            with the CRTC if possible.
1244	          </para>
1245	          <para>
1246	            If the frame buffer specified in the configuration is NULL, the driver
1247	            must detach all encoders connected to the CRTC and all connectors
1248	            attached to those encoders and disable them.
1249	          </para>
1250	          <para>
1251	            This operation is called with the mode config lock held.
1252	          </para>
1253	          <note><para>
1254		    Note that the drm core has no notion of restoring the mode setting
1255		    state after resume, since all resume handling is in the full
1256		    responsibility of the driver. The common mode setting helper library
1257		    though provides a helper which can be used for this:
1258		    <function>drm_helper_resume_force_mode</function>.
1259	          </para></note>
1260	        </sect4>
1261	        <sect4>
1262	          <title>Page Flipping</title>
1263	          <synopsis>int (*page_flip)(struct drm_crtc *crtc, struct drm_framebuffer *fb,
1264	                   struct drm_pending_vblank_event *event);</synopsis>
1265	          <para>
1266	            Schedule a page flip to the given frame buffer for the CRTC. This
1267	            operation is called with the mode config mutex held.
1268	          </para>
1269	          <para>
1270	            Page flipping is a synchronization mechanism that replaces the frame
1271	            buffer being scanned out by the CRTC with a new frame buffer during
1272	            vertical blanking, avoiding tearing. When an application requests a page
1273	            flip the DRM core verifies that the new frame buffer is large enough to
1274	            be scanned out by  the CRTC in the currently configured mode and then
1275	            calls the CRTC <methodname>page_flip</methodname> operation with a
1276	            pointer to the new frame buffer.
1277	          </para>
1278	          <para>
1279	            The <methodname>page_flip</methodname> operation schedules a page flip.
1280	            Once any pending rendering targeting the new frame buffer has
1281	            completed, the CRTC will be reprogrammed to display that frame buffer
1282	            after the next vertical refresh. The operation must return immediately
1283	            without waiting for rendering or page flip to complete and must block
1284	            any new rendering to the frame buffer until the page flip completes.
1285	          </para>
1286	          <para>
1287	            If a page flip can be successfully scheduled the driver must set the
1288	            <code>drm_crtc-&lt;fb</code> field to the new framebuffer pointed to
1289	            by <code>fb</code>. This is important so that the reference counting
1290	            on framebuffers stays balanced.
1291	          </para>
1292	          <para>
1293	            If a page flip is already pending, the
1294	            <methodname>page_flip</methodname> operation must return
1295	            -<errorname>EBUSY</errorname>.
1296	          </para>
1297	          <para>
1298	            To synchronize page flip to vertical blanking the driver will likely
1299	            need to enable vertical blanking interrupts. It should call
1300	            <function>drm_vblank_get</function> for that purpose, and call
1301	            <function>drm_vblank_put</function> after the page flip completes.
1302	          </para>
1303	          <para>
1304	            If the application has requested to be notified when page flip completes
1305	            the <methodname>page_flip</methodname> operation will be called with a
1306	            non-NULL <parameter>event</parameter> argument pointing to a
1307	            <structname>drm_pending_vblank_event</structname> instance. Upon page
1308	            flip completion the driver must call <methodname>drm_send_vblank_event</methodname>
1309	            to fill in the event and send to wake up any waiting processes.
1310	            This can be performed with
1311	            <programlisting><![CDATA[
1312	            spin_lock_irqsave(&dev->event_lock, flags);
1313	            ...
1314	            drm_send_vblank_event(dev, pipe, event);
1315	            spin_unlock_irqrestore(&dev->event_lock, flags);
1316	            ]]></programlisting>
1317	          </para>
1318	          <note><para>
1319	            FIXME: Could drivers that don't need to wait for rendering to complete
1320	            just add the event to <literal>dev-&gt;vblank_event_list</literal> and
1321	            let the DRM core handle everything, as for "normal" vertical blanking
1322	            events?
1323	          </para></note>
1324	          <para>
1325	            While waiting for the page flip to complete, the
1326	            <literal>event-&gt;base.link</literal> list head can be used freely by
1327	            the driver to store the pending event in a driver-specific list.
1328	          </para>
1329	          <para>
1330	            If the file handle is closed before the event is signaled, drivers must
1331	            take care to destroy the event in their
1332	            <methodname>preclose</methodname> operation (and, if needed, call
1333	            <function>drm_vblank_put</function>).
1334	          </para>
1335	        </sect4>
1336	        <sect4>
1337	          <title>Miscellaneous</title>
1338	          <itemizedlist>
1339	            <listitem>
1340	              <synopsis>void (*set_property)(struct drm_crtc *crtc,
1341	                     struct drm_property *property, uint64_t value);</synopsis>
1342	              <para>
1343	                Set the value of the given CRTC property to
1344	                <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1345	                for more information about properties.
1346	              </para>
1347	            </listitem>
1348	            <listitem>
1349	              <synopsis>void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b,
1350	                        uint32_t start, uint32_t size);</synopsis>
1351	              <para>
1352	                Apply a gamma table to the device. The operation is optional.
1353	              </para>
1354	            </listitem>
1355	            <listitem>
1356	              <synopsis>void (*destroy)(struct drm_crtc *crtc);</synopsis>
1357	              <para>
1358	                Destroy the CRTC when not needed anymore. See
1359	                <xref linkend="drm-kms-init"/>.
1360	              </para>
1361	            </listitem>
1362	          </itemizedlist>
1363	        </sect4>
1364	      </sect3>
1365	    </sect2>
1366	    <sect2>
1367	      <title>Planes (struct <structname>drm_plane</structname>)</title>
1368	      <para>
1369	        A plane represents an image source that can be blended with or overlayed
1370		on top of a CRTC during the scanout process. Planes are associated with
1371		a frame buffer to crop a portion of the image memory (source) and
1372		optionally scale it to a destination size. The result is then blended
1373		with or overlayed on top of a CRTC.
1374	      </para>
1375	      <para>
1376	      The DRM core recognizes three types of planes:
1377	      <itemizedlist>
1378	        <listitem>
1379	        DRM_PLANE_TYPE_PRIMARY represents a "main" plane for a CRTC.  Primary
1380	        planes are the planes operated upon by by CRTC modesetting and flipping
1381	        operations described in <xref linkend="drm-kms-crtcops"/>.
1382	        </listitem>
1383	        <listitem>
1384	        DRM_PLANE_TYPE_CURSOR represents a "cursor" plane for a CRTC.  Cursor
1385	        planes are the planes operated upon by the DRM_IOCTL_MODE_CURSOR and
1386	        DRM_IOCTL_MODE_CURSOR2 ioctls.
1387	        </listitem>
1388	        <listitem>
1389	        DRM_PLANE_TYPE_OVERLAY represents all non-primary, non-cursor planes.
1390	        Some drivers refer to these types of planes as "sprites" internally.
1391	        </listitem>
1392	      </itemizedlist>
1393	      For compatibility with legacy userspace, only overlay planes are made
1394	      available to userspace by default.  Userspace clients may set the
1395	      DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate that
1396	      they wish to receive a universal plane list containing all plane types.
1397	      </para>
1398	      <sect3>
1399	        <title>Plane Initialization</title>
1400	        <para>
1401	          To create a plane, a KMS drivers allocates and
1402	          zeroes an instances of struct <structname>drm_plane</structname>
1403	          (possibly as part of a larger structure) and registers it with a call
1404	          to <function>drm_universal_plane_init</function>. The function takes a bitmask
1405	          of the CRTCs that can be associated with the plane, a pointer to the
1406	          plane functions, a list of format supported formats, and the type of
1407	          plane (primary, cursor, or overlay) being initialized.
1408	        </para>
1409	        <para>
1410	          Cursor and overlay planes are optional.  All drivers should provide
1411	          one primary plane per CRTC (although this requirement may change in
1412	          the future); drivers that do not wish to provide special handling for
1413	          primary planes may make use of the helper functions described in
1414	          <xref linkend="drm-kms-planehelpers"/> to create and register a
1415	          primary plane with standard capabilities.
1416	        </para>
1417	      </sect3>
1418	      <sect3>
1419	        <title>Plane Operations</title>
1420	        <itemizedlist>
1421	          <listitem>
1422	            <synopsis>int (*update_plane)(struct drm_plane *plane, struct drm_crtc *crtc,
1423	                        struct drm_framebuffer *fb, int crtc_x, int crtc_y,
1424	                        unsigned int crtc_w, unsigned int crtc_h,
1425	                        uint32_t src_x, uint32_t src_y,
1426	                        uint32_t src_w, uint32_t src_h);</synopsis>
1427	            <para>
1428	              Enable and configure the plane to use the given CRTC and frame buffer.
1429	            </para>
1430	            <para>
1431	              The source rectangle in frame buffer memory coordinates is given by
1432	              the <parameter>src_x</parameter>, <parameter>src_y</parameter>,
1433	              <parameter>src_w</parameter> and <parameter>src_h</parameter>
1434	              parameters (as 16.16 fixed point values). Devices that don't support
1435	              subpixel plane coordinates can ignore the fractional part.
1436	            </para>
1437	            <para>
1438	              The destination rectangle in CRTC coordinates is given by the
1439	              <parameter>crtc_x</parameter>, <parameter>crtc_y</parameter>,
1440	              <parameter>crtc_w</parameter> and <parameter>crtc_h</parameter>
1441	              parameters (as integer values). Devices scale the source rectangle to
1442	              the destination rectangle. If scaling is not supported, and the source
1443	              rectangle size doesn't match the destination rectangle size, the
1444	              driver must return a -<errorname>EINVAL</errorname> error.
1445	            </para>
1446	          </listitem>
1447	          <listitem>
1448	            <synopsis>int (*disable_plane)(struct drm_plane *plane);</synopsis>
1449	            <para>
1450	              Disable the plane. The DRM core calls this method in response to a
1451	              DRM_IOCTL_MODE_SETPLANE ioctl call with the frame buffer ID set to 0.
1452	              Disabled planes must not be processed by the CRTC.
1453	            </para>
1454	          </listitem>
1455	          <listitem>
1456	            <synopsis>void (*destroy)(struct drm_plane *plane);</synopsis>
1457	            <para>
1458	              Destroy the plane when not needed anymore. See
1459	              <xref linkend="drm-kms-init"/>.
1460	            </para>
1461	          </listitem>
1462	        </itemizedlist>
1463	      </sect3>
1464	    </sect2>
1465	    <sect2>
1466	      <title>Encoders (struct <structname>drm_encoder</structname>)</title>
1467	      <para>
1468	        An encoder takes pixel data from a CRTC and converts it to a format
1469		suitable for any attached connectors. On some devices, it may be
1470		possible to have a CRTC send data to more than one encoder. In that
1471		case, both encoders would receive data from the same scanout buffer,
1472		resulting in a "cloned" display configuration across the connectors
1473		attached to each encoder.
1474	      </para>
1475	      <sect3>
1476	        <title>Encoder Initialization</title>
1477	        <para>
1478	          As for CRTCs, a KMS driver must create, initialize and register at
1479	          least one struct <structname>drm_encoder</structname> instance. The
1480	          instance is allocated and zeroed by the driver, possibly as part of a
1481	          larger structure.
1482	        </para>
1483	        <para>
1484	          Drivers must initialize the struct <structname>drm_encoder</structname>
1485	          <structfield>possible_crtcs</structfield> and
1486	          <structfield>possible_clones</structfield> fields before registering the
1487	          encoder. Both fields are bitmasks of respectively the CRTCs that the
1488	          encoder can be connected to, and sibling encoders candidate for cloning.
1489	        </para>
1490	        <para>
1491	          After being initialized, the encoder must be registered with a call to
1492	          <function>drm_encoder_init</function>. The function takes a pointer to
1493	          the encoder functions and an encoder type. Supported types are
1494	          <itemizedlist>
1495	            <listitem>
1496	              DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A
1497	              </listitem>
1498	            <listitem>
1499	              DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort
1500	            </listitem>
1501	            <listitem>
1502	              DRM_MODE_ENCODER_LVDS for display panels
1503	            </listitem>
1504	            <listitem>
1505	              DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, Component,
1506	              SCART)
1507	            </listitem>
1508	            <listitem>
1509	              DRM_MODE_ENCODER_VIRTUAL for virtual machine displays
1510	            </listitem>
1511	          </itemizedlist>
1512	        </para>
1513	        <para>
1514	          Encoders must be attached to a CRTC to be used. DRM drivers leave
1515	          encoders unattached at initialization time. Applications (or the fbdev
1516	          compatibility layer when implemented) are responsible for attaching the
1517	          encoders they want to use to a CRTC.
1518	        </para>
1519	      </sect3>
1520	      <sect3>
1521	        <title>Encoder Operations</title>
1522	        <itemizedlist>
1523	          <listitem>
1524	            <synopsis>void (*destroy)(struct drm_encoder *encoder);</synopsis>
1525	            <para>
1526	              Called to destroy the encoder when not needed anymore. See
1527	              <xref linkend="drm-kms-init"/>.
1528	            </para>
1529	          </listitem>
1530	          <listitem>
1531	            <synopsis>void (*set_property)(struct drm_plane *plane,
1532	                     struct drm_property *property, uint64_t value);</synopsis>
1533	            <para>
1534	              Set the value of the given plane property to
1535	              <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1536	              for more information about properties.
1537	            </para>
1538	          </listitem>
1539	        </itemizedlist>
1540	      </sect3>
1541	    </sect2>
1542	    <sect2>
1543	      <title>Connectors (struct <structname>drm_connector</structname>)</title>
1544	      <para>
1545	        A connector is the final destination for pixel data on a device, and
1546		usually connects directly to an external display device like a monitor
1547		or laptop panel. A connector can only be attached to one encoder at a
1548		time. The connector is also the structure where information about the
1549		attached display is kept, so it contains fields for display data, EDID
1550		data, DPMS &amp; connection status, and information about modes
1551		supported on the attached displays.
1552	      </para>
1553	      <sect3>
1554	        <title>Connector Initialization</title>
1555	        <para>
1556	          Finally a KMS driver must create, initialize, register and attach at
1557	          least one struct <structname>drm_connector</structname> instance. The
1558	          instance is created as other KMS objects and initialized by setting the
1559	          following fields.
1560	        </para>
1561	        <variablelist>
1562	          <varlistentry>
1563	            <term><structfield>interlace_allowed</structfield></term>
1564	            <listitem><para>
1565	              Whether the connector can handle interlaced modes.
1566	            </para></listitem>
1567	          </varlistentry>
1568	          <varlistentry>
1569	            <term><structfield>doublescan_allowed</structfield></term>
1570	            <listitem><para>
1571	              Whether the connector can handle doublescan.
1572	            </para></listitem>
1573	          </varlistentry>
1574	          <varlistentry>
1575	            <term><structfield>display_info
1576	            </structfield></term>
1577	            <listitem><para>
1578	              Display information is filled from EDID information when a display
1579	              is detected. For non hot-pluggable displays such as flat panels in
1580	              embedded systems, the driver should initialize the
1581	              <structfield>display_info</structfield>.<structfield>width_mm</structfield>
1582	              and
1583	              <structfield>display_info</structfield>.<structfield>height_mm</structfield>
1584	              fields with the physical size of the display.
1585	            </para></listitem>
1586	          </varlistentry>
1587	          <varlistentry>
1588	            <term id="drm-kms-connector-polled"><structfield>polled</structfield></term>
1589	            <listitem><para>
1590	              Connector polling mode, a combination of
1591	              <variablelist>
1592	                <varlistentry>
1593	                  <term>DRM_CONNECTOR_POLL_HPD</term>
1594	                  <listitem><para>
1595	                    The connector generates hotplug events and doesn't need to be
1596	                    periodically polled. The CONNECT and DISCONNECT flags must not
1597	                    be set together with the HPD flag.
1598	                  </para></listitem>
1599	                </varlistentry>
1600	                <varlistentry>
1601	                  <term>DRM_CONNECTOR_POLL_CONNECT</term>
1602	                  <listitem><para>
1603	                    Periodically poll the connector for connection.
1604	                  </para></listitem>
1605	                </varlistentry>
1606	                <varlistentry>
1607	                  <term>DRM_CONNECTOR_POLL_DISCONNECT</term>
1608	                  <listitem><para>
1609	                    Periodically poll the connector for disconnection.
1610	                  </para></listitem>
1611	                </varlistentry>
1612	              </variablelist>
1613	              Set to 0 for connectors that don't support connection status
1614	              discovery.
1615	            </para></listitem>
1616	          </varlistentry>
1617	        </variablelist>
1618	        <para>
1619	          The connector is then registered with a call to
1620	          <function>drm_connector_init</function> with a pointer to the connector
1621	          functions and a connector type, and exposed through sysfs with a call to
1622	          <function>drm_connector_register</function>.
1623	        </para>
1624	        <para>
1625	          Supported connector types are
1626	          <itemizedlist>
1627	            <listitem>DRM_MODE_CONNECTOR_VGA</listitem>
1628	            <listitem>DRM_MODE_CONNECTOR_DVII</listitem>
1629	            <listitem>DRM_MODE_CONNECTOR_DVID</listitem>
1630	            <listitem>DRM_MODE_CONNECTOR_DVIA</listitem>
1631	            <listitem>DRM_MODE_CONNECTOR_Composite</listitem>
1632	            <listitem>DRM_MODE_CONNECTOR_SVIDEO</listitem>
1633	            <listitem>DRM_MODE_CONNECTOR_LVDS</listitem>
1634	            <listitem>DRM_MODE_CONNECTOR_Component</listitem>
1635	            <listitem>DRM_MODE_CONNECTOR_9PinDIN</listitem>
1636	            <listitem>DRM_MODE_CONNECTOR_DisplayPort</listitem>
1637	            <listitem>DRM_MODE_CONNECTOR_HDMIA</listitem>
1638	            <listitem>DRM_MODE_CONNECTOR_HDMIB</listitem>
1639	            <listitem>DRM_MODE_CONNECTOR_TV</listitem>
1640	            <listitem>DRM_MODE_CONNECTOR_eDP</listitem>
1641	            <listitem>DRM_MODE_CONNECTOR_VIRTUAL</listitem>
1642	          </itemizedlist>
1643	        </para>
1644	        <para>
1645	          Connectors must be attached to an encoder to be used. For devices that
1646	          map connectors to encoders 1:1, the connector should be attached at
1647	          initialization time with a call to
1648	          <function>drm_mode_connector_attach_encoder</function>. The driver must
1649	          also set the <structname>drm_connector</structname>
1650	          <structfield>encoder</structfield> field to point to the attached
1651	          encoder.
1652	        </para>
1653	        <para>
1654	          Finally, drivers must initialize the connectors state change detection
1655	          with a call to <function>drm_kms_helper_poll_init</function>. If at
1656	          least one connector is pollable but can't generate hotplug interrupts
1657	          (indicated by the DRM_CONNECTOR_POLL_CONNECT and
1658	          DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will
1659	          automatically be queued to periodically poll for changes. Connectors
1660	          that can generate hotplug interrupts must be marked with the
1661	          DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must
1662	          call <function>drm_helper_hpd_irq_event</function>. The function will
1663	          queue a delayed work to check the state of all connectors, but no
1664	          periodic polling will be done.
1665	        </para>
1666	      </sect3>
1667	      <sect3>
1668	        <title>Connector Operations</title>
1669	        <note><para>
1670	          Unless otherwise state, all operations are mandatory.
1671	        </para></note>
1672	        <sect4>
1673	          <title>DPMS</title>
1674	          <synopsis>void (*dpms)(struct drm_connector *connector, int mode);</synopsis>
1675	          <para>
1676	            The DPMS operation sets the power state of a connector. The mode
1677	            argument is one of
1678	            <itemizedlist>
1679	              <listitem><para>DRM_MODE_DPMS_ON</para></listitem>
1680	              <listitem><para>DRM_MODE_DPMS_STANDBY</para></listitem>
1681	              <listitem><para>DRM_MODE_DPMS_SUSPEND</para></listitem>
1682	              <listitem><para>DRM_MODE_DPMS_OFF</para></listitem>
1683	            </itemizedlist>
1684	          </para>
1685	          <para>
1686	            In all but DPMS_ON mode the encoder to which the connector is attached
1687	            should put the display in low-power mode by driving its signals
1688	            appropriately. If more than one connector is attached to the encoder
1689	            care should be taken not to change the power state of other displays as
1690	            a side effect. Low-power mode should be propagated to the encoders and
1691	            CRTCs when all related connectors are put in low-power mode.
1692	          </para>
1693	        </sect4>
1694	        <sect4>
1695	          <title>Modes</title>
1696	          <synopsis>int (*fill_modes)(struct drm_connector *connector, uint32_t max_width,
1697	                      uint32_t max_height);</synopsis>
1698	          <para>
1699	            Fill the mode list with all supported modes for the connector. If the
1700	            <parameter>max_width</parameter> and <parameter>max_height</parameter>
1701	            arguments are non-zero, the implementation must ignore all modes wider
1702	            than <parameter>max_width</parameter> or higher than
1703	            <parameter>max_height</parameter>.
1704	          </para>
1705	          <para>
1706	            The connector must also fill in this operation its
1707	            <structfield>display_info</structfield>
1708	            <structfield>width_mm</structfield> and
1709	            <structfield>height_mm</structfield> fields with the connected display
1710	            physical size in millimeters. The fields should be set to 0 if the value
1711	            isn't known or is not applicable (for instance for projector devices).
1712	          </para>
1713	        </sect4>
1714	        <sect4>
1715	          <title>Connection Status</title>
1716	          <para>
1717	            The connection status is updated through polling or hotplug events when
1718	            supported (see <xref linkend="drm-kms-connector-polled"/>). The status
1719	            value is reported to userspace through ioctls and must not be used
1720	            inside the driver, as it only gets initialized by a call to
1721	            <function>drm_mode_getconnector</function> from userspace.
1722	          </para>
1723	          <synopsis>enum drm_connector_status (*detect)(struct drm_connector *connector,
1724	                                        bool force);</synopsis>
1725	          <para>
1726	            Check to see if anything is attached to the connector. The
1727	            <parameter>force</parameter> parameter is set to false whilst polling or
1728	            to true when checking the connector due to user request.
1729	            <parameter>force</parameter> can be used by the driver to avoid
1730	            expensive, destructive operations during automated probing.
1731	          </para>
1732	          <para>
1733	            Return connector_status_connected if something is connected to the
1734	            connector, connector_status_disconnected if nothing is connected and
1735	            connector_status_unknown if the connection state isn't known.
1736	          </para>
1737	          <para>
1738	            Drivers should only return connector_status_connected if the connection
1739	            status has really been probed as connected. Connectors that can't detect
1740	            the connection status, or failed connection status probes, should return
1741	            connector_status_unknown.
1742	          </para>
1743	        </sect4>
1744	        <sect4>
1745	          <title>Miscellaneous</title>
1746	          <itemizedlist>
1747	            <listitem>
1748	              <synopsis>void (*set_property)(struct drm_connector *connector,
1749	                     struct drm_property *property, uint64_t value);</synopsis>
1750	              <para>
1751	                Set the value of the given connector property to
1752	                <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1753	                for more information about properties.
1754	              </para>
1755	            </listitem>
1756	            <listitem>
1757	              <synopsis>void (*destroy)(struct drm_connector *connector);</synopsis>
1758	              <para>
1759	                Destroy the connector when not needed anymore. See
1760	                <xref linkend="drm-kms-init"/>.
1761	              </para>
1762	            </listitem>
1763	          </itemizedlist>
1764	        </sect4>
1765	      </sect3>
1766	    </sect2>
1767	    <sect2>
1768	      <title>Cleanup</title>
1769	      <para>
1770	        The DRM core manages its objects' lifetime. When an object is not needed
1771		anymore the core calls its destroy function, which must clean up and
1772		free every resource allocated for the object. Every
1773		<function>drm_*_init</function> call must be matched with a
1774		corresponding <function>drm_*_cleanup</function> call to cleanup CRTCs
1775		(<function>drm_crtc_cleanup</function>), planes
1776		(<function>drm_plane_cleanup</function>), encoders
1777		(<function>drm_encoder_cleanup</function>) and connectors
1778		(<function>drm_connector_cleanup</function>). Furthermore, connectors
1779		that have been added to sysfs must be removed by a call to
1780		<function>drm_connector_unregister</function> before calling
1781		<function>drm_connector_cleanup</function>.
1782	      </para>
1783	      <para>
1784	        Connectors state change detection must be cleanup up with a call to
1785		<function>drm_kms_helper_poll_fini</function>.
1786	      </para>
1787	    </sect2>
1788	    <sect2>
1789	      <title>Output discovery and initialization example</title>
1790	      <programlisting><![CDATA[
1791	void intel_crt_init(struct drm_device *dev)
1792	{
1793		struct drm_connector *connector;
1794		struct intel_output *intel_output;
1795	
1796		intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL);
1797		if (!intel_output)
1798			return;
1799	
1800		connector = &intel_output->base;
1801		drm_connector_init(dev, &intel_output->base,
1802				   &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA);
1803	
1804		drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs,
1805				 DRM_MODE_ENCODER_DAC);
1806	
1807		drm_mode_connector_attach_encoder(&intel_output->base,
1808						  &intel_output->enc);
1809	
1810		/* Set up the DDC bus. */
1811		intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A");
1812		if (!intel_output->ddc_bus) {
1813			dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration "
1814				   "failed.\n");
1815			return;
1816		}
1817	
1818		intel_output->type = INTEL_OUTPUT_ANALOG;
1819		connector->interlace_allowed = 0;
1820		connector->doublescan_allowed = 0;
1821	
1822		drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs);
1823		drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs);
1824	
1825		drm_connector_register(connector);
1826	}]]></programlisting>
1827	      <para>
1828	        In the example above (taken from the i915 driver), a CRTC, connector and
1829	        encoder combination is created. A device-specific i2c bus is also
1830	        created for fetching EDID data and performing monitor detection. Once
1831	        the process is complete, the new connector is registered with sysfs to
1832	        make its properties available to applications.
1833	      </para>
1834	    </sect2>
1835	    <sect2>
1836	      <title>KMS API Functions</title>
1837	!Edrivers/gpu/drm/drm_crtc.c
1838	    </sect2>
1839	    <sect2>
1840	      <title>KMS Data Structures</title>
1841	!Iinclude/drm/drm_crtc.h
1842	    </sect2>
1843	    <sect2>
1844	      <title>KMS Locking</title>
1845	!Pdrivers/gpu/drm/drm_modeset_lock.c kms locking
1846	!Iinclude/drm/drm_modeset_lock.h
1847	!Edrivers/gpu/drm/drm_modeset_lock.c
1848	    </sect2>
1849	  </sect1>
1850	
1851	  <!-- Internals: kms helper functions -->
1852	
1853	  <sect1>
1854	    <title>Mode Setting Helper Functions</title>
1855	    <para>
1856	      The plane, CRTC, encoder and connector functions provided by the drivers
1857	      implement the DRM API. They're called by the DRM core and ioctl handlers
1858	      to handle device state changes and configuration request. As implementing
1859	      those functions often requires logic not specific to drivers, mid-layer
1860	      helper functions are available to avoid duplicating boilerplate code.
1861	    </para>
1862	    <para>
1863	      The DRM core contains one mid-layer implementation. The mid-layer provides
1864	      implementations of several plane, CRTC, encoder and connector functions
1865	      (called from the top of the mid-layer) that pre-process requests and call
1866	      lower-level functions provided by the driver (at the bottom of the
1867	      mid-layer). For instance, the
1868	      <function>drm_crtc_helper_set_config</function> function can be used to
1869	      fill the struct <structname>drm_crtc_funcs</structname>
1870	      <structfield>set_config</structfield> field. When called, it will split
1871	      the <methodname>set_config</methodname> operation in smaller, simpler
1872	      operations and call the driver to handle them.
1873	    </para>
1874	    <para>
1875	      To use the mid-layer, drivers call <function>drm_crtc_helper_add</function>,
1876	      <function>drm_encoder_helper_add</function> and
1877	      <function>drm_connector_helper_add</function> functions to install their
1878	      mid-layer bottom operations handlers, and fill the
1879	      <structname>drm_crtc_funcs</structname>,
1880	      <structname>drm_encoder_funcs</structname> and
1881	      <structname>drm_connector_funcs</structname> structures with pointers to
1882	      the mid-layer top API functions. Installing the mid-layer bottom operation
1883	      handlers is best done right after registering the corresponding KMS object.
1884	    </para>
1885	    <para>
1886	      The mid-layer is not split between CRTC, encoder and connector operations.
1887	      To use it, a driver must provide bottom functions for all of the three KMS
1888	      entities.
1889	    </para>
1890	    <sect2>
1891	      <title>Helper Functions</title>
1892	      <itemizedlist>
1893	        <listitem>
1894	          <synopsis>int drm_crtc_helper_set_config(struct drm_mode_set *set);</synopsis>
1895	          <para>
1896	            The <function>drm_crtc_helper_set_config</function> helper function
1897	            is a CRTC <methodname>set_config</methodname> implementation. It
1898	            first tries to locate the best encoder for each connector by calling
1899	            the connector <methodname>best_encoder</methodname> helper
1900	            operation.
1901	          </para>
1902	          <para>
1903	            After locating the appropriate encoders, the helper function will
1904	            call the <methodname>mode_fixup</methodname> encoder and CRTC helper
1905	            operations to adjust the requested mode, or reject it completely in
1906	            which case an error will be returned to the application. If the new
1907	            configuration after mode adjustment is identical to the current
1908	            configuration the helper function will return without performing any
1909	            other operation.
1910	          </para>
1911	          <para>
1912	            If the adjusted mode is identical to the current mode but changes to
1913	            the frame buffer need to be applied, the
1914	            <function>drm_crtc_helper_set_config</function> function will call
1915	            the CRTC <methodname>mode_set_base</methodname> helper operation. If
1916	            the adjusted mode differs from the current mode, or if the
1917	            <methodname>mode_set_base</methodname> helper operation is not
1918	            provided, the helper function performs a full mode set sequence by
1919	            calling the <methodname>prepare</methodname>,
1920	            <methodname>mode_set</methodname> and
1921	            <methodname>commit</methodname> CRTC and encoder helper operations,
1922	            in that order.
1923	          </para>
1924	        </listitem>
1925	        <listitem>
1926	          <synopsis>void drm_helper_connector_dpms(struct drm_connector *connector, int mode);</synopsis>
1927	          <para>
1928	            The <function>drm_helper_connector_dpms</function> helper function
1929	            is a connector <methodname>dpms</methodname> implementation that
1930	            tracks power state of connectors. To use the function, drivers must
1931	            provide <methodname>dpms</methodname> helper operations for CRTCs
1932	            and encoders to apply the DPMS state to the device.
1933	          </para>
1934	          <para>
1935	            The mid-layer doesn't track the power state of CRTCs and encoders.
1936	            The <methodname>dpms</methodname> helper operations can thus be
1937	            called with a mode identical to the currently active mode.
1938	          </para>
1939	        </listitem>
1940	        <listitem>
1941	          <synopsis>int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
1942	                                            uint32_t maxX, uint32_t maxY);</synopsis>
1943	          <para>
1944	            The <function>drm_helper_probe_single_connector_modes</function> helper
1945	            function is a connector <methodname>fill_modes</methodname>
1946	            implementation that updates the connection status for the connector
1947	            and then retrieves a list of modes by calling the connector
1948	            <methodname>get_modes</methodname> helper operation.
1949	          </para>
1950	         <para>
1951	            If the helper operation returns no mode, and if the connector status
1952	            is connector_status_connected, standard VESA DMT modes up to
1953	            1024x768 are automatically added to the modes list by a call to
1954	            <function>drm_add_modes_noedid</function>.
1955	          </para>
1956	          <para>
1957	            The function then filters out modes larger than
1958	            <parameter>max_width</parameter> and <parameter>max_height</parameter>
1959	            if specified. It finally calls the optional connector
1960	            <methodname>mode_valid</methodname> helper operation for each mode in
1961	            the probed list to check whether the mode is valid for the connector.
1962	          </para>
1963	        </listitem>
1964	      </itemizedlist>
1965	    </sect2>
1966	    <sect2>
1967	      <title>CRTC Helper Operations</title>
1968	      <itemizedlist>
1969	        <listitem id="drm-helper-crtc-mode-fixup">
1970	          <synopsis>bool (*mode_fixup)(struct drm_crtc *crtc,
1971	                       const struct drm_display_mode *mode,
1972	                       struct drm_display_mode *adjusted_mode);</synopsis>
1973	          <para>
1974	            Let CRTCs adjust the requested mode or reject it completely. This
1975	            operation returns true if the mode is accepted (possibly after being
1976	            adjusted) or false if it is rejected.
1977	          </para>
1978	          <para>
1979	            The <methodname>mode_fixup</methodname> operation should reject the
1980	            mode if it can't reasonably use it. The definition of "reasonable"
1981	            is currently fuzzy in this context. One possible behaviour would be
1982	            to set the adjusted mode to the panel timings when a fixed-mode
1983	            panel is used with hardware capable of scaling. Another behaviour
1984	            would be to accept any input mode and adjust it to the closest mode
1985	            supported by the hardware (FIXME: This needs to be clarified).
1986	          </para>
1987	        </listitem>
1988	        <listitem>
1989	          <synopsis>int (*mode_set_base)(struct drm_crtc *crtc, int x, int y,
1990	                     struct drm_framebuffer *old_fb)</synopsis>
1991	          <para>
1992	            Move the CRTC on the current frame buffer (stored in
1993	            <literal>crtc-&gt;fb</literal>) to position (x,y). Any of the frame
1994	            buffer, x position or y position may have been modified.
1995	          </para>
1996	          <para>
1997	            This helper operation is optional. If not provided, the
1998	            <function>drm_crtc_helper_set_config</function> function will fall
1999	            back to the <methodname>mode_set</methodname> helper operation.
2000	          </para>
2001	          <note><para>
2002	            FIXME: Why are x and y passed as arguments, as they can be accessed
2003	            through <literal>crtc-&gt;x</literal> and
2004	            <literal>crtc-&gt;y</literal>?
2005	          </para></note>
2006	        </listitem>
2007	        <listitem>
2008	          <synopsis>void (*prepare)(struct drm_crtc *crtc);</synopsis>
2009	          <para>
2010	            Prepare the CRTC for mode setting. This operation is called after
2011	            validating the requested mode. Drivers use it to perform
2012	            device-specific operations required before setting the new mode.
2013	          </para>
2014	        </listitem>
2015	        <listitem>
2016	          <synopsis>int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,
2017	                struct drm_display_mode *adjusted_mode, int x, int y,
2018	                struct drm_framebuffer *old_fb);</synopsis>
2019	          <para>
2020	            Set a new mode, position and frame buffer. Depending on the device
2021	            requirements, the mode can be stored internally by the driver and
2022	            applied in the <methodname>commit</methodname> operation, or
2023	            programmed to the hardware immediately.
2024	          </para>
2025	          <para>
2026	            The <methodname>mode_set</methodname> operation returns 0 on success
2027		    or a negative error code if an error occurs.
2028	          </para>
2029	        </listitem>
2030	        <listitem>
2031	          <synopsis>void (*commit)(struct drm_crtc *crtc);</synopsis>
2032	          <para>
2033	            Commit a mode. This operation is called after setting the new mode.
2034	            Upon return the device must use the new mode and be fully
2035	            operational.
2036	          </para>
2037	        </listitem>
2038	      </itemizedlist>
2039	    </sect2>
2040	    <sect2>
2041	      <title>Encoder Helper Operations</title>
2042	      <itemizedlist>
2043	        <listitem>
2044	          <synopsis>bool (*mode_fixup)(struct drm_encoder *encoder,
2045	                       const struct drm_display_mode *mode,
2046	                       struct drm_display_mode *adjusted_mode);</synopsis>
2047	          <para>
2048	            Let encoders adjust the requested mode or reject it completely. This
2049	            operation returns true if the mode is accepted (possibly after being
2050	            adjusted) or false if it is rejected. See the
2051	            <link linkend="drm-helper-crtc-mode-fixup">mode_fixup CRTC helper
2052	            operation</link> for an explanation of the allowed adjustments.
2053	          </para>
2054	        </listitem>
2055	        <listitem>
2056	          <synopsis>void (*prepare)(struct drm_encoder *encoder);</synopsis>
2057	          <para>
2058	            Prepare the encoder for mode setting. This operation is called after
2059	            validating the requested mode. Drivers use it to perform
2060	            device-specific operations required before setting the new mode.
2061	          </para>
2062	        </listitem>
2063	        <listitem>
2064	          <synopsis>void (*mode_set)(struct drm_encoder *encoder,
2065	                 struct drm_display_mode *mode,
2066	                 struct drm_display_mode *adjusted_mode);</synopsis>
2067	          <para>
2068	            Set a new mode. Depending on the device requirements, the mode can
2069	            be stored internally by the driver and applied in the
2070	            <methodname>commit</methodname> operation, or programmed to the
2071	            hardware immediately.
2072	          </para>
2073	        </listitem>
2074	        <listitem>
2075	          <synopsis>void (*commit)(struct drm_encoder *encoder);</synopsis>
2076	          <para>
2077	            Commit a mode. This operation is called after setting the new mode.
2078	            Upon return the device must use the new mode and be fully
2079	            operational.
2080	          </para>
2081	        </listitem>
2082	      </itemizedlist>
2083	    </sect2>
2084	    <sect2>
2085	      <title>Connector Helper Operations</title>
2086	      <itemizedlist>
2087	        <listitem>
2088	          <synopsis>struct drm_encoder *(*best_encoder)(struct drm_connector *connector);</synopsis>
2089	          <para>
2090	            Return a pointer to the best encoder for the connecter. Device that
2091	            map connectors to encoders 1:1 simply return the pointer to the
2092	            associated encoder. This operation is mandatory.
2093	          </para>
2094	        </listitem>
2095	        <listitem>
2096	          <synopsis>int (*get_modes)(struct drm_connector *connector);</synopsis>
2097	          <para>
2098	            Fill the connector's <structfield>probed_modes</structfield> list
2099	            by parsing EDID data with <function>drm_add_edid_modes</function>,
2100	            adding standard VESA DMT modes with <function>drm_add_modes_noedid</function>,
2101	            or calling <function>drm_mode_probed_add</function> directly for every
2102	            supported mode and return the number of modes it has detected. This
2103	            operation is mandatory.
2104	          </para>
2105	          <para>
2106	            Note that the caller function will automatically add standard VESA
2107	            DMT modes up to 1024x768 if the <methodname>get_modes</methodname>
2108	            helper operation returns no mode and if the connector status is
2109	            connector_status_connected. There is no need to call
2110	            <function>drm_add_edid_modes</function> manually in that case.
2111	          </para>
2112	          <para>
2113	            When adding modes manually the driver creates each mode with a call to
2114	            <function>drm_mode_create</function> and must fill the following fields.
2115	            <itemizedlist>
2116	              <listitem>
2117	                <synopsis>__u32 type;</synopsis>
2118	                <para>
2119	                  Mode type bitmask, a combination of
2120	                  <variablelist>
2121	                    <varlistentry>
2122	                      <term>DRM_MODE_TYPE_BUILTIN</term>
2123	                      <listitem><para>not used?</para></listitem>
2124	                    </varlistentry>
2125	                    <varlistentry>
2126	                      <term>DRM_MODE_TYPE_CLOCK_C</term>
2127	                      <listitem><para>not used?</para></listitem>
2128	                    </varlistentry>
2129	                    <varlistentry>
2130	                      <term>DRM_MODE_TYPE_CRTC_C</term>
2131	                      <listitem><para>not used?</para></listitem>
2132	                    </varlistentry>
2133	                    <varlistentry>
2134	                      <term>
2135	        DRM_MODE_TYPE_PREFERRED - The preferred mode for the connector
2136	                      </term>
2137	                      <listitem>
2138	                        <para>not used?</para>
2139	                      </listitem>
2140	                    </varlistentry>
2141	                    <varlistentry>
2142	                      <term>DRM_MODE_TYPE_DEFAULT</term>
2143	                      <listitem><para>not used?</para></listitem>
2144	                    </varlistentry>
2145	                    <varlistentry>
2146	                      <term>DRM_MODE_TYPE_USERDEF</term>
2147	                      <listitem><para>not used?</para></listitem>
2148	                    </varlistentry>
2149	                    <varlistentry>
2150	                      <term>DRM_MODE_TYPE_DRIVER</term>
2151	                      <listitem>
2152	                        <para>
2153	                          The mode has been created by the driver (as opposed to
2154	                          to user-created modes).
2155	                        </para>
2156	                      </listitem>
2157	                    </varlistentry>
2158	                  </variablelist>
2159	                  Drivers must set the DRM_MODE_TYPE_DRIVER bit for all modes they
2160	                  create, and set the DRM_MODE_TYPE_PREFERRED bit for the preferred
2161	                  mode.
2162	                </para>
2163	              </listitem>
2164	              <listitem>
2165	                <synopsis>__u32 clock;</synopsis>
2166	                <para>Pixel clock frequency in kHz unit</para>
2167	              </listitem>
2168	              <listitem>
2169	                <synopsis>__u16 hdisplay, hsync_start, hsync_end, htotal;
2170	    __u16 vdisplay, vsync_start, vsync_end, vtotal;</synopsis>
2171	                <para>Horizontal and vertical timing information</para>
2172	                <screen><![CDATA[
2173	             Active                 Front           Sync           Back
2174	             Region                 Porch                          Porch
2175	    <-----------------------><----------------><-------------><-------------->
2176	
2177	      //////////////////////|
2178	     ////////////////////// |
2179	    //////////////////////  |..................               ................
2180	                                               _______________
2181	
2182	    <----- [hv]display ----->
2183	    <------------- [hv]sync_start ------------>
2184	    <--------------------- [hv]sync_end --------------------->
2185	    <-------------------------------- [hv]total ----------------------------->
2186	]]></screen>
2187	              </listitem>
2188	              <listitem>
2189	                <synopsis>__u16 hskew;
2190	    __u16 vscan;</synopsis>
2191	                <para>Unknown</para>
2192	              </listitem>
2193	              <listitem>
2194	                <synopsis>__u32 flags;</synopsis>
2195	                <para>
2196	                  Mode flags, a combination of
2197	                  <variablelist>
2198	                    <varlistentry>
2199	                      <term>DRM_MODE_FLAG_PHSYNC</term>
2200	                      <listitem><para>
2201	                        Horizontal sync is active high
2202	                      </para></listitem>
2203	                    </varlistentry>
2204	                    <varlistentry>
2205	                      <term>DRM_MODE_FLAG_NHSYNC</term>
2206	                      <listitem><para>
2207	                        Horizontal sync is active low
2208	                      </para></listitem>
2209	                    </varlistentry>
2210	                    <varlistentry>
2211	                      <term>DRM_MODE_FLAG_PVSYNC</term>
2212	                      <listitem><para>
2213	                        Vertical sync is active high
2214	                      </para></listitem>
2215	                    </varlistentry>
2216	                    <varlistentry>
2217	                      <term>DRM_MODE_FLAG_NVSYNC</term>
2218	                      <listitem><para>
2219	                        Vertical sync is active low
2220	                      </para></listitem>
2221	                    </varlistentry>
2222	                    <varlistentry>
2223	                      <term>DRM_MODE_FLAG_INTERLACE</term>
2224	                      <listitem><para>
2225	                        Mode is interlaced
2226	                      </para></listitem>
2227	                    </varlistentry>
2228	                    <varlistentry>
2229	                      <term>DRM_MODE_FLAG_DBLSCAN</term>
2230	                      <listitem><para>
2231	                        Mode uses doublescan
2232	                      </para></listitem>
2233	                    </varlistentry>
2234	                    <varlistentry>
2235	                      <term>DRM_MODE_FLAG_CSYNC</term>
2236	                      <listitem><para>
2237	                        Mode uses composite sync
2238	                      </para></listitem>
2239	                    </varlistentry>
2240	                    <varlistentry>
2241	                      <term>DRM_MODE_FLAG_PCSYNC</term>
2242	                      <listitem><para>
2243	                        Composite sync is active high
2244	                      </para></listitem>
2245	                    </varlistentry>
2246	                    <varlistentry>
2247	                      <term>DRM_MODE_FLAG_NCSYNC</term>
2248	                      <listitem><para>
2249	                        Composite sync is active low
2250	                      </para></listitem>
2251	                    </varlistentry>
2252	                    <varlistentry>
2253	                      <term>DRM_MODE_FLAG_HSKEW</term>
2254	                      <listitem><para>
2255	                        hskew provided (not used?)
2256	                      </para></listitem>
2257	                    </varlistentry>
2258	                    <varlistentry>
2259	                      <term>DRM_MODE_FLAG_BCAST</term>
2260	                      <listitem><para>
2261	                        not used?
2262	                      </para></listitem>
2263	                    </varlistentry>
2264	                    <varlistentry>
2265	                      <term>DRM_MODE_FLAG_PIXMUX</term>
2266	                      <listitem><para>
2267	                        not used?
2268	                      </para></listitem>
2269	                    </varlistentry>
2270	                    <varlistentry>
2271	                      <term>DRM_MODE_FLAG_DBLCLK</term>
2272	                      <listitem><para>
2273	                        not used?
2274	                      </para></listitem>
2275	                    </varlistentry>
2276	                    <varlistentry>
2277	                      <term>DRM_MODE_FLAG_CLKDIV2</term>
2278	                      <listitem><para>
2279	                        ?
2280	                      </para></listitem>
2281	                    </varlistentry>
2282	                  </variablelist>
2283	                </para>
2284	                <para>
2285	                  Note that modes marked with the INTERLACE or DBLSCAN flags will be
2286	                  filtered out by
2287	                  <function>drm_helper_probe_single_connector_modes</function> if
2288	                  the connector's <structfield>interlace_allowed</structfield> or
2289	                  <structfield>doublescan_allowed</structfield> field is set to 0.
2290	                </para>
2291	              </listitem>
2292	              <listitem>
2293	                <synopsis>char name[DRM_DISPLAY_MODE_LEN];</synopsis>
2294	                <para>
2295	                  Mode name. The driver must call
2296	                  <function>drm_mode_set_name</function> to fill the mode name from
2297	                  <structfield>hdisplay</structfield>,
2298	                  <structfield>vdisplay</structfield> and interlace flag after
2299	                  filling the corresponding fields.
2300	                </para>
2301	              </listitem>
2302	            </itemizedlist>
2303	          </para>
2304	          <para>
2305	            The <structfield>vrefresh</structfield> value is computed by
2306	            <function>drm_helper_probe_single_connector_modes</function>.
2307	          </para>
2308	          <para>
2309	            When parsing EDID data, <function>drm_add_edid_modes</function> fills the
2310	            connector <structfield>display_info</structfield>
2311	            <structfield>width_mm</structfield> and
2312	            <structfield>height_mm</structfield> fields. When creating modes
2313	            manually the <methodname>get_modes</methodname> helper operation must
2314	            set the <structfield>display_info</structfield>
2315	            <structfield>width_mm</structfield> and
2316	            <structfield>height_mm</structfield> fields if they haven't been set
2317	            already (for instance at initialization time when a fixed-size panel is
2318	            attached to the connector). The mode <structfield>width_mm</structfield>
2319	            and <structfield>height_mm</structfield> fields are only used internally
2320	            during EDID parsing and should not be set when creating modes manually.
2321	          </para>
2322	        </listitem>
2323	        <listitem>
2324	          <synopsis>int (*mode_valid)(struct drm_connector *connector,
2325			  struct drm_display_mode *mode);</synopsis>
2326	          <para>
2327	            Verify whether a mode is valid for the connector. Return MODE_OK for
2328	            supported modes and one of the enum drm_mode_status values (MODE_*)
2329	            for unsupported modes. This operation is optional.
2330	          </para>
2331	          <para>
2332	            As the mode rejection reason is currently not used beside for
2333	            immediately removing the unsupported mode, an implementation can
2334	            return MODE_BAD regardless of the exact reason why the mode is not
2335	            valid.
2336	          </para>
2337	          <note><para>
2338	            Note that the <methodname>mode_valid</methodname> helper operation is
2339	            only called for modes detected by the device, and
2340	            <emphasis>not</emphasis> for modes set by the user through the CRTC
2341	            <methodname>set_config</methodname> operation.
2342	          </para></note>
2343	        </listitem>
2344	      </itemizedlist>
2345	    </sect2>
2346	    <sect2>
2347	      <title>Atomic Modeset Helper Functions Reference</title>
2348	      <sect3>
2349		<title>Overview</title>
2350	!Pdrivers/gpu/drm/drm_atomic_helper.c overview
2351	      </sect3>
2352	      <sect3>
2353		<title>Implementing Asynchronous Atomic Commit</title>
2354	!Pdrivers/gpu/drm/drm_atomic_helper.c implementing async commit
2355	      </sect3>
2356	      <sect3>
2357		<title>Atomic State Reset and Initialization</title>
2358	!Pdrivers/gpu/drm/drm_atomic_helper.c atomic state reset and initialization
2359	      </sect3>
2360	!Iinclude/drm/drm_atomic_helper.h
2361	!Edrivers/gpu/drm/drm_atomic_helper.c
2362	    </sect2>
2363	    <sect2>
2364	      <title>Modeset Helper Functions Reference</title>
2365	!Edrivers/gpu/drm/drm_crtc_helper.c
2366	!Pdrivers/gpu/drm/drm_crtc_helper.c overview
2367	    </sect2>
2368	    <sect2>
2369	      <title>Output Probing Helper Functions Reference</title>
2370	!Pdrivers/gpu/drm/drm_probe_helper.c output probing helper overview
2371	!Edrivers/gpu/drm/drm_probe_helper.c
2372	    </sect2>
2373	    <sect2>
2374	      <title>fbdev Helper Functions Reference</title>
2375	!Pdrivers/gpu/drm/drm_fb_helper.c fbdev helpers
2376	!Edrivers/gpu/drm/drm_fb_helper.c
2377	!Iinclude/drm/drm_fb_helper.h
2378	    </sect2>
2379	    <sect2>
2380	      <title>Display Port Helper Functions Reference</title>
2381	!Pdrivers/gpu/drm/drm_dp_helper.c dp helpers
2382	!Iinclude/drm/drm_dp_helper.h
2383	!Edrivers/gpu/drm/drm_dp_helper.c
2384	    </sect2>
2385	    <sect2>
2386	      <title>Display Port MST Helper Functions Reference</title>
2387	!Pdrivers/gpu/drm/drm_dp_mst_topology.c dp mst helper
2388	!Iinclude/drm/drm_dp_mst_helper.h
2389	!Edrivers/gpu/drm/drm_dp_mst_topology.c
2390	    </sect2>
2391	    <sect2>
2392	      <title>MIPI DSI Helper Functions Reference</title>
2393	!Pdrivers/gpu/drm/drm_mipi_dsi.c dsi helpers
2394	!Iinclude/drm/drm_mipi_dsi.h
2395	!Edrivers/gpu/drm/drm_mipi_dsi.c
2396	    </sect2>
2397	    <sect2>
2398	      <title>EDID Helper Functions Reference</title>
2399	!Edrivers/gpu/drm/drm_edid.c
2400	    </sect2>
2401	    <sect2>
2402	      <title>Rectangle Utilities Reference</title>
2403	!Pinclude/drm/drm_rect.h rect utils
2404	!Iinclude/drm/drm_rect.h
2405	!Edrivers/gpu/drm/drm_rect.c
2406	    </sect2>
2407	    <sect2>
2408	      <title>Flip-work Helper Reference</title>
2409	!Pinclude/drm/drm_flip_work.h flip utils
2410	!Iinclude/drm/drm_flip_work.h
2411	!Edrivers/gpu/drm/drm_flip_work.c
2412	    </sect2>
2413	    <sect2>
2414	      <title>HDMI Infoframes Helper Reference</title>
2415	      <para>
2416		Strictly speaking this is not a DRM helper library but generally useable
2417		by any driver interfacing with HDMI outputs like v4l or alsa drivers.
2418		But it nicely fits into the overall topic of mode setting helper
2419		libraries and hence is also included here.
2420	      </para>
2421	!Iinclude/linux/hdmi.h
2422	!Edrivers/video/hdmi.c
2423	    </sect2>
2424	    <sect2>
2425	      <title id="drm-kms-planehelpers">Plane Helper Reference</title>
2426	!Edrivers/gpu/drm/drm_plane_helper.c
2427	!Pdrivers/gpu/drm/drm_plane_helper.c overview
2428	    </sect2>
2429	    <sect2>
2430		  <title>Tile group</title>
2431	!Pdrivers/gpu/drm/drm_crtc.c Tile group
2432	    </sect2>
2433	  </sect1>
2434	
2435	  <!-- Internals: kms properties -->
2436	
2437	  <sect1 id="drm-kms-properties">
2438	    <title>KMS Properties</title>
2439	    <para>
2440	      Drivers may need to expose additional parameters to applications than
2441	      those described in the previous sections. KMS supports attaching
2442	      properties to CRTCs, connectors and planes and offers a userspace API to
2443	      list, get and set the property values.
2444	    </para>
2445	    <para>
2446	      Properties are identified by a name that uniquely defines the property
2447	      purpose, and store an associated value. For all property types except blob
2448	      properties the value is a 64-bit unsigned integer.
2449	    </para>
2450	    <para>
2451	      KMS differentiates between properties and property instances. Drivers
2452	      first create properties and then create and associate individual instances
2453	      of those properties to objects. A property can be instantiated multiple
2454	      times and associated with different objects. Values are stored in property
2455	      instances, and all other property information are stored in the property
2456	      and shared between all instances of the property.
2457	    </para>
2458	    <para>
2459	      Every property is created with a type that influences how the KMS core
2460	      handles the property. Supported property types are
2461	      <variablelist>
2462	        <varlistentry>
2463	          <term>DRM_MODE_PROP_RANGE</term>
2464	          <listitem><para>Range properties report their minimum and maximum
2465	            admissible values. The KMS core verifies that values set by
2466	            application fit in that range.</para></listitem>
2467	        </varlistentry>
2468	        <varlistentry>
2469	          <term>DRM_MODE_PROP_ENUM</term>
2470	          <listitem><para>Enumerated properties take a numerical value that
2471	            ranges from 0 to the number of enumerated values defined by the
2472	            property minus one, and associate a free-formed string name to each
2473	            value. Applications can retrieve the list of defined value-name pairs
2474	            and use the numerical value to get and set property instance values.
2475	            </para></listitem>
2476	        </varlistentry>
2477	        <varlistentry>
2478	          <term>DRM_MODE_PROP_BITMASK</term>
2479	          <listitem><para>Bitmask properties are enumeration properties that
2480	            additionally restrict all enumerated values to the 0..63 range.
2481	            Bitmask property instance values combine one or more of the
2482	            enumerated bits defined by the property.</para></listitem>
2483	        </varlistentry>
2484	        <varlistentry>
2485	          <term>DRM_MODE_PROP_BLOB</term>
2486	          <listitem><para>Blob properties store a binary blob without any format
2487	            restriction. The binary blobs are created as KMS standalone objects,
2488	            and blob property instance values store the ID of their associated
2489	            blob object.</para>
2490		    <para>Blob properties are only used for the connector EDID property
2491		    and cannot be created by drivers.</para></listitem>
2492	        </varlistentry>
2493	      </variablelist>
2494	    </para>
2495	    <para>
2496	      To create a property drivers call one of the following functions depending
2497	      on the property type. All property creation functions take property flags
2498	      and name, as well as type-specific arguments.
2499	      <itemizedlist>
2500	        <listitem>
2501	          <synopsis>struct drm_property *drm_property_create_range(struct drm_device *dev, int flags,
2502	                                               const char *name,
2503	                                               uint64_t min, uint64_t max);</synopsis>
2504	          <para>Create a range property with the given minimum and maximum
2505	            values.</para>
2506	        </listitem>
2507	        <listitem>
2508	          <synopsis>struct drm_property *drm_property_create_enum(struct drm_device *dev, int flags,
2509	                                              const char *name,
2510	                                              const struct drm_prop_enum_list *props,
2511	                                              int num_values);</synopsis>
2512	          <para>Create an enumerated property. The <parameter>props</parameter>
2513	            argument points to an array of <parameter>num_values</parameter>
2514	            value-name pairs.</para>
2515	        </listitem>
2516	        <listitem>
2517	          <synopsis>struct drm_property *drm_property_create_bitmask(struct drm_device *dev,
2518	                                                 int flags, const char *name,
2519	                                                 const struct drm_prop_enum_list *props,
2520	                                                 int num_values);</synopsis>
2521	          <para>Create a bitmask property. The <parameter>props</parameter>
2522	            argument points to an array of <parameter>num_values</parameter>
2523	            value-name pairs.</para>
2524	        </listitem>
2525	      </itemizedlist>
2526	    </para>
2527	    <para>
2528	      Properties can additionally be created as immutable, in which case they
2529	      will be read-only for applications but can be modified by the driver. To
2530	      create an immutable property drivers must set the DRM_MODE_PROP_IMMUTABLE
2531	      flag at property creation time.
2532	    </para>
2533	    <para>
2534	      When no array of value-name pairs is readily available at property
2535	      creation time for enumerated or range properties, drivers can create
2536	      the property using the <function>drm_property_create</function> function
2537	      and manually add enumeration value-name pairs by calling the
2538	      <function>drm_property_add_enum</function> function. Care must be taken to
2539	      properly specify the property type through the <parameter>flags</parameter>
2540	      argument.
2541	    </para>
2542	    <para>
2543	      After creating properties drivers can attach property instances to CRTC,
2544	      connector and plane objects by calling the
2545	      <function>drm_object_attach_property</function>. The function takes a
2546	      pointer to the target object, a pointer to the previously created property
2547	      and an initial instance value.
2548	    </para>
2549	    <sect2>
2550		<title>Existing KMS Properties</title>
2551		<para>
2552		The following table gives description of drm properties exposed by various
2553		modules/drivers.
2554		</para>
2555		<table border="1" cellpadding="0" cellspacing="0">
2556		<tbody>
2557		<tr style="font-weight: bold;">
2558		<td valign="top" >Owner Module/Drivers</td>
2559		<td valign="top" >Group</td>
2560		<td valign="top" >Property Name</td>
2561		<td valign="top" >Type</td>
2562		<td valign="top" >Property Values</td>
2563		<td valign="top" >Object attached</td>
2564		<td valign="top" >Description/Restrictions</td>
2565		</tr>
2566		<tr>
2567		<td rowspan="25" valign="top" >DRM</td>
2568		<td rowspan="4" valign="top" >Generic</td>
2569		<td valign="top" >“EDID”</td>
2570		<td valign="top" >BLOB | IMMUTABLE</td>
2571		<td valign="top" >0</td>
2572		<td valign="top" >Connector</td>
2573		<td valign="top" >Contains id of edid blob ptr object.</td>
2574		</tr>
2575		<tr>
2576		<td valign="top" >“DPMS”</td>
2577		<td valign="top" >ENUM</td>
2578		<td valign="top" >{ “On”, “Standby”, “Suspend”, “Off” }</td>
2579		<td valign="top" >Connector</td>
2580		<td valign="top" >Contains DPMS operation mode value.</td>
2581		</tr>
2582		<tr>
2583		<td valign="top" >“PATH”</td>
2584		<td valign="top" >BLOB | IMMUTABLE</td>
2585		<td valign="top" >0</td>
2586		<td valign="top" >Connector</td>
2587		<td valign="top" >Contains topology path to a connector.</td>
2588		</tr>
2589		<tr>
2590		<td valign="top" >“TILE”</td>
2591		<td valign="top" >BLOB | IMMUTABLE</td>
2592		<td valign="top" >0</td>
2593		<td valign="top" >Connector</td>
2594		<td valign="top" >Contains tiling information for a connector.</td>
2595		</tr>
2596		<tr>
2597		<td rowspan="1" valign="top" >Plane</td>
2598		<td valign="top" >“type”</td>
2599		<td valign="top" >ENUM | IMMUTABLE</td>
2600		<td valign="top" >{ "Overlay", "Primary", "Cursor" }</td>
2601		<td valign="top" >Plane</td>
2602		<td valign="top" >Plane type</td>
2603		</tr>
2604		<tr>
2605		<td rowspan="2" valign="top" >DVI-I</td>
2606		<td valign="top" >“subconnector”</td>
2607		<td valign="top" >ENUM</td>
2608		<td valign="top" >{ “Unknown”, “DVI-D”, “DVI-A” }</td>
2609		<td valign="top" >Connector</td>
2610		<td valign="top" >TBD</td>
2611		</tr>
2612		<tr>
2613		<td valign="top" >“select subconnector”</td>
2614		<td valign="top" >ENUM</td>
2615		<td valign="top" >{ “Automatic”, “DVI-D”, “DVI-A” }</td>
2616		<td valign="top" >Connector</td>
2617		<td valign="top" >TBD</td>
2618		</tr>
2619		<tr>
2620		<td rowspan="13" valign="top" >TV</td>
2621		<td valign="top" >“subconnector”</td>
2622		<td valign="top" >ENUM</td>
2623		<td valign="top" >{ "Unknown", "Composite", "SVIDEO", "Component", "SCART" }</td>
2624		<td valign="top" >Connector</td>
2625		<td valign="top" >TBD</td>
2626		</tr>
2627		<tr>
2628		<td valign="top" >“select subconnector”</td>
2629		<td valign="top" >ENUM</td>
2630		<td valign="top" >{ "Automatic", "Composite", "SVIDEO", "Component", "SCART" }</td>
2631		<td valign="top" >Connector</td>
2632		<td valign="top" >TBD</td>
2633		</tr>
2634		<tr>
2635		<td valign="top" >“mode”</td>
2636		<td valign="top" >ENUM</td>
2637		<td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2638		<td valign="top" >Connector</td>
2639		<td valign="top" >TBD</td>
2640		</tr>
2641		<tr>
2642		<td valign="top" >“left margin”</td>
2643		<td valign="top" >RANGE</td>
2644		<td valign="top" >Min=0, Max=100</td>
2645		<td valign="top" >Connector</td>
2646		<td valign="top" >TBD</td>
2647		</tr>
2648		<tr>
2649		<td valign="top" >“right margin”</td>
2650		<td valign="top" >RANGE</td>
2651		<td valign="top" >Min=0, Max=100</td>
2652		<td valign="top" >Connector</td>
2653		<td valign="top" >TBD</td>
2654		</tr>
2655		<tr>
2656		<td valign="top" >“top margin”</td>
2657		<td valign="top" >RANGE</td>
2658		<td valign="top" >Min=0, Max=100</td>
2659		<td valign="top" >Connector</td>
2660		<td valign="top" >TBD</td>
2661		</tr>
2662		<tr>
2663		<td valign="top" >“bottom margin”</td>
2664		<td valign="top" >RANGE</td>
2665		<td valign="top" >Min=0, Max=100</td>
2666		<td valign="top" >Connector</td>
2667		<td valign="top" >TBD</td>
2668		</tr>
2669		<tr>
2670		<td valign="top" >“brightness”</td>
2671		<td valign="top" >RANGE</td>
2672		<td valign="top" >Min=0, Max=100</td>
2673		<td valign="top" >Connector</td>
2674		<td valign="top" >TBD</td>
2675		</tr>
2676		<tr>
2677		<td valign="top" >“contrast”</td>
2678		<td valign="top" >RANGE</td>
2679		<td valign="top" >Min=0, Max=100</td>
2680		<td valign="top" >Connector</td>
2681		<td valign="top" >TBD</td>
2682		</tr>
2683		<tr>
2684		<td valign="top" >“flicker reduction”</td>
2685		<td valign="top" >RANGE</td>
2686		<td valign="top" >Min=0, Max=100</td>
2687		<td valign="top" >Connector</td>
2688		<td valign="top" >TBD</td>
2689		</tr>
2690		<tr>
2691		<td valign="top" >“overscan”</td>
2692		<td valign="top" >RANGE</td>
2693		<td valign="top" >Min=0, Max=100</td>
2694		<td valign="top" >Connector</td>
2695		<td valign="top" >TBD</td>
2696		</tr>
2697		<tr>
2698		<td valign="top" >“saturation”</td>
2699		<td valign="top" >RANGE</td>
2700		<td valign="top" >Min=0, Max=100</td>
2701		<td valign="top" >Connector</td>
2702		<td valign="top" >TBD</td>
2703		</tr>
2704		<tr>
2705		<td valign="top" >“hue”</td>
2706		<td valign="top" >RANGE</td>
2707		<td valign="top" >Min=0, Max=100</td>
2708		<td valign="top" >Connector</td>
2709		<td valign="top" >TBD</td>
2710		</tr>
2711		<tr>
2712		<td rowspan="2" valign="top" >Virtual GPU</td>
2713		<td valign="top" >“suggested X”</td>
2714		<td valign="top" >RANGE</td>
2715		<td valign="top" >Min=0, Max=0xffffffff</td>
2716		<td valign="top" >Connector</td>
2717		<td valign="top" >property to suggest an X offset for a connector</td>
2718		</tr>
2719		<tr>
2720		<td valign="top" >“suggested Y”</td>
2721		<td valign="top" >RANGE</td>
2722		<td valign="top" >Min=0, Max=0xffffffff</td>
2723		<td valign="top" >Connector</td>
2724		<td valign="top" >property to suggest an Y offset for a connector</td>
2725		</tr>
2726		<tr>
2727		<td rowspan="3" valign="top" >Optional</td>
2728		<td valign="top" >“scaling mode”</td>
2729		<td valign="top" >ENUM</td>
2730		<td valign="top" >{ "None", "Full", "Center", "Full aspect" }</td>
2731		<td valign="top" >Connector</td>
2732		<td valign="top" >TBD</td>
2733		</tr>
2734		<tr>
2735		<td valign="top" >"aspect ratio"</td>
2736		<td valign="top" >ENUM</td>
2737		<td valign="top" >{ "None", "4:3", "16:9" }</td>
2738		<td valign="top" >Connector</td>
2739		<td valign="top" >DRM property to set aspect ratio from user space app.
2740			This enum is made generic to allow addition of custom aspect
2741			ratios.</td>
2742		</tr>
2743		<tr>
2744		<td valign="top" >“dirty”</td>
2745		<td valign="top" >ENUM | IMMUTABLE</td>
2746		<td valign="top" >{ "Off", "On", "Annotate" }</td>
2747		<td valign="top" >Connector</td>
2748		<td valign="top" >TBD</td>
2749		</tr>
2750		<tr>
2751		<td rowspan="21" valign="top" >i915</td>
2752		<td rowspan="2" valign="top" >Generic</td>
2753		<td valign="top" >"Broadcast RGB"</td>
2754		<td valign="top" >ENUM</td>
2755		<td valign="top" >{ "Automatic", "Full", "Limited 16:235" }</td>
2756		<td valign="top" >Connector</td>
2757		<td valign="top" >TBD</td>
2758		</tr>
2759		<tr>
2760		<td valign="top" >“audio”</td>
2761		<td valign="top" >ENUM</td>
2762		<td valign="top" >{ "force-dvi", "off", "auto", "on" }</td>
2763		<td valign="top" >Connector</td>
2764		<td valign="top" >TBD</td>
2765		</tr>
2766		<tr>
2767		<td rowspan="1" valign="top" >Plane</td>
2768		<td valign="top" >“rotation”</td>
2769		<td valign="top" >BITMASK</td>
2770		<td valign="top" >{ 0, "rotate-0" }, { 2, "rotate-180" }</td>
2771		<td valign="top" >Plane</td>
2772		<td valign="top" >TBD</td>
2773		</tr>
2774		<tr>
2775		<td rowspan="17" valign="top" >SDVO-TV</td>
2776		<td valign="top" >“mode”</td>
2777		<td valign="top" >ENUM</td>
2778		<td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2779		<td valign="top" >Connector</td>
2780		<td valign="top" >TBD</td>
2781		</tr>
2782		<tr>
2783		<td valign="top" >"left_margin"</td>
2784		<td valign="top" >RANGE</td>
2785		<td valign="top" >Min=0, Max= SDVO dependent</td>
2786		<td valign="top" >Connector</td>
2787		<td valign="top" >TBD</td>
2788		</tr>
2789		<tr>
2790		<td valign="top" >"right_margin"</td>
2791		<td valign="top" >RANGE</td>
2792		<td valign="top" >Min=0, Max= SDVO dependent</td>
2793		<td valign="top" >Connector</td>
2794		<td valign="top" >TBD</td>
2795		</tr>
2796		<tr>
2797		<td valign="top" >"top_margin"</td>
2798		<td valign="top" >RANGE</td>
2799		<td valign="top" >Min=0, Max= SDVO dependent</td>
2800		<td valign="top" >Connector</td>
2801		<td valign="top" >TBD</td>
2802		</tr>
2803		<tr>
2804		<td valign="top" >"bottom_margin"</td>
2805		<td valign="top" >RANGE</td>
2806		<td valign="top" >Min=0, Max= SDVO dependent</td>
2807		<td valign="top" >Connector</td>
2808		<td valign="top" >TBD</td>
2809		</tr>
2810		<tr>
2811		<td valign="top" >“hpos”</td>
2812		<td valign="top" >RANGE</td>
2813		<td valign="top" >Min=0, Max= SDVO dependent</td>
2814		<td valign="top" >Connector</td>
2815		<td valign="top" >TBD</td>
2816		</tr>
2817		<tr>
2818		<td valign="top" >“vpos”</td>
2819		<td valign="top" >RANGE</td>
2820		<td valign="top" >Min=0, Max= SDVO dependent</td>
2821		<td valign="top" >Connector</td>
2822		<td valign="top" >TBD</td>
2823		</tr>
2824		<tr>
2825		<td valign="top" >“contrast”</td>
2826		<td valign="top" >RANGE</td>
2827		<td valign="top" >Min=0, Max= SDVO dependent</td>
2828		<td valign="top" >Connector</td>
2829		<td valign="top" >TBD</td>
2830		</tr>
2831		<tr>
2832		<td valign="top" >“saturation”</td>
2833		<td valign="top" >RANGE</td>
2834		<td valign="top" >Min=0, Max= SDVO dependent</td>
2835		<td valign="top" >Connector</td>
2836		<td valign="top" >TBD</td>
2837		</tr>
2838		<tr>
2839		<td valign="top" >“hue”</td>
2840		<td valign="top" >RANGE</td>
2841		<td valign="top" >Min=0, Max= SDVO dependent</td>
2842		<td valign="top" >Connector</td>
2843		<td valign="top" >TBD</td>
2844		</tr>
2845		<tr>
2846		<td valign="top" >“sharpness”</td>
2847		<td valign="top" >RANGE</td>
2848		<td valign="top" >Min=0, Max= SDVO dependent</td>
2849		<td valign="top" >Connector</td>
2850		<td valign="top" >TBD</td>
2851		</tr>
2852		<tr>
2853		<td valign="top" >“flicker_filter”</td>
2854		<td valign="top" >RANGE</td>
2855		<td valign="top" >Min=0, Max= SDVO dependent</td>
2856		<td valign="top" >Connector</td>
2857		<td valign="top" >TBD</td>
2858		</tr>
2859		<tr>
2860		<td valign="top" >“flicker_filter_adaptive”</td>
2861		<td valign="top" >RANGE</td>
2862		<td valign="top" >Min=0, Max= SDVO dependent</td>
2863		<td valign="top" >Connector</td>
2864		<td valign="top" >TBD</td>
2865		</tr>
2866		<tr>
2867		<td valign="top" >“flicker_filter_2d”</td>
2868		<td valign="top" >RANGE</td>
2869		<td valign="top" >Min=0, Max= SDVO dependent</td>
2870		<td valign="top" >Connector</td>
2871		<td valign="top" >TBD</td>
2872		</tr>
2873		<tr>
2874		<td valign="top" >“tv_chroma_filter”</td>
2875		<td valign="top" >RANGE</td>
2876		<td valign="top" >Min=0, Max= SDVO dependent</td>
2877		<td valign="top" >Connector</td>
2878		<td valign="top" >TBD</td>
2879		</tr>
2880		<tr>
2881		<td valign="top" >“tv_luma_filter”</td>
2882		<td valign="top" >RANGE</td>
2883		<td valign="top" >Min=0, Max= SDVO dependent</td>
2884		<td valign="top" >Connector</td>
2885		<td valign="top" >TBD</td>
2886		</tr>
2887		<tr>
2888		<td valign="top" >“dot_crawl”</td>
2889		<td valign="top" >RANGE</td>
2890		<td valign="top" >Min=0, Max=1</td>
2891		<td valign="top" >Connector</td>
2892		<td valign="top" >TBD</td>
2893		</tr>
2894		<tr>
2895		<td valign="top" >SDVO-TV/LVDS</td>
2896		<td valign="top" >“brightness”</td>
2897		<td valign="top" >RANGE</td>
2898		<td valign="top" >Min=0, Max= SDVO dependent</td>
2899		<td valign="top" >Connector</td>
2900		<td valign="top" >TBD</td>
2901		</tr>
2902		<tr>
2903		<td rowspan="2" valign="top" >CDV gma-500</td>
2904		<td rowspan="2" valign="top" >Generic</td>
2905		<td valign="top" >"Broadcast RGB"</td>
2906		<td valign="top" >ENUM</td>
2907		<td valign="top" >{ “Full”, “Limited 16:235” }</td>
2908		<td valign="top" >Connector</td>
2909		<td valign="top" >TBD</td>
2910		</tr>
2911		<tr>
2912		<td valign="top" >"Broadcast RGB"</td>
2913		<td valign="top" >ENUM</td>
2914		<td valign="top" >{ “off”, “auto”, “on” }</td>
2915		<td valign="top" >Connector</td>
2916		<td valign="top" >TBD</td>
2917		</tr>
2918		<tr>
2919		<td rowspan="19" valign="top" >Poulsbo</td>
2920		<td rowspan="1" valign="top" >Generic</td>
2921		<td valign="top" >“backlight”</td>
2922		<td valign="top" >RANGE</td>
2923		<td valign="top" >Min=0, Max=100</td>
2924		<td valign="top" >Connector</td>
2925		<td valign="top" >TBD</td>
2926		</tr>
2927		<tr>
2928		<td rowspan="17" valign="top" >SDVO-TV</td>
2929		<td valign="top" >“mode”</td>
2930		<td valign="top" >ENUM</td>
2931		<td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2932		<td valign="top" >Connector</td>
2933		<td valign="top" >TBD</td>
2934		</tr>
2935		<tr>
2936		<td valign="top" >"left_margin"</td>
2937		<td valign="top" >RANGE</td>
2938		<td valign="top" >Min=0, Max= SDVO dependent</td>
2939		<td valign="top" >Connector</td>
2940		<td valign="top" >TBD</td>
2941		</tr>
2942		<tr>
2943		<td valign="top" >"right_margin"</td>
2944		<td valign="top" >RANGE</td>
2945		<td valign="top" >Min=0, Max= SDVO dependent</td>
2946		<td valign="top" >Connector</td>
2947		<td valign="top" >TBD</td>
2948		</tr>
2949		<tr>
2950		<td valign="top" >"top_margin"</td>
2951		<td valign="top" >RANGE</td>
2952		<td valign="top" >Min=0, Max= SDVO dependent</td>
2953		<td valign="top" >Connector</td>
2954		<td valign="top" >TBD</td>
2955		</tr>
2956		<tr>
2957		<td valign="top" >"bottom_margin"</td>
2958		<td valign="top" >RANGE</td>
2959		<td valign="top" >Min=0, Max= SDVO dependent</td>
2960		<td valign="top" >Connector</td>
2961		<td valign="top" >TBD</td>
2962		</tr>
2963		<tr>
2964		<td valign="top" >“hpos”</td>
2965		<td valign="top" >RANGE</td>
2966		<td valign="top" >Min=0, Max= SDVO dependent</td>
2967		<td valign="top" >Connector</td>
2968		<td valign="top" >TBD</td>
2969		</tr>
2970		<tr>
2971		<td valign="top" >“vpos”</td>
2972		<td valign="top" >RANGE</td>
2973		<td valign="top" >Min=0, Max= SDVO dependent</td>
2974		<td valign="top" >Connector</td>
2975		<td valign="top" >TBD</td>
2976		</tr>
2977		<tr>
2978		<td valign="top" >“contrast”</td>
2979		<td valign="top" >RANGE</td>
2980		<td valign="top" >Min=0, Max= SDVO dependent</td>
2981		<td valign="top" >Connector</td>
2982		<td valign="top" >TBD</td>
2983		</tr>
2984		<tr>
2985		<td valign="top" >“saturation”</td>
2986		<td valign="top" >RANGE</td>
2987		<td valign="top" >Min=0, Max= SDVO dependent</td>
2988		<td valign="top" >Connector</td>
2989		<td valign="top" >TBD</td>
2990		</tr>
2991		<tr>
2992		<td valign="top" >“hue”</td>
2993		<td valign="top" >RANGE</td>
2994		<td valign="top" >Min=0, Max= SDVO dependent</td>
2995		<td valign="top" >Connector</td>
2996		<td valign="top" >TBD</td>
2997		</tr>
2998		<tr>
2999		<td valign="top" >“sharpness”</td>
3000		<td valign="top" >RANGE</td>
3001		<td valign="top" >Min=0, Max= SDVO dependent</td>
3002		<td valign="top" >Connector</td>
3003		<td valign="top" >TBD</td>
3004		</tr>
3005		<tr>
3006		<td valign="top" >“flicker_filter”</td>
3007		<td valign="top" >RANGE</td>
3008		<td valign="top" >Min=0, Max= SDVO dependent</td>
3009		<td valign="top" >Connector</td>
3010		<td valign="top" >TBD</td>
3011		</tr>
3012		<tr>
3013		<td valign="top" >“flicker_filter_adaptive”</td>
3014		<td valign="top" >RANGE</td>
3015		<td valign="top" >Min=0, Max= SDVO dependent</td>
3016		<td valign="top" >Connector</td>
3017		<td valign="top" >TBD</td>
3018		</tr>
3019		<tr>
3020		<td valign="top" >“flicker_filter_2d”</td>
3021		<td valign="top" >RANGE</td>
3022		<td valign="top" >Min=0, Max= SDVO dependent</td>
3023		<td valign="top" >Connector</td>
3024		<td valign="top" >TBD</td>
3025		</tr>
3026		<tr>
3027		<td valign="top" >“tv_chroma_filter”</td>
3028		<td valign="top" >RANGE</td>
3029		<td valign="top" >Min=0, Max= SDVO dependent</td>
3030		<td valign="top" >Connector</td>
3031		<td valign="top" >TBD</td>
3032		</tr>
3033		<tr>
3034		<td valign="top" >“tv_luma_filter”</td>
3035		<td valign="top" >RANGE</td>
3036		<td valign="top" >Min=0, Max= SDVO dependent</td>
3037		<td valign="top" >Connector</td>
3038		<td valign="top" >TBD</td>
3039		</tr>
3040		<tr>
3041		<td valign="top" >“dot_crawl”</td>
3042		<td valign="top" >RANGE</td>
3043		<td valign="top" >Min=0, Max=1</td>
3044		<td valign="top" >Connector</td>
3045		<td valign="top" >TBD</td>
3046		</tr>
3047		<tr>
3048		<td valign="top" >SDVO-TV/LVDS</td>
3049		<td valign="top" >“brightness”</td>
3050		<td valign="top" >RANGE</td>
3051		<td valign="top" >Min=0, Max= SDVO dependent</td>
3052		<td valign="top" >Connector</td>
3053		<td valign="top" >TBD</td>
3054		</tr>
3055		<tr>
3056		<td rowspan="11" valign="top" >armada</td>
3057		<td rowspan="2" valign="top" >CRTC</td>
3058		<td valign="top" >"CSC_YUV"</td>
3059		<td valign="top" >ENUM</td>
3060		<td valign="top" >{ "Auto" , "CCIR601", "CCIR709" }</td>
3061		<td valign="top" >CRTC</td>
3062		<td valign="top" >TBD</td>
3063		</tr>
3064		<tr>
3065		<td valign="top" >"CSC_RGB"</td>
3066		<td valign="top" >ENUM</td>
3067		<td valign="top" >{ "Auto", "Computer system", "Studio" }</td>
3068		<td valign="top" >CRTC</td>
3069		<td valign="top" >TBD</td>
3070		</tr>
3071		<tr>
3072		<td rowspan="9" valign="top" >Overlay</td>
3073		<td valign="top" >"colorkey"</td>
3074		<td valign="top" >RANGE</td>
3075		<td valign="top" >Min=0, Max=0xffffff</td>
3076		<td valign="top" >Plane</td>
3077		<td valign="top" >TBD</td>
3078		</tr>
3079		<tr>
3080		<td valign="top" >"colorkey_min"</td>
3081		<td valign="top" >RANGE</td>
3082		<td valign="top" >Min=0, Max=0xffffff</td>
3083		<td valign="top" >Plane</td>
3084		<td valign="top" >TBD</td>
3085		</tr>
3086		<tr>
3087		<td valign="top" >"colorkey_max"</td>
3088		<td valign="top" >RANGE</td>
3089		<td valign="top" >Min=0, Max=0xffffff</td>
3090		<td valign="top" >Plane</td>
3091		<td valign="top" >TBD</td>
3092		</tr>
3093		<tr>
3094		<td valign="top" >"colorkey_val"</td>
3095		<td valign="top" >RANGE</td>
3096		<td valign="top" >Min=0, Max=0xffffff</td>
3097		<td valign="top" >Plane</td>
3098		<td valign="top" >TBD</td>
3099		</tr>
3100		<tr>
3101		<td valign="top" >"colorkey_alpha"</td>
3102		<td valign="top" >RANGE</td>
3103		<td valign="top" >Min=0, Max=0xffffff</td>
3104		<td valign="top" >Plane</td>
3105		<td valign="top" >TBD</td>
3106		</tr>
3107		<tr>
3108		<td valign="top" >"colorkey_mode"</td>
3109		<td valign="top" >ENUM</td>
3110		<td valign="top" >{ "disabled", "Y component", "U component"
3111		, "V component", "RGB", “R component", "G component", "B component" }</td>
3112		<td valign="top" >Plane</td>
3113		<td valign="top" >TBD</td>
3114		</tr>
3115		<tr>
3116		<td valign="top" >"brightness"</td>
3117		<td valign="top" >RANGE</td>
3118		<td valign="top" >Min=0, Max=256 + 255</td>
3119		<td valign="top" >Plane</td>
3120		<td valign="top" >TBD</td>
3121		</tr>
3122		<tr>
3123		<td valign="top" >"contrast"</td>
3124		<td valign="top" >RANGE</td>
3125		<td valign="top" >Min=0, Max=0x7fff</td>
3126		<td valign="top" >Plane</td>
3127		<td valign="top" >TBD</td>
3128		</tr>
3129		<tr>
3130		<td valign="top" >"saturation"</td>
3131		<td valign="top" >RANGE</td>
3132		<td valign="top" >Min=0, Max=0x7fff</td>
3133		<td valign="top" >Plane</td>
3134		<td valign="top" >TBD</td>
3135		</tr>
3136		<tr>
3137		<td rowspan="2" valign="top" >exynos</td>
3138		<td valign="top" >CRTC</td>
3139		<td valign="top" >“mode”</td>
3140		<td valign="top" >ENUM</td>
3141		<td valign="top" >{ "normal", "blank" }</td>
3142		<td valign="top" >CRTC</td>
3143		<td valign="top" >TBD</td>
3144		</tr>
3145		<tr>
3146		<td valign="top" >Overlay</td>
3147		<td valign="top" >“zpos”</td>
3148		<td valign="top" >RANGE</td>
3149		<td valign="top" >Min=0, Max=MAX_PLANE-1</td>
3150		<td valign="top" >Plane</td>
3151		<td valign="top" >TBD</td>
3152		</tr>
3153		<tr>
3154		<td rowspan="2" valign="top" >i2c/ch7006_drv</td>
3155		<td valign="top" >Generic</td>
3156		<td valign="top" >“scale”</td>
3157		<td valign="top" >RANGE</td>
3158		<td valign="top" >Min=0, Max=2</td>
3159		<td valign="top" >Connector</td>
3160		<td valign="top" >TBD</td>
3161		</tr>
3162		<tr>
3163		<td rowspan="1" valign="top" >TV</td>
3164		<td valign="top" >“mode”</td>
3165		<td valign="top" >ENUM</td>
3166		<td valign="top" >{ "PAL", "PAL-M","PAL-N"}, ”PAL-Nc"
3167		, "PAL-60", "NTSC-M", "NTSC-J" }</td>
3168		<td valign="top" >Connector</td>
3169		<td valign="top" >TBD</td>
3170		</tr>
3171		<tr>
3172		<td rowspan="15" valign="top" >nouveau</td>
3173		<td rowspan="6" valign="top" >NV10 Overlay</td>
3174		<td valign="top" >"colorkey"</td>
3175		<td valign="top" >RANGE</td>
3176		<td valign="top" >Min=0, Max=0x01ffffff</td>
3177		<td valign="top" >Plane</td>
3178		<td valign="top" >TBD</td>
3179		</tr>
3180		<tr>
3181		<td valign="top" >“contrast”</td>
3182		<td valign="top" >RANGE</td>
3183		<td valign="top" >Min=0, Max=8192-1</td>
3184		<td valign="top" >Plane</td>
3185		<td valign="top" >TBD</td>
3186		</tr>
3187		<tr>
3188		<td valign="top" >“brightness”</td>
3189		<td valign="top" >RANGE</td>
3190		<td valign="top" >Min=0, Max=1024</td>
3191		<td valign="top" >Plane</td>
3192		<td valign="top" >TBD</td>
3193		</tr>
3194		<tr>
3195		<td valign="top" >“hue”</td>
3196		<td valign="top" >RANGE</td>
3197		<td valign="top" >Min=0, Max=359</td>
3198		<td valign="top" >Plane</td>
3199		<td valign="top" >TBD</td>
3200		</tr>
3201		<tr>
3202		<td valign="top" >“saturation”</td>
3203		<td valign="top" >RANGE</td>
3204		<td valign="top" >Min=0, Max=8192-1</td>
3205		<td valign="top" >Plane</td>
3206		<td valign="top" >TBD</td>
3207		</tr>
3208		<tr>
3209		<td valign="top" >“iturbt_709”</td>
3210		<td valign="top" >RANGE</td>
3211		<td valign="top" >Min=0, Max=1</td>
3212		<td valign="top" >Plane</td>
3213		<td valign="top" >TBD</td>
3214		</tr>
3215		<tr>
3216		<td rowspan="2" valign="top" >Nv04 Overlay</td>
3217		<td valign="top" >“colorkey”</td>
3218		<td valign="top" >RANGE</td>
3219		<td valign="top" >Min=0, Max=0x01ffffff</td>
3220		<td valign="top" >Plane</td>
3221		<td valign="top" >TBD</td>
3222		</tr>
3223		<tr>
3224		<td valign="top" >“brightness”</td>
3225		<td valign="top" >RANGE</td>
3226		<td valign="top" >Min=0, Max=1024</td>
3227		<td valign="top" >Plane</td>
3228		<td valign="top" >TBD</td>
3229		</tr>
3230		<tr>
3231		<td rowspan="7" valign="top" >Display</td>
3232		<td valign="top" >“dithering mode”</td>
3233		<td valign="top" >ENUM</td>
3234		<td valign="top" >{ "auto", "off", "on" }</td>
3235		<td valign="top" >Connector</td>
3236		<td valign="top" >TBD</td>
3237		</tr>
3238		<tr>
3239		<td valign="top" >“dithering depth”</td>
3240		<td valign="top" >ENUM</td>
3241		<td valign="top" >{ "auto", "off", "on", "static 2x2", "dynamic 2x2", "temporal" }</td>
3242		<td valign="top" >Connector</td>
3243		<td valign="top" >TBD</td>
3244		</tr>
3245		<tr>
3246		<td valign="top" >“underscan”</td>
3247		<td valign="top" >ENUM</td>
3248		<td valign="top" >{ "auto", "6 bpc", "8 bpc" }</td>
3249		<td valign="top" >Connector</td>
3250		<td valign="top" >TBD</td>
3251		</tr>
3252		<tr>
3253		<td valign="top" >“underscan hborder”</td>
3254		<td valign="top" >RANGE</td>
3255		<td valign="top" >Min=0, Max=128</td>
3256		<td valign="top" >Connector</td>
3257		<td valign="top" >TBD</td>
3258		</tr>
3259		<tr>
3260		<td valign="top" >“underscan vborder”</td>
3261		<td valign="top" >RANGE</td>
3262		<td valign="top" >Min=0, Max=128</td>
3263		<td valign="top" >Connector</td>
3264		<td valign="top" >TBD</td>
3265		</tr>
3266		<tr>
3267		<td valign="top" >“vibrant hue”</td>
3268		<td valign="top" >RANGE</td>
3269		<td valign="top" >Min=0, Max=180</td>
3270		<td valign="top" >Connector</td>
3271		<td valign="top" >TBD</td>
3272		</tr>
3273		<tr>
3274		<td valign="top" >“color vibrance”</td>
3275		<td valign="top" >RANGE</td>
3276		<td valign="top" >Min=0, Max=200</td>
3277		<td valign="top" >Connector</td>
3278		<td valign="top" >TBD</td>
3279		</tr>
3280		<tr>
3281		<td rowspan="2" valign="top" >omap</td>
3282		<td rowspan="2" valign="top" >Generic</td>
3283		<td valign="top" >“rotation”</td>
3284		<td valign="top" >BITMASK</td>
3285		<td valign="top" >{ 0, "rotate-0" },
3286		{ 1, "rotate-90" },
3287		{ 2, "rotate-180" },
3288		{ 3, "rotate-270" },
3289		{ 4, "reflect-x" },
3290		{ 5, "reflect-y" }</td>
3291		<td valign="top" >CRTC, Plane</td>
3292		<td valign="top" >TBD</td>
3293		</tr>
3294		<tr>
3295		<td valign="top" >“zorder”</td>
3296		<td valign="top" >RANGE</td>
3297		<td valign="top" >Min=0, Max=3</td>
3298		<td valign="top" >CRTC, Plane</td>
3299		<td valign="top" >TBD</td>
3300		</tr>
3301		<tr>
3302		<td valign="top" >qxl</td>
3303		<td valign="top" >Generic</td>
3304		<td valign="top" >“hotplug_mode_update"</td>
3305		<td valign="top" >RANGE</td>
3306		<td valign="top" >Min=0, Max=1</td>
3307		<td valign="top" >Connector</td>
3308		<td valign="top" >TBD</td>
3309		</tr>
3310		<tr>
3311		<td rowspan="9" valign="top" >radeon</td>
3312		<td valign="top" >DVI-I</td>
3313		<td valign="top" >“coherent”</td>
3314		<td valign="top" >RANGE</td>
3315		<td valign="top" >Min=0, Max=1</td>
3316		<td valign="top" >Connector</td>
3317		<td valign="top" >TBD</td>
3318		</tr>
3319		<tr>
3320		<td valign="top" >DAC enable load detect</td>
3321		<td valign="top" >“load detection”</td>
3322		<td valign="top" >RANGE</td>
3323		<td valign="top" >Min=0, Max=1</td>
3324		<td valign="top" >Connector</td>
3325		<td valign="top" >TBD</td>
3326		</tr>
3327		<tr>
3328		<td valign="top" >TV Standard</td>
3329		<td valign="top" >"tv standard"</td>
3330		<td valign="top" >ENUM</td>
3331		<td valign="top" >{ "ntsc", "pal", "pal-m", "pal-60", "ntsc-j"
3332		, "scart-pal", "pal-cn", "secam" }</td>
3333		<td valign="top" >Connector</td>
3334		<td valign="top" >TBD</td>
3335		</tr>
3336		<tr>
3337		<td valign="top" >legacy TMDS PLL detect</td>
3338		<td valign="top" >"tmds_pll"</td>
3339		<td valign="top" >ENUM</td>
3340		<td valign="top" >{ "driver", "bios" }</td>
3341		<td valign="top" >-</td>
3342		<td valign="top" >TBD</td>
3343		</tr>
3344		<tr>
3345		<td rowspan="3" valign="top" >Underscan</td>
3346		<td valign="top" >"underscan"</td>
3347		<td valign="top" >ENUM</td>
3348		<td valign="top" >{ "off", "on", "auto" }</td>
3349		<td valign="top" >Connector</td>
3350		<td valign="top" >TBD</td>
3351		</tr>
3352		<tr>
3353		<td valign="top" >"underscan hborder"</td>
3354		<td valign="top" >RANGE</td>
3355		<td valign="top" >Min=0, Max=128</td>
3356		<td valign="top" >Connector</td>
3357		<td valign="top" >TBD</td>
3358		</tr>
3359		<tr>
3360		<td valign="top" >"underscan vborder"</td>
3361		<td valign="top" >RANGE</td>
3362		<td valign="top" >Min=0, Max=128</td>
3363		<td valign="top" >Connector</td>
3364		<td valign="top" >TBD</td>
3365		</tr>
3366		<tr>
3367		<td valign="top" >Audio</td>
3368		<td valign="top" >“audio”</td>
3369		<td valign="top" >ENUM</td>
3370		<td valign="top" >{ "off", "on", "auto" }</td>
3371		<td valign="top" >Connector</td>
3372		<td valign="top" >TBD</td>
3373		</tr>
3374		<tr>
3375		<td valign="top" >FMT Dithering</td>
3376		<td valign="top" >“dither”</td>
3377		<td valign="top" >ENUM</td>
3378		<td valign="top" >{ "off", "on" }</td>
3379		<td valign="top" >Connector</td>
3380		<td valign="top" >TBD</td>
3381		</tr>
3382		<tr>
3383		<td rowspan="3" valign="top" >rcar-du</td>
3384		<td rowspan="3" valign="top" >Generic</td>
3385		<td valign="top" >"alpha"</td>
3386		<td valign="top" >RANGE</td>
3387		<td valign="top" >Min=0, Max=255</td>
3388		<td valign="top" >Plane</td>
3389		<td valign="top" >TBD</td>
3390		</tr>
3391		<tr>
3392		<td valign="top" >"colorkey"</td>
3393		<td valign="top" >RANGE</td>
3394		<td valign="top" >Min=0, Max=0x01ffffff</td>
3395		<td valign="top" >Plane</td>
3396		<td valign="top" >TBD</td>
3397		</tr>
3398		<tr>
3399		<td valign="top" >"zpos"</td>
3400		<td valign="top" >RANGE</td>
3401		<td valign="top" >Min=1, Max=7</td>
3402		<td valign="top" >Plane</td>
3403		<td valign="top" >TBD</td>
3404		</tr>
3405		</tbody>
3406		</table>
3407	    </sect2>
3408	  </sect1>
3409	
3410	  <!-- Internals: vertical blanking -->
3411	
3412	  <sect1 id="drm-vertical-blank">
3413	    <title>Vertical Blanking</title>
3414	    <para>
3415	      Vertical blanking plays a major role in graphics rendering. To achieve
3416	      tear-free display, users must synchronize page flips and/or rendering to
3417	      vertical blanking. The DRM API offers ioctls to perform page flips
3418	      synchronized to vertical blanking and wait for vertical blanking.
3419	    </para>
3420	    <para>
3421	      The DRM core handles most of the vertical blanking management logic, which
3422	      involves filtering out spurious interrupts, keeping race-free blanking
3423	      counters, coping with counter wrap-around and resets and keeping use
3424	      counts. It relies on the driver to generate vertical blanking interrupts
3425	      and optionally provide a hardware vertical blanking counter. Drivers must
3426	      implement the following operations.
3427	    </para>
3428	    <itemizedlist>
3429	      <listitem>
3430	        <synopsis>int (*enable_vblank) (struct drm_device *dev, int crtc);
3431	void (*disable_vblank) (struct drm_device *dev, int crtc);</synopsis>
3432	        <para>
3433		  Enable or disable vertical blanking interrupts for the given CRTC.
3434		</para>
3435	      </listitem>
3436	      <listitem>
3437	        <synopsis>u32 (*get_vblank_counter) (struct drm_device *dev, int crtc);</synopsis>
3438	        <para>
3439		  Retrieve the value of the vertical blanking counter for the given
3440		  CRTC. If the hardware maintains a vertical blanking counter its value
3441		  should be returned. Otherwise drivers can use the
3442		  <function>drm_vblank_count</function> helper function to handle this
3443		  operation.
3444		</para>
3445	      </listitem>
3446	    </itemizedlist>
3447	    <para>
3448	      Drivers must initialize the vertical blanking handling core with a call to
3449	      <function>drm_vblank_init</function> in their
3450	      <methodname>load</methodname> operation. The function will set the struct
3451	      <structname>drm_device</structname>
3452	      <structfield>vblank_disable_allowed</structfield> field to 0. This will
3453	      keep vertical blanking interrupts enabled permanently until the first mode
3454	      set operation, where <structfield>vblank_disable_allowed</structfield> is
3455	      set to 1. The reason behind this is not clear. Drivers can set the field
3456	      to 1 after <function>calling drm_vblank_init</function> to make vertical
3457	      blanking interrupts dynamically managed from the beginning.
3458	    </para>
3459	    <para>
3460	      Vertical blanking interrupts can be enabled by the DRM core or by drivers
3461	      themselves (for instance to handle page flipping operations). The DRM core
3462	      maintains a vertical blanking use count to ensure that the interrupts are
3463	      not disabled while a user still needs them. To increment the use count,
3464	      drivers call <function>drm_vblank_get</function>. Upon return vertical
3465	      blanking interrupts are guaranteed to be enabled.
3466	    </para>
3467	    <para>
3468	      To decrement the use count drivers call
3469	      <function>drm_vblank_put</function>. Only when the use count drops to zero
3470	      will the DRM core disable the vertical blanking interrupts after a delay
3471	      by scheduling a timer. The delay is accessible through the vblankoffdelay
3472	      module parameter or the <varname>drm_vblank_offdelay</varname> global
3473	      variable and expressed in milliseconds. Its default value is 5000 ms.
3474	      Zero means never disable, and a negative value means disable immediately.
3475	      Drivers may override the behaviour by setting the
3476	      <structname>drm_device</structname>
3477	      <structfield>vblank_disable_immediate</structfield> flag, which when set
3478	      causes vblank interrupts to be disabled immediately regardless of the
3479	      drm_vblank_offdelay value. The flag should only be set if there's a
3480	      properly working hardware vblank counter present.
3481	    </para>
3482	    <para>
3483	      When a vertical blanking interrupt occurs drivers only need to call the
3484	      <function>drm_handle_vblank</function> function to account for the
3485	      interrupt.
3486	    </para>
3487	    <para>
3488	      Resources allocated by <function>drm_vblank_init</function> must be freed
3489	      with a call to <function>drm_vblank_cleanup</function> in the driver
3490	      <methodname>unload</methodname> operation handler.
3491	    </para>
3492	    <sect2>
3493	      <title>Vertical Blanking and Interrupt Handling Functions Reference</title>
3494	!Edrivers/gpu/drm/drm_irq.c
3495	!Finclude/drm/drmP.h drm_crtc_vblank_waitqueue
3496	    </sect2>
3497	  </sect1>
3498	
3499	  <!-- Internals: open/close, file operations and ioctls -->
3500	
3501	  <sect1>
3502	    <title>Open/Close, File Operations and IOCTLs</title>
3503	    <sect2>
3504	      <title>Open and Close</title>
3505	      <synopsis>int (*firstopen) (struct drm_device *);
3506	void (*lastclose) (struct drm_device *);
3507	int (*open) (struct drm_device *, struct drm_file *);
3508	void (*preclose) (struct drm_device *, struct drm_file *);
3509	void (*postclose) (struct drm_device *, struct drm_file *);</synopsis>
3510	      <abstract>Open and close handlers. None of those methods are mandatory.
3511	      </abstract>
3512	      <para>
3513	        The <methodname>firstopen</methodname> method is called by the DRM core
3514		for legacy UMS (User Mode Setting) drivers only when an application
3515		opens a device that has no other opened file handle. UMS drivers can
3516		implement it to acquire device resources. KMS drivers can't use the
3517		method and must acquire resources in the <methodname>load</methodname>
3518		method instead.
3519	      </para>
3520	      <para>
3521		Similarly the <methodname>lastclose</methodname> method is called when
3522		the last application holding a file handle opened on the device closes
3523		it, for both UMS and KMS drivers. Additionally, the method is also
3524		called at module unload time or, for hot-pluggable devices, when the
3525		device is unplugged. The <methodname>firstopen</methodname> and
3526		<methodname>lastclose</methodname> calls can thus be unbalanced.
3527	      </para>
3528	      <para>
3529	        The <methodname>open</methodname> method is called every time the device
3530		is opened by an application. Drivers can allocate per-file private data
3531		in this method and store them in the struct
3532		<structname>drm_file</structname> <structfield>driver_priv</structfield>
3533		field. Note that the <methodname>open</methodname> method is called
3534		before <methodname>firstopen</methodname>.
3535	      </para>
3536	      <para>
3537	        The close operation is split into <methodname>preclose</methodname> and
3538		<methodname>postclose</methodname> methods. Drivers must stop and
3539		cleanup all per-file operations in the <methodname>preclose</methodname>
3540		method. For instance pending vertical blanking and page flip events must
3541		be cancelled. No per-file operation is allowed on the file handle after
3542		returning from the <methodname>preclose</methodname> method.
3543	      </para>
3544	      <para>
3545	        Finally the <methodname>postclose</methodname> method is called as the
3546		last step of the close operation, right before calling the
3547		<methodname>lastclose</methodname> method if no other open file handle
3548		exists for the device. Drivers that have allocated per-file private data
3549		in the <methodname>open</methodname> method should free it here.
3550	      </para>
3551	      <para>
3552	        The <methodname>lastclose</methodname> method should restore CRTC and
3553		plane properties to default value, so that a subsequent open of the
3554		device will not inherit state from the previous user. It can also be
3555		used to execute delayed power switching state changes, e.g. in
3556		conjunction with the vga-switcheroo infrastructure. Beyond that KMS
3557		drivers should not do any further cleanup. Only legacy UMS drivers might
3558		need to clean up device state so that the vga console or an independent
3559		fbdev driver could take over.
3560	      </para>
3561	    </sect2>
3562	    <sect2>
3563	      <title>File Operations</title>
3564	      <synopsis>const struct file_operations *fops</synopsis>
3565	      <abstract>File operations for the DRM device node.</abstract>
3566	      <para>
3567	        Drivers must define the file operations structure that forms the DRM
3568		userspace API entry point, even though most of those operations are
3569		implemented in the DRM core. The <methodname>open</methodname>,
3570		<methodname>release</methodname> and <methodname>ioctl</methodname>
3571		operations are handled by
3572		<programlisting>
3573		.owner = THIS_MODULE,
3574		.open = drm_open,
3575		.release = drm_release,
3576		.unlocked_ioctl = drm_ioctl,
3577	  #ifdef CONFIG_COMPAT
3578		.compat_ioctl = drm_compat_ioctl,
3579	  #endif
3580	        </programlisting>
3581	      </para>
3582	      <para>
3583	        Drivers that implement private ioctls that requires 32/64bit
3584		compatibility support must provide their own
3585		<methodname>compat_ioctl</methodname> handler that processes private
3586		ioctls and calls <function>drm_compat_ioctl</function> for core ioctls.
3587	      </para>
3588	      <para>
3589	        The <methodname>read</methodname> and <methodname>poll</methodname>
3590		operations provide support for reading DRM events and polling them. They
3591		are implemented by
3592		<programlisting>
3593		.poll = drm_poll,
3594		.read = drm_read,
3595		.llseek = no_llseek,
3596		</programlisting>
3597	      </para>
3598	      <para>
3599	        The memory mapping implementation varies depending on how the driver
3600		manages memory. Pre-GEM drivers will use <function>drm_mmap</function>,
3601		while GEM-aware drivers will use <function>drm_gem_mmap</function>. See
3602		<xref linkend="drm-gem"/>.
3603		<programlisting>
3604		.mmap = drm_gem_mmap,
3605		</programlisting>
3606	      </para>
3607	      <para>
3608	        No other file operation is supported by the DRM API.
3609	      </para>
3610	    </sect2>
3611	    <sect2>
3612	      <title>IOCTLs</title>
3613	      <synopsis>struct drm_ioctl_desc *ioctls;
3614	int num_ioctls;</synopsis>
3615	      <abstract>Driver-specific ioctls descriptors table.</abstract>
3616	      <para>
3617	        Driver-specific ioctls numbers start at DRM_COMMAND_BASE. The ioctls
3618		descriptors table is indexed by the ioctl number offset from the base
3619		value. Drivers can use the DRM_IOCTL_DEF_DRV() macro to initialize the
3620		table entries.
3621	      </para>
3622	      <para>
3623	        <programlisting>DRM_IOCTL_DEF_DRV(ioctl, func, flags)</programlisting>
3624		<para>
3625		  <parameter>ioctl</parameter> is the ioctl name. Drivers must define
3626		  the DRM_##ioctl and DRM_IOCTL_##ioctl macros to the ioctl number
3627		  offset from DRM_COMMAND_BASE and the ioctl number respectively. The
3628		  first macro is private to the device while the second must be exposed
3629		  to userspace in a public header.
3630		</para>
3631		<para>
3632		  <parameter>func</parameter> is a pointer to the ioctl handler function
3633		  compatible with the <type>drm_ioctl_t</type> type.
3634		  <programlisting>typedef int drm_ioctl_t(struct drm_device *dev, void *data,
3635			struct drm_file *file_priv);</programlisting>
3636		</para>
3637		<para>
3638		  <parameter>flags</parameter> is a bitmask combination of the following
3639		  values. It restricts how the ioctl is allowed to be called.
3640		  <itemizedlist>
3641		    <listitem><para>
3642		      DRM_AUTH - Only authenticated callers allowed
3643		    </para></listitem>
3644		    <listitem><para>
3645		      DRM_MASTER - The ioctl can only be called on the master file
3646		      handle
3647		    </para></listitem>
3648	            <listitem><para>
3649		      DRM_ROOT_ONLY - Only callers with the SYSADMIN capability allowed
3650		    </para></listitem>
3651	            <listitem><para>
3652		      DRM_CONTROL_ALLOW - The ioctl can only be called on a control
3653		      device
3654		    </para></listitem>
3655	            <listitem><para>
3656		      DRM_UNLOCKED - The ioctl handler will be called without locking
3657		      the DRM global mutex
3658		    </para></listitem>
3659		  </itemizedlist>
3660		</para>
3661	      </para>
3662	    </sect2>
3663	  </sect1>
3664	  <sect1>
3665	    <title>Legacy Support Code</title>
3666	    <para>
3667	      The section very briefly covers some of the old legacy support code which
3668	      is only used by old DRM drivers which have done a so-called shadow-attach
3669	      to the underlying device instead of registering as a real driver. This
3670	      also includes some of the old generic buffer management and command
3671	      submission code. Do not use any of this in new and modern drivers.
3672	    </para>
3673	
3674	    <sect2>
3675	      <title>Legacy Suspend/Resume</title>
3676	      <para>
3677		The DRM core provides some suspend/resume code, but drivers wanting full
3678		suspend/resume support should provide save() and restore() functions.
3679		These are called at suspend, hibernate, or resume time, and should perform
3680		any state save or restore required by your device across suspend or
3681		hibernate states.
3682	      </para>
3683	      <synopsis>int (*suspend) (struct drm_device *, pm_message_t state);
3684	  int (*resume) (struct drm_device *);</synopsis>
3685	      <para>
3686		Those are legacy suspend and resume methods which
3687		<emphasis>only</emphasis> work with the legacy shadow-attach driver
3688		registration functions. New driver should use the power management
3689		interface provided by their bus type (usually through
3690		the struct <structname>device_driver</structname> dev_pm_ops) and set
3691		these methods to NULL.
3692	      </para>
3693	    </sect2>
3694	
3695	    <sect2>
3696	      <title>Legacy DMA Services</title>
3697	      <para>
3698		This should cover how DMA mapping etc. is supported by the core.
3699		These functions are deprecated and should not be used.
3700	      </para>
3701	    </sect2>
3702	  </sect1>
3703	  </chapter>
3704	
3705	<!-- TODO
3706	
3707	- Add a glossary
3708	- Document the struct_mutex catch-all lock
3709	- Document connector properties
3710	
3711	- Why is the load method optional?
3712	- What are drivers supposed to set the initial display state to, and how?
3713	  Connector's DPMS states are not initialized and are thus equal to
3714	  DRM_MODE_DPMS_ON. The fbcon compatibility layer calls
3715	  drm_helper_disable_unused_functions(), which disables unused encoders and
3716	  CRTCs, but doesn't touch the connectors' DPMS state, and
3717	  drm_helper_connector_dpms() in reaction to fbdev blanking events. Do drivers
3718	  that don't implement (or just don't use) fbcon compatibility need to call
3719	  those functions themselves?
3720	- KMS drivers must call drm_vblank_pre_modeset() and drm_vblank_post_modeset()
3721	  around mode setting. Should this be done in the DRM core?
3722	- vblank_disable_allowed is set to 1 in the first drm_vblank_post_modeset()
3723	  call and never set back to 0. It seems to be safe to permanently set it to 1
3724	  in drm_vblank_init() for KMS driver, and it might be safe for UMS drivers as
3725	  well. This should be investigated.
3726	- crtc and connector .save and .restore operations are only used internally in
3727	  drivers, should they be removed from the core?
3728	- encoder mid-layer .save and .restore operations are only used internally in
3729	  drivers, should they be removed from the core?
3730	- encoder mid-layer .detect operation is only used internally in drivers,
3731	  should it be removed from the core?
3732	-->
3733	
3734	  <!-- External interfaces -->
3735	
3736	  <chapter id="drmExternals">
3737	    <title>Userland interfaces</title>
3738	    <para>
3739	      The DRM core exports several interfaces to applications,
3740	      generally intended to be used through corresponding libdrm
3741	      wrapper functions.  In addition, drivers export device-specific
3742	      interfaces for use by userspace drivers &amp; device-aware
3743	      applications through ioctls and sysfs files.
3744	    </para>
3745	    <para>
3746	      External interfaces include: memory mapping, context management,
3747	      DMA operations, AGP management, vblank control, fence
3748	      management, memory management, and output management.
3749	    </para>
3750	    <para>
3751	      Cover generic ioctls and sysfs layout here.  We only need high-level
3752	      info, since man pages should cover the rest.
3753	    </para>
3754	
3755	  <!-- External: render nodes -->
3756	
3757	    <sect1>
3758	      <title>Render nodes</title>
3759	      <para>
3760	        DRM core provides multiple character-devices for user-space to use.
3761	        Depending on which device is opened, user-space can perform a different
3762	        set of operations (mainly ioctls). The primary node is always created
3763	        and called card&lt;num&gt;. Additionally, a currently
3764	        unused control node, called controlD&lt;num&gt; is also
3765	        created. The primary node provides all legacy operations and
3766	        historically was the only interface used by userspace. With KMS, the
3767	        control node was introduced. However, the planned KMS control interface
3768	        has never been written and so the control node stays unused to date.
3769	      </para>
3770	      <para>
3771	        With the increased use of offscreen renderers and GPGPU applications,
3772	        clients no longer require running compositors or graphics servers to
3773	        make use of a GPU. But the DRM API required unprivileged clients to
3774	        authenticate to a DRM-Master prior to getting GPU access. To avoid this
3775	        step and to grant clients GPU access without authenticating, render
3776	        nodes were introduced. Render nodes solely serve render clients, that
3777	        is, no modesetting or privileged ioctls can be issued on render nodes.
3778	        Only non-global rendering commands are allowed. If a driver supports
3779	        render nodes, it must advertise it via the DRIVER_RENDER
3780	        DRM driver capability. If not supported, the primary node must be used
3781	        for render clients together with the legacy drmAuth authentication
3782	        procedure.
3783	      </para>
3784	      <para>
3785	        If a driver advertises render node support, DRM core will create a
3786	        separate render node called renderD&lt;num&gt;. There will
3787	        be one render node per device. No ioctls except  PRIME-related ioctls
3788	        will be allowed on this node. Especially GEM_OPEN will be
3789	        explicitly prohibited. Render nodes are designed to avoid the
3790	        buffer-leaks, which occur if clients guess the flink names or mmap
3791	        offsets on the legacy interface. Additionally to this basic interface,
3792	        drivers must mark their driver-dependent render-only ioctls as
3793	        DRM_RENDER_ALLOW so render clients can use them. Driver
3794	        authors must be careful not to allow any privileged ioctls on render
3795	        nodes.
3796	      </para>
3797	      <para>
3798	        With render nodes, user-space can now control access to the render node
3799	        via basic file-system access-modes. A running graphics server which
3800	        authenticates clients on the privileged primary/legacy node is no longer
3801	        required. Instead, a client can open the render node and is immediately
3802	        granted GPU access. Communication between clients (or servers) is done
3803	        via PRIME. FLINK from render node to legacy node is not supported. New
3804	        clients must not use the insecure FLINK interface.
3805	      </para>
3806	      <para>
3807	        Besides dropping all modeset/global ioctls, render nodes also drop the
3808	        DRM-Master concept. There is no reason to associate render clients with
3809	        a DRM-Master as they are independent of any graphics server. Besides,
3810	        they must work without any running master, anyway.
3811	        Drivers must be able to run without a master object if they support
3812	        render nodes. If, on the other hand, a driver requires shared state
3813	        between clients which is visible to user-space and accessible beyond
3814	        open-file boundaries, they cannot support render nodes.
3815	      </para>
3816	    </sect1>
3817	
3818	  <!-- External: vblank handling -->
3819	
3820	    <sect1>
3821	      <title>VBlank event handling</title>
3822	      <para>
3823	        The DRM core exposes two vertical blank related ioctls:
3824	        <variablelist>
3825	          <varlistentry>
3826	            <term>DRM_IOCTL_WAIT_VBLANK</term>
3827	            <listitem>
3828	              <para>
3829	                This takes a struct drm_wait_vblank structure as its argument,
3830	                and it is used to block or request a signal when a specified
3831	                vblank event occurs.
3832	              </para>
3833	            </listitem>
3834	          </varlistentry>
3835	          <varlistentry>
3836	            <term>DRM_IOCTL_MODESET_CTL</term>
3837	            <listitem>
3838	              <para>
3839			This was only used for user-mode-settind drivers around
3840			modesetting changes to allow the kernel to update the vblank
3841			interrupt after mode setting, since on many devices the vertical
3842			blank counter is reset to 0 at some point during modeset. Modern
3843			drivers should not call this any more since with kernel mode
3844			setting it is a no-op.
3845	              </para>
3846	            </listitem>
3847	          </varlistentry>
3848	        </variablelist>
3849	      </para>
3850	    </sect1>
3851	
3852	  </chapter>
3853	</part>
3854	<part id="drmDrivers">
3855	  <title>DRM Drivers</title>
3856	
3857	  <partintro>
3858	    <para>
3859	      This second part of the DRM Developer's Guide documents driver code,
3860	      implementation details and also all the driver-specific userspace
3861	      interfaces. Especially since all hardware-acceleration interfaces to
3862	      userspace are driver specific for efficiency and other reasons these
3863	      interfaces can be rather substantial. Hence every driver has its own
3864	      chapter.
3865	    </para>
3866	  </partintro>
3867	
3868	  <chapter id="drmI915">
3869	    <title>drm/i915 Intel GFX Driver</title>
3870	    <para>
3871	      The drm/i915 driver supports all (with the exception of some very early
3872	      models) integrated GFX chipsets with both Intel display and rendering
3873	      blocks. This excludes a set of SoC platforms with an SGX rendering unit,
3874	      those have basic support through the gma500 drm driver.
3875	    </para>
3876	    <sect1>
3877	      <title>Core Driver Infrastructure</title>
3878	      <para>
3879		This section covers core driver infrastructure used by both the display
3880		and the GEM parts of the driver.
3881	      </para>
3882	      <sect2>
3883	        <title>Runtime Power Management</title>
3884	!Pdrivers/gpu/drm/i915/intel_runtime_pm.c runtime pm
3885	!Idrivers/gpu/drm/i915/intel_runtime_pm.c
3886	      </sect2>
3887	      <sect2>
3888	        <title>Interrupt Handling</title>
3889	!Pdrivers/gpu/drm/i915/i915_irq.c interrupt handling
3890	!Fdrivers/gpu/drm/i915/i915_irq.c intel_irq_init intel_irq_init_hw intel_hpd_init
3891	!Fdrivers/gpu/drm/i915/i915_irq.c intel_irq_fini
3892	!Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_disable_interrupts
3893	!Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_enable_interrupts
3894	      </sect2>
3895	    </sect1>
3896	    <sect1>
3897	      <title>Display Hardware Handling</title>
3898	      <para>
3899	        This section covers everything related to the display hardware including
3900	        the mode setting infrastructure, plane, sprite and cursor handling and
3901	        display, output probing and related topics.
3902	      </para>
3903	      <sect2>
3904	        <title>Mode Setting Infrastructure</title>
3905	        <para>
3906	          The i915 driver is thus far the only DRM driver which doesn't use the
3907	          common DRM helper code to implement mode setting sequences. Thus it
3908	          has its own tailor-made infrastructure for executing a display
3909	          configuration change.
3910	        </para>
3911	      </sect2>
3912	      <sect2>
3913	        <title>Frontbuffer Tracking</title>
3914	!Pdrivers/gpu/drm/i915/intel_frontbuffer.c frontbuffer tracking
3915	!Idrivers/gpu/drm/i915/intel_frontbuffer.c
3916	!Fdrivers/gpu/drm/i915/intel_drv.h intel_frontbuffer_flip
3917	!Fdrivers/gpu/drm/i915/i915_gem.c i915_gem_track_fb
3918	      </sect2>
3919	      <sect2>
3920	        <title>Display FIFO Underrun Reporting</title>
3921	!Pdrivers/gpu/drm/i915/intel_fifo_underrun.c fifo underrun handling
3922	!Idrivers/gpu/drm/i915/intel_fifo_underrun.c
3923	      </sect2>
3924	      <sect2>
3925	        <title>Plane Configuration</title>
3926	        <para>
3927		  This section covers plane configuration and composition with the
3928		  primary plane, sprites, cursors and overlays. This includes the
3929		  infrastructure to do atomic vsync'ed updates of all this state and
3930		  also tightly coupled topics like watermark setup and computation,
3931		  framebuffer compression and panel self refresh.
3932	        </para>
3933	      </sect2>
3934	      <sect2>
3935	        <title>Output Probing</title>
3936	        <para>
3937		  This section covers output probing and related infrastructure like the
3938		  hotplug interrupt storm detection and mitigation code. Note that the
3939		  i915 driver still uses most of the common DRM helper code for output
3940		  probing, so those sections fully apply.
3941	        </para>
3942	      </sect2>
3943	      <sect2>
3944		<title>High Definition Audio</title>
3945	!Pdrivers/gpu/drm/i915/intel_audio.c High Definition Audio over HDMI and Display Port
3946	!Idrivers/gpu/drm/i915/intel_audio.c
3947	      </sect2>
3948	      <sect2>
3949		<title>Panel Self Refresh PSR (PSR/SRD)</title>
3950	!Pdrivers/gpu/drm/i915/intel_psr.c Panel Self Refresh (PSR/SRD)
3951	!Idrivers/gpu/drm/i915/intel_psr.c
3952	      </sect2>
3953	      <sect2>
3954	        <title>DPIO</title>
3955	!Pdrivers/gpu/drm/i915/i915_reg.h DPIO
3956		<table id="dpiox2">
3957		  <title>Dual channel PHY (VLV/CHV)</title>
3958		  <tgroup cols="8">
3959		    <colspec colname="c0" />
3960		    <colspec colname="c1" />
3961		    <colspec colname="c2" />
3962		    <colspec colname="c3" />
3963		    <colspec colname="c4" />
3964		    <colspec colname="c5" />
3965		    <colspec colname="c6" />
3966		    <colspec colname="c7" />
3967		    <spanspec spanname="ch0" namest="c0" nameend="c3" />
3968		    <spanspec spanname="ch1" namest="c4" nameend="c7" />
3969		    <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
3970		    <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
3971		    <spanspec spanname="ch1pcs01" namest="c4" nameend="c5" />
3972		    <spanspec spanname="ch1pcs23" namest="c6" nameend="c7" />
3973		    <thead>
3974		      <row>
3975			<entry spanname="ch0">CH0</entry>
3976			<entry spanname="ch1">CH1</entry>
3977		      </row>
3978		    </thead>
3979		    <tbody valign="top" align="center">
3980		      <row>
3981			<entry spanname="ch0">CMN/PLL/REF</entry>
3982			<entry spanname="ch1">CMN/PLL/REF</entry>
3983		      </row>
3984		      <row>
3985			<entry spanname="ch0pcs01">PCS01</entry>
3986			<entry spanname="ch0pcs23">PCS23</entry>
3987			<entry spanname="ch1pcs01">PCS01</entry>
3988			<entry spanname="ch1pcs23">PCS23</entry>
3989		      </row>
3990		      <row>
3991			<entry>TX0</entry>
3992			<entry>TX1</entry>
3993			<entry>TX2</entry>
3994			<entry>TX3</entry>
3995			<entry>TX0</entry>
3996			<entry>TX1</entry>
3997			<entry>TX2</entry>
3998			<entry>TX3</entry>
3999		      </row>
4000		      <row>
4001			<entry spanname="ch0">DDI0</entry>
4002			<entry spanname="ch1">DDI1</entry>
4003		      </row>
4004		    </tbody>
4005		  </tgroup>
4006		</table>
4007		<table id="dpiox1">
4008		  <title>Single channel PHY (CHV)</title>
4009		  <tgroup cols="4">
4010		    <colspec colname="c0" />
4011		    <colspec colname="c1" />
4012		    <colspec colname="c2" />
4013		    <colspec colname="c3" />
4014		    <spanspec spanname="ch0" namest="c0" nameend="c3" />
4015		    <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
4016		    <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
4017		    <thead>
4018		      <row>
4019			<entry spanname="ch0">CH0</entry>
4020		      </row>
4021		    </thead>
4022		    <tbody valign="top" align="center">
4023		      <row>
4024			<entry spanname="ch0">CMN/PLL/REF</entry>
4025		      </row>
4026		      <row>
4027			<entry spanname="ch0pcs01">PCS01</entry>
4028			<entry spanname="ch0pcs23">PCS23</entry>
4029		      </row>
4030		      <row>
4031			<entry>TX0</entry>
4032			<entry>TX1</entry>
4033			<entry>TX2</entry>
4034			<entry>TX3</entry>
4035		      </row>
4036		      <row>
4037			<entry spanname="ch0">DDI2</entry>
4038		      </row>
4039		    </tbody>
4040		  </tgroup>
4041		</table>
4042	      </sect2>
4043	    </sect1>
4044	
4045	    <sect1>
4046	      <title>Memory Management and Command Submission</title>
4047	      <para>
4048		This sections covers all things related to the GEM implementation in the
4049		i915 driver.
4050	      </para>
4051	      <sect2>
4052	        <title>Batchbuffer Parsing</title>
4053	!Pdrivers/gpu/drm/i915/i915_cmd_parser.c batch buffer command parser
4054	!Idrivers/gpu/drm/i915/i915_cmd_parser.c
4055	      </sect2>
4056	      <sect2>
4057	        <title>Logical Rings, Logical Ring Contexts and Execlists</title>
4058	!Pdrivers/gpu/drm/i915/intel_lrc.c Logical Rings, Logical Ring Contexts and Execlists
4059	!Idrivers/gpu/drm/i915/intel_lrc.c
4060	      </sect2>
4061	    </sect1>
4062	
4063	    <sect1>
4064	      <title> Tracing </title>
4065	      <para>
4066	    This sections covers all things related to the tracepoints implemented in
4067	    the i915 driver.
4068	      </para>
4069	      <sect2>
4070	        <title> i915_ppgtt_create and i915_ppgtt_release </title>
4071	!Pdrivers/gpu/drm/i915/i915_trace.h i915_ppgtt_create and i915_ppgtt_release tracepoints
4072	      </sect2>
4073	      <sect2>
4074	        <title> i915_context_create and i915_context_free </title>
4075	!Pdrivers/gpu/drm/i915/i915_trace.h i915_context_create and i915_context_free tracepoints
4076	      </sect2>
4077	      <sect2>
4078	        <title> switch_mm </title>
4079	!Pdrivers/gpu/drm/i915/i915_trace.h switch_mm tracepoint
4080	      </sect2>
4081	    </sect1>
4082	
4083	  </chapter>
4084	!Cdrivers/gpu/drm/i915/i915_irq.c
4085	</part>
4086	</book>
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