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Based on kernel version 3.16. Page generated on 2014-08-06 21:38 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, USB and platform devices, respectively.
295	      </para>
296	!Edrivers/gpu/drm/drm_pci.c
297	!Edrivers/gpu/drm/drm_usb.c
298	!Edrivers/gpu/drm/drm_platform.c
299	      <para>
300	        New drivers that no longer rely on the services provided by the
301	        <structname>drm_bus</structname> structure can call the low-level
302	        device registration functions directly. The
303	        <function>drm_dev_alloc()</function> function can be used to allocate
304	        and initialize a new <structname>drm_device</structname> structure.
305	        Drivers will typically want to perform some additional setup on this
306	        structure, such as allocating driver-specific data and storing a
307	        pointer to it in the DRM device's <structfield>dev_private</structfield>
308	        field. Drivers should also set the device's unique name using the
309	        <function>drm_dev_set_unique()</function> function. After it has been
310	        set up a device can be registered with the DRM subsystem by calling
311	        <function>drm_dev_register()</function>. This will cause the device to
312	        be exposed to userspace and will call the driver's
313	        <structfield>.load()</structfield> implementation. When a device is
314	        removed, the DRM device can safely be unregistered and freed by calling
315	        <function>drm_dev_unregister()</function> followed by a call to
316	        <function>drm_dev_unref()</function>.
317	      </para>
318	!Edrivers/gpu/drm/drm_stub.c
319	    </sect2>
320	    <sect2>
321	      <title>Driver Load</title>
322	      <para>
323	        The <methodname>load</methodname> method is the driver and device
324	        initialization entry point. The method is responsible for allocating and
325		initializing driver private data, performing resource allocation and
326		mapping (e.g. acquiring
327	        clocks, mapping registers or allocating command buffers), initializing
328	        the memory manager (<xref linkend="drm-memory-management"/>), installing
329	        the IRQ handler (<xref linkend="drm-irq-registration"/>), setting up
330	        vertical blanking handling (<xref linkend="drm-vertical-blank"/>), mode
331		setting (<xref linkend="drm-mode-setting"/>) and initial output
332		configuration (<xref linkend="drm-kms-init"/>).
333	      </para>
334	      <note><para>
335	        If compatibility is a concern (e.g. with drivers converted over from
336	        User Mode Setting to Kernel Mode Setting), care must be taken to prevent
337	        device initialization and control that is incompatible with currently
338	        active userspace drivers. For instance, if user level mode setting
339	        drivers are in use, it would be problematic to perform output discovery
340	        &amp; configuration at load time. Likewise, if user-level drivers
341	        unaware of memory management are in use, memory management and command
342	        buffer setup may need to be omitted. These requirements are
343	        driver-specific, and care needs to be taken to keep both old and new
344	        applications and libraries working.
345	      </para></note>
346	      <synopsis>int (*load) (struct drm_device *, unsigned long flags);</synopsis>
347	      <para>
348	        The method takes two arguments, a pointer to the newly created
349		<structname>drm_device</structname> and flags. The flags are used to
350		pass the <structfield>driver_data</structfield> field of the device id
351		corresponding to the device passed to <function>drm_*_init()</function>.
352		Only PCI devices currently use this, USB and platform DRM drivers have
353		their <methodname>load</methodname> method called with flags to 0.
354	      </para>
355	      <sect3>
356	        <title>Driver Private Data</title>
357	        <para>
358	          The driver private hangs off the main
359	          <structname>drm_device</structname> structure and can be used for
360	          tracking various device-specific bits of information, like register
361	          offsets, command buffer status, register state for suspend/resume, etc.
362	          At load time, a driver may simply allocate one and set
363	          <structname>drm_device</structname>.<structfield>dev_priv</structfield>
364	          appropriately; it should be freed and
365	          <structname>drm_device</structname>.<structfield>dev_priv</structfield>
366	          set to NULL when the driver is unloaded.
367	        </para>
368	      </sect3>
369	      <sect3 id="drm-irq-registration">
370	        <title>IRQ Registration</title>
371	        <para>
372	          The DRM core tries to facilitate IRQ handler registration and
373	          unregistration by providing <function>drm_irq_install</function> and
374	          <function>drm_irq_uninstall</function> functions. Those functions only
375	          support a single interrupt per device, devices that use more than one
376	          IRQs need to be handled manually.
377	        </para>
378	        <sect4>
379	          <title>Managed IRQ Registration</title>
380	          <para>
381	            <function>drm_irq_install</function> starts by calling the
382	            <methodname>irq_preinstall</methodname> driver operation. The operation
383	            is optional and must make sure that the interrupt will not get fired by
384	            clearing all pending interrupt flags or disabling the interrupt.
385	          </para>
386	          <para>
387	            The passed-in IRQ will then be requested by a call to
388	            <function>request_irq</function>. If the DRIVER_IRQ_SHARED driver
389	            feature flag is set, a shared (IRQF_SHARED) IRQ handler will be
390	            requested.
391	          </para>
392	          <para>
393	            The IRQ handler function must be provided as the mandatory irq_handler
394	            driver operation. It will get passed directly to
395	            <function>request_irq</function> and thus has the same prototype as all
396	            IRQ handlers. It will get called with a pointer to the DRM device as the
397	            second argument.
398	          </para>
399	          <para>
400	            Finally the function calls the optional
401	            <methodname>irq_postinstall</methodname> driver operation. The operation
402	            usually enables interrupts (excluding the vblank interrupt, which is
403	            enabled separately), but drivers may choose to enable/disable interrupts
404	            at a different time.
405	          </para>
406	          <para>
407	            <function>drm_irq_uninstall</function> is similarly used to uninstall an
408	            IRQ handler. It starts by waking up all processes waiting on a vblank
409	            interrupt to make sure they don't hang, and then calls the optional
410	            <methodname>irq_uninstall</methodname> driver operation. The operation
411	            must disable all hardware interrupts. Finally the function frees the IRQ
412	            by calling <function>free_irq</function>.
413	          </para>
414	        </sect4>
415	        <sect4>
416	          <title>Manual IRQ Registration</title>
417	          <para>
418	            Drivers that require multiple interrupt handlers can't use the managed
419	            IRQ registration functions. In that case IRQs must be registered and
420	            unregistered manually (usually with the <function>request_irq</function>
421	            and <function>free_irq</function> functions, or their devm_* equivalent).
422	          </para>
423	          <para>
424	            When manually registering IRQs, drivers must not set the DRIVER_HAVE_IRQ
425	            driver feature flag, and must not provide the
426		    <methodname>irq_handler</methodname> driver operation. They must set the
427		    <structname>drm_device</structname> <structfield>irq_enabled</structfield>
428		    field to 1 upon registration of the IRQs, and clear it to 0 after
429		    unregistering the IRQs.
430	          </para>
431	        </sect4>
432	      </sect3>
433	      <sect3>
434	        <title>Memory Manager Initialization</title>
435	        <para>
436	          Every DRM driver requires a memory manager which must be initialized at
437	          load time. DRM currently contains two memory managers, the Translation
438	          Table Manager (TTM) and the Graphics Execution Manager (GEM).
439	          This document describes the use of the GEM memory manager only. See
440	          <xref linkend="drm-memory-management"/> for details.
441	        </para>
442	      </sect3>
443	      <sect3>
444	        <title>Miscellaneous Device Configuration</title>
445	        <para>
446	          Another task that may be necessary for PCI devices during configuration
447	          is mapping the video BIOS. On many devices, the VBIOS describes device
448	          configuration, LCD panel timings (if any), and contains flags indicating
449	          device state. Mapping the BIOS can be done using the pci_map_rom() call,
450	          a convenience function that takes care of mapping the actual ROM,
451	          whether it has been shadowed into memory (typically at address 0xc0000)
452	          or exists on the PCI device in the ROM BAR. Note that after the ROM has
453	          been mapped and any necessary information has been extracted, it should
454	          be unmapped; on many devices, the ROM address decoder is shared with
455	          other BARs, so leaving it mapped could cause undesired behaviour like
456	          hangs or memory corruption.
457	  <!--!Fdrivers/pci/rom.c pci_map_rom-->
458	        </para>
459	      </sect3>
460	    </sect2>
461	  </sect1>
462	
463	  <!-- Internals: memory management -->
464	
465	  <sect1 id="drm-memory-management">
466	    <title>Memory management</title>
467	    <para>
468	      Modern Linux systems require large amount of graphics memory to store
469	      frame buffers, textures, vertices and other graphics-related data. Given
470	      the very dynamic nature of many of that data, managing graphics memory
471	      efficiently is thus crucial for the graphics stack and plays a central
472	      role in the DRM infrastructure.
473	    </para>
474	    <para>
475	      The DRM core includes two memory managers, namely Translation Table Maps
476	      (TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory
477	      manager to be developed and tried to be a one-size-fits-them all
478	      solution. It provides a single userspace API to accommodate the need of
479	      all hardware, supporting both Unified Memory Architecture (UMA) devices
480	      and devices with dedicated video RAM (i.e. most discrete video cards).
481	      This resulted in a large, complex piece of code that turned out to be
482	      hard to use for driver development.
483	    </para>
484	    <para>
485	      GEM started as an Intel-sponsored project in reaction to TTM's
486	      complexity. Its design philosophy is completely different: instead of
487	      providing a solution to every graphics memory-related problems, GEM
488	      identified common code between drivers and created a support library to
489	      share it. GEM has simpler initialization and execution requirements than
490	      TTM, but has no video RAM management capabilities and is thus limited to
491	      UMA devices.
492	    </para>
493	    <sect2>
494	      <title>The Translation Table Manager (TTM)</title>
495	      <para>
496		TTM design background and information belongs here.
497	      </para>
498	      <sect3>
499		<title>TTM initialization</title>
500	        <warning><para>This section is outdated.</para></warning>
501	        <para>
502	          Drivers wishing to support TTM must fill out a drm_bo_driver
503	          structure. The structure contains several fields with function
504	          pointers for initializing the TTM, allocating and freeing memory,
505	          waiting for command completion and fence synchronization, and memory
506	          migration. See the radeon_ttm.c file for an example of usage.
507		</para>
508		<para>
509		  The ttm_global_reference structure is made up of several fields:
510		</para>
511		<programlisting>
512		  struct ttm_global_reference {
513		  	enum ttm_global_types global_type;
514		  	size_t size;
515		  	void *object;
516		  	int (*init) (struct ttm_global_reference *);
517		  	void (*release) (struct ttm_global_reference *);
518		  };
519		</programlisting>
520		<para>
521		  There should be one global reference structure for your memory
522		  manager as a whole, and there will be others for each object
523		  created by the memory manager at runtime.  Your global TTM should
524		  have a type of TTM_GLOBAL_TTM_MEM.  The size field for the global
525		  object should be sizeof(struct ttm_mem_global), and the init and
526		  release hooks should point at your driver-specific init and
527		  release routines, which probably eventually call
528		  ttm_mem_global_init and ttm_mem_global_release, respectively.
529		</para>
530		<para>
531		  Once your global TTM accounting structure is set up and initialized
532		  by calling ttm_global_item_ref() on it,
533		  you need to create a buffer object TTM to
534		  provide a pool for buffer object allocation by clients and the
535		  kernel itself.  The type of this object should be TTM_GLOBAL_TTM_BO,
536		  and its size should be sizeof(struct ttm_bo_global).  Again,
537		  driver-specific init and release functions may be provided,
538		  likely eventually calling ttm_bo_global_init() and
539		  ttm_bo_global_release(), respectively.  Also, like the previous
540		  object, ttm_global_item_ref() is used to create an initial reference
541		  count for the TTM, which will call your initialization function.
542		</para>
543	      </sect3>
544	    </sect2>
545	    <sect2 id="drm-gem">
546	      <title>The Graphics Execution Manager (GEM)</title>
547	      <para>
548	        The GEM design approach has resulted in a memory manager that doesn't
549	        provide full coverage of all (or even all common) use cases in its
550	        userspace or kernel API. GEM exposes a set of standard memory-related
551	        operations to userspace and a set of helper functions to drivers, and let
552	        drivers implement hardware-specific operations with their own private API.
553	      </para>
554	      <para>
555	        The GEM userspace API is described in the
556	        <ulink url="http://lwn.net/Articles/283798/"><citetitle>GEM - the Graphics
557	        Execution Manager</citetitle></ulink> article on LWN. While slightly
558	        outdated, the document provides a good overview of the GEM API principles.
559	        Buffer allocation and read and write operations, described as part of the
560	        common GEM API, are currently implemented using driver-specific ioctls.
561	      </para>
562	      <para>
563	        GEM is data-agnostic. It manages abstract buffer objects without knowing
564	        what individual buffers contain. APIs that require knowledge of buffer
565	        contents or purpose, such as buffer allocation or synchronization
566	        primitives, are thus outside of the scope of GEM and must be implemented
567	        using driver-specific ioctls.
568	      </para>
569	      <para>
570		On a fundamental level, GEM involves several operations:
571		<itemizedlist>
572		  <listitem>Memory allocation and freeing</listitem>
573		  <listitem>Command execution</listitem>
574		  <listitem>Aperture management at command execution time</listitem>
575		</itemizedlist>
576		Buffer object allocation is relatively straightforward and largely
577	        provided by Linux's shmem layer, which provides memory to back each
578	        object.
579	      </para>
580	      <para>
581	        Device-specific operations, such as command execution, pinning, buffer
582		read &amp; write, mapping, and domain ownership transfers are left to
583	        driver-specific ioctls.
584	      </para>
585	      <sect3>
586	        <title>GEM Initialization</title>
587	        <para>
588	          Drivers that use GEM must set the DRIVER_GEM bit in the struct
589	          <structname>drm_driver</structname>
590	          <structfield>driver_features</structfield> field. The DRM core will
591	          then automatically initialize the GEM core before calling the
592	          <methodname>load</methodname> operation. Behind the scene, this will
593	          create a DRM Memory Manager object which provides an address space
594	          pool for object allocation.
595	        </para>
596	        <para>
597	          In a KMS configuration, drivers need to allocate and initialize a
598	          command ring buffer following core GEM initialization if required by
599	          the hardware. UMA devices usually have what is called a "stolen"
600	          memory region, which provides space for the initial framebuffer and
601	          large, contiguous memory regions required by the device. This space is
602	          typically not managed by GEM, and must be initialized separately into
603	          its own DRM MM object.
604	        </para>
605	      </sect3>
606	      <sect3>
607	        <title>GEM Objects Creation</title>
608	        <para>
609	          GEM splits creation of GEM objects and allocation of the memory that
610	          backs them in two distinct operations.
611	        </para>
612	        <para>
613	          GEM objects are represented by an instance of struct
614	          <structname>drm_gem_object</structname>. Drivers usually need to extend
615	          GEM objects with private information and thus create a driver-specific
616	          GEM object structure type that embeds an instance of struct
617	          <structname>drm_gem_object</structname>.
618	        </para>
619	        <para>
620	          To create a GEM object, a driver allocates memory for an instance of its
621	          specific GEM object type and initializes the embedded struct
622	          <structname>drm_gem_object</structname> with a call to
623	          <function>drm_gem_object_init</function>. The function takes a pointer to
624	          the DRM device, a pointer to the GEM object and the buffer object size
625	          in bytes.
626	        </para>
627	        <para>
628	          GEM uses shmem to allocate anonymous pageable memory.
629	          <function>drm_gem_object_init</function> will create an shmfs file of
630	          the requested size and store it into the struct
631	          <structname>drm_gem_object</structname> <structfield>filp</structfield>
632	          field. The memory is used as either main storage for the object when the
633	          graphics hardware uses system memory directly or as a backing store
634	          otherwise.
635	        </para>
636	        <para>
637	          Drivers are responsible for the actual physical pages allocation by
638	          calling <function>shmem_read_mapping_page_gfp</function> for each page.
639	          Note that they can decide to allocate pages when initializing the GEM
640	          object, or to delay allocation until the memory is needed (for instance
641	          when a page fault occurs as a result of a userspace memory access or
642	          when the driver needs to start a DMA transfer involving the memory).
643	        </para>
644	        <para>
645	          Anonymous pageable memory allocation is not always desired, for instance
646	          when the hardware requires physically contiguous system memory as is
647	          often the case in embedded devices. Drivers can create GEM objects with
648	          no shmfs backing (called private GEM objects) by initializing them with
649	          a call to <function>drm_gem_private_object_init</function> instead of
650	          <function>drm_gem_object_init</function>. Storage for private GEM
651	          objects must be managed by drivers.
652	        </para>
653	        <para>
654	          Drivers that do not need to extend GEM objects with private information
655	          can call the <function>drm_gem_object_alloc</function> function to
656	          allocate and initialize a struct <structname>drm_gem_object</structname>
657	          instance. The GEM core will call the optional driver
658	          <methodname>gem_init_object</methodname> operation after initializing
659	          the GEM object with <function>drm_gem_object_init</function>.
660	          <synopsis>int (*gem_init_object) (struct drm_gem_object *obj);</synopsis>
661	        </para>
662	        <para>
663	          No alloc-and-init function exists for private GEM objects.
664	        </para>
665	      </sect3>
666	      <sect3>
667	        <title>GEM Objects Lifetime</title>
668	        <para>
669	          All GEM objects are reference-counted by the GEM core. References can be
670	          acquired and release by <function>calling drm_gem_object_reference</function>
671	          and <function>drm_gem_object_unreference</function> respectively. The
672	          caller must hold the <structname>drm_device</structname>
673	          <structfield>struct_mutex</structfield> lock. As a convenience, GEM
674	          provides the <function>drm_gem_object_reference_unlocked</function> and
675	          <function>drm_gem_object_unreference_unlocked</function> functions that
676	          can be called without holding the lock.
677	        </para>
678	        <para>
679	          When the last reference to a GEM object is released the GEM core calls
680	          the <structname>drm_driver</structname>
681	          <methodname>gem_free_object</methodname> operation. That operation is
682	          mandatory for GEM-enabled drivers and must free the GEM object and all
683	          associated resources.
684	        </para>
685	        <para>
686	          <synopsis>void (*gem_free_object) (struct drm_gem_object *obj);</synopsis>
687	          Drivers are responsible for freeing all GEM object resources, including
688	          the resources created by the GEM core. If an mmap offset has been
689	          created for the object (in which case
690	          <structname>drm_gem_object</structname>::<structfield>map_list</structfield>::<structfield>map</structfield>
691	          is not NULL) it must be freed by a call to
692	          <function>drm_gem_free_mmap_offset</function>. The shmfs backing store
693	          must be released by calling <function>drm_gem_object_release</function>
694	          (that function can safely be called if no shmfs backing store has been
695	          created).
696	        </para>
697	      </sect3>
698	      <sect3>
699	        <title>GEM Objects Naming</title>
700	        <para>
701	          Communication between userspace and the kernel refers to GEM objects
702	          using local handles, global names or, more recently, file descriptors.
703	          All of those are 32-bit integer values; the usual Linux kernel limits
704	          apply to the file descriptors.
705	        </para>
706	        <para>
707	          GEM handles are local to a DRM file. Applications get a handle to a GEM
708	          object through a driver-specific ioctl, and can use that handle to refer
709	          to the GEM object in other standard or driver-specific ioctls. Closing a
710	          DRM file handle frees all its GEM handles and dereferences the
711	          associated GEM objects.
712	        </para>
713	        <para>
714	          To create a handle for a GEM object drivers call
715	          <function>drm_gem_handle_create</function>. The function takes a pointer
716	          to the DRM file and the GEM object and returns a locally unique handle.
717	          When the handle is no longer needed drivers delete it with a call to
718	          <function>drm_gem_handle_delete</function>. Finally the GEM object
719	          associated with a handle can be retrieved by a call to
720	          <function>drm_gem_object_lookup</function>.
721	        </para>
722	        <para>
723	          Handles don't take ownership of GEM objects, they only take a reference
724	          to the object that will be dropped when the handle is destroyed. To
725	          avoid leaking GEM objects, drivers must make sure they drop the
726	          reference(s) they own (such as the initial reference taken at object
727	          creation time) as appropriate, without any special consideration for the
728	          handle. For example, in the particular case of combined GEM object and
729	          handle creation in the implementation of the
730	          <methodname>dumb_create</methodname> operation, drivers must drop the
731	          initial reference to the GEM object before returning the handle.
732	        </para>
733	        <para>
734	          GEM names are similar in purpose to handles but are not local to DRM
735	          files. They can be passed between processes to reference a GEM object
736	          globally. Names can't be used directly to refer to objects in the DRM
737	          API, applications must convert handles to names and names to handles
738	          using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls
739	          respectively. The conversion is handled by the DRM core without any
740	          driver-specific support.
741	        </para>
742		<para>
743		  GEM also supports buffer sharing with dma-buf file descriptors through
744		  PRIME. GEM-based drivers must use the provided helpers functions to
745		  implement the exporting and importing correctly. See <xref linkend="drm-prime-support" />.
746		  Since sharing file descriptors is inherently more secure than the
747		  easily guessable and global GEM names it is the preferred buffer
748		  sharing mechanism. Sharing buffers through GEM names is only supported
749		  for legacy userspace. Furthermore PRIME also allows cross-device
750		  buffer sharing since it is based on dma-bufs.
751		</para>
752	      </sect3>
753	      <sect3 id="drm-gem-objects-mapping">
754	        <title>GEM Objects Mapping</title>
755	        <para>
756	          Because mapping operations are fairly heavyweight GEM favours
757	          read/write-like access to buffers, implemented through driver-specific
758	          ioctls, over mapping buffers to userspace. However, when random access
759	          to the buffer is needed (to perform software rendering for instance),
760	          direct access to the object can be more efficient.
761	        </para>
762	        <para>
763	          The mmap system call can't be used directly to map GEM objects, as they
764	          don't have their own file handle. Two alternative methods currently
765	          co-exist to map GEM objects to userspace. The first method uses a
766	          driver-specific ioctl to perform the mapping operation, calling
767	          <function>do_mmap</function> under the hood. This is often considered
768	          dubious, seems to be discouraged for new GEM-enabled drivers, and will
769	          thus not be described here.
770	        </para>
771	        <para>
772	          The second method uses the mmap system call on the DRM file handle.
773	          <synopsis>void *mmap(void *addr, size_t length, int prot, int flags, int fd,
774	             off_t offset);</synopsis>
775	          DRM identifies the GEM object to be mapped by a fake offset passed
776	          through the mmap offset argument. Prior to being mapped, a GEM object
777	          must thus be associated with a fake offset. To do so, drivers must call
778	          <function>drm_gem_create_mmap_offset</function> on the object. The
779	          function allocates a fake offset range from a pool and stores the
780	          offset divided by PAGE_SIZE in
781	          <literal>obj-&gt;map_list.hash.key</literal>. Care must be taken not to
782	          call <function>drm_gem_create_mmap_offset</function> if a fake offset
783	          has already been allocated for the object. This can be tested by
784	          <literal>obj-&gt;map_list.map</literal> being non-NULL.
785	        </para>
786	        <para>
787	          Once allocated, the fake offset value
788	          (<literal>obj-&gt;map_list.hash.key &lt;&lt; PAGE_SHIFT</literal>)
789	          must be passed to the application in a driver-specific way and can then
790	          be used as the mmap offset argument.
791	        </para>
792	        <para>
793	          The GEM core provides a helper method <function>drm_gem_mmap</function>
794	          to handle object mapping. The method can be set directly as the mmap
795	          file operation handler. It will look up the GEM object based on the
796	          offset value and set the VMA operations to the
797	          <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
798	          field. Note that <function>drm_gem_mmap</function> doesn't map memory to
799	          userspace, but relies on the driver-provided fault handler to map pages
800	          individually.
801	        </para>
802	        <para>
803	          To use <function>drm_gem_mmap</function>, drivers must fill the struct
804	          <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
805	          field with a pointer to VM operations.
806	        </para>
807	        <para>
808	          <synopsis>struct vm_operations_struct *gem_vm_ops
809	
810	  struct vm_operations_struct {
811	          void (*open)(struct vm_area_struct * area);
812	          void (*close)(struct vm_area_struct * area);
813	          int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf);
814	  };</synopsis>
815	        </para>
816	        <para>
817	          The <methodname>open</methodname> and <methodname>close</methodname>
818	          operations must update the GEM object reference count. Drivers can use
819	          the <function>drm_gem_vm_open</function> and
820	          <function>drm_gem_vm_close</function> helper functions directly as open
821	          and close handlers.
822	        </para>
823	        <para>
824	          The fault operation handler is responsible for mapping individual pages
825	          to userspace when a page fault occurs. Depending on the memory
826	          allocation scheme, drivers can allocate pages at fault time, or can
827	          decide to allocate memory for the GEM object at the time the object is
828	          created.
829	        </para>
830	        <para>
831	          Drivers that want to map the GEM object upfront instead of handling page
832	          faults can implement their own mmap file operation handler.
833	        </para>
834	      </sect3>
835	      <sect3>
836	        <title>Memory Coherency</title>
837	        <para>
838	          When mapped to the device or used in a command buffer, backing pages
839	          for an object are flushed to memory and marked write combined so as to
840	          be coherent with the GPU. Likewise, if the CPU accesses an object
841	          after the GPU has finished rendering to the object, then the object
842	          must be made coherent with the CPU's view of memory, usually involving
843	          GPU cache flushing of various kinds. This core CPU&lt;-&gt;GPU
844	          coherency management is provided by a device-specific ioctl, which
845	          evaluates an object's current domain and performs any necessary
846	          flushing or synchronization to put the object into the desired
847	          coherency domain (note that the object may be busy, i.e. an active
848	          render target; in that case, setting the domain blocks the client and
849	          waits for rendering to complete before performing any necessary
850	          flushing operations).
851	        </para>
852	      </sect3>
853	      <sect3>
854	        <title>Command Execution</title>
855	        <para>
856		  Perhaps the most important GEM function for GPU devices is providing a
857	          command execution interface to clients. Client programs construct
858	          command buffers containing references to previously allocated memory
859	          objects, and then submit them to GEM. At that point, GEM takes care to
860	          bind all the objects into the GTT, execute the buffer, and provide
861	          necessary synchronization between clients accessing the same buffers.
862	          This often involves evicting some objects from the GTT and re-binding
863	          others (a fairly expensive operation), and providing relocation
864	          support which hides fixed GTT offsets from clients. Clients must take
865	          care not to submit command buffers that reference more objects than
866	          can fit in the GTT; otherwise, GEM will reject them and no rendering
867	          will occur. Similarly, if several objects in the buffer require fence
868	          registers to be allocated for correct rendering (e.g. 2D blits on
869	          pre-965 chips), care must be taken not to require more fence registers
870	          than are available to the client. Such resource management should be
871	          abstracted from the client in libdrm.
872	        </para>
873	      </sect3>
874	      <sect3>
875	        <title>GEM Function Reference</title>
876	!Edrivers/gpu/drm/drm_gem.c
877	      </sect3>
878	      </sect2>
879	      <sect2>
880		<title>VMA Offset Manager</title>
881	!Pdrivers/gpu/drm/drm_vma_manager.c vma offset manager
882	!Edrivers/gpu/drm/drm_vma_manager.c
883	!Iinclude/drm/drm_vma_manager.h
884	      </sect2>
885	      <sect2 id="drm-prime-support">
886		<title>PRIME Buffer Sharing</title>
887		<para>
888		  PRIME is the cross device buffer sharing framework in drm, originally
889		  created for the OPTIMUS range of multi-gpu platforms. To userspace
890		  PRIME buffers are dma-buf based file descriptors.
891		</para>
892		<sect3>
893		  <title>Overview and Driver Interface</title>
894		  <para>
895		    Similar to GEM global names, PRIME file descriptors are
896		    also used to share buffer objects across processes. They offer
897		    additional security: as file descriptors must be explicitly sent over
898		    UNIX domain sockets to be shared between applications, they can't be
899		    guessed like the globally unique GEM names.
900		  </para>
901		  <para>
902		    Drivers that support the PRIME
903		    API must set the DRIVER_PRIME bit in the struct
904		    <structname>drm_driver</structname>
905		    <structfield>driver_features</structfield> field, and implement the
906		    <methodname>prime_handle_to_fd</methodname> and
907		    <methodname>prime_fd_to_handle</methodname> operations.
908		  </para>
909		  <para>
910		    <synopsis>int (*prime_handle_to_fd)(struct drm_device *dev,
911				  struct drm_file *file_priv, uint32_t handle,
912				  uint32_t flags, int *prime_fd);
913	int (*prime_fd_to_handle)(struct drm_device *dev,
914				  struct drm_file *file_priv, int prime_fd,
915				  uint32_t *handle);</synopsis>
916		    Those two operations convert a handle to a PRIME file descriptor and
917		    vice versa. Drivers must use the kernel dma-buf buffer sharing framework
918		    to manage the PRIME file descriptors. Similar to the mode setting
919		    API PRIME is agnostic to the underlying buffer object manager, as
920		    long as handles are 32bit unsigned integers.
921		  </para>
922		  <para>
923		    While non-GEM drivers must implement the operations themselves, GEM
924		    drivers must use the <function>drm_gem_prime_handle_to_fd</function>
925		    and <function>drm_gem_prime_fd_to_handle</function> helper functions.
926		    Those helpers rely on the driver
927		    <methodname>gem_prime_export</methodname> and
928		    <methodname>gem_prime_import</methodname> operations to create a dma-buf
929		    instance from a GEM object (dma-buf exporter role) and to create a GEM
930		    object from a dma-buf instance (dma-buf importer role).
931		  </para>
932		  <para>
933		    <synopsis>struct dma_buf * (*gem_prime_export)(struct drm_device *dev,
934					     struct drm_gem_object *obj,
935					     int flags);
936	struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev,
937						    struct dma_buf *dma_buf);</synopsis>
938		    These two operations are mandatory for GEM drivers that support
939		    PRIME.
940		  </para>
941		</sect3>
942	        <sect3>
943	          <title>PRIME Helper Functions</title>
944	!Pdrivers/gpu/drm/drm_prime.c PRIME Helpers
945	        </sect3>
946	      </sect2>
947	      <sect2>
948		<title>PRIME Function References</title>
949	!Edrivers/gpu/drm/drm_prime.c
950	      </sect2>
951	      <sect2>
952		<title>DRM MM Range Allocator</title>
953		<sect3>
954		  <title>Overview</title>
955	!Pdrivers/gpu/drm/drm_mm.c Overview
956		</sect3>
957		<sect3>
958		  <title>LRU Scan/Eviction Support</title>
959	!Pdrivers/gpu/drm/drm_mm.c lru scan roaster
960		</sect3>
961	      </sect2>
962	      <sect2>
963		<title>DRM MM Range Allocator Function References</title>
964	!Edrivers/gpu/drm/drm_mm.c
965	!Iinclude/drm/drm_mm.h
966	      </sect2>
967	  </sect1>
968	
969	  <!-- Internals: mode setting -->
970	
971	  <sect1 id="drm-mode-setting">
972	    <title>Mode Setting</title>
973	    <para>
974	      Drivers must initialize the mode setting core by calling
975	      <function>drm_mode_config_init</function> on the DRM device. The function
976	      initializes the <structname>drm_device</structname>
977	      <structfield>mode_config</structfield> field and never fails. Once done,
978	      mode configuration must be setup by initializing the following fields.
979	    </para>
980	    <itemizedlist>
981	      <listitem>
982	        <synopsis>int min_width, min_height;
983	int max_width, max_height;</synopsis>
984	        <para>
985		  Minimum and maximum width and height of the frame buffers in pixel
986		  units.
987		</para>
988	      </listitem>
989	      <listitem>
990	        <synopsis>struct drm_mode_config_funcs *funcs;</synopsis>
991		<para>Mode setting functions.</para>
992	      </listitem>
993	    </itemizedlist>
994	    <sect2>
995	      <title>Display Modes Function Reference</title>
996	!Iinclude/drm/drm_modes.h
997	!Edrivers/gpu/drm/drm_modes.c
998	    </sect2>
999	    <sect2>
1000	      <title>Frame Buffer Creation</title>
1001	      <synopsis>struct drm_framebuffer *(*fb_create)(struct drm_device *dev,
1002					     struct drm_file *file_priv,
1003					     struct drm_mode_fb_cmd2 *mode_cmd);</synopsis>
1004	      <para>
1005	        Frame buffers are abstract memory objects that provide a source of
1006	        pixels to scanout to a CRTC. Applications explicitly request the
1007	        creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls and
1008	        receive an opaque handle that can be passed to the KMS CRTC control,
1009	        plane configuration and page flip functions.
1010	      </para>
1011	      <para>
1012	        Frame buffers rely on the underneath memory manager for low-level memory
1013	        operations. When creating a frame buffer applications pass a memory
1014	        handle (or a list of memory handles for multi-planar formats) through
1015		the <parameter>drm_mode_fb_cmd2</parameter> argument. For drivers using
1016		GEM as their userspace buffer management interface this would be a GEM
1017		handle.  Drivers are however free to use their own backing storage object
1018		handles, e.g. vmwgfx directly exposes special TTM handles to userspace
1019		and so expects TTM handles in the create ioctl and not GEM handles.
1020	      </para>
1021	      <para>
1022	        Drivers must first validate the requested frame buffer parameters passed
1023	        through the mode_cmd argument. In particular this is where invalid
1024	        sizes, pixel formats or pitches can be caught.
1025	      </para>
1026	      <para>
1027	        If the parameters are deemed valid, drivers then create, initialize and
1028	        return an instance of struct <structname>drm_framebuffer</structname>.
1029	        If desired the instance can be embedded in a larger driver-specific
1030		structure. Drivers must fill its <structfield>width</structfield>,
1031		<structfield>height</structfield>, <structfield>pitches</structfield>,
1032	        <structfield>offsets</structfield>, <structfield>depth</structfield>,
1033	        <structfield>bits_per_pixel</structfield> and
1034	        <structfield>pixel_format</structfield> fields from the values passed
1035	        through the <parameter>drm_mode_fb_cmd2</parameter> argument. They
1036	        should call the <function>drm_helper_mode_fill_fb_struct</function>
1037	        helper function to do so.
1038	      </para>
1039	
1040	      <para>
1041		The initialization of the new framebuffer instance is finalized with a
1042		call to <function>drm_framebuffer_init</function> which takes a pointer
1043		to DRM frame buffer operations (struct
1044		<structname>drm_framebuffer_funcs</structname>). Note that this function
1045		publishes the framebuffer and so from this point on it can be accessed
1046		concurrently from other threads. Hence it must be the last step in the
1047		driver's framebuffer initialization sequence. Frame buffer operations
1048		are
1049	        <itemizedlist>
1050	          <listitem>
1051	            <synopsis>int (*create_handle)(struct drm_framebuffer *fb,
1052			     struct drm_file *file_priv, unsigned int *handle);</synopsis>
1053	            <para>
1054	              Create a handle to the frame buffer underlying memory object. If
1055	              the frame buffer uses a multi-plane format, the handle will
1056	              reference the memory object associated with the first plane.
1057	            </para>
1058	            <para>
1059	              Drivers call <function>drm_gem_handle_create</function> to create
1060	              the handle.
1061	            </para>
1062	          </listitem>
1063	          <listitem>
1064	            <synopsis>void (*destroy)(struct drm_framebuffer *framebuffer);</synopsis>
1065	            <para>
1066	              Destroy the frame buffer object and frees all associated
1067	              resources. Drivers must call
1068	              <function>drm_framebuffer_cleanup</function> to free resources
1069	              allocated by the DRM core for the frame buffer object, and must
1070	              make sure to unreference all memory objects associated with the
1071	              frame buffer. Handles created by the
1072	              <methodname>create_handle</methodname> operation are released by
1073	              the DRM core.
1074	            </para>
1075	          </listitem>
1076	          <listitem>
1077	            <synopsis>int (*dirty)(struct drm_framebuffer *framebuffer,
1078		     struct drm_file *file_priv, unsigned flags, unsigned color,
1079		     struct drm_clip_rect *clips, unsigned num_clips);</synopsis>
1080	            <para>
1081	              This optional operation notifies the driver that a region of the
1082	              frame buffer has changed in response to a DRM_IOCTL_MODE_DIRTYFB
1083	              ioctl call.
1084	            </para>
1085	          </listitem>
1086	        </itemizedlist>
1087	      </para>
1088	      <para>
1089		The lifetime of a drm framebuffer is controlled with a reference count,
1090		drivers can grab additional references with
1091		<function>drm_framebuffer_reference</function>and drop them
1092		again with <function>drm_framebuffer_unreference</function>. For
1093		driver-private framebuffers for which the last reference is never
1094		dropped (e.g. for the fbdev framebuffer when the struct
1095		<structname>drm_framebuffer</structname> is embedded into the fbdev
1096		helper struct) drivers can manually clean up a framebuffer at module
1097		unload time with
1098		<function>drm_framebuffer_unregister_private</function>.
1099	      </para>
1100	    </sect2>
1101	    <sect2>
1102	      <title>Dumb Buffer Objects</title>
1103	      <para>
1104		The KMS API doesn't standardize backing storage object creation and
1105		leaves it to driver-specific ioctls. Furthermore actually creating a
1106		buffer object even for GEM-based drivers is done through a
1107		driver-specific ioctl - GEM only has a common userspace interface for
1108		sharing and destroying objects. While not an issue for full-fledged
1109		graphics stacks that include device-specific userspace components (in
1110		libdrm for instance), this limit makes DRM-based early boot graphics
1111		unnecessarily complex.
1112	      </para>
1113	      <para>
1114	        Dumb objects partly alleviate the problem by providing a standard
1115	        API to create dumb buffers suitable for scanout, which can then be used
1116	        to create KMS frame buffers.
1117	      </para>
1118	      <para>
1119	        To support dumb objects drivers must implement the
1120	        <methodname>dumb_create</methodname>,
1121	        <methodname>dumb_destroy</methodname> and
1122	        <methodname>dumb_map_offset</methodname> operations.
1123	      </para>
1124	      <itemizedlist>
1125	        <listitem>
1126	          <synopsis>int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev,
1127	                   struct drm_mode_create_dumb *args);</synopsis>
1128	          <para>
1129	            The <methodname>dumb_create</methodname> operation creates a driver
1130		    object (GEM or TTM handle) suitable for scanout based on the
1131		    width, height and depth from the struct
1132		    <structname>drm_mode_create_dumb</structname> argument. It fills the
1133		    argument's <structfield>handle</structfield>,
1134		    <structfield>pitch</structfield> and <structfield>size</structfield>
1135		    fields with a handle for the newly created object and its line
1136	            pitch and size in bytes.
1137	          </para>
1138	        </listitem>
1139	        <listitem>
1140	          <synopsis>int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev,
1141	                    uint32_t handle);</synopsis>
1142	          <para>
1143	            The <methodname>dumb_destroy</methodname> operation destroys a dumb
1144	            object created by <methodname>dumb_create</methodname>.
1145	          </para>
1146	        </listitem>
1147	        <listitem>
1148	          <synopsis>int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev,
1149	                       uint32_t handle, uint64_t *offset);</synopsis>
1150	          <para>
1151	            The <methodname>dumb_map_offset</methodname> operation associates an
1152	            mmap fake offset with the object given by the handle and returns
1153	            it. Drivers must use the
1154	            <function>drm_gem_create_mmap_offset</function> function to
1155	            associate the fake offset as described in
1156	            <xref linkend="drm-gem-objects-mapping"/>.
1157	          </para>
1158	        </listitem>
1159	      </itemizedlist>
1160	      <para>
1161	        Note that dumb objects may not be used for gpu acceleration, as has been
1162		attempted on some ARM embedded platforms. Such drivers really must have
1163		a hardware-specific ioctl to allocate suitable buffer objects.
1164	      </para>
1165	    </sect2>
1166	    <sect2>
1167	      <title>Output Polling</title>
1168	      <synopsis>void (*output_poll_changed)(struct drm_device *dev);</synopsis>
1169	      <para>
1170	        This operation notifies the driver that the status of one or more
1171	        connectors has changed. Drivers that use the fb helper can just call the
1172	        <function>drm_fb_helper_hotplug_event</function> function to handle this
1173	        operation.
1174	      </para>
1175	    </sect2>
1176	    <sect2>
1177	      <title>Locking</title>
1178	      <para>
1179	        Beside some lookup structures with their own locking (which is hidden
1180		behind the interface functions) most of the modeset state is protected
1181		by the <code>dev-&lt;mode_config.lock</code> mutex and additionally
1182		per-crtc locks to allow cursor updates, pageflips and similar operations
1183		to occur concurrently with background tasks like output detection.
1184		Operations which cross domains like a full modeset always grab all
1185		locks. Drivers there need to protect resources shared between crtcs with
1186		additional locking. They also need to be careful to always grab the
1187		relevant crtc locks if a modset functions touches crtc state, e.g. for
1188		load detection (which does only grab the <code>mode_config.lock</code>
1189		to allow concurrent screen updates on live crtcs).
1190	      </para>
1191	    </sect2>
1192	  </sect1>
1193	
1194	  <!-- Internals: kms initialization and cleanup -->
1195	
1196	  <sect1 id="drm-kms-init">
1197	    <title>KMS Initialization and Cleanup</title>
1198	    <para>
1199	      A KMS device is abstracted and exposed as a set of planes, CRTCs, encoders
1200	      and connectors. KMS drivers must thus create and initialize all those
1201	      objects at load time after initializing mode setting.
1202	    </para>
1203	    <sect2>
1204	      <title>CRTCs (struct <structname>drm_crtc</structname>)</title>
1205	      <para>
1206	        A CRTC is an abstraction representing a part of the chip that contains a
1207		pointer to a scanout buffer. Therefore, the number of CRTCs available
1208		determines how many independent scanout buffers can be active at any
1209		given time. The CRTC structure contains several fields to support this:
1210		a pointer to some video memory (abstracted as a frame buffer object), a
1211		display mode, and an (x, y) offset into the video memory to support
1212		panning or configurations where one piece of video memory spans multiple
1213		CRTCs.
1214	      </para>
1215	      <sect3>
1216	        <title>CRTC Initialization</title>
1217	        <para>
1218	          A KMS device must create and register at least one struct
1219	          <structname>drm_crtc</structname> instance. The instance is allocated
1220	          and zeroed by the driver, possibly as part of a larger structure, and
1221	          registered with a call to <function>drm_crtc_init</function> with a
1222	          pointer to CRTC functions.
1223	        </para>
1224	      </sect3>
1225	      <sect3 id="drm-kms-crtcops">
1226	        <title>CRTC Operations</title>
1227	        <sect4>
1228	          <title>Set Configuration</title>
1229	          <synopsis>int (*set_config)(struct drm_mode_set *set);</synopsis>
1230	          <para>
1231	            Apply a new CRTC configuration to the device. The configuration
1232	            specifies a CRTC, a frame buffer to scan out from, a (x,y) position in
1233	            the frame buffer, a display mode and an array of connectors to drive
1234	            with the CRTC if possible.
1235	          </para>
1236	          <para>
1237	            If the frame buffer specified in the configuration is NULL, the driver
1238	            must detach all encoders connected to the CRTC and all connectors
1239	            attached to those encoders and disable them.
1240	          </para>
1241	          <para>
1242	            This operation is called with the mode config lock held.
1243	          </para>
1244	          <note><para>
1245		    Note that the drm core has no notion of restoring the mode setting
1246		    state after resume, since all resume handling is in the full
1247		    responsibility of the driver. The common mode setting helper library
1248		    though provides a helper which can be used for this:
1249		    <function>drm_helper_resume_force_mode</function>.
1250	          </para></note>
1251	        </sect4>
1252	        <sect4>
1253	          <title>Page Flipping</title>
1254	          <synopsis>int (*page_flip)(struct drm_crtc *crtc, struct drm_framebuffer *fb,
1255	                   struct drm_pending_vblank_event *event);</synopsis>
1256	          <para>
1257	            Schedule a page flip to the given frame buffer for the CRTC. This
1258	            operation is called with the mode config mutex held.
1259	          </para>
1260	          <para>
1261	            Page flipping is a synchronization mechanism that replaces the frame
1262	            buffer being scanned out by the CRTC with a new frame buffer during
1263	            vertical blanking, avoiding tearing. When an application requests a page
1264	            flip the DRM core verifies that the new frame buffer is large enough to
1265	            be scanned out by  the CRTC in the currently configured mode and then
1266	            calls the CRTC <methodname>page_flip</methodname> operation with a
1267	            pointer to the new frame buffer.
1268	          </para>
1269	          <para>
1270	            The <methodname>page_flip</methodname> operation schedules a page flip.
1271	            Once any pending rendering targeting the new frame buffer has
1272	            completed, the CRTC will be reprogrammed to display that frame buffer
1273	            after the next vertical refresh. The operation must return immediately
1274	            without waiting for rendering or page flip to complete and must block
1275	            any new rendering to the frame buffer until the page flip completes.
1276	          </para>
1277	          <para>
1278	            If a page flip can be successfully scheduled the driver must set the
1279	            <code>drm_crtc-&lt;fb</code> field to the new framebuffer pointed to
1280	            by <code>fb</code>. This is important so that the reference counting
1281	            on framebuffers stays balanced.
1282	          </para>
1283	          <para>
1284	            If a page flip is already pending, the
1285	            <methodname>page_flip</methodname> operation must return
1286	            -<errorname>EBUSY</errorname>.
1287	          </para>
1288	          <para>
1289	            To synchronize page flip to vertical blanking the driver will likely
1290	            need to enable vertical blanking interrupts. It should call
1291	            <function>drm_vblank_get</function> for that purpose, and call
1292	            <function>drm_vblank_put</function> after the page flip completes.
1293	          </para>
1294	          <para>
1295	            If the application has requested to be notified when page flip completes
1296	            the <methodname>page_flip</methodname> operation will be called with a
1297	            non-NULL <parameter>event</parameter> argument pointing to a
1298	            <structname>drm_pending_vblank_event</structname> instance. Upon page
1299	            flip completion the driver must call <methodname>drm_send_vblank_event</methodname>
1300	            to fill in the event and send to wake up any waiting processes.
1301	            This can be performed with
1302	            <programlisting><![CDATA[
1303	            spin_lock_irqsave(&dev->event_lock, flags);
1304	            ...
1305	            drm_send_vblank_event(dev, pipe, event);
1306	            spin_unlock_irqrestore(&dev->event_lock, flags);
1307	            ]]></programlisting>
1308	          </para>
1309	          <note><para>
1310	            FIXME: Could drivers that don't need to wait for rendering to complete
1311	            just add the event to <literal>dev-&gt;vblank_event_list</literal> and
1312	            let the DRM core handle everything, as for "normal" vertical blanking
1313	            events?
1314	          </para></note>
1315	          <para>
1316	            While waiting for the page flip to complete, the
1317	            <literal>event-&gt;base.link</literal> list head can be used freely by
1318	            the driver to store the pending event in a driver-specific list.
1319	          </para>
1320	          <para>
1321	            If the file handle is closed before the event is signaled, drivers must
1322	            take care to destroy the event in their
1323	            <methodname>preclose</methodname> operation (and, if needed, call
1324	            <function>drm_vblank_put</function>).
1325	          </para>
1326	        </sect4>
1327	        <sect4>
1328	          <title>Miscellaneous</title>
1329	          <itemizedlist>
1330	            <listitem>
1331	              <synopsis>void (*set_property)(struct drm_crtc *crtc,
1332	                     struct drm_property *property, uint64_t value);</synopsis>
1333	              <para>
1334	                Set the value of the given CRTC property to
1335	                <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1336	                for more information about properties.
1337	              </para>
1338	            </listitem>
1339	            <listitem>
1340	              <synopsis>void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b,
1341	                        uint32_t start, uint32_t size);</synopsis>
1342	              <para>
1343	                Apply a gamma table to the device. The operation is optional.
1344	              </para>
1345	            </listitem>
1346	            <listitem>
1347	              <synopsis>void (*destroy)(struct drm_crtc *crtc);</synopsis>
1348	              <para>
1349	                Destroy the CRTC when not needed anymore. See
1350	                <xref linkend="drm-kms-init"/>.
1351	              </para>
1352	            </listitem>
1353	          </itemizedlist>
1354	        </sect4>
1355	      </sect3>
1356	    </sect2>
1357	    <sect2>
1358	      <title>Planes (struct <structname>drm_plane</structname>)</title>
1359	      <para>
1360	        A plane represents an image source that can be blended with or overlayed
1361		on top of a CRTC during the scanout process. Planes are associated with
1362		a frame buffer to crop a portion of the image memory (source) and
1363		optionally scale it to a destination size. The result is then blended
1364		with or overlayed on top of a CRTC.
1365	      </para>
1366	      <para>
1367	      The DRM core recognizes three types of planes:
1368	      <itemizedlist>
1369	        <listitem>
1370	        DRM_PLANE_TYPE_PRIMARY represents a "main" plane for a CRTC.  Primary
1371	        planes are the planes operated upon by by CRTC modesetting and flipping
1372	        operations described in <xref linkend="drm-kms-crtcops"/>.
1373	        </listitem>
1374	        <listitem>
1375	        DRM_PLANE_TYPE_CURSOR represents a "cursor" plane for a CRTC.  Cursor
1376	        planes are the planes operated upon by the DRM_IOCTL_MODE_CURSOR and
1377	        DRM_IOCTL_MODE_CURSOR2 ioctls.
1378	        </listitem>
1379	        <listitem>
1380	        DRM_PLANE_TYPE_OVERLAY represents all non-primary, non-cursor planes.
1381	        Some drivers refer to these types of planes as "sprites" internally.
1382	        </listitem>
1383	      </itemizedlist>
1384	      For compatibility with legacy userspace, only overlay planes are made
1385	      available to userspace by default.  Userspace clients may set the
1386	      DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate that
1387	      they wish to receive a universal plane list containing all plane types.
1388	      </para>
1389	      <sect3>
1390	        <title>Plane Initialization</title>
1391	        <para>
1392	          To create a plane, a KMS drivers allocates and
1393	          zeroes an instances of struct <structname>drm_plane</structname>
1394	          (possibly as part of a larger structure) and registers it with a call
1395	          to <function>drm_universal_plane_init</function>. The function takes a bitmask
1396	          of the CRTCs that can be associated with the plane, a pointer to the
1397	          plane functions, a list of format supported formats, and the type of
1398	          plane (primary, cursor, or overlay) being initialized.
1399	        </para>
1400	        <para>
1401	          Cursor and overlay planes are optional.  All drivers should provide
1402	          one primary plane per CRTC (although this requirement may change in
1403	          the future); drivers that do not wish to provide special handling for
1404	          primary planes may make use of the helper functions described in
1405	          <xref linkend="drm-kms-planehelpers"/> to create and register a
1406	          primary plane with standard capabilities.
1407	        </para>
1408	      </sect3>
1409	      <sect3>
1410	        <title>Plane Operations</title>
1411	        <itemizedlist>
1412	          <listitem>
1413	            <synopsis>int (*update_plane)(struct drm_plane *plane, struct drm_crtc *crtc,
1414	                        struct drm_framebuffer *fb, int crtc_x, int crtc_y,
1415	                        unsigned int crtc_w, unsigned int crtc_h,
1416	                        uint32_t src_x, uint32_t src_y,
1417	                        uint32_t src_w, uint32_t src_h);</synopsis>
1418	            <para>
1419	              Enable and configure the plane to use the given CRTC and frame buffer.
1420	            </para>
1421	            <para>
1422	              The source rectangle in frame buffer memory coordinates is given by
1423	              the <parameter>src_x</parameter>, <parameter>src_y</parameter>,
1424	              <parameter>src_w</parameter> and <parameter>src_h</parameter>
1425	              parameters (as 16.16 fixed point values). Devices that don't support
1426	              subpixel plane coordinates can ignore the fractional part.
1427	            </para>
1428	            <para>
1429	              The destination rectangle in CRTC coordinates is given by the
1430	              <parameter>crtc_x</parameter>, <parameter>crtc_y</parameter>,
1431	              <parameter>crtc_w</parameter> and <parameter>crtc_h</parameter>
1432	              parameters (as integer values). Devices scale the source rectangle to
1433	              the destination rectangle. If scaling is not supported, and the source
1434	              rectangle size doesn't match the destination rectangle size, the
1435	              driver must return a -<errorname>EINVAL</errorname> error.
1436	            </para>
1437	          </listitem>
1438	          <listitem>
1439	            <synopsis>int (*disable_plane)(struct drm_plane *plane);</synopsis>
1440	            <para>
1441	              Disable the plane. The DRM core calls this method in response to a
1442	              DRM_IOCTL_MODE_SETPLANE ioctl call with the frame buffer ID set to 0.
1443	              Disabled planes must not be processed by the CRTC.
1444	            </para>
1445	          </listitem>
1446	          <listitem>
1447	            <synopsis>void (*destroy)(struct drm_plane *plane);</synopsis>
1448	            <para>
1449	              Destroy the plane when not needed anymore. See
1450	              <xref linkend="drm-kms-init"/>.
1451	            </para>
1452	          </listitem>
1453	        </itemizedlist>
1454	      </sect3>
1455	    </sect2>
1456	    <sect2>
1457	      <title>Encoders (struct <structname>drm_encoder</structname>)</title>
1458	      <para>
1459	        An encoder takes pixel data from a CRTC and converts it to a format
1460		suitable for any attached connectors. On some devices, it may be
1461		possible to have a CRTC send data to more than one encoder. In that
1462		case, both encoders would receive data from the same scanout buffer,
1463		resulting in a "cloned" display configuration across the connectors
1464		attached to each encoder.
1465	      </para>
1466	      <sect3>
1467	        <title>Encoder Initialization</title>
1468	        <para>
1469	          As for CRTCs, a KMS driver must create, initialize and register at
1470	          least one struct <structname>drm_encoder</structname> instance. The
1471	          instance is allocated and zeroed by the driver, possibly as part of a
1472	          larger structure.
1473	        </para>
1474	        <para>
1475	          Drivers must initialize the struct <structname>drm_encoder</structname>
1476	          <structfield>possible_crtcs</structfield> and
1477	          <structfield>possible_clones</structfield> fields before registering the
1478	          encoder. Both fields are bitmasks of respectively the CRTCs that the
1479	          encoder can be connected to, and sibling encoders candidate for cloning.
1480	        </para>
1481	        <para>
1482	          After being initialized, the encoder must be registered with a call to
1483	          <function>drm_encoder_init</function>. The function takes a pointer to
1484	          the encoder functions and an encoder type. Supported types are
1485	          <itemizedlist>
1486	            <listitem>
1487	              DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A
1488	              </listitem>
1489	            <listitem>
1490	              DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort
1491	            </listitem>
1492	            <listitem>
1493	              DRM_MODE_ENCODER_LVDS for display panels
1494	            </listitem>
1495	            <listitem>
1496	              DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, Component,
1497	              SCART)
1498	            </listitem>
1499	            <listitem>
1500	              DRM_MODE_ENCODER_VIRTUAL for virtual machine displays
1501	            </listitem>
1502	          </itemizedlist>
1503	        </para>
1504	        <para>
1505	          Encoders must be attached to a CRTC to be used. DRM drivers leave
1506	          encoders unattached at initialization time. Applications (or the fbdev
1507	          compatibility layer when implemented) are responsible for attaching the
1508	          encoders they want to use to a CRTC.
1509	        </para>
1510	      </sect3>
1511	      <sect3>
1512	        <title>Encoder Operations</title>
1513	        <itemizedlist>
1514	          <listitem>
1515	            <synopsis>void (*destroy)(struct drm_encoder *encoder);</synopsis>
1516	            <para>
1517	              Called to destroy the encoder when not needed anymore. See
1518	              <xref linkend="drm-kms-init"/>.
1519	            </para>
1520	          </listitem>
1521	          <listitem>
1522	            <synopsis>void (*set_property)(struct drm_plane *plane,
1523	                     struct drm_property *property, uint64_t value);</synopsis>
1524	            <para>
1525	              Set the value of the given plane property to
1526	              <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1527	              for more information about properties.
1528	            </para>
1529	          </listitem>
1530	        </itemizedlist>
1531	      </sect3>
1532	    </sect2>
1533	    <sect2>
1534	      <title>Connectors (struct <structname>drm_connector</structname>)</title>
1535	      <para>
1536	        A connector is the final destination for pixel data on a device, and
1537		usually connects directly to an external display device like a monitor
1538		or laptop panel. A connector can only be attached to one encoder at a
1539		time. The connector is also the structure where information about the
1540		attached display is kept, so it contains fields for display data, EDID
1541		data, DPMS &amp; connection status, and information about modes
1542		supported on the attached displays.
1543	      </para>
1544	      <sect3>
1545	        <title>Connector Initialization</title>
1546	        <para>
1547	          Finally a KMS driver must create, initialize, register and attach at
1548	          least one struct <structname>drm_connector</structname> instance. The
1549	          instance is created as other KMS objects and initialized by setting the
1550	          following fields.
1551	        </para>
1552	        <variablelist>
1553	          <varlistentry>
1554	            <term><structfield>interlace_allowed</structfield></term>
1555	            <listitem><para>
1556	              Whether the connector can handle interlaced modes.
1557	            </para></listitem>
1558	          </varlistentry>
1559	          <varlistentry>
1560	            <term><structfield>doublescan_allowed</structfield></term>
1561	            <listitem><para>
1562	              Whether the connector can handle doublescan.
1563	            </para></listitem>
1564	          </varlistentry>
1565	          <varlistentry>
1566	            <term><structfield>display_info
1567	            </structfield></term>
1568	            <listitem><para>
1569	              Display information is filled from EDID information when a display
1570	              is detected. For non hot-pluggable displays such as flat panels in
1571	              embedded systems, the driver should initialize the
1572	              <structfield>display_info</structfield>.<structfield>width_mm</structfield>
1573	              and
1574	              <structfield>display_info</structfield>.<structfield>height_mm</structfield>
1575	              fields with the physical size of the display.
1576	            </para></listitem>
1577	          </varlistentry>
1578	          <varlistentry>
1579	            <term id="drm-kms-connector-polled"><structfield>polled</structfield></term>
1580	            <listitem><para>
1581	              Connector polling mode, a combination of
1582	              <variablelist>
1583	                <varlistentry>
1584	                  <term>DRM_CONNECTOR_POLL_HPD</term>
1585	                  <listitem><para>
1586	                    The connector generates hotplug events and doesn't need to be
1587	                    periodically polled. The CONNECT and DISCONNECT flags must not
1588	                    be set together with the HPD flag.
1589	                  </para></listitem>
1590	                </varlistentry>
1591	                <varlistentry>
1592	                  <term>DRM_CONNECTOR_POLL_CONNECT</term>
1593	                  <listitem><para>
1594	                    Periodically poll the connector for connection.
1595	                  </para></listitem>
1596	                </varlistentry>
1597	                <varlistentry>
1598	                  <term>DRM_CONNECTOR_POLL_DISCONNECT</term>
1599	                  <listitem><para>
1600	                    Periodically poll the connector for disconnection.
1601	                  </para></listitem>
1602	                </varlistentry>
1603	              </variablelist>
1604	              Set to 0 for connectors that don't support connection status
1605	              discovery.
1606	            </para></listitem>
1607	          </varlistentry>
1608	        </variablelist>
1609	        <para>
1610	          The connector is then registered with a call to
1611	          <function>drm_connector_init</function> with a pointer to the connector
1612	          functions and a connector type, and exposed through sysfs with a call to
1613	          <function>drm_sysfs_connector_add</function>.
1614	        </para>
1615	        <para>
1616	          Supported connector types are
1617	          <itemizedlist>
1618	            <listitem>DRM_MODE_CONNECTOR_VGA</listitem>
1619	            <listitem>DRM_MODE_CONNECTOR_DVII</listitem>
1620	            <listitem>DRM_MODE_CONNECTOR_DVID</listitem>
1621	            <listitem>DRM_MODE_CONNECTOR_DVIA</listitem>
1622	            <listitem>DRM_MODE_CONNECTOR_Composite</listitem>
1623	            <listitem>DRM_MODE_CONNECTOR_SVIDEO</listitem>
1624	            <listitem>DRM_MODE_CONNECTOR_LVDS</listitem>
1625	            <listitem>DRM_MODE_CONNECTOR_Component</listitem>
1626	            <listitem>DRM_MODE_CONNECTOR_9PinDIN</listitem>
1627	            <listitem>DRM_MODE_CONNECTOR_DisplayPort</listitem>
1628	            <listitem>DRM_MODE_CONNECTOR_HDMIA</listitem>
1629	            <listitem>DRM_MODE_CONNECTOR_HDMIB</listitem>
1630	            <listitem>DRM_MODE_CONNECTOR_TV</listitem>
1631	            <listitem>DRM_MODE_CONNECTOR_eDP</listitem>
1632	            <listitem>DRM_MODE_CONNECTOR_VIRTUAL</listitem>
1633	          </itemizedlist>
1634	        </para>
1635	        <para>
1636	          Connectors must be attached to an encoder to be used. For devices that
1637	          map connectors to encoders 1:1, the connector should be attached at
1638	          initialization time with a call to
1639	          <function>drm_mode_connector_attach_encoder</function>. The driver must
1640	          also set the <structname>drm_connector</structname>
1641	          <structfield>encoder</structfield> field to point to the attached
1642	          encoder.
1643	        </para>
1644	        <para>
1645	          Finally, drivers must initialize the connectors state change detection
1646	          with a call to <function>drm_kms_helper_poll_init</function>. If at
1647	          least one connector is pollable but can't generate hotplug interrupts
1648	          (indicated by the DRM_CONNECTOR_POLL_CONNECT and
1649	          DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will
1650	          automatically be queued to periodically poll for changes. Connectors
1651	          that can generate hotplug interrupts must be marked with the
1652	          DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must
1653	          call <function>drm_helper_hpd_irq_event</function>. The function will
1654	          queue a delayed work to check the state of all connectors, but no
1655	          periodic polling will be done.
1656	        </para>
1657	      </sect3>
1658	      <sect3>
1659	        <title>Connector Operations</title>
1660	        <note><para>
1661	          Unless otherwise state, all operations are mandatory.
1662	        </para></note>
1663	        <sect4>
1664	          <title>DPMS</title>
1665	          <synopsis>void (*dpms)(struct drm_connector *connector, int mode);</synopsis>
1666	          <para>
1667	            The DPMS operation sets the power state of a connector. The mode
1668	            argument is one of
1669	            <itemizedlist>
1670	              <listitem><para>DRM_MODE_DPMS_ON</para></listitem>
1671	              <listitem><para>DRM_MODE_DPMS_STANDBY</para></listitem>
1672	              <listitem><para>DRM_MODE_DPMS_SUSPEND</para></listitem>
1673	              <listitem><para>DRM_MODE_DPMS_OFF</para></listitem>
1674	            </itemizedlist>
1675	          </para>
1676	          <para>
1677	            In all but DPMS_ON mode the encoder to which the connector is attached
1678	            should put the display in low-power mode by driving its signals
1679	            appropriately. If more than one connector is attached to the encoder
1680	            care should be taken not to change the power state of other displays as
1681	            a side effect. Low-power mode should be propagated to the encoders and
1682	            CRTCs when all related connectors are put in low-power mode.
1683	          </para>
1684	        </sect4>
1685	        <sect4>
1686	          <title>Modes</title>
1687	          <synopsis>int (*fill_modes)(struct drm_connector *connector, uint32_t max_width,
1688	                      uint32_t max_height);</synopsis>
1689	          <para>
1690	            Fill the mode list with all supported modes for the connector. If the
1691	            <parameter>max_width</parameter> and <parameter>max_height</parameter>
1692	            arguments are non-zero, the implementation must ignore all modes wider
1693	            than <parameter>max_width</parameter> or higher than
1694	            <parameter>max_height</parameter>.
1695	          </para>
1696	          <para>
1697	            The connector must also fill in this operation its
1698	            <structfield>display_info</structfield>
1699	            <structfield>width_mm</structfield> and
1700	            <structfield>height_mm</structfield> fields with the connected display
1701	            physical size in millimeters. The fields should be set to 0 if the value
1702	            isn't known or is not applicable (for instance for projector devices).
1703	          </para>
1704	        </sect4>
1705	        <sect4>
1706	          <title>Connection Status</title>
1707	          <para>
1708	            The connection status is updated through polling or hotplug events when
1709	            supported (see <xref linkend="drm-kms-connector-polled"/>). The status
1710	            value is reported to userspace through ioctls and must not be used
1711	            inside the driver, as it only gets initialized by a call to
1712	            <function>drm_mode_getconnector</function> from userspace.
1713	          </para>
1714	          <synopsis>enum drm_connector_status (*detect)(struct drm_connector *connector,
1715	                                        bool force);</synopsis>
1716	          <para>
1717	            Check to see if anything is attached to the connector. The
1718	            <parameter>force</parameter> parameter is set to false whilst polling or
1719	            to true when checking the connector due to user request.
1720	            <parameter>force</parameter> can be used by the driver to avoid
1721	            expensive, destructive operations during automated probing.
1722	          </para>
1723	          <para>
1724	            Return connector_status_connected if something is connected to the
1725	            connector, connector_status_disconnected if nothing is connected and
1726	            connector_status_unknown if the connection state isn't known.
1727	          </para>
1728	          <para>
1729	            Drivers should only return connector_status_connected if the connection
1730	            status has really been probed as connected. Connectors that can't detect
1731	            the connection status, or failed connection status probes, should return
1732	            connector_status_unknown.
1733	          </para>
1734	        </sect4>
1735	        <sect4>
1736	          <title>Miscellaneous</title>
1737	          <itemizedlist>
1738	            <listitem>
1739	              <synopsis>void (*set_property)(struct drm_connector *connector,
1740	                     struct drm_property *property, uint64_t value);</synopsis>
1741	              <para>
1742	                Set the value of the given connector property to
1743	                <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1744	                for more information about properties.
1745	              </para>
1746	            </listitem>
1747	            <listitem>
1748	              <synopsis>void (*destroy)(struct drm_connector *connector);</synopsis>
1749	              <para>
1750	                Destroy the connector when not needed anymore. See
1751	                <xref linkend="drm-kms-init"/>.
1752	              </para>
1753	            </listitem>
1754	          </itemizedlist>
1755	        </sect4>
1756	      </sect3>
1757	    </sect2>
1758	    <sect2>
1759	      <title>Cleanup</title>
1760	      <para>
1761	        The DRM core manages its objects' lifetime. When an object is not needed
1762		anymore the core calls its destroy function, which must clean up and
1763		free every resource allocated for the object. Every
1764		<function>drm_*_init</function> call must be matched with a
1765		corresponding <function>drm_*_cleanup</function> call to cleanup CRTCs
1766		(<function>drm_crtc_cleanup</function>), planes
1767		(<function>drm_plane_cleanup</function>), encoders
1768		(<function>drm_encoder_cleanup</function>) and connectors
1769		(<function>drm_connector_cleanup</function>). Furthermore, connectors
1770		that have been added to sysfs must be removed by a call to
1771		<function>drm_sysfs_connector_remove</function> before calling
1772		<function>drm_connector_cleanup</function>.
1773	      </para>
1774	      <para>
1775	        Connectors state change detection must be cleanup up with a call to
1776		<function>drm_kms_helper_poll_fini</function>.
1777	      </para>
1778	    </sect2>
1779	    <sect2>
1780	      <title>Output discovery and initialization example</title>
1781	      <programlisting><![CDATA[
1782	void intel_crt_init(struct drm_device *dev)
1783	{
1784		struct drm_connector *connector;
1785		struct intel_output *intel_output;
1786	
1787		intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL);
1788		if (!intel_output)
1789			return;
1790	
1791		connector = &intel_output->base;
1792		drm_connector_init(dev, &intel_output->base,
1793				   &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA);
1794	
1795		drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs,
1796				 DRM_MODE_ENCODER_DAC);
1797	
1798		drm_mode_connector_attach_encoder(&intel_output->base,
1799						  &intel_output->enc);
1800	
1801		/* Set up the DDC bus. */
1802		intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A");
1803		if (!intel_output->ddc_bus) {
1804			dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration "
1805				   "failed.\n");
1806			return;
1807		}
1808	
1809		intel_output->type = INTEL_OUTPUT_ANALOG;
1810		connector->interlace_allowed = 0;
1811		connector->doublescan_allowed = 0;
1812	
1813		drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs);
1814		drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs);
1815	
1816		drm_sysfs_connector_add(connector);
1817	}]]></programlisting>
1818	      <para>
1819	        In the example above (taken from the i915 driver), a CRTC, connector and
1820	        encoder combination is created. A device-specific i2c bus is also
1821	        created for fetching EDID data and performing monitor detection. Once
1822	        the process is complete, the new connector is registered with sysfs to
1823	        make its properties available to applications.
1824	      </para>
1825	    </sect2>
1826	    <sect2>
1827	      <title>KMS API Functions</title>
1828	!Edrivers/gpu/drm/drm_crtc.c
1829	    </sect2>
1830	    <sect2>
1831	      <title>KMS Locking</title>
1832	!Pdrivers/gpu/drm/drm_modeset_lock.c kms locking
1833	!Iinclude/drm/drm_modeset_lock.h
1834	!Edrivers/gpu/drm/drm_modeset_lock.c
1835	    </sect2>
1836	  </sect1>
1837	
1838	  <!-- Internals: kms helper functions -->
1839	
1840	  <sect1>
1841	    <title>Mode Setting Helper Functions</title>
1842	    <para>
1843	      The plane, CRTC, encoder and connector functions provided by the drivers
1844	      implement the DRM API. They're called by the DRM core and ioctl handlers
1845	      to handle device state changes and configuration request. As implementing
1846	      those functions often requires logic not specific to drivers, mid-layer
1847	      helper functions are available to avoid duplicating boilerplate code.
1848	    </para>
1849	    <para>
1850	      The DRM core contains one mid-layer implementation. The mid-layer provides
1851	      implementations of several plane, CRTC, encoder and connector functions
1852	      (called from the top of the mid-layer) that pre-process requests and call
1853	      lower-level functions provided by the driver (at the bottom of the
1854	      mid-layer). For instance, the
1855	      <function>drm_crtc_helper_set_config</function> function can be used to
1856	      fill the struct <structname>drm_crtc_funcs</structname>
1857	      <structfield>set_config</structfield> field. When called, it will split
1858	      the <methodname>set_config</methodname> operation in smaller, simpler
1859	      operations and call the driver to handle them.
1860	    </para>
1861	    <para>
1862	      To use the mid-layer, drivers call <function>drm_crtc_helper_add</function>,
1863	      <function>drm_encoder_helper_add</function> and
1864	      <function>drm_connector_helper_add</function> functions to install their
1865	      mid-layer bottom operations handlers, and fill the
1866	      <structname>drm_crtc_funcs</structname>,
1867	      <structname>drm_encoder_funcs</structname> and
1868	      <structname>drm_connector_funcs</structname> structures with pointers to
1869	      the mid-layer top API functions. Installing the mid-layer bottom operation
1870	      handlers is best done right after registering the corresponding KMS object.
1871	    </para>
1872	    <para>
1873	      The mid-layer is not split between CRTC, encoder and connector operations.
1874	      To use it, a driver must provide bottom functions for all of the three KMS
1875	      entities.
1876	    </para>
1877	    <sect2>
1878	      <title>Helper Functions</title>
1879	      <itemizedlist>
1880	        <listitem>
1881	          <synopsis>int drm_crtc_helper_set_config(struct drm_mode_set *set);</synopsis>
1882	          <para>
1883	            The <function>drm_crtc_helper_set_config</function> helper function
1884	            is a CRTC <methodname>set_config</methodname> implementation. It
1885	            first tries to locate the best encoder for each connector by calling
1886	            the connector <methodname>best_encoder</methodname> helper
1887	            operation.
1888	          </para>
1889	          <para>
1890	            After locating the appropriate encoders, the helper function will
1891	            call the <methodname>mode_fixup</methodname> encoder and CRTC helper
1892	            operations to adjust the requested mode, or reject it completely in
1893	            which case an error will be returned to the application. If the new
1894	            configuration after mode adjustment is identical to the current
1895	            configuration the helper function will return without performing any
1896	            other operation.
1897	          </para>
1898	          <para>
1899	            If the adjusted mode is identical to the current mode but changes to
1900	            the frame buffer need to be applied, the
1901	            <function>drm_crtc_helper_set_config</function> function will call
1902	            the CRTC <methodname>mode_set_base</methodname> helper operation. If
1903	            the adjusted mode differs from the current mode, or if the
1904	            <methodname>mode_set_base</methodname> helper operation is not
1905	            provided, the helper function performs a full mode set sequence by
1906	            calling the <methodname>prepare</methodname>,
1907	            <methodname>mode_set</methodname> and
1908	            <methodname>commit</methodname> CRTC and encoder helper operations,
1909	            in that order.
1910	          </para>
1911	        </listitem>
1912	        <listitem>
1913	          <synopsis>void drm_helper_connector_dpms(struct drm_connector *connector, int mode);</synopsis>
1914	          <para>
1915	            The <function>drm_helper_connector_dpms</function> helper function
1916	            is a connector <methodname>dpms</methodname> implementation that
1917	            tracks power state of connectors. To use the function, drivers must
1918	            provide <methodname>dpms</methodname> helper operations for CRTCs
1919	            and encoders to apply the DPMS state to the device.
1920	          </para>
1921	          <para>
1922	            The mid-layer doesn't track the power state of CRTCs and encoders.
1923	            The <methodname>dpms</methodname> helper operations can thus be
1924	            called with a mode identical to the currently active mode.
1925	          </para>
1926	        </listitem>
1927	        <listitem>
1928	          <synopsis>int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
1929	                                            uint32_t maxX, uint32_t maxY);</synopsis>
1930	          <para>
1931	            The <function>drm_helper_probe_single_connector_modes</function> helper
1932	            function is a connector <methodname>fill_modes</methodname>
1933	            implementation that updates the connection status for the connector
1934	            and then retrieves a list of modes by calling the connector
1935	            <methodname>get_modes</methodname> helper operation.
1936	          </para>
1937	          <para>
1938	            The function filters out modes larger than
1939	            <parameter>max_width</parameter> and <parameter>max_height</parameter>
1940	            if specified. It then calls the optional connector
1941	            <methodname>mode_valid</methodname> helper operation for each mode in
1942	            the probed list to check whether the mode is valid for the connector.
1943	          </para>
1944	        </listitem>
1945	      </itemizedlist>
1946	    </sect2>
1947	    <sect2>
1948	      <title>CRTC Helper Operations</title>
1949	      <itemizedlist>
1950	        <listitem id="drm-helper-crtc-mode-fixup">
1951	          <synopsis>bool (*mode_fixup)(struct drm_crtc *crtc,
1952	                       const struct drm_display_mode *mode,
1953	                       struct drm_display_mode *adjusted_mode);</synopsis>
1954	          <para>
1955	            Let CRTCs adjust the requested mode or reject it completely. This
1956	            operation returns true if the mode is accepted (possibly after being
1957	            adjusted) or false if it is rejected.
1958	          </para>
1959	          <para>
1960	            The <methodname>mode_fixup</methodname> operation should reject the
1961	            mode if it can't reasonably use it. The definition of "reasonable"
1962	            is currently fuzzy in this context. One possible behaviour would be
1963	            to set the adjusted mode to the panel timings when a fixed-mode
1964	            panel is used with hardware capable of scaling. Another behaviour
1965	            would be to accept any input mode and adjust it to the closest mode
1966	            supported by the hardware (FIXME: This needs to be clarified).
1967	          </para>
1968	        </listitem>
1969	        <listitem>
1970	          <synopsis>int (*mode_set_base)(struct drm_crtc *crtc, int x, int y,
1971	                     struct drm_framebuffer *old_fb)</synopsis>
1972	          <para>
1973	            Move the CRTC on the current frame buffer (stored in
1974	            <literal>crtc-&gt;fb</literal>) to position (x,y). Any of the frame
1975	            buffer, x position or y position may have been modified.
1976	          </para>
1977	          <para>
1978	            This helper operation is optional. If not provided, the
1979	            <function>drm_crtc_helper_set_config</function> function will fall
1980	            back to the <methodname>mode_set</methodname> helper operation.
1981	          </para>
1982	          <note><para>
1983	            FIXME: Why are x and y passed as arguments, as they can be accessed
1984	            through <literal>crtc-&gt;x</literal> and
1985	            <literal>crtc-&gt;y</literal>?
1986	          </para></note>
1987	        </listitem>
1988	        <listitem>
1989	          <synopsis>void (*prepare)(struct drm_crtc *crtc);</synopsis>
1990	          <para>
1991	            Prepare the CRTC for mode setting. This operation is called after
1992	            validating the requested mode. Drivers use it to perform
1993	            device-specific operations required before setting the new mode.
1994	          </para>
1995	        </listitem>
1996	        <listitem>
1997	          <synopsis>int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,
1998	                struct drm_display_mode *adjusted_mode, int x, int y,
1999	                struct drm_framebuffer *old_fb);</synopsis>
2000	          <para>
2001	            Set a new mode, position and frame buffer. Depending on the device
2002	            requirements, the mode can be stored internally by the driver and
2003	            applied in the <methodname>commit</methodname> operation, or
2004	            programmed to the hardware immediately.
2005	          </para>
2006	          <para>
2007	            The <methodname>mode_set</methodname> operation returns 0 on success
2008		    or a negative error code if an error occurs.
2009	          </para>
2010	        </listitem>
2011	        <listitem>
2012	          <synopsis>void (*commit)(struct drm_crtc *crtc);</synopsis>
2013	          <para>
2014	            Commit a mode. This operation is called after setting the new mode.
2015	            Upon return the device must use the new mode and be fully
2016	            operational.
2017	          </para>
2018	        </listitem>
2019	      </itemizedlist>
2020	    </sect2>
2021	    <sect2>
2022	      <title>Encoder Helper Operations</title>
2023	      <itemizedlist>
2024	        <listitem>
2025	          <synopsis>bool (*mode_fixup)(struct drm_encoder *encoder,
2026	                       const struct drm_display_mode *mode,
2027	                       struct drm_display_mode *adjusted_mode);</synopsis>
2028	          <para>
2029	            Let encoders adjust the requested mode or reject it completely. This
2030	            operation returns true if the mode is accepted (possibly after being
2031	            adjusted) or false if it is rejected. See the
2032	            <link linkend="drm-helper-crtc-mode-fixup">mode_fixup CRTC helper
2033	            operation</link> for an explanation of the allowed adjustments.
2034	          </para>
2035	        </listitem>
2036	        <listitem>
2037	          <synopsis>void (*prepare)(struct drm_encoder *encoder);</synopsis>
2038	          <para>
2039	            Prepare the encoder for mode setting. This operation is called after
2040	            validating the requested mode. Drivers use it to perform
2041	            device-specific operations required before setting the new mode.
2042	          </para>
2043	        </listitem>
2044	        <listitem>
2045	          <synopsis>void (*mode_set)(struct drm_encoder *encoder,
2046	                 struct drm_display_mode *mode,
2047	                 struct drm_display_mode *adjusted_mode);</synopsis>
2048	          <para>
2049	            Set a new mode. Depending on the device requirements, the mode can
2050	            be stored internally by the driver and applied in the
2051	            <methodname>commit</methodname> operation, or programmed to the
2052	            hardware immediately.
2053	          </para>
2054	        </listitem>
2055	        <listitem>
2056	          <synopsis>void (*commit)(struct drm_encoder *encoder);</synopsis>
2057	          <para>
2058	            Commit a mode. This operation is called after setting the new mode.
2059	            Upon return the device must use the new mode and be fully
2060	            operational.
2061	          </para>
2062	        </listitem>
2063	      </itemizedlist>
2064	    </sect2>
2065	    <sect2>
2066	      <title>Connector Helper Operations</title>
2067	      <itemizedlist>
2068	        <listitem>
2069	          <synopsis>struct drm_encoder *(*best_encoder)(struct drm_connector *connector);</synopsis>
2070	          <para>
2071	            Return a pointer to the best encoder for the connecter. Device that
2072	            map connectors to encoders 1:1 simply return the pointer to the
2073	            associated encoder. This operation is mandatory.
2074	          </para>
2075	        </listitem>
2076	        <listitem>
2077	          <synopsis>int (*get_modes)(struct drm_connector *connector);</synopsis>
2078	          <para>
2079	            Fill the connector's <structfield>probed_modes</structfield> list
2080	            by parsing EDID data with <function>drm_add_edid_modes</function> or
2081	            calling <function>drm_mode_probed_add</function> directly for every
2082	            supported mode and return the number of modes it has detected. This
2083	            operation is mandatory.
2084	          </para>
2085	          <para>
2086	            When adding modes manually the driver creates each mode with a call to
2087	            <function>drm_mode_create</function> and must fill the following fields.
2088	            <itemizedlist>
2089	              <listitem>
2090	                <synopsis>__u32 type;</synopsis>
2091	                <para>
2092	                  Mode type bitmask, a combination of
2093	                  <variablelist>
2094	                    <varlistentry>
2095	                      <term>DRM_MODE_TYPE_BUILTIN</term>
2096	                      <listitem><para>not used?</para></listitem>
2097	                    </varlistentry>
2098	                    <varlistentry>
2099	                      <term>DRM_MODE_TYPE_CLOCK_C</term>
2100	                      <listitem><para>not used?</para></listitem>
2101	                    </varlistentry>
2102	                    <varlistentry>
2103	                      <term>DRM_MODE_TYPE_CRTC_C</term>
2104	                      <listitem><para>not used?</para></listitem>
2105	                    </varlistentry>
2106	                    <varlistentry>
2107	                      <term>
2108	        DRM_MODE_TYPE_PREFERRED - The preferred mode for the connector
2109	                      </term>
2110	                      <listitem>
2111	                        <para>not used?</para>
2112	                      </listitem>
2113	                    </varlistentry>
2114	                    <varlistentry>
2115	                      <term>DRM_MODE_TYPE_DEFAULT</term>
2116	                      <listitem><para>not used?</para></listitem>
2117	                    </varlistentry>
2118	                    <varlistentry>
2119	                      <term>DRM_MODE_TYPE_USERDEF</term>
2120	                      <listitem><para>not used?</para></listitem>
2121	                    </varlistentry>
2122	                    <varlistentry>
2123	                      <term>DRM_MODE_TYPE_DRIVER</term>
2124	                      <listitem>
2125	                        <para>
2126	                          The mode has been created by the driver (as opposed to
2127	                          to user-created modes).
2128	                        </para>
2129	                      </listitem>
2130	                    </varlistentry>
2131	                  </variablelist>
2132	                  Drivers must set the DRM_MODE_TYPE_DRIVER bit for all modes they
2133	                  create, and set the DRM_MODE_TYPE_PREFERRED bit for the preferred
2134	                  mode.
2135	                </para>
2136	              </listitem>
2137	              <listitem>
2138	                <synopsis>__u32 clock;</synopsis>
2139	                <para>Pixel clock frequency in kHz unit</para>
2140	              </listitem>
2141	              <listitem>
2142	                <synopsis>__u16 hdisplay, hsync_start, hsync_end, htotal;
2143	    __u16 vdisplay, vsync_start, vsync_end, vtotal;</synopsis>
2144	                <para>Horizontal and vertical timing information</para>
2145	                <screen><![CDATA[
2146	             Active                 Front           Sync           Back
2147	             Region                 Porch                          Porch
2148	    <-----------------------><----------------><-------------><-------------->
2149	
2150	      //////////////////////|
2151	     ////////////////////// |
2152	    //////////////////////  |..................               ................
2153	                                               _______________
2154	
2155	    <----- [hv]display ----->
2156	    <------------- [hv]sync_start ------------>
2157	    <--------------------- [hv]sync_end --------------------->
2158	    <-------------------------------- [hv]total ----------------------------->
2159	]]></screen>
2160	              </listitem>
2161	              <listitem>
2162	                <synopsis>__u16 hskew;
2163	    __u16 vscan;</synopsis>
2164	                <para>Unknown</para>
2165	              </listitem>
2166	              <listitem>
2167	                <synopsis>__u32 flags;</synopsis>
2168	                <para>
2169	                  Mode flags, a combination of
2170	                  <variablelist>
2171	                    <varlistentry>
2172	                      <term>DRM_MODE_FLAG_PHSYNC</term>
2173	                      <listitem><para>
2174	                        Horizontal sync is active high
2175	                      </para></listitem>
2176	                    </varlistentry>
2177	                    <varlistentry>
2178	                      <term>DRM_MODE_FLAG_NHSYNC</term>
2179	                      <listitem><para>
2180	                        Horizontal sync is active low
2181	                      </para></listitem>
2182	                    </varlistentry>
2183	                    <varlistentry>
2184	                      <term>DRM_MODE_FLAG_PVSYNC</term>
2185	                      <listitem><para>
2186	                        Vertical sync is active high
2187	                      </para></listitem>
2188	                    </varlistentry>
2189	                    <varlistentry>
2190	                      <term>DRM_MODE_FLAG_NVSYNC</term>
2191	                      <listitem><para>
2192	                        Vertical sync is active low
2193	                      </para></listitem>
2194	                    </varlistentry>
2195	                    <varlistentry>
2196	                      <term>DRM_MODE_FLAG_INTERLACE</term>
2197	                      <listitem><para>
2198	                        Mode is interlaced
2199	                      </para></listitem>
2200	                    </varlistentry>
2201	                    <varlistentry>
2202	                      <term>DRM_MODE_FLAG_DBLSCAN</term>
2203	                      <listitem><para>
2204	                        Mode uses doublescan
2205	                      </para></listitem>
2206	                    </varlistentry>
2207	                    <varlistentry>
2208	                      <term>DRM_MODE_FLAG_CSYNC</term>
2209	                      <listitem><para>
2210	                        Mode uses composite sync
2211	                      </para></listitem>
2212	                    </varlistentry>
2213	                    <varlistentry>
2214	                      <term>DRM_MODE_FLAG_PCSYNC</term>
2215	                      <listitem><para>
2216	                        Composite sync is active high
2217	                      </para></listitem>
2218	                    </varlistentry>
2219	                    <varlistentry>
2220	                      <term>DRM_MODE_FLAG_NCSYNC</term>
2221	                      <listitem><para>
2222	                        Composite sync is active low
2223	                      </para></listitem>
2224	                    </varlistentry>
2225	                    <varlistentry>
2226	                      <term>DRM_MODE_FLAG_HSKEW</term>
2227	                      <listitem><para>
2228	                        hskew provided (not used?)
2229	                      </para></listitem>
2230	                    </varlistentry>
2231	                    <varlistentry>
2232	                      <term>DRM_MODE_FLAG_BCAST</term>
2233	                      <listitem><para>
2234	                        not used?
2235	                      </para></listitem>
2236	                    </varlistentry>
2237	                    <varlistentry>
2238	                      <term>DRM_MODE_FLAG_PIXMUX</term>
2239	                      <listitem><para>
2240	                        not used?
2241	                      </para></listitem>
2242	                    </varlistentry>
2243	                    <varlistentry>
2244	                      <term>DRM_MODE_FLAG_DBLCLK</term>
2245	                      <listitem><para>
2246	                        not used?
2247	                      </para></listitem>
2248	                    </varlistentry>
2249	                    <varlistentry>
2250	                      <term>DRM_MODE_FLAG_CLKDIV2</term>
2251	                      <listitem><para>
2252	                        ?
2253	                      </para></listitem>
2254	                    </varlistentry>
2255	                  </variablelist>
2256	                </para>
2257	                <para>
2258	                  Note that modes marked with the INTERLACE or DBLSCAN flags will be
2259	                  filtered out by
2260	                  <function>drm_helper_probe_single_connector_modes</function> if
2261	                  the connector's <structfield>interlace_allowed</structfield> or
2262	                  <structfield>doublescan_allowed</structfield> field is set to 0.
2263	                </para>
2264	              </listitem>
2265	              <listitem>
2266	                <synopsis>char name[DRM_DISPLAY_MODE_LEN];</synopsis>
2267	                <para>
2268	                  Mode name. The driver must call
2269	                  <function>drm_mode_set_name</function> to fill the mode name from
2270	                  <structfield>hdisplay</structfield>,
2271	                  <structfield>vdisplay</structfield> and interlace flag after
2272	                  filling the corresponding fields.
2273	                </para>
2274	              </listitem>
2275	            </itemizedlist>
2276	          </para>
2277	          <para>
2278	            The <structfield>vrefresh</structfield> value is computed by
2279	            <function>drm_helper_probe_single_connector_modes</function>.
2280	          </para>
2281	          <para>
2282	            When parsing EDID data, <function>drm_add_edid_modes</function> fill the
2283	            connector <structfield>display_info</structfield>
2284	            <structfield>width_mm</structfield> and
2285	            <structfield>height_mm</structfield> fields. When creating modes
2286	            manually the <methodname>get_modes</methodname> helper operation must
2287	            set the <structfield>display_info</structfield>
2288	            <structfield>width_mm</structfield> and
2289	            <structfield>height_mm</structfield> fields if they haven't been set
2290	            already (for instance at initialization time when a fixed-size panel is
2291	            attached to the connector). The mode <structfield>width_mm</structfield>
2292	            and <structfield>height_mm</structfield> fields are only used internally
2293	            during EDID parsing and should not be set when creating modes manually.
2294	          </para>
2295	        </listitem>
2296	        <listitem>
2297	          <synopsis>int (*mode_valid)(struct drm_connector *connector,
2298			  struct drm_display_mode *mode);</synopsis>
2299	          <para>
2300	            Verify whether a mode is valid for the connector. Return MODE_OK for
2301	            supported modes and one of the enum drm_mode_status values (MODE_*)
2302	            for unsupported modes. This operation is optional.
2303	          </para>
2304	          <para>
2305	            As the mode rejection reason is currently not used beside for
2306	            immediately removing the unsupported mode, an implementation can
2307	            return MODE_BAD regardless of the exact reason why the mode is not
2308	            valid.
2309	          </para>
2310	          <note><para>
2311	            Note that the <methodname>mode_valid</methodname> helper operation is
2312	            only called for modes detected by the device, and
2313	            <emphasis>not</emphasis> for modes set by the user through the CRTC
2314	            <methodname>set_config</methodname> operation.
2315	          </para></note>
2316	        </listitem>
2317	      </itemizedlist>
2318	    </sect2>
2319	    <sect2>
2320	      <title>Modeset Helper Functions Reference</title>
2321	!Edrivers/gpu/drm/drm_crtc_helper.c
2322	    </sect2>
2323	    <sect2>
2324	      <title>Output Probing Helper Functions Reference</title>
2325	!Pdrivers/gpu/drm/drm_probe_helper.c output probing helper overview
2326	!Edrivers/gpu/drm/drm_probe_helper.c
2327	    </sect2>
2328	    <sect2>
2329	      <title>fbdev Helper Functions Reference</title>
2330	!Pdrivers/gpu/drm/drm_fb_helper.c fbdev helpers
2331	!Edrivers/gpu/drm/drm_fb_helper.c
2332	!Iinclude/drm/drm_fb_helper.h
2333	    </sect2>
2334	    <sect2>
2335	      <title>Display Port Helper Functions Reference</title>
2336	!Pdrivers/gpu/drm/drm_dp_helper.c dp helpers
2337	!Iinclude/drm/drm_dp_helper.h
2338	!Edrivers/gpu/drm/drm_dp_helper.c
2339	    </sect2>
2340	    <sect2>
2341	      <title>EDID Helper Functions Reference</title>
2342	!Edrivers/gpu/drm/drm_edid.c
2343	    </sect2>
2344	    <sect2>
2345	      <title>Rectangle Utilities Reference</title>
2346	!Pinclude/drm/drm_rect.h rect utils
2347	!Iinclude/drm/drm_rect.h
2348	!Edrivers/gpu/drm/drm_rect.c
2349	    </sect2>
2350	    <sect2>
2351	      <title>Flip-work Helper Reference</title>
2352	!Pinclude/drm/drm_flip_work.h flip utils
2353	!Iinclude/drm/drm_flip_work.h
2354	!Edrivers/gpu/drm/drm_flip_work.c
2355	    </sect2>
2356	    <sect2>
2357	      <title>HDMI Infoframes Helper Reference</title>
2358	      <para>
2359		Strictly speaking this is not a DRM helper library but generally useable
2360		by any driver interfacing with HDMI outputs like v4l or alsa drivers.
2361		But it nicely fits into the overall topic of mode setting helper
2362		libraries and hence is also included here.
2363	      </para>
2364	!Iinclude/linux/hdmi.h
2365	!Edrivers/video/hdmi.c
2366	    </sect2>
2367	    <sect2>
2368	      <title id="drm-kms-planehelpers">Plane Helper Reference</title>
2369	!Edrivers/gpu/drm/drm_plane_helper.c Plane Helpers
2370	    </sect2>
2371	  </sect1>
2372	
2373	  <!-- Internals: kms properties -->
2374	
2375	  <sect1 id="drm-kms-properties">
2376	    <title>KMS Properties</title>
2377	    <para>
2378	      Drivers may need to expose additional parameters to applications than
2379	      those described in the previous sections. KMS supports attaching
2380	      properties to CRTCs, connectors and planes and offers a userspace API to
2381	      list, get and set the property values.
2382	    </para>
2383	    <para>
2384	      Properties are identified by a name that uniquely defines the property
2385	      purpose, and store an associated value. For all property types except blob
2386	      properties the value is a 64-bit unsigned integer.
2387	    </para>
2388	    <para>
2389	      KMS differentiates between properties and property instances. Drivers
2390	      first create properties and then create and associate individual instances
2391	      of those properties to objects. A property can be instantiated multiple
2392	      times and associated with different objects. Values are stored in property
2393	      instances, and all other property information are stored in the property
2394	      and shared between all instances of the property.
2395	    </para>
2396	    <para>
2397	      Every property is created with a type that influences how the KMS core
2398	      handles the property. Supported property types are
2399	      <variablelist>
2400	        <varlistentry>
2401	          <term>DRM_MODE_PROP_RANGE</term>
2402	          <listitem><para>Range properties report their minimum and maximum
2403	            admissible values. The KMS core verifies that values set by
2404	            application fit in that range.</para></listitem>
2405	        </varlistentry>
2406	        <varlistentry>
2407	          <term>DRM_MODE_PROP_ENUM</term>
2408	          <listitem><para>Enumerated properties take a numerical value that
2409	            ranges from 0 to the number of enumerated values defined by the
2410	            property minus one, and associate a free-formed string name to each
2411	            value. Applications can retrieve the list of defined value-name pairs
2412	            and use the numerical value to get and set property instance values.
2413	            </para></listitem>
2414	        </varlistentry>
2415	        <varlistentry>
2416	          <term>DRM_MODE_PROP_BITMASK</term>
2417	          <listitem><para>Bitmask properties are enumeration properties that
2418	            additionally restrict all enumerated values to the 0..63 range.
2419	            Bitmask property instance values combine one or more of the
2420	            enumerated bits defined by the property.</para></listitem>
2421	        </varlistentry>
2422	        <varlistentry>
2423	          <term>DRM_MODE_PROP_BLOB</term>
2424	          <listitem><para>Blob properties store a binary blob without any format
2425	            restriction. The binary blobs are created as KMS standalone objects,
2426	            and blob property instance values store the ID of their associated
2427	            blob object.</para>
2428		    <para>Blob properties are only used for the connector EDID property
2429		    and cannot be created by drivers.</para></listitem>
2430	        </varlistentry>
2431	      </variablelist>
2432	    </para>
2433	    <para>
2434	      To create a property drivers call one of the following functions depending
2435	      on the property type. All property creation functions take property flags
2436	      and name, as well as type-specific arguments.
2437	      <itemizedlist>
2438	        <listitem>
2439	          <synopsis>struct drm_property *drm_property_create_range(struct drm_device *dev, int flags,
2440	                                               const char *name,
2441	                                               uint64_t min, uint64_t max);</synopsis>
2442	          <para>Create a range property with the given minimum and maximum
2443	            values.</para>
2444	        </listitem>
2445	        <listitem>
2446	          <synopsis>struct drm_property *drm_property_create_enum(struct drm_device *dev, int flags,
2447	                                              const char *name,
2448	                                              const struct drm_prop_enum_list *props,
2449	                                              int num_values);</synopsis>
2450	          <para>Create an enumerated property. The <parameter>props</parameter>
2451	            argument points to an array of <parameter>num_values</parameter>
2452	            value-name pairs.</para>
2453	        </listitem>
2454	        <listitem>
2455	          <synopsis>struct drm_property *drm_property_create_bitmask(struct drm_device *dev,
2456	                                                 int flags, const char *name,
2457	                                                 const struct drm_prop_enum_list *props,
2458	                                                 int num_values);</synopsis>
2459	          <para>Create a bitmask property. The <parameter>props</parameter>
2460	            argument points to an array of <parameter>num_values</parameter>
2461	            value-name pairs.</para>
2462	        </listitem>
2463	      </itemizedlist>
2464	    </para>
2465	    <para>
2466	      Properties can additionally be created as immutable, in which case they
2467	      will be read-only for applications but can be modified by the driver. To
2468	      create an immutable property drivers must set the DRM_MODE_PROP_IMMUTABLE
2469	      flag at property creation time.
2470	    </para>
2471	    <para>
2472	      When no array of value-name pairs is readily available at property
2473	      creation time for enumerated or range properties, drivers can create
2474	      the property using the <function>drm_property_create</function> function
2475	      and manually add enumeration value-name pairs by calling the
2476	      <function>drm_property_add_enum</function> function. Care must be taken to
2477	      properly specify the property type through the <parameter>flags</parameter>
2478	      argument.
2479	    </para>
2480	    <para>
2481	      After creating properties drivers can attach property instances to CRTC,
2482	      connector and plane objects by calling the
2483	      <function>drm_object_attach_property</function>. The function takes a
2484	      pointer to the target object, a pointer to the previously created property
2485	      and an initial instance value.
2486	    </para>
2487	    <sect2>
2488		<title>Existing KMS Properties</title>
2489		<para>
2490		The following table gives description of drm properties exposed by various
2491		modules/drivers.
2492		</para>
2493		<table border="1" cellpadding="0" cellspacing="0">
2494		<tbody>
2495		<tr style="font-weight: bold;">
2496		<td valign="top" >Owner Module/Drivers</td>
2497		<td valign="top" >Group</td>
2498		<td valign="top" >Property Name</td>
2499		<td valign="top" >Type</td>
2500		<td valign="top" >Property Values</td>
2501		<td valign="top" >Object attached</td>
2502		<td valign="top" >Description/Restrictions</td>
2503		</tr>
2504		<tr>
2505		<td rowspan="20" valign="top" >DRM</td>
2506		<td rowspan="2" valign="top" >Generic</td>
2507		<td valign="top" >âEDIDâ</td>
2508		<td valign="top" >BLOB | IMMUTABLE</td>
2509		<td valign="top" >0</td>
2510		<td valign="top" >Connector</td>
2511		<td valign="top" >Contains id of edid blob ptr object.</td>
2512		</tr>
2513		<tr>
2514		<td valign="top" >âDPMSâ</td>
2515		<td valign="top" >ENUM</td>
2516		<td valign="top" >{ âOnâ, âStandbyâ, âSuspendâ, âOffâ }</td>
2517		<td valign="top" >Connector</td>
2518		<td valign="top" >Contains DPMS operation mode value.</td>
2519		</tr>
2520		<tr>
2521		<td rowspan="1" valign="top" >Plane</td>
2522		<td valign="top" >âtypeâ</td>
2523		<td valign="top" >ENUM | IMMUTABLE</td>
2524		<td valign="top" >{ "Overlay", "Primary", "Cursor" }</td>
2525		<td valign="top" >Plane</td>
2526		<td valign="top" >Plane type</td>
2527		</tr>
2528		<tr>
2529		<td rowspan="2" valign="top" >DVI-I</td>
2530		<td valign="top" >âsubconnectorâ</td>
2531		<td valign="top" >ENUM</td>
2532		<td valign="top" >{ âUnknownâ, âDVI-Dâ, âDVI-Aâ }</td>
2533		<td valign="top" >Connector</td>
2534		<td valign="top" >TBD</td>
2535		</tr>
2536		<tr>
2537		<td valign="top" >âselect subconnectorâ</td>
2538		<td valign="top" >ENUM</td>
2539		<td valign="top" >{ âAutomaticâ, âDVI-Dâ, âDVI-Aâ }</td>
2540		<td valign="top" >Connector</td>
2541		<td valign="top" >TBD</td>
2542		</tr>
2543		<tr>
2544		<td rowspan="13" valign="top" >TV</td>
2545		<td valign="top" >âsubconnectorâ</td>
2546		<td valign="top" >ENUM</td>
2547		<td valign="top" >{ "Unknown", "Composite", "SVIDEO", "Component", "SCART" }</td>
2548		<td valign="top" >Connector</td>
2549		<td valign="top" >TBD</td>
2550		</tr>
2551		<tr>
2552		<td valign="top" >âselect subconnectorâ</td>
2553		<td valign="top" >ENUM</td>
2554		<td valign="top" >{ "Automatic", "Composite", "SVIDEO", "Component", "SCART" }</td>
2555		<td valign="top" >Connector</td>
2556		<td valign="top" >TBD</td>
2557		</tr>
2558		<tr>
2559		<td valign="top" >âmodeâ</td>
2560		<td valign="top" >ENUM</td>
2561		<td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2562		<td valign="top" >Connector</td>
2563		<td valign="top" >TBD</td>
2564		</tr>
2565		<tr>
2566		<td valign="top" >âleft marginâ</td>
2567		<td valign="top" >RANGE</td>
2568		<td valign="top" >Min=0, Max=100</td>
2569		<td valign="top" >Connector</td>
2570		<td valign="top" >TBD</td>
2571		</tr>
2572		<tr>
2573		<td valign="top" >âright marginâ</td>
2574		<td valign="top" >RANGE</td>
2575		<td valign="top" >Min=0, Max=100</td>
2576		<td valign="top" >Connector</td>
2577		<td valign="top" >TBD</td>
2578		</tr>
2579		<tr>
2580		<td valign="top" >âtop marginâ</td>
2581		<td valign="top" >RANGE</td>
2582		<td valign="top" >Min=0, Max=100</td>
2583		<td valign="top" >Connector</td>
2584		<td valign="top" >TBD</td>
2585		</tr>
2586		<tr>
2587		<td valign="top" >âbottom marginâ</td>
2588		<td valign="top" >RANGE</td>
2589		<td valign="top" >Min=0, Max=100</td>
2590		<td valign="top" >Connector</td>
2591		<td valign="top" >TBD</td>
2592		</tr>
2593		<tr>
2594		<td valign="top" >âbrightnessâ</td>
2595		<td valign="top" >RANGE</td>
2596		<td valign="top" >Min=0, Max=100</td>
2597		<td valign="top" >Connector</td>
2598		<td valign="top" >TBD</td>
2599		</tr>
2600		<tr>
2601		<td valign="top" >âcontrastâ</td>
2602		<td valign="top" >RANGE</td>
2603		<td valign="top" >Min=0, Max=100</td>
2604		<td valign="top" >Connector</td>
2605		<td valign="top" >TBD</td>
2606		</tr>
2607		<tr>
2608		<td valign="top" >âflicker reductionâ</td>
2609		<td valign="top" >RANGE</td>
2610		<td valign="top" >Min=0, Max=100</td>
2611		<td valign="top" >Connector</td>
2612		<td valign="top" >TBD</td>
2613		</tr>
2614		<tr>
2615		<td valign="top" >âoverscanâ</td>
2616		<td valign="top" >RANGE</td>
2617		<td valign="top" >Min=0, Max=100</td>
2618		<td valign="top" >Connector</td>
2619		<td valign="top" >TBD</td>
2620		</tr>
2621		<tr>
2622		<td valign="top" >âsaturationâ</td>
2623		<td valign="top" >RANGE</td>
2624		<td valign="top" >Min=0, Max=100</td>
2625		<td valign="top" >Connector</td>
2626		<td valign="top" >TBD</td>
2627		</tr>
2628		<tr>
2629		<td valign="top" >âhueâ</td>
2630		<td valign="top" >RANGE</td>
2631		<td valign="top" >Min=0, Max=100</td>
2632		<td valign="top" >Connector</td>
2633		<td valign="top" >TBD</td>
2634		</tr>
2635		<tr>
2636		<td rowspan="2" valign="top" >Optional</td>
2637		<td valign="top" >âscaling modeâ</td>
2638		<td valign="top" >ENUM</td>
2639		<td valign="top" >{ "None", "Full", "Center", "Full aspect" }</td>
2640		<td valign="top" >Connector</td>
2641		<td valign="top" >TBD</td>
2642		</tr>
2643		<tr>
2644		<td valign="top" >âdirtyâ</td>
2645		<td valign="top" >ENUM | IMMUTABLE</td>
2646		<td valign="top" >{ "Off", "On", "Annotate" }</td>
2647		<td valign="top" >Connector</td>
2648		<td valign="top" >TBD</td>
2649		</tr>
2650		<tr>
2651		<td rowspan="21" valign="top" >i915</td>
2652		<td rowspan="3" valign="top" >Generic</td>
2653		<td valign="top" >"Broadcast RGB"</td>
2654		<td valign="top" >ENUM</td>
2655		<td valign="top" >{ "Automatic", "Full", "Limited 16:235" }</td>
2656		<td valign="top" >Connector</td>
2657		<td valign="top" >TBD</td>
2658		</tr>
2659		<tr>
2660		<td valign="top" >âaudioâ</td>
2661		<td valign="top" >ENUM</td>
2662		<td valign="top" >{ "force-dvi", "off", "auto", "on" }</td>
2663		<td valign="top" >Connector</td>
2664		<td valign="top" >TBD</td>
2665		</tr>
2666		<tr>
2667		<td valign="top" >Standard name as in DRM</td>
2668		<td valign="top" >Standard type as in DRM</td>
2669		<td valign="top" >Standard value as in DRM</td>
2670		<td valign="top" >Standard Object as in DRM</td>
2671		<td valign="top" >TBD</td>
2672		</tr>
2673		<tr>
2674		<td rowspan="17" valign="top" >SDVO-TV</td>
2675		<td valign="top" >âmodeâ</td>
2676		<td valign="top" >ENUM</td>
2677		<td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2678		<td valign="top" >Connector</td>
2679		<td valign="top" >TBD</td>
2680		</tr>
2681		<tr>
2682		<td valign="top" >"left_margin"</td>
2683		<td valign="top" >RANGE</td>
2684		<td valign="top" >Min=0, Max= SDVO dependent</td>
2685		<td valign="top" >Connector</td>
2686		<td valign="top" >TBD</td>
2687		</tr>
2688		<tr>
2689		<td valign="top" >"right_margin"</td>
2690		<td valign="top" >RANGE</td>
2691		<td valign="top" >Min=0, Max= SDVO dependent</td>
2692		<td valign="top" >Connector</td>
2693		<td valign="top" >TBD</td>
2694		</tr>
2695		<tr>
2696		<td valign="top" >"top_margin"</td>
2697		<td valign="top" >RANGE</td>
2698		<td valign="top" >Min=0, Max= SDVO dependent</td>
2699		<td valign="top" >Connector</td>
2700		<td valign="top" >TBD</td>
2701		</tr>
2702		<tr>
2703		<td valign="top" >"bottom_margin"</td>
2704		<td valign="top" >RANGE</td>
2705		<td valign="top" >Min=0, Max= SDVO dependent</td>
2706		<td valign="top" >Connector</td>
2707		<td valign="top" >TBD</td>
2708		</tr>
2709		<tr>
2710		<td valign="top" >âhposâ</td>
2711		<td valign="top" >RANGE</td>
2712		<td valign="top" >Min=0, Max= SDVO dependent</td>
2713		<td valign="top" >Connector</td>
2714		<td valign="top" >TBD</td>
2715		</tr>
2716		<tr>
2717		<td valign="top" >âvposâ</td>
2718		<td valign="top" >RANGE</td>
2719		<td valign="top" >Min=0, Max= SDVO dependent</td>
2720		<td valign="top" >Connector</td>
2721		<td valign="top" >TBD</td>
2722		</tr>
2723		<tr>
2724		<td valign="top" >âcontrastâ</td>
2725		<td valign="top" >RANGE</td>
2726		<td valign="top" >Min=0, Max= SDVO dependent</td>
2727		<td valign="top" >Connector</td>
2728		<td valign="top" >TBD</td>
2729		</tr>
2730		<tr>
2731		<td valign="top" >âsaturationâ</td>
2732		<td valign="top" >RANGE</td>
2733		<td valign="top" >Min=0, Max= SDVO dependent</td>
2734		<td valign="top" >Connector</td>
2735		<td valign="top" >TBD</td>
2736		</tr>
2737		<tr>
2738		<td valign="top" >âhueâ</td>
2739		<td valign="top" >RANGE</td>
2740		<td valign="top" >Min=0, Max= SDVO dependent</td>
2741		<td valign="top" >Connector</td>
2742		<td valign="top" >TBD</td>
2743		</tr>
2744		<tr>
2745		<td valign="top" >âsharpnessâ</td>
2746		<td valign="top" >RANGE</td>
2747		<td valign="top" >Min=0, Max= SDVO dependent</td>
2748		<td valign="top" >Connector</td>
2749		<td valign="top" >TBD</td>
2750		</tr>
2751		<tr>
2752		<td valign="top" >âflicker_filterâ</td>
2753		<td valign="top" >RANGE</td>
2754		<td valign="top" >Min=0, Max= SDVO dependent</td>
2755		<td valign="top" >Connector</td>
2756		<td valign="top" >TBD</td>
2757		</tr>
2758		<tr>
2759		<td valign="top" >âflicker_filter_adaptiveâ</td>
2760		<td valign="top" >RANGE</td>
2761		<td valign="top" >Min=0, Max= SDVO dependent</td>
2762		<td valign="top" >Connector</td>
2763		<td valign="top" >TBD</td>
2764		</tr>
2765		<tr>
2766		<td valign="top" >âflicker_filter_2dâ</td>
2767		<td valign="top" >RANGE</td>
2768		<td valign="top" >Min=0, Max= SDVO dependent</td>
2769		<td valign="top" >Connector</td>
2770		<td valign="top" >TBD</td>
2771		</tr>
2772		<tr>
2773		<td valign="top" >âtv_chroma_filterâ</td>
2774		<td valign="top" >RANGE</td>
2775		<td valign="top" >Min=0, Max= SDVO dependent</td>
2776		<td valign="top" >Connector</td>
2777		<td valign="top" >TBD</td>
2778		</tr>
2779		<tr>
2780		<td valign="top" >âtv_luma_filterâ</td>
2781		<td valign="top" >RANGE</td>
2782		<td valign="top" >Min=0, Max= SDVO dependent</td>
2783		<td valign="top" >Connector</td>
2784		<td valign="top" >TBD</td>
2785		</tr>
2786		<tr>
2787		<td valign="top" >âdot_crawlâ</td>
2788		<td valign="top" >RANGE</td>
2789		<td valign="top" >Min=0, Max=1</td>
2790		<td valign="top" >Connector</td>
2791		<td valign="top" >TBD</td>
2792		</tr>
2793		<tr>
2794		<td valign="top" >SDVO-TV/LVDS</td>
2795		<td valign="top" >âbrightnessâ</td>
2796		<td valign="top" >RANGE</td>
2797		<td valign="top" >Min=0, Max= SDVO dependent</td>
2798		<td valign="top" >Connector</td>
2799		<td valign="top" >TBD</td>
2800		</tr>
2801		<tr>
2802		<td rowspan="3" valign="top" >CDV gma-500</td>
2803		<td rowspan="3" valign="top" >Generic</td>
2804		<td valign="top" >"Broadcast RGB"</td>
2805		<td valign="top" >ENUM</td>
2806		<td valign="top" >{ âFullâ, âLimited 16:235â }</td>
2807		<td valign="top" >Connector</td>
2808		<td valign="top" >TBD</td>
2809		</tr>
2810		<tr>
2811		<td valign="top" >"Broadcast RGB"</td>
2812		<td valign="top" >ENUM</td>
2813		<td valign="top" >{ âoffâ, âautoâ, âonâ }</td>
2814		<td valign="top" >Connector</td>
2815		<td valign="top" >TBD</td>
2816		</tr>
2817		<tr>
2818		<td valign="top" >Standard name as in DRM</td>
2819		<td valign="top" >Standard type as in DRM</td>
2820		<td valign="top" >Standard value as in DRM</td>
2821		<td valign="top" >Standard Object as in DRM</td>
2822		<td valign="top" >TBD</td>
2823		</tr>
2824		<tr>
2825		<td rowspan="20" valign="top" >Poulsbo</td>
2826		<td rowspan="2" valign="top" >Generic</td>
2827		<td valign="top" >âbacklightâ</td>
2828		<td valign="top" >RANGE</td>
2829		<td valign="top" >Min=0, Max=100</td>
2830		<td valign="top" >Connector</td>
2831		<td valign="top" >TBD</td>
2832		</tr>
2833		<tr>
2834		<td valign="top" >Standard name as in DRM</td>
2835		<td valign="top" >Standard type as in DRM</td>
2836		<td valign="top" >Standard value as in DRM</td>
2837		<td valign="top" >Standard Object as in DRM</td>
2838		<td valign="top" >TBD</td>
2839		</tr>
2840		<tr>
2841		<td rowspan="17" valign="top" >SDVO-TV</td>
2842		<td valign="top" >âmodeâ</td>
2843		<td valign="top" >ENUM</td>
2844		<td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2845		<td valign="top" >Connector</td>
2846		<td valign="top" >TBD</td>
2847		</tr>
2848		<tr>
2849		<td valign="top" >"left_margin"</td>
2850		<td valign="top" >RANGE</td>
2851		<td valign="top" >Min=0, Max= SDVO dependent</td>
2852		<td valign="top" >Connector</td>
2853		<td valign="top" >TBD</td>
2854		</tr>
2855		<tr>
2856		<td valign="top" >"right_margin"</td>
2857		<td valign="top" >RANGE</td>
2858		<td valign="top" >Min=0, Max= SDVO dependent</td>
2859		<td valign="top" >Connector</td>
2860		<td valign="top" >TBD</td>
2861		</tr>
2862		<tr>
2863		<td valign="top" >"top_margin"</td>
2864		<td valign="top" >RANGE</td>
2865		<td valign="top" >Min=0, Max= SDVO dependent</td>
2866		<td valign="top" >Connector</td>
2867		<td valign="top" >TBD</td>
2868		</tr>
2869		<tr>
2870		<td valign="top" >"bottom_margin"</td>
2871		<td valign="top" >RANGE</td>
2872		<td valign="top" >Min=0, Max= SDVO dependent</td>
2873		<td valign="top" >Connector</td>
2874		<td valign="top" >TBD</td>
2875		</tr>
2876		<tr>
2877		<td valign="top" >âhposâ</td>
2878		<td valign="top" >RANGE</td>
2879		<td valign="top" >Min=0, Max= SDVO dependent</td>
2880		<td valign="top" >Connector</td>
2881		<td valign="top" >TBD</td>
2882		</tr>
2883		<tr>
2884		<td valign="top" >âvposâ</td>
2885		<td valign="top" >RANGE</td>
2886		<td valign="top" >Min=0, Max= SDVO dependent</td>
2887		<td valign="top" >Connector</td>
2888		<td valign="top" >TBD</td>
2889		</tr>
2890		<tr>
2891		<td valign="top" >âcontrastâ</td>
2892		<td valign="top" >RANGE</td>
2893		<td valign="top" >Min=0, Max= SDVO dependent</td>
2894		<td valign="top" >Connector</td>
2895		<td valign="top" >TBD</td>
2896		</tr>
2897		<tr>
2898		<td valign="top" >âsaturationâ</td>
2899		<td valign="top" >RANGE</td>
2900		<td valign="top" >Min=0, Max= SDVO dependent</td>
2901		<td valign="top" >Connector</td>
2902		<td valign="top" >TBD</td>
2903		</tr>
2904		<tr>
2905		<td valign="top" >âhueâ</td>
2906		<td valign="top" >RANGE</td>
2907		<td valign="top" >Min=0, Max= SDVO dependent</td>
2908		<td valign="top" >Connector</td>
2909		<td valign="top" >TBD</td>
2910		</tr>
2911		<tr>
2912		<td valign="top" >âsharpnessâ</td>
2913		<td valign="top" >RANGE</td>
2914		<td valign="top" >Min=0, Max= SDVO dependent</td>
2915		<td valign="top" >Connector</td>
2916		<td valign="top" >TBD</td>
2917		</tr>
2918		<tr>
2919		<td valign="top" >âflicker_filterâ</td>
2920		<td valign="top" >RANGE</td>
2921		<td valign="top" >Min=0, Max= SDVO dependent</td>
2922		<td valign="top" >Connector</td>
2923		<td valign="top" >TBD</td>
2924		</tr>
2925		<tr>
2926		<td valign="top" >âflicker_filter_adaptiveâ</td>
2927		<td valign="top" >RANGE</td>
2928		<td valign="top" >Min=0, Max= SDVO dependent</td>
2929		<td valign="top" >Connector</td>
2930		<td valign="top" >TBD</td>
2931		</tr>
2932		<tr>
2933		<td valign="top" >âflicker_filter_2dâ</td>
2934		<td valign="top" >RANGE</td>
2935		<td valign="top" >Min=0, Max= SDVO dependent</td>
2936		<td valign="top" >Connector</td>
2937		<td valign="top" >TBD</td>
2938		</tr>
2939		<tr>
2940		<td valign="top" >âtv_chroma_filterâ</td>
2941		<td valign="top" >RANGE</td>
2942		<td valign="top" >Min=0, Max= SDVO dependent</td>
2943		<td valign="top" >Connector</td>
2944		<td valign="top" >TBD</td>
2945		</tr>
2946		<tr>
2947		<td valign="top" >âtv_luma_filterâ</td>
2948		<td valign="top" >RANGE</td>
2949		<td valign="top" >Min=0, Max= SDVO dependent</td>
2950		<td valign="top" >Connector</td>
2951		<td valign="top" >TBD</td>
2952		</tr>
2953		<tr>
2954		<td valign="top" >âdot_crawlâ</td>
2955		<td valign="top" >RANGE</td>
2956		<td valign="top" >Min=0, Max=1</td>
2957		<td valign="top" >Connector</td>
2958		<td valign="top" >TBD</td>
2959		</tr>
2960		<tr>
2961		<td valign="top" >SDVO-TV/LVDS</td>
2962		<td valign="top" >âbrightnessâ</td>
2963		<td valign="top" >RANGE</td>
2964		<td valign="top" >Min=0, Max= SDVO dependent</td>
2965		<td valign="top" >Connector</td>
2966		<td valign="top" >TBD</td>
2967		</tr>
2968		<tr>
2969		<td rowspan="11" valign="top" >armada</td>
2970		<td rowspan="2" valign="top" >CRTC</td>
2971		<td valign="top" >"CSC_YUV"</td>
2972		<td valign="top" >ENUM</td>
2973		<td valign="top" >{ "Auto" , "CCIR601", "CCIR709" }</td>
2974		<td valign="top" >CRTC</td>
2975		<td valign="top" >TBD</td>
2976		</tr>
2977		<tr>
2978		<td valign="top" >"CSC_RGB"</td>
2979		<td valign="top" >ENUM</td>
2980		<td valign="top" >{ "Auto", "Computer system", "Studio" }</td>
2981		<td valign="top" >CRTC</td>
2982		<td valign="top" >TBD</td>
2983		</tr>
2984		<tr>
2985		<td rowspan="9" valign="top" >Overlay</td>
2986		<td valign="top" >"colorkey"</td>
2987		<td valign="top" >RANGE</td>
2988		<td valign="top" >Min=0, Max=0xffffff</td>
2989		<td valign="top" >Plane</td>
2990		<td valign="top" >TBD</td>
2991		</tr>
2992		<tr>
2993		<td valign="top" >"colorkey_min"</td>
2994		<td valign="top" >RANGE</td>
2995		<td valign="top" >Min=0, Max=0xffffff</td>
2996		<td valign="top" >Plane</td>
2997		<td valign="top" >TBD</td>
2998		</tr>
2999		<tr>
3000		<td valign="top" >"colorkey_max"</td>
3001		<td valign="top" >RANGE</td>
3002		<td valign="top" >Min=0, Max=0xffffff</td>
3003		<td valign="top" >Plane</td>
3004		<td valign="top" >TBD</td>
3005		</tr>
3006		<tr>
3007		<td valign="top" >"colorkey_val"</td>
3008		<td valign="top" >RANGE</td>
3009		<td valign="top" >Min=0, Max=0xffffff</td>
3010		<td valign="top" >Plane</td>
3011		<td valign="top" >TBD</td>
3012		</tr>
3013		<tr>
3014		<td valign="top" >"colorkey_alpha"</td>
3015		<td valign="top" >RANGE</td>
3016		<td valign="top" >Min=0, Max=0xffffff</td>
3017		<td valign="top" >Plane</td>
3018		<td valign="top" >TBD</td>
3019		</tr>
3020		<tr>
3021		<td valign="top" >"colorkey_mode"</td>
3022		<td valign="top" >ENUM</td>
3023		<td valign="top" >{ "disabled", "Y component", "U component"
3024		, "V component", "RGB", âR component", "G component", "B component" }</td>
3025		<td valign="top" >Plane</td>
3026		<td valign="top" >TBD</td>
3027		</tr>
3028		<tr>
3029		<td valign="top" >"brightness"</td>
3030		<td valign="top" >RANGE</td>
3031		<td valign="top" >Min=0, Max=256 + 255</td>
3032		<td valign="top" >Plane</td>
3033		<td valign="top" >TBD</td>
3034		</tr>
3035		<tr>
3036		<td valign="top" >"contrast"</td>
3037		<td valign="top" >RANGE</td>
3038		<td valign="top" >Min=0, Max=0x7fff</td>
3039		<td valign="top" >Plane</td>
3040		<td valign="top" >TBD</td>
3041		</tr>
3042		<tr>
3043		<td valign="top" >"saturation"</td>
3044		<td valign="top" >RANGE</td>
3045		<td valign="top" >Min=0, Max=0x7fff</td>
3046		<td valign="top" >Plane</td>
3047		<td valign="top" >TBD</td>
3048		</tr>
3049		<tr>
3050		<td rowspan="2" valign="top" >exynos</td>
3051		<td valign="top" >CRTC</td>
3052		<td valign="top" >âmodeâ</td>
3053		<td valign="top" >ENUM</td>
3054		<td valign="top" >{ "normal", "blank" }</td>
3055		<td valign="top" >CRTC</td>
3056		<td valign="top" >TBD</td>
3057		</tr>
3058		<tr>
3059		<td valign="top" >Overlay</td>
3060		<td valign="top" >âzposâ</td>
3061		<td valign="top" >RANGE</td>
3062		<td valign="top" >Min=0, Max=MAX_PLANE-1</td>
3063		<td valign="top" >Plane</td>
3064		<td valign="top" >TBD</td>
3065		</tr>
3066		<tr>
3067		<td rowspan="3" valign="top" >i2c/ch7006_drv</td>
3068		<td valign="top" >Generic</td>
3069		<td valign="top" >âscaleâ</td>
3070		<td valign="top" >RANGE</td>
3071		<td valign="top" >Min=0, Max=2</td>
3072		<td valign="top" >Connector</td>
3073		<td valign="top" >TBD</td>
3074		</tr>
3075		<tr>
3076		<td rowspan="2" valign="top" >TV</td>
3077		<td valign="top" >Standard names as in DRM</td>
3078		<td valign="top" >Standard types as in DRM</td>
3079		<td valign="top" >Standard Values as in DRM</td>
3080		<td valign="top" >Standard object as in DRM</td>
3081		<td valign="top" >TBD</td>
3082		</tr>
3083		<tr>
3084		<td valign="top" >âmodeâ</td>
3085		<td valign="top" >ENUM</td>
3086		<td valign="top" >{ "PAL", "PAL-M","PAL-N"}, âPAL-Nc"
3087		, "PAL-60", "NTSC-M", "NTSC-J" }</td>
3088		<td valign="top" >Connector</td>
3089		<td valign="top" >TBD</td>
3090		</tr>
3091		<tr>
3092		<td rowspan="16" valign="top" >nouveau</td>
3093		<td rowspan="6" valign="top" >NV10 Overlay</td>
3094		<td valign="top" >"colorkey"</td>
3095		<td valign="top" >RANGE</td>
3096		<td valign="top" >Min=0, Max=0x01ffffff</td>
3097		<td valign="top" >Plane</td>
3098		<td valign="top" >TBD</td>
3099		</tr>
3100		<tr>
3101		<td valign="top" >âcontrastâ</td>
3102		<td valign="top" >RANGE</td>
3103		<td valign="top" >Min=0, Max=8192-1</td>
3104		<td valign="top" >Plane</td>
3105		<td valign="top" >TBD</td>
3106		</tr>
3107		<tr>
3108		<td valign="top" >âbrightnessâ</td>
3109		<td valign="top" >RANGE</td>
3110		<td valign="top" >Min=0, Max=1024</td>
3111		<td valign="top" >Plane</td>
3112		<td valign="top" >TBD</td>
3113		</tr>
3114		<tr>
3115		<td valign="top" >âhueâ</td>
3116		<td valign="top" >RANGE</td>
3117		<td valign="top" >Min=0, Max=359</td>
3118		<td valign="top" >Plane</td>
3119		<td valign="top" >TBD</td>
3120		</tr>
3121		<tr>
3122		<td valign="top" >âsaturationâ</td>
3123		<td valign="top" >RANGE</td>
3124		<td valign="top" >Min=0, Max=8192-1</td>
3125		<td valign="top" >Plane</td>
3126		<td valign="top" >TBD</td>
3127		</tr>
3128		<tr>
3129		<td valign="top" >âiturbt_709â</td>
3130		<td valign="top" >RANGE</td>
3131		<td valign="top" >Min=0, Max=1</td>
3132		<td valign="top" >Plane</td>
3133		<td valign="top" >TBD</td>
3134		</tr>
3135		<tr>
3136		<td rowspan="2" valign="top" >Nv04 Overlay</td>
3137		<td valign="top" >âcolorkeyâ</td>
3138		<td valign="top" >RANGE</td>
3139		<td valign="top" >Min=0, Max=0x01ffffff</td>
3140		<td valign="top" >Plane</td>
3141		<td valign="top" >TBD</td>
3142		</tr>
3143		<tr>
3144		<td valign="top" >âbrightnessâ</td>
3145		<td valign="top" >RANGE</td>
3146		<td valign="top" >Min=0, Max=1024</td>
3147		<td valign="top" >Plane</td>
3148		<td valign="top" >TBD</td>
3149		</tr>
3150		<tr>
3151		<td rowspan="7" valign="top" >Display</td>
3152		<td valign="top" >âdithering modeâ</td>
3153		<td valign="top" >ENUM</td>
3154		<td valign="top" >{ "auto", "off", "on" }</td>
3155		<td valign="top" >Connector</td>
3156		<td valign="top" >TBD</td>
3157		</tr>
3158		<tr>
3159		<td valign="top" >âdithering depthâ</td>
3160		<td valign="top" >ENUM</td>
3161		<td valign="top" >{ "auto", "off", "on", "static 2x2", "dynamic 2x2", "temporal" }</td>
3162		<td valign="top" >Connector</td>
3163		<td valign="top" >TBD</td>
3164		</tr>
3165		<tr>
3166		<td valign="top" >âunderscanâ</td>
3167		<td valign="top" >ENUM</td>
3168		<td valign="top" >{ "auto", "6 bpc", "8 bpc" }</td>
3169		<td valign="top" >Connector</td>
3170		<td valign="top" >TBD</td>
3171		</tr>
3172		<tr>
3173		<td valign="top" >âunderscan hborderâ</td>
3174		<td valign="top" >RANGE</td>
3175		<td valign="top" >Min=0, Max=128</td>
3176		<td valign="top" >Connector</td>
3177		<td valign="top" >TBD</td>
3178		</tr>
3179		<tr>
3180		<td valign="top" >âunderscan vborderâ</td>
3181		<td valign="top" >RANGE</td>
3182		<td valign="top" >Min=0, Max=128</td>
3183		<td valign="top" >Connector</td>
3184		<td valign="top" >TBD</td>
3185		</tr>
3186		<tr>
3187		<td valign="top" >âvibrant hueâ</td>
3188		<td valign="top" >RANGE</td>
3189		<td valign="top" >Min=0, Max=180</td>
3190		<td valign="top" >Connector</td>
3191		<td valign="top" >TBD</td>
3192		</tr>
3193		<tr>
3194		<td valign="top" >âcolor vibranceâ</td>
3195		<td valign="top" >RANGE</td>
3196		<td valign="top" >Min=0, Max=200</td>
3197		<td valign="top" >Connector</td>
3198		<td valign="top" >TBD</td>
3199		</tr>
3200		<tr>
3201		<td valign="top" >Generic</td>
3202		<td valign="top" >Standard name as in DRM</td>
3203		<td valign="top" >Standard type as in DRM</td>
3204		<td valign="top" >Standard value as in DRM</td>
3205		<td valign="top" >Standard Object as in DRM</td>
3206		<td valign="top" >TBD</td>
3207		</tr>
3208		<tr>
3209		<td rowspan="2" valign="top" >omap</td>
3210		<td rowspan="2" valign="top" >Generic</td>
3211		<td valign="top" >ârotationâ</td>
3212		<td valign="top" >BITMASK</td>
3213		<td valign="top" >{ 0, "rotate-0" },
3214		{ 1, "rotate-90" },
3215		{ 2, "rotate-180" },
3216		{ 3, "rotate-270" },
3217		{ 4, "reflect-x" },
3218		{ 5, "reflect-y" }</td>
3219		<td valign="top" >CRTC, Plane</td>
3220		<td valign="top" >TBD</td>
3221		</tr>
3222		<tr>
3223		<td valign="top" >âzorderâ</td>
3224		<td valign="top" >RANGE</td>
3225		<td valign="top" >Min=0, Max=3</td>
3226		<td valign="top" >CRTC, Plane</td>
3227		<td valign="top" >TBD</td>
3228		</tr>
3229		<tr>
3230		<td valign="top" >qxl</td>
3231		<td valign="top" >Generic</td>
3232		<td valign="top" >âhotplug_mode_update"</td>
3233		<td valign="top" >RANGE</td>
3234		<td valign="top" >Min=0, Max=1</td>
3235		<td valign="top" >Connector</td>
3236		<td valign="top" >TBD</td>
3237		</tr>
3238		<tr>
3239		<td rowspan="10" valign="top" >radeon</td>
3240		<td valign="top" >DVI-I</td>
3241		<td valign="top" >âcoherentâ</td>
3242		<td valign="top" >RANGE</td>
3243		<td valign="top" >Min=0, Max=1</td>
3244		<td valign="top" >Connector</td>
3245		<td valign="top" >TBD</td>
3246		</tr>
3247		<tr>
3248		<td valign="top" >DAC enable load detect</td>
3249		<td valign="top" >âload detectionâ</td>
3250		<td valign="top" >RANGE</td>
3251		<td valign="top" >Min=0, Max=1</td>
3252		<td valign="top" >Connector</td>
3253		<td valign="top" >TBD</td>
3254		</tr>
3255		<tr>
3256		<td valign="top" >TV Standard</td>
3257		<td valign="top" >"tv standard"</td>
3258		<td valign="top" >ENUM</td>
3259		<td valign="top" >{ "ntsc", "pal", "pal-m", "pal-60", "ntsc-j"
3260		, "scart-pal", "pal-cn", "secam" }</td>
3261		<td valign="top" >Connector</td>
3262		<td valign="top" >TBD</td>
3263		</tr>
3264		<tr>
3265		<td valign="top" >legacy TMDS PLL detect</td>
3266		<td valign="top" >"tmds_pll"</td>
3267		<td valign="top" >ENUM</td>
3268		<td valign="top" >{ "driver", "bios" }</td>
3269		<td valign="top" >-</td>
3270		<td valign="top" >TBD</td>
3271		</tr>
3272		<tr>
3273		<td rowspan="3" valign="top" >Underscan</td>
3274		<td valign="top" >"underscan"</td>
3275		<td valign="top" >ENUM</td>
3276		<td valign="top" >{ "off", "on", "auto" }</td>
3277		<td valign="top" >Connector</td>
3278		<td valign="top" >TBD</td>
3279		</tr>
3280		<tr>
3281		<td valign="top" >"underscan hborder"</td>
3282		<td valign="top" >RANGE</td>
3283		<td valign="top" >Min=0, Max=128</td>
3284		<td valign="top" >Connector</td>
3285		<td valign="top" >TBD</td>
3286		</tr>
3287		<tr>
3288		<td valign="top" >"underscan vborder"</td>
3289		<td valign="top" >RANGE</td>
3290		<td valign="top" >Min=0, Max=128</td>
3291		<td valign="top" >Connector</td>
3292		<td valign="top" >TBD</td>
3293		</tr>
3294		<tr>
3295		<td valign="top" >Audio</td>
3296		<td valign="top" >âaudioâ</td>
3297		<td valign="top" >ENUM</td>
3298		<td valign="top" >{ "off", "on", "auto" }</td>
3299		<td valign="top" >Connector</td>
3300		<td valign="top" >TBD</td>
3301		</tr>
3302		<tr>
3303		<td valign="top" >FMT Dithering</td>
3304		<td valign="top" >âditherâ</td>
3305		<td valign="top" >ENUM</td>
3306		<td valign="top" >{ "off", "on" }</td>
3307		<td valign="top" >Connector</td>
3308		<td valign="top" >TBD</td>
3309		</tr>
3310		<tr>
3311		<td valign="top" >Generic</td>
3312		<td valign="top" >Standard name as in DRM</td>
3313		<td valign="top" >Standard type as in DRM</td>
3314		<td valign="top" >Standard value as in DRM</td>
3315		<td valign="top" >Standard Object as in DRM</td>
3316		<td valign="top" >TBD</td>
3317		</tr>
3318		<tr>
3319		<td rowspan="3" valign="top" >rcar-du</td>
3320		<td rowspan="3" valign="top" >Generic</td>
3321		<td valign="top" >"alpha"</td>
3322		<td valign="top" >RANGE</td>
3323		<td valign="top" >Min=0, Max=255</td>
3324		<td valign="top" >Plane</td>
3325		<td valign="top" >TBD</td>
3326		</tr>
3327		<tr>
3328		<td valign="top" >"colorkey"</td>
3329		<td valign="top" >RANGE</td>
3330		<td valign="top" >Min=0, Max=0x01ffffff</td>
3331		<td valign="top" >Plane</td>
3332		<td valign="top" >TBD</td>
3333		</tr>
3334		<tr>
3335		<td valign="top" >"zpos"</td>
3336		<td valign="top" >RANGE</td>
3337		<td valign="top" >Min=1, Max=7</td>
3338		<td valign="top" >Plane</td>
3339		<td valign="top" >TBD</td>
3340		</tr>
3341		</tbody>
3342		</table>
3343	    </sect2>
3344	  </sect1>
3345	
3346	  <!-- Internals: vertical blanking -->
3347	
3348	  <sect1 id="drm-vertical-blank">
3349	    <title>Vertical Blanking</title>
3350	    <para>
3351	      Vertical blanking plays a major role in graphics rendering. To achieve
3352	      tear-free display, users must synchronize page flips and/or rendering to
3353	      vertical blanking. The DRM API offers ioctls to perform page flips
3354	      synchronized to vertical blanking and wait for vertical blanking.
3355	    </para>
3356	    <para>
3357	      The DRM core handles most of the vertical blanking management logic, which
3358	      involves filtering out spurious interrupts, keeping race-free blanking
3359	      counters, coping with counter wrap-around and resets and keeping use
3360	      counts. It relies on the driver to generate vertical blanking interrupts
3361	      and optionally provide a hardware vertical blanking counter. Drivers must
3362	      implement the following operations.
3363	    </para>
3364	    <itemizedlist>
3365	      <listitem>
3366	        <synopsis>int (*enable_vblank) (struct drm_device *dev, int crtc);
3367	void (*disable_vblank) (struct drm_device *dev, int crtc);</synopsis>
3368	        <para>
3369		  Enable or disable vertical blanking interrupts for the given CRTC.
3370		</para>
3371	      </listitem>
3372	      <listitem>
3373	        <synopsis>u32 (*get_vblank_counter) (struct drm_device *dev, int crtc);</synopsis>
3374	        <para>
3375		  Retrieve the value of the vertical blanking counter for the given
3376		  CRTC. If the hardware maintains a vertical blanking counter its value
3377		  should be returned. Otherwise drivers can use the
3378		  <function>drm_vblank_count</function> helper function to handle this
3379		  operation.
3380		</para>
3381	      </listitem>
3382	    </itemizedlist>
3383	    <para>
3384	      Drivers must initialize the vertical blanking handling core with a call to
3385	      <function>drm_vblank_init</function> in their
3386	      <methodname>load</methodname> operation. The function will set the struct
3387	      <structname>drm_device</structname>
3388	      <structfield>vblank_disable_allowed</structfield> field to 0. This will
3389	      keep vertical blanking interrupts enabled permanently until the first mode
3390	      set operation, where <structfield>vblank_disable_allowed</structfield> is
3391	      set to 1. The reason behind this is not clear. Drivers can set the field
3392	      to 1 after <function>calling drm_vblank_init</function> to make vertical
3393	      blanking interrupts dynamically managed from the beginning.
3394	    </para>
3395	    <para>
3396	      Vertical blanking interrupts can be enabled by the DRM core or by drivers
3397	      themselves (for instance to handle page flipping operations). The DRM core
3398	      maintains a vertical blanking use count to ensure that the interrupts are
3399	      not disabled while a user still needs them. To increment the use count,
3400	      drivers call <function>drm_vblank_get</function>. Upon return vertical
3401	      blanking interrupts are guaranteed to be enabled.
3402	    </para>
3403	    <para>
3404	      To decrement the use count drivers call
3405	      <function>drm_vblank_put</function>. Only when the use count drops to zero
3406	      will the DRM core disable the vertical blanking interrupts after a delay
3407	      by scheduling a timer. The delay is accessible through the vblankoffdelay
3408	      module parameter or the <varname>drm_vblank_offdelay</varname> global
3409	      variable and expressed in milliseconds. Its default value is 5000 ms.
3410	    </para>
3411	    <para>
3412	      When a vertical blanking interrupt occurs drivers only need to call the
3413	      <function>drm_handle_vblank</function> function to account for the
3414	      interrupt.
3415	    </para>
3416	    <para>
3417	      Resources allocated by <function>drm_vblank_init</function> must be freed
3418	      with a call to <function>drm_vblank_cleanup</function> in the driver
3419	      <methodname>unload</methodname> operation handler.
3420	    </para>
3421	    <sect2>
3422	      <title>Vertical Blanking and Interrupt Handling Functions Reference</title>
3423	!Edrivers/gpu/drm/drm_irq.c
3424	    </sect2>
3425	  </sect1>
3426	
3427	  <!-- Internals: open/close, file operations and ioctls -->
3428	
3429	  <sect1>
3430	    <title>Open/Close, File Operations and IOCTLs</title>
3431	    <sect2>
3432	      <title>Open and Close</title>
3433	      <synopsis>int (*firstopen) (struct drm_device *);
3434	void (*lastclose) (struct drm_device *);
3435	int (*open) (struct drm_device *, struct drm_file *);
3436	void (*preclose) (struct drm_device *, struct drm_file *);
3437	void (*postclose) (struct drm_device *, struct drm_file *);</synopsis>
3438	      <abstract>Open and close handlers. None of those methods are mandatory.
3439	      </abstract>
3440	      <para>
3441	        The <methodname>firstopen</methodname> method is called by the DRM core
3442		for legacy UMS (User Mode Setting) drivers only when an application
3443		opens a device that has no other opened file handle. UMS drivers can
3444		implement it to acquire device resources. KMS drivers can't use the
3445		method and must acquire resources in the <methodname>load</methodname>
3446		method instead.
3447	      </para>
3448	      <para>
3449		Similarly the <methodname>lastclose</methodname> method is called when
3450		the last application holding a file handle opened on the device closes
3451		it, for both UMS and KMS drivers. Additionally, the method is also
3452		called at module unload time or, for hot-pluggable devices, when the
3453		device is unplugged. The <methodname>firstopen</methodname> and
3454		<methodname>lastclose</methodname> calls can thus be unbalanced.
3455	      </para>
3456	      <para>
3457	        The <methodname>open</methodname> method is called every time the device
3458		is opened by an application. Drivers can allocate per-file private data
3459		in this method and store them in the struct
3460		<structname>drm_file</structname> <structfield>driver_priv</structfield>
3461		field. Note that the <methodname>open</methodname> method is called
3462		before <methodname>firstopen</methodname>.
3463	      </para>
3464	      <para>
3465	        The close operation is split into <methodname>preclose</methodname> and
3466		<methodname>postclose</methodname> methods. Drivers must stop and
3467		cleanup all per-file operations in the <methodname>preclose</methodname>
3468		method. For instance pending vertical blanking and page flip events must
3469		be cancelled. No per-file operation is allowed on the file handle after
3470		returning from the <methodname>preclose</methodname> method.
3471	      </para>
3472	      <para>
3473	        Finally the <methodname>postclose</methodname> method is called as the
3474		last step of the close operation, right before calling the
3475		<methodname>lastclose</methodname> method if no other open file handle
3476		exists for the device. Drivers that have allocated per-file private data
3477		in the <methodname>open</methodname> method should free it here.
3478	      </para>
3479	      <para>
3480	        The <methodname>lastclose</methodname> method should restore CRTC and
3481		plane properties to default value, so that a subsequent open of the
3482		device will not inherit state from the previous user. It can also be
3483		used to execute delayed power switching state changes, e.g. in
3484		conjunction with the vga-switcheroo infrastructure. Beyond that KMS
3485		drivers should not do any further cleanup. Only legacy UMS drivers might
3486		need to clean up device state so that the vga console or an independent
3487		fbdev driver could take over.
3488	      </para>
3489	    </sect2>
3490	    <sect2>
3491	      <title>File Operations</title>
3492	      <synopsis>const struct file_operations *fops</synopsis>
3493	      <abstract>File operations for the DRM device node.</abstract>
3494	      <para>
3495	        Drivers must define the file operations structure that forms the DRM
3496		userspace API entry point, even though most of those operations are
3497		implemented in the DRM core. The <methodname>open</methodname>,
3498		<methodname>release</methodname> and <methodname>ioctl</methodname>
3499		operations are handled by
3500		<programlisting>
3501		.owner = THIS_MODULE,
3502		.open = drm_open,
3503		.release = drm_release,
3504		.unlocked_ioctl = drm_ioctl,
3505	  #ifdef CONFIG_COMPAT
3506		.compat_ioctl = drm_compat_ioctl,
3507	  #endif
3508	        </programlisting>
3509	      </para>
3510	      <para>
3511	        Drivers that implement private ioctls that requires 32/64bit
3512		compatibility support must provide their own
3513		<methodname>compat_ioctl</methodname> handler that processes private
3514		ioctls and calls <function>drm_compat_ioctl</function> for core ioctls.
3515	      </para>
3516	      <para>
3517	        The <methodname>read</methodname> and <methodname>poll</methodname>
3518		operations provide support for reading DRM events and polling them. They
3519		are implemented by
3520		<programlisting>
3521		.poll = drm_poll,
3522		.read = drm_read,
3523		.llseek = no_llseek,
3524		</programlisting>
3525	      </para>
3526	      <para>
3527	        The memory mapping implementation varies depending on how the driver
3528		manages memory. Pre-GEM drivers will use <function>drm_mmap</function>,
3529		while GEM-aware drivers will use <function>drm_gem_mmap</function>. See
3530		<xref linkend="drm-gem"/>.
3531		<programlisting>
3532		.mmap = drm_gem_mmap,
3533		</programlisting>
3534	      </para>
3535	      <para>
3536	        No other file operation is supported by the DRM API.
3537	      </para>
3538	    </sect2>
3539	    <sect2>
3540	      <title>IOCTLs</title>
3541	      <synopsis>struct drm_ioctl_desc *ioctls;
3542	int num_ioctls;</synopsis>
3543	      <abstract>Driver-specific ioctls descriptors table.</abstract>
3544	      <para>
3545	        Driver-specific ioctls numbers start at DRM_COMMAND_BASE. The ioctls
3546		descriptors table is indexed by the ioctl number offset from the base
3547		value. Drivers can use the DRM_IOCTL_DEF_DRV() macro to initialize the
3548		table entries.
3549	      </para>
3550	      <para>
3551	        <programlisting>DRM_IOCTL_DEF_DRV(ioctl, func, flags)</programlisting>
3552		<para>
3553		  <parameter>ioctl</parameter> is the ioctl name. Drivers must define
3554		  the DRM_##ioctl and DRM_IOCTL_##ioctl macros to the ioctl number
3555		  offset from DRM_COMMAND_BASE and the ioctl number respectively. The
3556		  first macro is private to the device while the second must be exposed
3557		  to userspace in a public header.
3558		</para>
3559		<para>
3560		  <parameter>func</parameter> is a pointer to the ioctl handler function
3561		  compatible with the <type>drm_ioctl_t</type> type.
3562		  <programlisting>typedef int drm_ioctl_t(struct drm_device *dev, void *data,
3563			struct drm_file *file_priv);</programlisting>
3564		</para>
3565		<para>
3566		  <parameter>flags</parameter> is a bitmask combination of the following
3567		  values. It restricts how the ioctl is allowed to be called.
3568		  <itemizedlist>
3569		    <listitem><para>
3570		      DRM_AUTH - Only authenticated callers allowed
3571		    </para></listitem>
3572		    <listitem><para>
3573		      DRM_MASTER - The ioctl can only be called on the master file
3574		      handle
3575		    </para></listitem>
3576	            <listitem><para>
3577		      DRM_ROOT_ONLY - Only callers with the SYSADMIN capability allowed
3578		    </para></listitem>
3579	            <listitem><para>
3580		      DRM_CONTROL_ALLOW - The ioctl can only be called on a control
3581		      device
3582		    </para></listitem>
3583	            <listitem><para>
3584		      DRM_UNLOCKED - The ioctl handler will be called without locking
3585		      the DRM global mutex
3586		    </para></listitem>
3587		  </itemizedlist>
3588		</para>
3589	      </para>
3590	    </sect2>
3591	  </sect1>
3592	  <sect1>
3593	    <title>Legacy Support Code</title>
3594	    <para>
3595	      The section very briefly covers some of the old legacy support code which
3596	      is only used by old DRM drivers which have done a so-called shadow-attach
3597	      to the underlying device instead of registering as a real driver. This
3598	      also includes some of the old generic buffer management and command
3599	      submission code. Do not use any of this in new and modern drivers.
3600	    </para>
3601	
3602	    <sect2>
3603	      <title>Legacy Suspend/Resume</title>
3604	      <para>
3605		The DRM core provides some suspend/resume code, but drivers wanting full
3606		suspend/resume support should provide save() and restore() functions.
3607		These are called at suspend, hibernate, or resume time, and should perform
3608		any state save or restore required by your device across suspend or
3609		hibernate states.
3610	      </para>
3611	      <synopsis>int (*suspend) (struct drm_device *, pm_message_t state);
3612	  int (*resume) (struct drm_device *);</synopsis>
3613	      <para>
3614		Those are legacy suspend and resume methods which
3615		<emphasis>only</emphasis> work with the legacy shadow-attach driver
3616		registration functions. New driver should use the power management
3617		interface provided by their bus type (usually through
3618		the struct <structname>device_driver</structname> dev_pm_ops) and set
3619		these methods to NULL.
3620	      </para>
3621	    </sect2>
3622	
3623	    <sect2>
3624	      <title>Legacy DMA Services</title>
3625	      <para>
3626		This should cover how DMA mapping etc. is supported by the core.
3627		These functions are deprecated and should not be used.
3628	      </para>
3629	    </sect2>
3630	  </sect1>
3631	  </chapter>
3632	
3633	<!-- TODO
3634	
3635	- Add a glossary
3636	- Document the struct_mutex catch-all lock
3637	- Document connector properties
3638	
3639	- Why is the load method optional?
3640	- What are drivers supposed to set the initial display state to, and how?
3641	  Connector's DPMS states are not initialized and are thus equal to
3642	  DRM_MODE_DPMS_ON. The fbcon compatibility layer calls
3643	  drm_helper_disable_unused_functions(), which disables unused encoders and
3644	  CRTCs, but doesn't touch the connectors' DPMS state, and
3645	  drm_helper_connector_dpms() in reaction to fbdev blanking events. Do drivers
3646	  that don't implement (or just don't use) fbcon compatibility need to call
3647	  those functions themselves?
3648	- KMS drivers must call drm_vblank_pre_modeset() and drm_vblank_post_modeset()
3649	  around mode setting. Should this be done in the DRM core?
3650	- vblank_disable_allowed is set to 1 in the first drm_vblank_post_modeset()
3651	  call and never set back to 0. It seems to be safe to permanently set it to 1
3652	  in drm_vblank_init() for KMS driver, and it might be safe for UMS drivers as
3653	  well. This should be investigated.
3654	- crtc and connector .save and .restore operations are only used internally in
3655	  drivers, should they be removed from the core?
3656	- encoder mid-layer .save and .restore operations are only used internally in
3657	  drivers, should they be removed from the core?
3658	- encoder mid-layer .detect operation is only used internally in drivers,
3659	  should it be removed from the core?
3660	-->
3661	
3662	  <!-- External interfaces -->
3663	
3664	  <chapter id="drmExternals">
3665	    <title>Userland interfaces</title>
3666	    <para>
3667	      The DRM core exports several interfaces to applications,
3668	      generally intended to be used through corresponding libdrm
3669	      wrapper functions.  In addition, drivers export device-specific
3670	      interfaces for use by userspace drivers &amp; device-aware
3671	      applications through ioctls and sysfs files.
3672	    </para>
3673	    <para>
3674	      External interfaces include: memory mapping, context management,
3675	      DMA operations, AGP management, vblank control, fence
3676	      management, memory management, and output management.
3677	    </para>
3678	    <para>
3679	      Cover generic ioctls and sysfs layout here.  We only need high-level
3680	      info, since man pages should cover the rest.
3681	    </para>
3682	
3683	  <!-- External: render nodes -->
3684	
3685	    <sect1>
3686	      <title>Render nodes</title>
3687	      <para>
3688	        DRM core provides multiple character-devices for user-space to use.
3689	        Depending on which device is opened, user-space can perform a different
3690	        set of operations (mainly ioctls). The primary node is always created
3691	        and called card&lt;num&gt;. Additionally, a currently
3692	        unused control node, called controlD&lt;num&gt; is also
3693	        created. The primary node provides all legacy operations and
3694	        historically was the only interface used by userspace. With KMS, the
3695	        control node was introduced. However, the planned KMS control interface
3696	        has never been written and so the control node stays unused to date.
3697	      </para>
3698	      <para>
3699	        With the increased use of offscreen renderers and GPGPU applications,
3700	        clients no longer require running compositors or graphics servers to
3701	        make use of a GPU. But the DRM API required unprivileged clients to
3702	        authenticate to a DRM-Master prior to getting GPU access. To avoid this
3703	        step and to grant clients GPU access without authenticating, render
3704	        nodes were introduced. Render nodes solely serve render clients, that
3705	        is, no modesetting or privileged ioctls can be issued on render nodes.
3706	        Only non-global rendering commands are allowed. If a driver supports
3707	        render nodes, it must advertise it via the DRIVER_RENDER
3708	        DRM driver capability. If not supported, the primary node must be used
3709	        for render clients together with the legacy drmAuth authentication
3710	        procedure.
3711	      </para>
3712	      <para>
3713	        If a driver advertises render node support, DRM core will create a
3714	        separate render node called renderD&lt;num&gt;. There will
3715	        be one render node per device. No ioctls except  PRIME-related ioctls
3716	        will be allowed on this node. Especially GEM_OPEN will be
3717	        explicitly prohibited. Render nodes are designed to avoid the
3718	        buffer-leaks, which occur if clients guess the flink names or mmap
3719	        offsets on the legacy interface. Additionally to this basic interface,
3720	        drivers must mark their driver-dependent render-only ioctls as
3721	        DRM_RENDER_ALLOW so render clients can use them. Driver
3722	        authors must be careful not to allow any privileged ioctls on render
3723	        nodes.
3724	      </para>
3725	      <para>
3726	        With render nodes, user-space can now control access to the render node
3727	        via basic file-system access-modes. A running graphics server which
3728	        authenticates clients on the privileged primary/legacy node is no longer
3729	        required. Instead, a client can open the render node and is immediately
3730	        granted GPU access. Communication between clients (or servers) is done
3731	        via PRIME. FLINK from render node to legacy node is not supported. New
3732	        clients must not use the insecure FLINK interface.
3733	      </para>
3734	      <para>
3735	        Besides dropping all modeset/global ioctls, render nodes also drop the
3736	        DRM-Master concept. There is no reason to associate render clients with
3737	        a DRM-Master as they are independent of any graphics server. Besides,
3738	        they must work without any running master, anyway.
3739	        Drivers must be able to run without a master object if they support
3740	        render nodes. If, on the other hand, a driver requires shared state
3741	        between clients which is visible to user-space and accessible beyond
3742	        open-file boundaries, they cannot support render nodes.
3743	      </para>
3744	    </sect1>
3745	
3746	  <!-- External: vblank handling -->
3747	
3748	    <sect1>
3749	      <title>VBlank event handling</title>
3750	      <para>
3751	        The DRM core exposes two vertical blank related ioctls:
3752	        <variablelist>
3753	          <varlistentry>
3754	            <term>DRM_IOCTL_WAIT_VBLANK</term>
3755	            <listitem>
3756	              <para>
3757	                This takes a struct drm_wait_vblank structure as its argument,
3758	                and it is used to block or request a signal when a specified
3759	                vblank event occurs.
3760	              </para>
3761	            </listitem>
3762	          </varlistentry>
3763	          <varlistentry>
3764	            <term>DRM_IOCTL_MODESET_CTL</term>
3765	            <listitem>
3766	              <para>
3767			This was only used for user-mode-settind drivers around
3768			modesetting changes to allow the kernel to update the vblank
3769			interrupt after mode setting, since on many devices the vertical
3770			blank counter is reset to 0 at some point during modeset. Modern
3771			drivers should not call this any more since with kernel mode
3772			setting it is a no-op.
3773	              </para>
3774	            </listitem>
3775	          </varlistentry>
3776	        </variablelist>
3777	      </para>
3778	    </sect1>
3779	
3780	  </chapter>
3781	</part>
3782	<part id="drmDrivers">
3783	  <title>DRM Drivers</title>
3784	
3785	  <partintro>
3786	    <para>
3787	      This second part of the DRM Developer's Guide documents driver code,
3788	      implementation details and also all the driver-specific userspace
3789	      interfaces. Especially since all hardware-acceleration interfaces to
3790	      userspace are driver specific for efficiency and other reasons these
3791	      interfaces can be rather substantial. Hence every driver has its own
3792	      chapter.
3793	    </para>
3794	  </partintro>
3795	
3796	  <chapter id="drmI915">
3797	    <title>drm/i915 Intel GFX Driver</title>
3798	    <para>
3799	      The drm/i915 driver supports all (with the exception of some very early
3800	      models) integrated GFX chipsets with both Intel display and rendering
3801	      blocks. This excludes a set of SoC platforms with an SGX rendering unit,
3802	      those have basic support through the gma500 drm driver.
3803	    </para>
3804	    <sect1>
3805	      <title>Display Hardware Handling</title>
3806	      <para>
3807	        This section covers everything related to the display hardware including
3808	        the mode setting infrastructure, plane, sprite and cursor handling and
3809	        display, output probing and related topics.
3810	      </para>
3811	      <sect2>
3812	        <title>Mode Setting Infrastructure</title>
3813	        <para>
3814	          The i915 driver is thus far the only DRM driver which doesn't use the
3815	          common DRM helper code to implement mode setting sequences. Thus it
3816	          has its own tailor-made infrastructure for executing a display
3817	          configuration change.
3818	        </para>
3819	      </sect2>
3820	      <sect2>
3821	        <title>Plane Configuration</title>
3822	        <para>
3823		  This section covers plane configuration and composition with the
3824		  primary plane, sprites, cursors and overlays. This includes the
3825		  infrastructure to do atomic vsync'ed updates of all this state and
3826		  also tightly coupled topics like watermark setup and computation,
3827		  framebuffer compression and panel self refresh.
3828	        </para>
3829	      </sect2>
3830	      <sect2>
3831	        <title>Output Probing</title>
3832	        <para>
3833		  This section covers output probing and related infrastructure like the
3834		  hotplug interrupt storm detection and mitigation code. Note that the
3835		  i915 driver still uses most of the common DRM helper code for output
3836		  probing, so those sections fully apply.
3837	        </para>
3838	      </sect2>
3839	      <sect2>
3840	        <title>DPIO</title>
3841	!Pdrivers/gpu/drm/i915/i915_reg.h DPIO
3842		<table id="dpiox2">
3843		  <title>Dual channel PHY (VLV/CHV)</title>
3844		  <tgroup cols="8">
3845		    <colspec colname="c0" />
3846		    <colspec colname="c1" />
3847		    <colspec colname="c2" />
3848		    <colspec colname="c3" />
3849		    <colspec colname="c4" />
3850		    <colspec colname="c5" />
3851		    <colspec colname="c6" />
3852		    <colspec colname="c7" />
3853		    <spanspec spanname="ch0" namest="c0" nameend="c3" />
3854		    <spanspec spanname="ch1" namest="c4" nameend="c7" />
3855		    <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
3856		    <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
3857		    <spanspec spanname="ch1pcs01" namest="c4" nameend="c5" />
3858		    <spanspec spanname="ch1pcs23" namest="c6" nameend="c7" />
3859		    <thead>
3860		      <row>
3861			<entry spanname="ch0">CH0</entry>
3862			<entry spanname="ch1">CH1</entry>
3863		      </row>
3864		    </thead>
3865		    <tbody valign="top" align="center">
3866		      <row>
3867			<entry spanname="ch0">CMN/PLL/REF</entry>
3868			<entry spanname="ch1">CMN/PLL/REF</entry>
3869		      </row>
3870		      <row>
3871			<entry spanname="ch0pcs01">PCS01</entry>
3872			<entry spanname="ch0pcs23">PCS23</entry>
3873			<entry spanname="ch1pcs01">PCS01</entry>
3874			<entry spanname="ch1pcs23">PCS23</entry>
3875		      </row>
3876		      <row>
3877			<entry>TX0</entry>
3878			<entry>TX1</entry>
3879			<entry>TX2</entry>
3880			<entry>TX3</entry>
3881			<entry>TX0</entry>
3882			<entry>TX1</entry>
3883			<entry>TX2</entry>
3884			<entry>TX3</entry>
3885		      </row>
3886		      <row>
3887			<entry spanname="ch0">DDI0</entry>
3888			<entry spanname="ch1">DDI1</entry>
3889		      </row>
3890		    </tbody>
3891		  </tgroup>
3892		</table>
3893		<table id="dpiox1">
3894		  <title>Single channel PHY (CHV)</title>
3895		  <tgroup cols="4">
3896		    <colspec colname="c0" />
3897		    <colspec colname="c1" />
3898		    <colspec colname="c2" />
3899		    <colspec colname="c3" />
3900		    <spanspec spanname="ch0" namest="c0" nameend="c3" />
3901		    <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
3902		    <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
3903		    <thead>
3904		      <row>
3905			<entry spanname="ch0">CH0</entry>
3906		      </row>
3907		    </thead>
3908		    <tbody valign="top" align="center">
3909		      <row>
3910			<entry spanname="ch0">CMN/PLL/REF</entry>
3911		      </row>
3912		      <row>
3913			<entry spanname="ch0pcs01">PCS01</entry>
3914			<entry spanname="ch0pcs23">PCS23</entry>
3915		      </row>
3916		      <row>
3917			<entry>TX0</entry>
3918			<entry>TX1</entry>
3919			<entry>TX2</entry>
3920			<entry>TX3</entry>
3921		      </row>
3922		      <row>
3923			<entry spanname="ch0">DDI2</entry>
3924		      </row>
3925		    </tbody>
3926		  </tgroup>
3927		</table>
3928	      </sect2>
3929	    </sect1>
3930	
3931	    <sect1>
3932	      <title>Memory Management and Command Submission</title>
3933	      <para>
3934		This sections covers all things related to the GEM implementation in the
3935		i915 driver.
3936	      </para>
3937	      <sect2>
3938	        <title>Batchbuffer Parsing</title>
3939	!Pdrivers/gpu/drm/i915/i915_cmd_parser.c batch buffer command parser
3940	!Idrivers/gpu/drm/i915/i915_cmd_parser.c
3941	      </sect2>
3942	    </sect1>
3943	  </chapter>
3944	</part>
3945	</book>
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