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" []>
5 <book id="drmDevelopersGuide">
7 <title>Linux DRM Developer's Guide</title>
11 <firstname>Jesse</firstname>
12 <surname>Barnes</surname>
13 <contrib>Initial version</contrib>
15 <orgname>Intel Corporation</orgname>
17 <email>jesse.barnes@intel.com</email>
22 <firstname>Laurent</firstname>
23 <surname>Pinchart</surname>
24 <contrib>Driver internals</contrib>
26 <orgname>Ideas on board SPRL</orgname>
28 <email>laurent.pinchart@ideasonboard.com</email>
33 <firstname>Daniel</firstname>
34 <surname>Vetter</surname>
35 <contrib>Contributions all over the place</contrib>
37 <orgname>Intel Corporation</orgname>
39 <email>daniel.vetter@ffwll.ch</email>
46 <year>2008-2009</year>
47 <year>2013-2014</year>
48 <holder>Intel Corporation</holder>
52 <holder>Laurent Pinchart</holder>
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.
64 <!-- Put document revisions here, newest first. -->
66 <revnumber>1.0</revnumber>
67 <date>2012-07-13</date>
68 <authorinitials>LP</authorinitials>
69 <revremark>Added extensive documentation about driver internals.
78 <title>DRM Core</title>
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.
87 <chapter id="drmIntroduction">
88 <title>Introduction</title>
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.
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.
104 [Insert diagram of typical DRM stack here]
110 <chapter id="drmInternals">
111 <title>DRM Internals</title>
113 This chapter documents DRM internals relevant to driver authors
114 and developers working to add support for the latest features to
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.
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 & fencing, suspend/resume support, and DMA
134 <!-- Internals: driver init -->
137 <title>Driver Initialization</title>
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.
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.
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.
159 <title>Driver Information</title>
161 <title>Driver Features</title>
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>
170 <synopsis>u32 driver_features;</synopsis>
172 <title>Driver Feature Flags</title>
174 <term>DRIVER_USE_AGP</term>
176 Driver uses AGP interface, the DRM core will manage AGP resources.
180 <term>DRIVER_REQUIRE_AGP</term>
182 Driver needs AGP interface to function. AGP initialization failure
183 will become a fatal error.
187 <term>DRIVER_PCI_DMA</term>
189 Driver is capable of PCI DMA, mapping of PCI DMA buffers to
190 userspace will be enabled. Deprecated.
194 <term>DRIVER_SG</term>
196 Driver can perform scatter/gather DMA, allocation and mapping of
197 scatter/gather buffers will be enabled. Deprecated.
201 <term>DRIVER_HAVE_DMA</term>
203 Driver supports DMA, the userspace DMA API will be supported.
208 <term>DRIVER_HAVE_IRQ</term><term>DRIVER_IRQ_SHARED</term>
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 & handler
215 support shared IRQs (note that this is required of PCI drivers).
219 <term>DRIVER_GEM</term>
221 Driver use the GEM memory manager.
225 <term>DRIVER_MODESET</term>
227 Driver supports mode setting interfaces (KMS).
231 <term>DRIVER_PRIME</term>
233 Driver implements DRM PRIME buffer sharing.
237 <term>DRIVER_RENDER</term>
239 Driver supports dedicated render nodes.
243 <term>DRIVER_ATOMIC</term>
245 Driver supports atomic properties. In this case the driver
246 must implement appropriate obj->atomic_get_property() vfuncs
247 for any modeset objects with driver specific properties.
253 <title>Major, Minor and Patchlevel</title>
256 int patchlevel;</synopsis>
258 The DRM core identifies driver versions by a major, minor and patch
259 level triplet. The information is printed to the kernel log at
260 initialization time and passed to userspace through the
261 DRM_IOCTL_VERSION ioctl.
264 The major and minor numbers are also used to verify the requested driver
265 API version passed to DRM_IOCTL_SET_VERSION. When the driver API changes
266 between minor versions, applications can call DRM_IOCTL_SET_VERSION to
267 select a specific version of the API. If the requested major isn't equal
268 to the driver major, or the requested minor is larger than the driver
269 minor, the DRM_IOCTL_SET_VERSION call will return an error. Otherwise
270 the driver's set_version() method will be called with the requested
275 <title>Name, Description and Date</title>
276 <synopsis>char *name;
278 char *date;</synopsis>
280 The driver name is printed to the kernel log at initialization time,
281 used for IRQ registration and passed to userspace through
285 The driver description is a purely informative string passed to
286 userspace through the DRM_IOCTL_VERSION ioctl and otherwise unused by
290 The driver date, formatted as YYYYMMDD, is meant to identify the date of
291 the latest modification to the driver. However, as most drivers fail to
292 update it, its value is mostly useless. The DRM core prints it to the
293 kernel log at initialization time and passes it to userspace through the
294 DRM_IOCTL_VERSION ioctl.
299 <title>Device Registration</title>
301 A number of functions are provided to help with device registration.
302 The functions deal with PCI and platform devices, respectively.
304 !Edrivers/gpu/drm/drm_pci.c
305 !Edrivers/gpu/drm/drm_platform.c
307 New drivers that no longer rely on the services provided by the
308 <structname>drm_bus</structname> structure can call the low-level
309 device registration functions directly. The
310 <function>drm_dev_alloc()</function> function can be used to allocate
311 and initialize a new <structname>drm_device</structname> structure.
312 Drivers will typically want to perform some additional setup on this
313 structure, such as allocating driver-specific data and storing a
314 pointer to it in the DRM device's <structfield>dev_private</structfield>
315 field. Drivers should also set the device's unique name using the
316 <function>drm_dev_set_unique()</function> function. After it has been
317 set up a device can be registered with the DRM subsystem by calling
318 <function>drm_dev_register()</function>. This will cause the device to
319 be exposed to userspace and will call the driver's
320 <structfield>.load()</structfield> implementation. When a device is
321 removed, the DRM device can safely be unregistered and freed by calling
322 <function>drm_dev_unregister()</function> followed by a call to
323 <function>drm_dev_unref()</function>.
325 !Edrivers/gpu/drm/drm_drv.c
328 <title>Driver Load</title>
330 The <methodname>load</methodname> method is the driver and device
331 initialization entry point. The method is responsible for allocating and
332 initializing driver private data, performing resource allocation and
333 mapping (e.g. acquiring
334 clocks, mapping registers or allocating command buffers), initializing
335 the memory manager (<xref linkend="drm-memory-management"/>), installing
336 the IRQ handler (<xref linkend="drm-irq-registration"/>), setting up
337 vertical blanking handling (<xref linkend="drm-vertical-blank"/>), mode
338 setting (<xref linkend="drm-mode-setting"/>) and initial output
339 configuration (<xref linkend="drm-kms-init"/>).
342 If compatibility is a concern (e.g. with drivers converted over from
343 User Mode Setting to Kernel Mode Setting), care must be taken to prevent
344 device initialization and control that is incompatible with currently
345 active userspace drivers. For instance, if user level mode setting
346 drivers are in use, it would be problematic to perform output discovery
347 & configuration at load time. Likewise, if user-level drivers
348 unaware of memory management are in use, memory management and command
349 buffer setup may need to be omitted. These requirements are
350 driver-specific, and care needs to be taken to keep both old and new
351 applications and libraries working.
353 <synopsis>int (*load) (struct drm_device *, unsigned long flags);</synopsis>
355 The method takes two arguments, a pointer to the newly created
356 <structname>drm_device</structname> and flags. The flags are used to
357 pass the <structfield>driver_data</structfield> field of the device id
358 corresponding to the device passed to <function>drm_*_init()</function>.
359 Only PCI devices currently use this, USB and platform DRM drivers have
360 their <methodname>load</methodname> method called with flags to 0.
363 <title>Driver Private Data</title>
365 The driver private hangs off the main
366 <structname>drm_device</structname> structure and can be used for
367 tracking various device-specific bits of information, like register
368 offsets, command buffer status, register state for suspend/resume, etc.
369 At load time, a driver may simply allocate one and set
370 <structname>drm_device</structname>.<structfield>dev_priv</structfield>
371 appropriately; it should be freed and
372 <structname>drm_device</structname>.<structfield>dev_priv</structfield>
373 set to NULL when the driver is unloaded.
376 <sect3 id="drm-irq-registration">
377 <title>IRQ Registration</title>
379 The DRM core tries to facilitate IRQ handler registration and
380 unregistration by providing <function>drm_irq_install</function> and
381 <function>drm_irq_uninstall</function> functions. Those functions only
382 support a single interrupt per device, devices that use more than one
383 IRQs need to be handled manually.
386 <title>Managed IRQ Registration</title>
388 <function>drm_irq_install</function> starts by calling the
389 <methodname>irq_preinstall</methodname> driver operation. The operation
390 is optional and must make sure that the interrupt will not get fired by
391 clearing all pending interrupt flags or disabling the interrupt.
394 The passed-in IRQ will then be requested by a call to
395 <function>request_irq</function>. If the DRIVER_IRQ_SHARED driver
396 feature flag is set, a shared (IRQF_SHARED) IRQ handler will be
400 The IRQ handler function must be provided as the mandatory irq_handler
401 driver operation. It will get passed directly to
402 <function>request_irq</function> and thus has the same prototype as all
403 IRQ handlers. It will get called with a pointer to the DRM device as the
407 Finally the function calls the optional
408 <methodname>irq_postinstall</methodname> driver operation. The operation
409 usually enables interrupts (excluding the vblank interrupt, which is
410 enabled separately), but drivers may choose to enable/disable interrupts
414 <function>drm_irq_uninstall</function> is similarly used to uninstall an
415 IRQ handler. It starts by waking up all processes waiting on a vblank
416 interrupt to make sure they don't hang, and then calls the optional
417 <methodname>irq_uninstall</methodname> driver operation. The operation
418 must disable all hardware interrupts. Finally the function frees the IRQ
419 by calling <function>free_irq</function>.
423 <title>Manual IRQ Registration</title>
425 Drivers that require multiple interrupt handlers can't use the managed
426 IRQ registration functions. In that case IRQs must be registered and
427 unregistered manually (usually with the <function>request_irq</function>
428 and <function>free_irq</function> functions, or their devm_* equivalent).
431 When manually registering IRQs, drivers must not set the DRIVER_HAVE_IRQ
432 driver feature flag, and must not provide the
433 <methodname>irq_handler</methodname> driver operation. They must set the
434 <structname>drm_device</structname> <structfield>irq_enabled</structfield>
435 field to 1 upon registration of the IRQs, and clear it to 0 after
436 unregistering the IRQs.
441 <title>Memory Manager Initialization</title>
443 Every DRM driver requires a memory manager which must be initialized at
444 load time. DRM currently contains two memory managers, the Translation
445 Table Manager (TTM) and the Graphics Execution Manager (GEM).
446 This document describes the use of the GEM memory manager only. See
447 <xref linkend="drm-memory-management"/> for details.
451 <title>Miscellaneous Device Configuration</title>
453 Another task that may be necessary for PCI devices during configuration
454 is mapping the video BIOS. On many devices, the VBIOS describes device
455 configuration, LCD panel timings (if any), and contains flags indicating
456 device state. Mapping the BIOS can be done using the pci_map_rom() call,
457 a convenience function that takes care of mapping the actual ROM,
458 whether it has been shadowed into memory (typically at address 0xc0000)
459 or exists on the PCI device in the ROM BAR. Note that after the ROM has
460 been mapped and any necessary information has been extracted, it should
461 be unmapped; on many devices, the ROM address decoder is shared with
462 other BARs, so leaving it mapped could cause undesired behaviour like
463 hangs or memory corruption.
464 <!--!Fdrivers/pci/rom.c pci_map_rom-->
470 <!-- Internals: memory management -->
472 <sect1 id="drm-memory-management">
473 <title>Memory management</title>
475 Modern Linux systems require large amount of graphics memory to store
476 frame buffers, textures, vertices and other graphics-related data. Given
477 the very dynamic nature of many of that data, managing graphics memory
478 efficiently is thus crucial for the graphics stack and plays a central
479 role in the DRM infrastructure.
482 The DRM core includes two memory managers, namely Translation Table Maps
483 (TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory
484 manager to be developed and tried to be a one-size-fits-them all
485 solution. It provides a single userspace API to accommodate the need of
486 all hardware, supporting both Unified Memory Architecture (UMA) devices
487 and devices with dedicated video RAM (i.e. most discrete video cards).
488 This resulted in a large, complex piece of code that turned out to be
489 hard to use for driver development.
492 GEM started as an Intel-sponsored project in reaction to TTM's
493 complexity. Its design philosophy is completely different: instead of
494 providing a solution to every graphics memory-related problems, GEM
495 identified common code between drivers and created a support library to
496 share it. GEM has simpler initialization and execution requirements than
497 TTM, but has no video RAM management capabilities and is thus limited to
501 <title>The Translation Table Manager (TTM)</title>
503 TTM design background and information belongs here.
506 <title>TTM initialization</title>
507 <warning><para>This section is outdated.</para></warning>
509 Drivers wishing to support TTM must fill out a drm_bo_driver
510 structure. The structure contains several fields with function
511 pointers for initializing the TTM, allocating and freeing memory,
512 waiting for command completion and fence synchronization, and memory
513 migration. See the radeon_ttm.c file for an example of usage.
516 The ttm_global_reference structure is made up of several fields:
519 struct ttm_global_reference {
520 enum ttm_global_types global_type;
523 int (*init) (struct ttm_global_reference *);
524 void (*release) (struct ttm_global_reference *);
528 There should be one global reference structure for your memory
529 manager as a whole, and there will be others for each object
530 created by the memory manager at runtime. Your global TTM should
531 have a type of TTM_GLOBAL_TTM_MEM. The size field for the global
532 object should be sizeof(struct ttm_mem_global), and the init and
533 release hooks should point at your driver-specific init and
534 release routines, which probably eventually call
535 ttm_mem_global_init and ttm_mem_global_release, respectively.
538 Once your global TTM accounting structure is set up and initialized
539 by calling ttm_global_item_ref() on it,
540 you need to create a buffer object TTM to
541 provide a pool for buffer object allocation by clients and the
542 kernel itself. The type of this object should be TTM_GLOBAL_TTM_BO,
543 and its size should be sizeof(struct ttm_bo_global). Again,
544 driver-specific init and release functions may be provided,
545 likely eventually calling ttm_bo_global_init() and
546 ttm_bo_global_release(), respectively. Also, like the previous
547 object, ttm_global_item_ref() is used to create an initial reference
548 count for the TTM, which will call your initialization function.
553 <title>The Graphics Execution Manager (GEM)</title>
555 The GEM design approach has resulted in a memory manager that doesn't
556 provide full coverage of all (or even all common) use cases in its
557 userspace or kernel API. GEM exposes a set of standard memory-related
558 operations to userspace and a set of helper functions to drivers, and let
559 drivers implement hardware-specific operations with their own private API.
562 The GEM userspace API is described in the
563 <ulink url="http://lwn.net/Articles/283798/"><citetitle>GEM - the Graphics
564 Execution Manager</citetitle></ulink> article on LWN. While slightly
565 outdated, the document provides a good overview of the GEM API principles.
566 Buffer allocation and read and write operations, described as part of the
567 common GEM API, are currently implemented using driver-specific ioctls.
570 GEM is data-agnostic. It manages abstract buffer objects without knowing
571 what individual buffers contain. APIs that require knowledge of buffer
572 contents or purpose, such as buffer allocation or synchronization
573 primitives, are thus outside of the scope of GEM and must be implemented
574 using driver-specific ioctls.
577 On a fundamental level, GEM involves several operations:
579 <listitem>Memory allocation and freeing</listitem>
580 <listitem>Command execution</listitem>
581 <listitem>Aperture management at command execution time</listitem>
583 Buffer object allocation is relatively straightforward and largely
584 provided by Linux's shmem layer, which provides memory to back each
588 Device-specific operations, such as command execution, pinning, buffer
589 read & write, mapping, and domain ownership transfers are left to
590 driver-specific ioctls.
593 <title>GEM Initialization</title>
595 Drivers that use GEM must set the DRIVER_GEM bit in the struct
596 <structname>drm_driver</structname>
597 <structfield>driver_features</structfield> field. The DRM core will
598 then automatically initialize the GEM core before calling the
599 <methodname>load</methodname> operation. Behind the scene, this will
600 create a DRM Memory Manager object which provides an address space
601 pool for object allocation.
604 In a KMS configuration, drivers need to allocate and initialize a
605 command ring buffer following core GEM initialization if required by
606 the hardware. UMA devices usually have what is called a "stolen"
607 memory region, which provides space for the initial framebuffer and
608 large, contiguous memory regions required by the device. This space is
609 typically not managed by GEM, and must be initialized separately into
610 its own DRM MM object.
614 <title>GEM Objects Creation</title>
616 GEM splits creation of GEM objects and allocation of the memory that
617 backs them in two distinct operations.
620 GEM objects are represented by an instance of struct
621 <structname>drm_gem_object</structname>. Drivers usually need to extend
622 GEM objects with private information and thus create a driver-specific
623 GEM object structure type that embeds an instance of struct
624 <structname>drm_gem_object</structname>.
627 To create a GEM object, a driver allocates memory for an instance of its
628 specific GEM object type and initializes the embedded struct
629 <structname>drm_gem_object</structname> with a call to
630 <function>drm_gem_object_init</function>. The function takes a pointer to
631 the DRM device, a pointer to the GEM object and the buffer object size
635 GEM uses shmem to allocate anonymous pageable memory.
636 <function>drm_gem_object_init</function> will create an shmfs file of
637 the requested size and store it into the struct
638 <structname>drm_gem_object</structname> <structfield>filp</structfield>
639 field. The memory is used as either main storage for the object when the
640 graphics hardware uses system memory directly or as a backing store
644 Drivers are responsible for the actual physical pages allocation by
645 calling <function>shmem_read_mapping_page_gfp</function> for each page.
646 Note that they can decide to allocate pages when initializing the GEM
647 object, or to delay allocation until the memory is needed (for instance
648 when a page fault occurs as a result of a userspace memory access or
649 when the driver needs to start a DMA transfer involving the memory).
652 Anonymous pageable memory allocation is not always desired, for instance
653 when the hardware requires physically contiguous system memory as is
654 often the case in embedded devices. Drivers can create GEM objects with
655 no shmfs backing (called private GEM objects) by initializing them with
656 a call to <function>drm_gem_private_object_init</function> instead of
657 <function>drm_gem_object_init</function>. Storage for private GEM
658 objects must be managed by drivers.
661 Drivers that do not need to extend GEM objects with private information
662 can call the <function>drm_gem_object_alloc</function> function to
663 allocate and initialize a struct <structname>drm_gem_object</structname>
664 instance. The GEM core will call the optional driver
665 <methodname>gem_init_object</methodname> operation after initializing
666 the GEM object with <function>drm_gem_object_init</function>.
667 <synopsis>int (*gem_init_object) (struct drm_gem_object *obj);</synopsis>
670 No alloc-and-init function exists for private GEM objects.
674 <title>GEM Objects Lifetime</title>
676 All GEM objects are reference-counted by the GEM core. References can be
677 acquired and release by <function>calling drm_gem_object_reference</function>
678 and <function>drm_gem_object_unreference</function> respectively. The
679 caller must hold the <structname>drm_device</structname>
680 <structfield>struct_mutex</structfield> lock. As a convenience, GEM
681 provides the <function>drm_gem_object_reference_unlocked</function> and
682 <function>drm_gem_object_unreference_unlocked</function> functions that
683 can be called without holding the lock.
686 When the last reference to a GEM object is released the GEM core calls
687 the <structname>drm_driver</structname>
688 <methodname>gem_free_object</methodname> operation. That operation is
689 mandatory for GEM-enabled drivers and must free the GEM object and all
690 associated resources.
693 <synopsis>void (*gem_free_object) (struct drm_gem_object *obj);</synopsis>
694 Drivers are responsible for freeing all GEM object resources, including
695 the resources created by the GEM core. If an mmap offset has been
696 created for the object (in which case
697 <structname>drm_gem_object</structname>::<structfield>map_list</structfield>::<structfield>map</structfield>
698 is not NULL) it must be freed by a call to
699 <function>drm_gem_free_mmap_offset</function>. The shmfs backing store
700 must be released by calling <function>drm_gem_object_release</function>
701 (that function can safely be called if no shmfs backing store has been
706 <title>GEM Objects Naming</title>
708 Communication between userspace and the kernel refers to GEM objects
709 using local handles, global names or, more recently, file descriptors.
710 All of those are 32-bit integer values; the usual Linux kernel limits
711 apply to the file descriptors.
714 GEM handles are local to a DRM file. Applications get a handle to a GEM
715 object through a driver-specific ioctl, and can use that handle to refer
716 to the GEM object in other standard or driver-specific ioctls. Closing a
717 DRM file handle frees all its GEM handles and dereferences the
718 associated GEM objects.
721 To create a handle for a GEM object drivers call
722 <function>drm_gem_handle_create</function>. The function takes a pointer
723 to the DRM file and the GEM object and returns a locally unique handle.
724 When the handle is no longer needed drivers delete it with a call to
725 <function>drm_gem_handle_delete</function>. Finally the GEM object
726 associated with a handle can be retrieved by a call to
727 <function>drm_gem_object_lookup</function>.
730 Handles don't take ownership of GEM objects, they only take a reference
731 to the object that will be dropped when the handle is destroyed. To
732 avoid leaking GEM objects, drivers must make sure they drop the
733 reference(s) they own (such as the initial reference taken at object
734 creation time) as appropriate, without any special consideration for the
735 handle. For example, in the particular case of combined GEM object and
736 handle creation in the implementation of the
737 <methodname>dumb_create</methodname> operation, drivers must drop the
738 initial reference to the GEM object before returning the handle.
741 GEM names are similar in purpose to handles but are not local to DRM
742 files. They can be passed between processes to reference a GEM object
743 globally. Names can't be used directly to refer to objects in the DRM
744 API, applications must convert handles to names and names to handles
745 using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls
746 respectively. The conversion is handled by the DRM core without any
747 driver-specific support.
750 GEM also supports buffer sharing with dma-buf file descriptors through
751 PRIME. GEM-based drivers must use the provided helpers functions to
752 implement the exporting and importing correctly. See <xref linkend="drm-prime-support" />.
753 Since sharing file descriptors is inherently more secure than the
754 easily guessable and global GEM names it is the preferred buffer
755 sharing mechanism. Sharing buffers through GEM names is only supported
756 for legacy userspace. Furthermore PRIME also allows cross-device
757 buffer sharing since it is based on dma-bufs.
760 <sect3 id="drm-gem-objects-mapping">
761 <title>GEM Objects Mapping</title>
763 Because mapping operations are fairly heavyweight GEM favours
764 read/write-like access to buffers, implemented through driver-specific
765 ioctls, over mapping buffers to userspace. However, when random access
766 to the buffer is needed (to perform software rendering for instance),
767 direct access to the object can be more efficient.
770 The mmap system call can't be used directly to map GEM objects, as they
771 don't have their own file handle. Two alternative methods currently
772 co-exist to map GEM objects to userspace. The first method uses a
773 driver-specific ioctl to perform the mapping operation, calling
774 <function>do_mmap</function> under the hood. This is often considered
775 dubious, seems to be discouraged for new GEM-enabled drivers, and will
776 thus not be described here.
779 The second method uses the mmap system call on the DRM file handle.
780 <synopsis>void *mmap(void *addr, size_t length, int prot, int flags, int fd,
781 off_t offset);</synopsis>
782 DRM identifies the GEM object to be mapped by a fake offset passed
783 through the mmap offset argument. Prior to being mapped, a GEM object
784 must thus be associated with a fake offset. To do so, drivers must call
785 <function>drm_gem_create_mmap_offset</function> on the object. The
786 function allocates a fake offset range from a pool and stores the
787 offset divided by PAGE_SIZE in
788 <literal>obj->map_list.hash.key</literal>. Care must be taken not to
789 call <function>drm_gem_create_mmap_offset</function> if a fake offset
790 has already been allocated for the object. This can be tested by
791 <literal>obj->map_list.map</literal> being non-NULL.
794 Once allocated, the fake offset value
795 (<literal>obj->map_list.hash.key << PAGE_SHIFT</literal>)
796 must be passed to the application in a driver-specific way and can then
797 be used as the mmap offset argument.
800 The GEM core provides a helper method <function>drm_gem_mmap</function>
801 to handle object mapping. The method can be set directly as the mmap
802 file operation handler. It will look up the GEM object based on the
803 offset value and set the VMA operations to the
804 <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
805 field. Note that <function>drm_gem_mmap</function> doesn't map memory to
806 userspace, but relies on the driver-provided fault handler to map pages
810 To use <function>drm_gem_mmap</function>, drivers must fill the struct
811 <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
812 field with a pointer to VM operations.
815 <synopsis>struct vm_operations_struct *gem_vm_ops
817 struct vm_operations_struct {
818 void (*open)(struct vm_area_struct * area);
819 void (*close)(struct vm_area_struct * area);
820 int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf);
824 The <methodname>open</methodname> and <methodname>close</methodname>
825 operations must update the GEM object reference count. Drivers can use
826 the <function>drm_gem_vm_open</function> and
827 <function>drm_gem_vm_close</function> helper functions directly as open
831 The fault operation handler is responsible for mapping individual pages
832 to userspace when a page fault occurs. Depending on the memory
833 allocation scheme, drivers can allocate pages at fault time, or can
834 decide to allocate memory for the GEM object at the time the object is
838 Drivers that want to map the GEM object upfront instead of handling page
839 faults can implement their own mmap file operation handler.
843 <title>Memory Coherency</title>
845 When mapped to the device or used in a command buffer, backing pages
846 for an object are flushed to memory and marked write combined so as to
847 be coherent with the GPU. Likewise, if the CPU accesses an object
848 after the GPU has finished rendering to the object, then the object
849 must be made coherent with the CPU's view of memory, usually involving
850 GPU cache flushing of various kinds. This core CPU<->GPU
851 coherency management is provided by a device-specific ioctl, which
852 evaluates an object's current domain and performs any necessary
853 flushing or synchronization to put the object into the desired
854 coherency domain (note that the object may be busy, i.e. an active
855 render target; in that case, setting the domain blocks the client and
856 waits for rendering to complete before performing any necessary
857 flushing operations).
861 <title>Command Execution</title>
863 Perhaps the most important GEM function for GPU devices is providing a
864 command execution interface to clients. Client programs construct
865 command buffers containing references to previously allocated memory
866 objects, and then submit them to GEM. At that point, GEM takes care to
867 bind all the objects into the GTT, execute the buffer, and provide
868 necessary synchronization between clients accessing the same buffers.
869 This often involves evicting some objects from the GTT and re-binding
870 others (a fairly expensive operation), and providing relocation
871 support which hides fixed GTT offsets from clients. Clients must take
872 care not to submit command buffers that reference more objects than
873 can fit in the GTT; otherwise, GEM will reject them and no rendering
874 will occur. Similarly, if several objects in the buffer require fence
875 registers to be allocated for correct rendering (e.g. 2D blits on
876 pre-965 chips), care must be taken not to require more fence registers
877 than are available to the client. Such resource management should be
878 abstracted from the client in libdrm.
882 <title>GEM Function Reference</title>
883 !Edrivers/gpu/drm/drm_gem.c
887 <title>VMA Offset Manager</title>
888 !Pdrivers/gpu/drm/drm_vma_manager.c vma offset manager
889 !Edrivers/gpu/drm/drm_vma_manager.c
890 !Iinclude/drm/drm_vma_manager.h
892 <sect2 id="drm-prime-support">
893 <title>PRIME Buffer Sharing</title>
895 PRIME is the cross device buffer sharing framework in drm, originally
896 created for the OPTIMUS range of multi-gpu platforms. To userspace
897 PRIME buffers are dma-buf based file descriptors.
900 <title>Overview and Driver Interface</title>
902 Similar to GEM global names, PRIME file descriptors are
903 also used to share buffer objects across processes. They offer
904 additional security: as file descriptors must be explicitly sent over
905 UNIX domain sockets to be shared between applications, they can't be
906 guessed like the globally unique GEM names.
909 Drivers that support the PRIME
910 API must set the DRIVER_PRIME bit in the struct
911 <structname>drm_driver</structname>
912 <structfield>driver_features</structfield> field, and implement the
913 <methodname>prime_handle_to_fd</methodname> and
914 <methodname>prime_fd_to_handle</methodname> operations.
917 <synopsis>int (*prime_handle_to_fd)(struct drm_device *dev,
918 struct drm_file *file_priv, uint32_t handle,
919 uint32_t flags, int *prime_fd);
920 int (*prime_fd_to_handle)(struct drm_device *dev,
921 struct drm_file *file_priv, int prime_fd,
922 uint32_t *handle);</synopsis>
923 Those two operations convert a handle to a PRIME file descriptor and
924 vice versa. Drivers must use the kernel dma-buf buffer sharing framework
925 to manage the PRIME file descriptors. Similar to the mode setting
926 API PRIME is agnostic to the underlying buffer object manager, as
927 long as handles are 32bit unsigned integers.
930 While non-GEM drivers must implement the operations themselves, GEM
931 drivers must use the <function>drm_gem_prime_handle_to_fd</function>
932 and <function>drm_gem_prime_fd_to_handle</function> helper functions.
933 Those helpers rely on the driver
934 <methodname>gem_prime_export</methodname> and
935 <methodname>gem_prime_import</methodname> operations to create a dma-buf
936 instance from a GEM object (dma-buf exporter role) and to create a GEM
937 object from a dma-buf instance (dma-buf importer role).
940 <synopsis>struct dma_buf * (*gem_prime_export)(struct drm_device *dev,
941 struct drm_gem_object *obj,
943 struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev,
944 struct dma_buf *dma_buf);</synopsis>
945 These two operations are mandatory for GEM drivers that support
950 <title>PRIME Helper Functions</title>
951 !Pdrivers/gpu/drm/drm_prime.c PRIME Helpers
955 <title>PRIME Function References</title>
956 !Edrivers/gpu/drm/drm_prime.c
959 <title>DRM MM Range Allocator</title>
961 <title>Overview</title>
962 !Pdrivers/gpu/drm/drm_mm.c Overview
965 <title>LRU Scan/Eviction Support</title>
966 !Pdrivers/gpu/drm/drm_mm.c lru scan roaster
970 <title>DRM MM Range Allocator Function References</title>
971 !Edrivers/gpu/drm/drm_mm.c
972 !Iinclude/drm/drm_mm.h
975 <title>CMA Helper Functions Reference</title>
976 !Pdrivers/gpu/drm/drm_gem_cma_helper.c cma helpers
977 !Edrivers/gpu/drm/drm_gem_cma_helper.c
978 !Iinclude/drm/drm_gem_cma_helper.h
982 <!-- Internals: mode setting -->
984 <sect1 id="drm-mode-setting">
985 <title>Mode Setting</title>
987 Drivers must initialize the mode setting core by calling
988 <function>drm_mode_config_init</function> on the DRM device. The function
989 initializes the <structname>drm_device</structname>
990 <structfield>mode_config</structfield> field and never fails. Once done,
991 mode configuration must be setup by initializing the following fields.
995 <synopsis>int min_width, min_height;
996 int max_width, max_height;</synopsis>
998 Minimum and maximum width and height of the frame buffers in pixel
1003 <synopsis>struct drm_mode_config_funcs *funcs;</synopsis>
1004 <para>Mode setting functions.</para>
1008 <title>Display Modes Function Reference</title>
1009 !Iinclude/drm/drm_modes.h
1010 !Edrivers/gpu/drm/drm_modes.c
1013 <title>Atomic Mode Setting Function Reference</title>
1014 !Edrivers/gpu/drm/drm_atomic.c
1017 <title>Frame Buffer Creation</title>
1018 <synopsis>struct drm_framebuffer *(*fb_create)(struct drm_device *dev,
1019 struct drm_file *file_priv,
1020 struct drm_mode_fb_cmd2 *mode_cmd);</synopsis>
1022 Frame buffers are abstract memory objects that provide a source of
1023 pixels to scanout to a CRTC. Applications explicitly request the
1024 creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls and
1025 receive an opaque handle that can be passed to the KMS CRTC control,
1026 plane configuration and page flip functions.
1029 Frame buffers rely on the underneath memory manager for low-level memory
1030 operations. When creating a frame buffer applications pass a memory
1031 handle (or a list of memory handles for multi-planar formats) through
1032 the <parameter>drm_mode_fb_cmd2</parameter> argument. For drivers using
1033 GEM as their userspace buffer management interface this would be a GEM
1034 handle. Drivers are however free to use their own backing storage object
1035 handles, e.g. vmwgfx directly exposes special TTM handles to userspace
1036 and so expects TTM handles in the create ioctl and not GEM handles.
1039 Drivers must first validate the requested frame buffer parameters passed
1040 through the mode_cmd argument. In particular this is where invalid
1041 sizes, pixel formats or pitches can be caught.
1044 If the parameters are deemed valid, drivers then create, initialize and
1045 return an instance of struct <structname>drm_framebuffer</structname>.
1046 If desired the instance can be embedded in a larger driver-specific
1047 structure. Drivers must fill its <structfield>width</structfield>,
1048 <structfield>height</structfield>, <structfield>pitches</structfield>,
1049 <structfield>offsets</structfield>, <structfield>depth</structfield>,
1050 <structfield>bits_per_pixel</structfield> and
1051 <structfield>pixel_format</structfield> fields from the values passed
1052 through the <parameter>drm_mode_fb_cmd2</parameter> argument. They
1053 should call the <function>drm_helper_mode_fill_fb_struct</function>
1054 helper function to do so.
1058 The initialization of the new framebuffer instance is finalized with a
1059 call to <function>drm_framebuffer_init</function> which takes a pointer
1060 to DRM frame buffer operations (struct
1061 <structname>drm_framebuffer_funcs</structname>). Note that this function
1062 publishes the framebuffer and so from this point on it can be accessed
1063 concurrently from other threads. Hence it must be the last step in the
1064 driver's framebuffer initialization sequence. Frame buffer operations
1068 <synopsis>int (*create_handle)(struct drm_framebuffer *fb,
1069 struct drm_file *file_priv, unsigned int *handle);</synopsis>
1071 Create a handle to the frame buffer underlying memory object. If
1072 the frame buffer uses a multi-plane format, the handle will
1073 reference the memory object associated with the first plane.
1076 Drivers call <function>drm_gem_handle_create</function> to create
1081 <synopsis>void (*destroy)(struct drm_framebuffer *framebuffer);</synopsis>
1083 Destroy the frame buffer object and frees all associated
1084 resources. Drivers must call
1085 <function>drm_framebuffer_cleanup</function> to free resources
1086 allocated by the DRM core for the frame buffer object, and must
1087 make sure to unreference all memory objects associated with the
1088 frame buffer. Handles created by the
1089 <methodname>create_handle</methodname> operation are released by
1094 <synopsis>int (*dirty)(struct drm_framebuffer *framebuffer,
1095 struct drm_file *file_priv, unsigned flags, unsigned color,
1096 struct drm_clip_rect *clips, unsigned num_clips);</synopsis>
1098 This optional operation notifies the driver that a region of the
1099 frame buffer has changed in response to a DRM_IOCTL_MODE_DIRTYFB
1106 The lifetime of a drm framebuffer is controlled with a reference count,
1107 drivers can grab additional references with
1108 <function>drm_framebuffer_reference</function>and drop them
1109 again with <function>drm_framebuffer_unreference</function>. For
1110 driver-private framebuffers for which the last reference is never
1111 dropped (e.g. for the fbdev framebuffer when the struct
1112 <structname>drm_framebuffer</structname> is embedded into the fbdev
1113 helper struct) drivers can manually clean up a framebuffer at module
1115 <function>drm_framebuffer_unregister_private</function>.
1119 <title>Dumb Buffer Objects</title>
1121 The KMS API doesn't standardize backing storage object creation and
1122 leaves it to driver-specific ioctls. Furthermore actually creating a
1123 buffer object even for GEM-based drivers is done through a
1124 driver-specific ioctl - GEM only has a common userspace interface for
1125 sharing and destroying objects. While not an issue for full-fledged
1126 graphics stacks that include device-specific userspace components (in
1127 libdrm for instance), this limit makes DRM-based early boot graphics
1128 unnecessarily complex.
1131 Dumb objects partly alleviate the problem by providing a standard
1132 API to create dumb buffers suitable for scanout, which can then be used
1133 to create KMS frame buffers.
1136 To support dumb objects drivers must implement the
1137 <methodname>dumb_create</methodname>,
1138 <methodname>dumb_destroy</methodname> and
1139 <methodname>dumb_map_offset</methodname> operations.
1143 <synopsis>int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev,
1144 struct drm_mode_create_dumb *args);</synopsis>
1146 The <methodname>dumb_create</methodname> operation creates a driver
1147 object (GEM or TTM handle) suitable for scanout based on the
1148 width, height and depth from the struct
1149 <structname>drm_mode_create_dumb</structname> argument. It fills the
1150 argument's <structfield>handle</structfield>,
1151 <structfield>pitch</structfield> and <structfield>size</structfield>
1152 fields with a handle for the newly created object and its line
1153 pitch and size in bytes.
1157 <synopsis>int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev,
1158 uint32_t handle);</synopsis>
1160 The <methodname>dumb_destroy</methodname> operation destroys a dumb
1161 object created by <methodname>dumb_create</methodname>.
1165 <synopsis>int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev,
1166 uint32_t handle, uint64_t *offset);</synopsis>
1168 The <methodname>dumb_map_offset</methodname> operation associates an
1169 mmap fake offset with the object given by the handle and returns
1170 it. Drivers must use the
1171 <function>drm_gem_create_mmap_offset</function> function to
1172 associate the fake offset as described in
1173 <xref linkend="drm-gem-objects-mapping"/>.
1178 Note that dumb objects may not be used for gpu acceleration, as has been
1179 attempted on some ARM embedded platforms. Such drivers really must have
1180 a hardware-specific ioctl to allocate suitable buffer objects.
1184 <title>Output Polling</title>
1185 <synopsis>void (*output_poll_changed)(struct drm_device *dev);</synopsis>
1187 This operation notifies the driver that the status of one or more
1188 connectors has changed. Drivers that use the fb helper can just call the
1189 <function>drm_fb_helper_hotplug_event</function> function to handle this
1194 <title>Locking</title>
1196 Beside some lookup structures with their own locking (which is hidden
1197 behind the interface functions) most of the modeset state is protected
1198 by the <code>dev-<mode_config.lock</code> mutex and additionally
1199 per-crtc locks to allow cursor updates, pageflips and similar operations
1200 to occur concurrently with background tasks like output detection.
1201 Operations which cross domains like a full modeset always grab all
1202 locks. Drivers there need to protect resources shared between crtcs with
1203 additional locking. They also need to be careful to always grab the
1204 relevant crtc locks if a modset functions touches crtc state, e.g. for
1205 load detection (which does only grab the <code>mode_config.lock</code>
1206 to allow concurrent screen updates on live crtcs).
1211 <!-- Internals: kms initialization and cleanup -->
1213 <sect1 id="drm-kms-init">
1214 <title>KMS Initialization and Cleanup</title>
1216 A KMS device is abstracted and exposed as a set of planes, CRTCs, encoders
1217 and connectors. KMS drivers must thus create and initialize all those
1218 objects at load time after initializing mode setting.
1221 <title>CRTCs (struct <structname>drm_crtc</structname>)</title>
1223 A CRTC is an abstraction representing a part of the chip that contains a
1224 pointer to a scanout buffer. Therefore, the number of CRTCs available
1225 determines how many independent scanout buffers can be active at any
1226 given time. The CRTC structure contains several fields to support this:
1227 a pointer to some video memory (abstracted as a frame buffer object), a
1228 display mode, and an (x, y) offset into the video memory to support
1229 panning or configurations where one piece of video memory spans multiple
1233 <title>CRTC Initialization</title>
1235 A KMS device must create and register at least one struct
1236 <structname>drm_crtc</structname> instance. The instance is allocated
1237 and zeroed by the driver, possibly as part of a larger structure, and
1238 registered with a call to <function>drm_crtc_init</function> with a
1239 pointer to CRTC functions.
1242 <sect3 id="drm-kms-crtcops">
1243 <title>CRTC Operations</title>
1245 <title>Set Configuration</title>
1246 <synopsis>int (*set_config)(struct drm_mode_set *set);</synopsis>
1248 Apply a new CRTC configuration to the device. The configuration
1249 specifies a CRTC, a frame buffer to scan out from, a (x,y) position in
1250 the frame buffer, a display mode and an array of connectors to drive
1251 with the CRTC if possible.
1254 If the frame buffer specified in the configuration is NULL, the driver
1255 must detach all encoders connected to the CRTC and all connectors
1256 attached to those encoders and disable them.
1259 This operation is called with the mode config lock held.
1262 Note that the drm core has no notion of restoring the mode setting
1263 state after resume, since all resume handling is in the full
1264 responsibility of the driver. The common mode setting helper library
1265 though provides a helper which can be used for this:
1266 <function>drm_helper_resume_force_mode</function>.
1270 <title>Page Flipping</title>
1271 <synopsis>int (*page_flip)(struct drm_crtc *crtc, struct drm_framebuffer *fb,
1272 struct drm_pending_vblank_event *event);</synopsis>
1274 Schedule a page flip to the given frame buffer for the CRTC. This
1275 operation is called with the mode config mutex held.
1278 Page flipping is a synchronization mechanism that replaces the frame
1279 buffer being scanned out by the CRTC with a new frame buffer during
1280 vertical blanking, avoiding tearing. When an application requests a page
1281 flip the DRM core verifies that the new frame buffer is large enough to
1282 be scanned out by the CRTC in the currently configured mode and then
1283 calls the CRTC <methodname>page_flip</methodname> operation with a
1284 pointer to the new frame buffer.
1287 The <methodname>page_flip</methodname> operation schedules a page flip.
1288 Once any pending rendering targeting the new frame buffer has
1289 completed, the CRTC will be reprogrammed to display that frame buffer
1290 after the next vertical refresh. The operation must return immediately
1291 without waiting for rendering or page flip to complete and must block
1292 any new rendering to the frame buffer until the page flip completes.
1295 If a page flip can be successfully scheduled the driver must set the
1296 <code>drm_crtc-<fb</code> field to the new framebuffer pointed to
1297 by <code>fb</code>. This is important so that the reference counting
1298 on framebuffers stays balanced.
1301 If a page flip is already pending, the
1302 <methodname>page_flip</methodname> operation must return
1303 -<errorname>EBUSY</errorname>.
1306 To synchronize page flip to vertical blanking the driver will likely
1307 need to enable vertical blanking interrupts. It should call
1308 <function>drm_vblank_get</function> for that purpose, and call
1309 <function>drm_vblank_put</function> after the page flip completes.
1312 If the application has requested to be notified when page flip completes
1313 the <methodname>page_flip</methodname> operation will be called with a
1314 non-NULL <parameter>event</parameter> argument pointing to a
1315 <structname>drm_pending_vblank_event</structname> instance. Upon page
1316 flip completion the driver must call <methodname>drm_send_vblank_event</methodname>
1317 to fill in the event and send to wake up any waiting processes.
1318 This can be performed with
1319 <programlisting><![CDATA[
1320 spin_lock_irqsave(&dev->event_lock, flags);
1322 drm_send_vblank_event(dev, pipe, event);
1323 spin_unlock_irqrestore(&dev->event_lock, flags);
1324 ]]></programlisting>
1327 FIXME: Could drivers that don't need to wait for rendering to complete
1328 just add the event to <literal>dev->vblank_event_list</literal> and
1329 let the DRM core handle everything, as for "normal" vertical blanking
1333 While waiting for the page flip to complete, the
1334 <literal>event->base.link</literal> list head can be used freely by
1335 the driver to store the pending event in a driver-specific list.
1338 If the file handle is closed before the event is signaled, drivers must
1339 take care to destroy the event in their
1340 <methodname>preclose</methodname> operation (and, if needed, call
1341 <function>drm_vblank_put</function>).
1345 <title>Miscellaneous</title>
1348 <synopsis>void (*set_property)(struct drm_crtc *crtc,
1349 struct drm_property *property, uint64_t value);</synopsis>
1351 Set the value of the given CRTC property to
1352 <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1353 for more information about properties.
1357 <synopsis>void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b,
1358 uint32_t start, uint32_t size);</synopsis>
1360 Apply a gamma table to the device. The operation is optional.
1364 <synopsis>void (*destroy)(struct drm_crtc *crtc);</synopsis>
1366 Destroy the CRTC when not needed anymore. See
1367 <xref linkend="drm-kms-init"/>.
1375 <title>Planes (struct <structname>drm_plane</structname>)</title>
1377 A plane represents an image source that can be blended with or overlayed
1378 on top of a CRTC during the scanout process. Planes are associated with
1379 a frame buffer to crop a portion of the image memory (source) and
1380 optionally scale it to a destination size. The result is then blended
1381 with or overlayed on top of a CRTC.
1384 The DRM core recognizes three types of planes:
1387 DRM_PLANE_TYPE_PRIMARY represents a "main" plane for a CRTC. Primary
1388 planes are the planes operated upon by CRTC modesetting and flipping
1389 operations described in <xref linkend="drm-kms-crtcops"/>.
1392 DRM_PLANE_TYPE_CURSOR represents a "cursor" plane for a CRTC. Cursor
1393 planes are the planes operated upon by the DRM_IOCTL_MODE_CURSOR and
1394 DRM_IOCTL_MODE_CURSOR2 ioctls.
1397 DRM_PLANE_TYPE_OVERLAY represents all non-primary, non-cursor planes.
1398 Some drivers refer to these types of planes as "sprites" internally.
1401 For compatibility with legacy userspace, only overlay planes are made
1402 available to userspace by default. Userspace clients may set the
1403 DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate that
1404 they wish to receive a universal plane list containing all plane types.
1407 <title>Plane Initialization</title>
1409 To create a plane, a KMS drivers allocates and
1410 zeroes an instances of struct <structname>drm_plane</structname>
1411 (possibly as part of a larger structure) and registers it with a call
1412 to <function>drm_universal_plane_init</function>. The function takes a bitmask
1413 of the CRTCs that can be associated with the plane, a pointer to the
1414 plane functions, a list of format supported formats, and the type of
1415 plane (primary, cursor, or overlay) being initialized.
1418 Cursor and overlay planes are optional. All drivers should provide
1419 one primary plane per CRTC (although this requirement may change in
1420 the future); drivers that do not wish to provide special handling for
1421 primary planes may make use of the helper functions described in
1422 <xref linkend="drm-kms-planehelpers"/> to create and register a
1423 primary plane with standard capabilities.
1427 <title>Plane Operations</title>
1430 <synopsis>int (*update_plane)(struct drm_plane *plane, struct drm_crtc *crtc,
1431 struct drm_framebuffer *fb, int crtc_x, int crtc_y,
1432 unsigned int crtc_w, unsigned int crtc_h,
1433 uint32_t src_x, uint32_t src_y,
1434 uint32_t src_w, uint32_t src_h);</synopsis>
1436 Enable and configure the plane to use the given CRTC and frame buffer.
1439 The source rectangle in frame buffer memory coordinates is given by
1440 the <parameter>src_x</parameter>, <parameter>src_y</parameter>,
1441 <parameter>src_w</parameter> and <parameter>src_h</parameter>
1442 parameters (as 16.16 fixed point values). Devices that don't support
1443 subpixel plane coordinates can ignore the fractional part.
1446 The destination rectangle in CRTC coordinates is given by the
1447 <parameter>crtc_x</parameter>, <parameter>crtc_y</parameter>,
1448 <parameter>crtc_w</parameter> and <parameter>crtc_h</parameter>
1449 parameters (as integer values). Devices scale the source rectangle to
1450 the destination rectangle. If scaling is not supported, and the source
1451 rectangle size doesn't match the destination rectangle size, the
1452 driver must return a -<errorname>EINVAL</errorname> error.
1456 <synopsis>int (*disable_plane)(struct drm_plane *plane);</synopsis>
1458 Disable the plane. The DRM core calls this method in response to a
1459 DRM_IOCTL_MODE_SETPLANE ioctl call with the frame buffer ID set to 0.
1460 Disabled planes must not be processed by the CRTC.
1464 <synopsis>void (*destroy)(struct drm_plane *plane);</synopsis>
1466 Destroy the plane when not needed anymore. See
1467 <xref linkend="drm-kms-init"/>.
1474 <title>Encoders (struct <structname>drm_encoder</structname>)</title>
1476 An encoder takes pixel data from a CRTC and converts it to a format
1477 suitable for any attached connectors. On some devices, it may be
1478 possible to have a CRTC send data to more than one encoder. In that
1479 case, both encoders would receive data from the same scanout buffer,
1480 resulting in a "cloned" display configuration across the connectors
1481 attached to each encoder.
1484 <title>Encoder Initialization</title>
1486 As for CRTCs, a KMS driver must create, initialize and register at
1487 least one struct <structname>drm_encoder</structname> instance. The
1488 instance is allocated and zeroed by the driver, possibly as part of a
1492 Drivers must initialize the struct <structname>drm_encoder</structname>
1493 <structfield>possible_crtcs</structfield> and
1494 <structfield>possible_clones</structfield> fields before registering the
1495 encoder. Both fields are bitmasks of respectively the CRTCs that the
1496 encoder can be connected to, and sibling encoders candidate for cloning.
1499 After being initialized, the encoder must be registered with a call to
1500 <function>drm_encoder_init</function>. The function takes a pointer to
1501 the encoder functions and an encoder type. Supported types are
1504 DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A
1507 DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort
1510 DRM_MODE_ENCODER_LVDS for display panels
1513 DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, Component,
1517 DRM_MODE_ENCODER_VIRTUAL for virtual machine displays
1522 Encoders must be attached to a CRTC to be used. DRM drivers leave
1523 encoders unattached at initialization time. Applications (or the fbdev
1524 compatibility layer when implemented) are responsible for attaching the
1525 encoders they want to use to a CRTC.
1529 <title>Encoder Operations</title>
1532 <synopsis>void (*destroy)(struct drm_encoder *encoder);</synopsis>
1534 Called to destroy the encoder when not needed anymore. See
1535 <xref linkend="drm-kms-init"/>.
1539 <synopsis>void (*set_property)(struct drm_plane *plane,
1540 struct drm_property *property, uint64_t value);</synopsis>
1542 Set the value of the given plane property to
1543 <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1544 for more information about properties.
1551 <title>Connectors (struct <structname>drm_connector</structname>)</title>
1553 A connector is the final destination for pixel data on a device, and
1554 usually connects directly to an external display device like a monitor
1555 or laptop panel. A connector can only be attached to one encoder at a
1556 time. The connector is also the structure where information about the
1557 attached display is kept, so it contains fields for display data, EDID
1558 data, DPMS & connection status, and information about modes
1559 supported on the attached displays.
1562 <title>Connector Initialization</title>
1564 Finally a KMS driver must create, initialize, register and attach at
1565 least one struct <structname>drm_connector</structname> instance. The
1566 instance is created as other KMS objects and initialized by setting the
1571 <term><structfield>interlace_allowed</structfield></term>
1573 Whether the connector can handle interlaced modes.
1577 <term><structfield>doublescan_allowed</structfield></term>
1579 Whether the connector can handle doublescan.
1583 <term><structfield>display_info
1584 </structfield></term>
1586 Display information is filled from EDID information when a display
1587 is detected. For non hot-pluggable displays such as flat panels in
1588 embedded systems, the driver should initialize the
1589 <structfield>display_info</structfield>.<structfield>width_mm</structfield>
1591 <structfield>display_info</structfield>.<structfield>height_mm</structfield>
1592 fields with the physical size of the display.
1596 <term id="drm-kms-connector-polled"><structfield>polled</structfield></term>
1598 Connector polling mode, a combination of
1601 <term>DRM_CONNECTOR_POLL_HPD</term>
1603 The connector generates hotplug events and doesn't need to be
1604 periodically polled. The CONNECT and DISCONNECT flags must not
1605 be set together with the HPD flag.
1609 <term>DRM_CONNECTOR_POLL_CONNECT</term>
1611 Periodically poll the connector for connection.
1615 <term>DRM_CONNECTOR_POLL_DISCONNECT</term>
1617 Periodically poll the connector for disconnection.
1621 Set to 0 for connectors that don't support connection status
1627 The connector is then registered with a call to
1628 <function>drm_connector_init</function> with a pointer to the connector
1629 functions and a connector type, and exposed through sysfs with a call to
1630 <function>drm_connector_register</function>.
1633 Supported connector types are
1635 <listitem>DRM_MODE_CONNECTOR_VGA</listitem>
1636 <listitem>DRM_MODE_CONNECTOR_DVII</listitem>
1637 <listitem>DRM_MODE_CONNECTOR_DVID</listitem>
1638 <listitem>DRM_MODE_CONNECTOR_DVIA</listitem>
1639 <listitem>DRM_MODE_CONNECTOR_Composite</listitem>
1640 <listitem>DRM_MODE_CONNECTOR_SVIDEO</listitem>
1641 <listitem>DRM_MODE_CONNECTOR_LVDS</listitem>
1642 <listitem>DRM_MODE_CONNECTOR_Component</listitem>
1643 <listitem>DRM_MODE_CONNECTOR_9PinDIN</listitem>
1644 <listitem>DRM_MODE_CONNECTOR_DisplayPort</listitem>
1645 <listitem>DRM_MODE_CONNECTOR_HDMIA</listitem>
1646 <listitem>DRM_MODE_CONNECTOR_HDMIB</listitem>
1647 <listitem>DRM_MODE_CONNECTOR_TV</listitem>
1648 <listitem>DRM_MODE_CONNECTOR_eDP</listitem>
1649 <listitem>DRM_MODE_CONNECTOR_VIRTUAL</listitem>
1653 Connectors must be attached to an encoder to be used. For devices that
1654 map connectors to encoders 1:1, the connector should be attached at
1655 initialization time with a call to
1656 <function>drm_mode_connector_attach_encoder</function>. The driver must
1657 also set the <structname>drm_connector</structname>
1658 <structfield>encoder</structfield> field to point to the attached
1662 Finally, drivers must initialize the connectors state change detection
1663 with a call to <function>drm_kms_helper_poll_init</function>. If at
1664 least one connector is pollable but can't generate hotplug interrupts
1665 (indicated by the DRM_CONNECTOR_POLL_CONNECT and
1666 DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will
1667 automatically be queued to periodically poll for changes. Connectors
1668 that can generate hotplug interrupts must be marked with the
1669 DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must
1670 call <function>drm_helper_hpd_irq_event</function>. The function will
1671 queue a delayed work to check the state of all connectors, but no
1672 periodic polling will be done.
1676 <title>Connector Operations</title>
1678 Unless otherwise state, all operations are mandatory.
1682 <synopsis>void (*dpms)(struct drm_connector *connector, int mode);</synopsis>
1684 The DPMS operation sets the power state of a connector. The mode
1687 <listitem><para>DRM_MODE_DPMS_ON</para></listitem>
1688 <listitem><para>DRM_MODE_DPMS_STANDBY</para></listitem>
1689 <listitem><para>DRM_MODE_DPMS_SUSPEND</para></listitem>
1690 <listitem><para>DRM_MODE_DPMS_OFF</para></listitem>
1694 In all but DPMS_ON mode the encoder to which the connector is attached
1695 should put the display in low-power mode by driving its signals
1696 appropriately. If more than one connector is attached to the encoder
1697 care should be taken not to change the power state of other displays as
1698 a side effect. Low-power mode should be propagated to the encoders and
1699 CRTCs when all related connectors are put in low-power mode.
1703 <title>Modes</title>
1704 <synopsis>int (*fill_modes)(struct drm_connector *connector, uint32_t max_width,
1705 uint32_t max_height);</synopsis>
1707 Fill the mode list with all supported modes for the connector. If the
1708 <parameter>max_width</parameter> and <parameter>max_height</parameter>
1709 arguments are non-zero, the implementation must ignore all modes wider
1710 than <parameter>max_width</parameter> or higher than
1711 <parameter>max_height</parameter>.
1714 The connector must also fill in this operation its
1715 <structfield>display_info</structfield>
1716 <structfield>width_mm</structfield> and
1717 <structfield>height_mm</structfield> fields with the connected display
1718 physical size in millimeters. The fields should be set to 0 if the value
1719 isn't known or is not applicable (for instance for projector devices).
1723 <title>Connection Status</title>
1725 The connection status is updated through polling or hotplug events when
1726 supported (see <xref linkend="drm-kms-connector-polled"/>). The status
1727 value is reported to userspace through ioctls and must not be used
1728 inside the driver, as it only gets initialized by a call to
1729 <function>drm_mode_getconnector</function> from userspace.
1731 <synopsis>enum drm_connector_status (*detect)(struct drm_connector *connector,
1732 bool force);</synopsis>
1734 Check to see if anything is attached to the connector. The
1735 <parameter>force</parameter> parameter is set to false whilst polling or
1736 to true when checking the connector due to user request.
1737 <parameter>force</parameter> can be used by the driver to avoid
1738 expensive, destructive operations during automated probing.
1741 Return connector_status_connected if something is connected to the
1742 connector, connector_status_disconnected if nothing is connected and
1743 connector_status_unknown if the connection state isn't known.
1746 Drivers should only return connector_status_connected if the connection
1747 status has really been probed as connected. Connectors that can't detect
1748 the connection status, or failed connection status probes, should return
1749 connector_status_unknown.
1753 <title>Miscellaneous</title>
1756 <synopsis>void (*set_property)(struct drm_connector *connector,
1757 struct drm_property *property, uint64_t value);</synopsis>
1759 Set the value of the given connector property to
1760 <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1761 for more information about properties.
1765 <synopsis>void (*destroy)(struct drm_connector *connector);</synopsis>
1767 Destroy the connector when not needed anymore. See
1768 <xref linkend="drm-kms-init"/>.
1776 <title>Cleanup</title>
1778 The DRM core manages its objects' lifetime. When an object is not needed
1779 anymore the core calls its destroy function, which must clean up and
1780 free every resource allocated for the object. Every
1781 <function>drm_*_init</function> call must be matched with a
1782 corresponding <function>drm_*_cleanup</function> call to cleanup CRTCs
1783 (<function>drm_crtc_cleanup</function>), planes
1784 (<function>drm_plane_cleanup</function>), encoders
1785 (<function>drm_encoder_cleanup</function>) and connectors
1786 (<function>drm_connector_cleanup</function>). Furthermore, connectors
1787 that have been added to sysfs must be removed by a call to
1788 <function>drm_connector_unregister</function> before calling
1789 <function>drm_connector_cleanup</function>.
1792 Connectors state change detection must be cleanup up with a call to
1793 <function>drm_kms_helper_poll_fini</function>.
1797 <title>Output discovery and initialization example</title>
1798 <programlisting><![CDATA[
1799 void intel_crt_init(struct drm_device *dev)
1801 struct drm_connector *connector;
1802 struct intel_output *intel_output;
1804 intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL);
1808 connector = &intel_output->base;
1809 drm_connector_init(dev, &intel_output->base,
1810 &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA);
1812 drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs,
1813 DRM_MODE_ENCODER_DAC);
1815 drm_mode_connector_attach_encoder(&intel_output->base,
1816 &intel_output->enc);
1818 /* Set up the DDC bus. */
1819 intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A");
1820 if (!intel_output->ddc_bus) {
1821 dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration "
1826 intel_output->type = INTEL_OUTPUT_ANALOG;
1827 connector->interlace_allowed = 0;
1828 connector->doublescan_allowed = 0;
1830 drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs);
1831 drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs);
1833 drm_connector_register(connector);
1834 }]]></programlisting>
1836 In the example above (taken from the i915 driver), a CRTC, connector and
1837 encoder combination is created. A device-specific i2c bus is also
1838 created for fetching EDID data and performing monitor detection. Once
1839 the process is complete, the new connector is registered with sysfs to
1840 make its properties available to applications.
1844 <title>KMS API Functions</title>
1845 !Edrivers/gpu/drm/drm_crtc.c
1848 <title>KMS Data Structures</title>
1849 !Iinclude/drm/drm_crtc.h
1852 <title>KMS Locking</title>
1853 !Pdrivers/gpu/drm/drm_modeset_lock.c kms locking
1854 !Iinclude/drm/drm_modeset_lock.h
1855 !Edrivers/gpu/drm/drm_modeset_lock.c
1859 <!-- Internals: kms helper functions -->
1862 <title>Mode Setting Helper Functions</title>
1864 The plane, CRTC, encoder and connector functions provided by the drivers
1865 implement the DRM API. They're called by the DRM core and ioctl handlers
1866 to handle device state changes and configuration request. As implementing
1867 those functions often requires logic not specific to drivers, mid-layer
1868 helper functions are available to avoid duplicating boilerplate code.
1871 The DRM core contains one mid-layer implementation. The mid-layer provides
1872 implementations of several plane, CRTC, encoder and connector functions
1873 (called from the top of the mid-layer) that pre-process requests and call
1874 lower-level functions provided by the driver (at the bottom of the
1875 mid-layer). For instance, the
1876 <function>drm_crtc_helper_set_config</function> function can be used to
1877 fill the struct <structname>drm_crtc_funcs</structname>
1878 <structfield>set_config</structfield> field. When called, it will split
1879 the <methodname>set_config</methodname> operation in smaller, simpler
1880 operations and call the driver to handle them.
1883 To use the mid-layer, drivers call <function>drm_crtc_helper_add</function>,
1884 <function>drm_encoder_helper_add</function> and
1885 <function>drm_connector_helper_add</function> functions to install their
1886 mid-layer bottom operations handlers, and fill the
1887 <structname>drm_crtc_funcs</structname>,
1888 <structname>drm_encoder_funcs</structname> and
1889 <structname>drm_connector_funcs</structname> structures with pointers to
1890 the mid-layer top API functions. Installing the mid-layer bottom operation
1891 handlers is best done right after registering the corresponding KMS object.
1894 The mid-layer is not split between CRTC, encoder and connector operations.
1895 To use it, a driver must provide bottom functions for all of the three KMS
1899 <title>Helper Functions</title>
1902 <synopsis>int drm_crtc_helper_set_config(struct drm_mode_set *set);</synopsis>
1904 The <function>drm_crtc_helper_set_config</function> helper function
1905 is a CRTC <methodname>set_config</methodname> implementation. It
1906 first tries to locate the best encoder for each connector by calling
1907 the connector <methodname>best_encoder</methodname> helper
1911 After locating the appropriate encoders, the helper function will
1912 call the <methodname>mode_fixup</methodname> encoder and CRTC helper
1913 operations to adjust the requested mode, or reject it completely in
1914 which case an error will be returned to the application. If the new
1915 configuration after mode adjustment is identical to the current
1916 configuration the helper function will return without performing any
1920 If the adjusted mode is identical to the current mode but changes to
1921 the frame buffer need to be applied, the
1922 <function>drm_crtc_helper_set_config</function> function will call
1923 the CRTC <methodname>mode_set_base</methodname> helper operation. If
1924 the adjusted mode differs from the current mode, or if the
1925 <methodname>mode_set_base</methodname> helper operation is not
1926 provided, the helper function performs a full mode set sequence by
1927 calling the <methodname>prepare</methodname>,
1928 <methodname>mode_set</methodname> and
1929 <methodname>commit</methodname> CRTC and encoder helper operations,
1934 <synopsis>void drm_helper_connector_dpms(struct drm_connector *connector, int mode);</synopsis>
1936 The <function>drm_helper_connector_dpms</function> helper function
1937 is a connector <methodname>dpms</methodname> implementation that
1938 tracks power state of connectors. To use the function, drivers must
1939 provide <methodname>dpms</methodname> helper operations for CRTCs
1940 and encoders to apply the DPMS state to the device.
1943 The mid-layer doesn't track the power state of CRTCs and encoders.
1944 The <methodname>dpms</methodname> helper operations can thus be
1945 called with a mode identical to the currently active mode.
1949 <synopsis>int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
1950 uint32_t maxX, uint32_t maxY);</synopsis>
1952 The <function>drm_helper_probe_single_connector_modes</function> helper
1953 function is a connector <methodname>fill_modes</methodname>
1954 implementation that updates the connection status for the connector
1955 and then retrieves a list of modes by calling the connector
1956 <methodname>get_modes</methodname> helper operation.
1959 If the helper operation returns no mode, and if the connector status
1960 is connector_status_connected, standard VESA DMT modes up to
1961 1024x768 are automatically added to the modes list by a call to
1962 <function>drm_add_modes_noedid</function>.
1965 The function then filters out modes larger than
1966 <parameter>max_width</parameter> and <parameter>max_height</parameter>
1967 if specified. It finally calls the optional connector
1968 <methodname>mode_valid</methodname> helper operation for each mode in
1969 the probed list to check whether the mode is valid for the connector.
1975 <title>CRTC Helper Operations</title>
1977 <listitem id="drm-helper-crtc-mode-fixup">
1978 <synopsis>bool (*mode_fixup)(struct drm_crtc *crtc,
1979 const struct drm_display_mode *mode,
1980 struct drm_display_mode *adjusted_mode);</synopsis>
1982 Let CRTCs adjust the requested mode or reject it completely. This
1983 operation returns true if the mode is accepted (possibly after being
1984 adjusted) or false if it is rejected.
1987 The <methodname>mode_fixup</methodname> operation should reject the
1988 mode if it can't reasonably use it. The definition of "reasonable"
1989 is currently fuzzy in this context. One possible behaviour would be
1990 to set the adjusted mode to the panel timings when a fixed-mode
1991 panel is used with hardware capable of scaling. Another behaviour
1992 would be to accept any input mode and adjust it to the closest mode
1993 supported by the hardware (FIXME: This needs to be clarified).
1997 <synopsis>int (*mode_set_base)(struct drm_crtc *crtc, int x, int y,
1998 struct drm_framebuffer *old_fb)</synopsis>
2000 Move the CRTC on the current frame buffer (stored in
2001 <literal>crtc->fb</literal>) to position (x,y). Any of the frame
2002 buffer, x position or y position may have been modified.
2005 This helper operation is optional. If not provided, the
2006 <function>drm_crtc_helper_set_config</function> function will fall
2007 back to the <methodname>mode_set</methodname> helper operation.
2010 FIXME: Why are x and y passed as arguments, as they can be accessed
2011 through <literal>crtc->x</literal> and
2012 <literal>crtc->y</literal>?
2016 <synopsis>void (*prepare)(struct drm_crtc *crtc);</synopsis>
2018 Prepare the CRTC for mode setting. This operation is called after
2019 validating the requested mode. Drivers use it to perform
2020 device-specific operations required before setting the new mode.
2024 <synopsis>int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,
2025 struct drm_display_mode *adjusted_mode, int x, int y,
2026 struct drm_framebuffer *old_fb);</synopsis>
2028 Set a new mode, position and frame buffer. Depending on the device
2029 requirements, the mode can be stored internally by the driver and
2030 applied in the <methodname>commit</methodname> operation, or
2031 programmed to the hardware immediately.
2034 The <methodname>mode_set</methodname> operation returns 0 on success
2035 or a negative error code if an error occurs.
2039 <synopsis>void (*commit)(struct drm_crtc *crtc);</synopsis>
2041 Commit a mode. This operation is called after setting the new mode.
2042 Upon return the device must use the new mode and be fully
2049 <title>Encoder Helper Operations</title>
2052 <synopsis>bool (*mode_fixup)(struct drm_encoder *encoder,
2053 const struct drm_display_mode *mode,
2054 struct drm_display_mode *adjusted_mode);</synopsis>
2056 Let encoders adjust the requested mode or reject it completely. This
2057 operation returns true if the mode is accepted (possibly after being
2058 adjusted) or false if it is rejected. See the
2059 <link linkend="drm-helper-crtc-mode-fixup">mode_fixup CRTC helper
2060 operation</link> for an explanation of the allowed adjustments.
2064 <synopsis>void (*prepare)(struct drm_encoder *encoder);</synopsis>
2066 Prepare the encoder for mode setting. This operation is called after
2067 validating the requested mode. Drivers use it to perform
2068 device-specific operations required before setting the new mode.
2072 <synopsis>void (*mode_set)(struct drm_encoder *encoder,
2073 struct drm_display_mode *mode,
2074 struct drm_display_mode *adjusted_mode);</synopsis>
2076 Set a new mode. Depending on the device requirements, the mode can
2077 be stored internally by the driver and applied in the
2078 <methodname>commit</methodname> operation, or programmed to the
2079 hardware immediately.
2083 <synopsis>void (*commit)(struct drm_encoder *encoder);</synopsis>
2085 Commit a mode. This operation is called after setting the new mode.
2086 Upon return the device must use the new mode and be fully
2093 <title>Connector Helper Operations</title>
2096 <synopsis>struct drm_encoder *(*best_encoder)(struct drm_connector *connector);</synopsis>
2098 Return a pointer to the best encoder for the connecter. Device that
2099 map connectors to encoders 1:1 simply return the pointer to the
2100 associated encoder. This operation is mandatory.
2104 <synopsis>int (*get_modes)(struct drm_connector *connector);</synopsis>
2106 Fill the connector's <structfield>probed_modes</structfield> list
2107 by parsing EDID data with <function>drm_add_edid_modes</function>,
2108 adding standard VESA DMT modes with <function>drm_add_modes_noedid</function>,
2109 or calling <function>drm_mode_probed_add</function> directly for every
2110 supported mode and return the number of modes it has detected. This
2111 operation is mandatory.
2114 Note that the caller function will automatically add standard VESA
2115 DMT modes up to 1024x768 if the <methodname>get_modes</methodname>
2116 helper operation returns no mode and if the connector status is
2117 connector_status_connected. There is no need to call
2118 <function>drm_add_edid_modes</function> manually in that case.
2121 When adding modes manually the driver creates each mode with a call to
2122 <function>drm_mode_create</function> and must fill the following fields.
2125 <synopsis>__u32 type;</synopsis>
2127 Mode type bitmask, a combination of
2130 <term>DRM_MODE_TYPE_BUILTIN</term>
2131 <listitem><para>not used?</para></listitem>
2134 <term>DRM_MODE_TYPE_CLOCK_C</term>
2135 <listitem><para>not used?</para></listitem>
2138 <term>DRM_MODE_TYPE_CRTC_C</term>
2139 <listitem><para>not used?</para></listitem>
2143 DRM_MODE_TYPE_PREFERRED - The preferred mode for the connector
2146 <para>not used?</para>
2150 <term>DRM_MODE_TYPE_DEFAULT</term>
2151 <listitem><para>not used?</para></listitem>
2154 <term>DRM_MODE_TYPE_USERDEF</term>
2155 <listitem><para>not used?</para></listitem>
2158 <term>DRM_MODE_TYPE_DRIVER</term>
2161 The mode has been created by the driver (as opposed to
2162 to user-created modes).
2167 Drivers must set the DRM_MODE_TYPE_DRIVER bit for all modes they
2168 create, and set the DRM_MODE_TYPE_PREFERRED bit for the preferred
2173 <synopsis>__u32 clock;</synopsis>
2174 <para>Pixel clock frequency in kHz unit</para>
2177 <synopsis>__u16 hdisplay, hsync_start, hsync_end, htotal;
2178 __u16 vdisplay, vsync_start, vsync_end, vtotal;</synopsis>
2179 <para>Horizontal and vertical timing information</para>
2181 Active Front Sync Back
2183 <-----------------------><----------------><-------------><-------------->
2185 //////////////////////|
2186 ////////////////////// |
2187 ////////////////////// |.................. ................
2190 <----- [hv]display ----->
2191 <------------- [hv]sync_start ------------>
2192 <--------------------- [hv]sync_end --------------------->
2193 <-------------------------------- [hv]total ----------------------------->
2197 <synopsis>__u16 hskew;
2198 __u16 vscan;</synopsis>
2199 <para>Unknown</para>
2202 <synopsis>__u32 flags;</synopsis>
2204 Mode flags, a combination of
2207 <term>DRM_MODE_FLAG_PHSYNC</term>
2209 Horizontal sync is active high
2213 <term>DRM_MODE_FLAG_NHSYNC</term>
2215 Horizontal sync is active low
2219 <term>DRM_MODE_FLAG_PVSYNC</term>
2221 Vertical sync is active high
2225 <term>DRM_MODE_FLAG_NVSYNC</term>
2227 Vertical sync is active low
2231 <term>DRM_MODE_FLAG_INTERLACE</term>
2237 <term>DRM_MODE_FLAG_DBLSCAN</term>
2239 Mode uses doublescan
2243 <term>DRM_MODE_FLAG_CSYNC</term>
2245 Mode uses composite sync
2249 <term>DRM_MODE_FLAG_PCSYNC</term>
2251 Composite sync is active high
2255 <term>DRM_MODE_FLAG_NCSYNC</term>
2257 Composite sync is active low
2261 <term>DRM_MODE_FLAG_HSKEW</term>
2263 hskew provided (not used?)
2267 <term>DRM_MODE_FLAG_BCAST</term>
2273 <term>DRM_MODE_FLAG_PIXMUX</term>
2279 <term>DRM_MODE_FLAG_DBLCLK</term>
2285 <term>DRM_MODE_FLAG_CLKDIV2</term>
2293 Note that modes marked with the INTERLACE or DBLSCAN flags will be
2295 <function>drm_helper_probe_single_connector_modes</function> if
2296 the connector's <structfield>interlace_allowed</structfield> or
2297 <structfield>doublescan_allowed</structfield> field is set to 0.
2301 <synopsis>char name[DRM_DISPLAY_MODE_LEN];</synopsis>
2303 Mode name. The driver must call
2304 <function>drm_mode_set_name</function> to fill the mode name from
2305 <structfield>hdisplay</structfield>,
2306 <structfield>vdisplay</structfield> and interlace flag after
2307 filling the corresponding fields.
2313 The <structfield>vrefresh</structfield> value is computed by
2314 <function>drm_helper_probe_single_connector_modes</function>.
2317 When parsing EDID data, <function>drm_add_edid_modes</function> fills the
2318 connector <structfield>display_info</structfield>
2319 <structfield>width_mm</structfield> and
2320 <structfield>height_mm</structfield> fields. When creating modes
2321 manually the <methodname>get_modes</methodname> helper operation must
2322 set the <structfield>display_info</structfield>
2323 <structfield>width_mm</structfield> and
2324 <structfield>height_mm</structfield> fields if they haven't been set
2325 already (for instance at initialization time when a fixed-size panel is
2326 attached to the connector). The mode <structfield>width_mm</structfield>
2327 and <structfield>height_mm</structfield> fields are only used internally
2328 during EDID parsing and should not be set when creating modes manually.
2332 <synopsis>int (*mode_valid)(struct drm_connector *connector,
2333 struct drm_display_mode *mode);</synopsis>
2335 Verify whether a mode is valid for the connector. Return MODE_OK for
2336 supported modes and one of the enum drm_mode_status values (MODE_*)
2337 for unsupported modes. This operation is optional.
2340 As the mode rejection reason is currently not used beside for
2341 immediately removing the unsupported mode, an implementation can
2342 return MODE_BAD regardless of the exact reason why the mode is not
2346 Note that the <methodname>mode_valid</methodname> helper operation is
2347 only called for modes detected by the device, and
2348 <emphasis>not</emphasis> for modes set by the user through the CRTC
2349 <methodname>set_config</methodname> operation.
2355 <title>Atomic Modeset Helper Functions Reference</title>
2357 <title>Overview</title>
2358 !Pdrivers/gpu/drm/drm_atomic_helper.c overview
2361 <title>Implementing Asynchronous Atomic Commit</title>
2362 !Pdrivers/gpu/drm/drm_atomic_helper.c implementing async commit
2365 <title>Atomic State Reset and Initialization</title>
2366 !Pdrivers/gpu/drm/drm_atomic_helper.c atomic state reset and initialization
2368 !Iinclude/drm/drm_atomic_helper.h
2369 !Edrivers/gpu/drm/drm_atomic_helper.c
2372 <title>Modeset Helper Functions Reference</title>
2373 !Iinclude/drm/drm_crtc_helper.h
2374 !Edrivers/gpu/drm/drm_crtc_helper.c
2375 !Pdrivers/gpu/drm/drm_crtc_helper.c overview
2378 <title>Output Probing Helper Functions Reference</title>
2379 !Pdrivers/gpu/drm/drm_probe_helper.c output probing helper overview
2380 !Edrivers/gpu/drm/drm_probe_helper.c
2383 <title>fbdev Helper Functions Reference</title>
2384 !Pdrivers/gpu/drm/drm_fb_helper.c fbdev helpers
2385 !Edrivers/gpu/drm/drm_fb_helper.c
2386 !Iinclude/drm/drm_fb_helper.h
2389 <title>Display Port Helper Functions Reference</title>
2390 !Pdrivers/gpu/drm/drm_dp_helper.c dp helpers
2391 !Iinclude/drm/drm_dp_helper.h
2392 !Edrivers/gpu/drm/drm_dp_helper.c
2395 <title>Display Port MST Helper Functions Reference</title>
2396 !Pdrivers/gpu/drm/drm_dp_mst_topology.c dp mst helper
2397 !Iinclude/drm/drm_dp_mst_helper.h
2398 !Edrivers/gpu/drm/drm_dp_mst_topology.c
2401 <title>MIPI DSI Helper Functions Reference</title>
2402 !Pdrivers/gpu/drm/drm_mipi_dsi.c dsi helpers
2403 !Iinclude/drm/drm_mipi_dsi.h
2404 !Edrivers/gpu/drm/drm_mipi_dsi.c
2407 <title>EDID Helper Functions Reference</title>
2408 !Edrivers/gpu/drm/drm_edid.c
2411 <title>Rectangle Utilities Reference</title>
2412 !Pinclude/drm/drm_rect.h rect utils
2413 !Iinclude/drm/drm_rect.h
2414 !Edrivers/gpu/drm/drm_rect.c
2417 <title>Flip-work Helper Reference</title>
2418 !Pinclude/drm/drm_flip_work.h flip utils
2419 !Iinclude/drm/drm_flip_work.h
2420 !Edrivers/gpu/drm/drm_flip_work.c
2423 <title>HDMI Infoframes Helper Reference</title>
2425 Strictly speaking this is not a DRM helper library but generally useable
2426 by any driver interfacing with HDMI outputs like v4l or alsa drivers.
2427 But it nicely fits into the overall topic of mode setting helper
2428 libraries and hence is also included here.
2430 !Iinclude/linux/hdmi.h
2431 !Edrivers/video/hdmi.c
2434 <title id="drm-kms-planehelpers">Plane Helper Reference</title>
2435 !Edrivers/gpu/drm/drm_plane_helper.c
2436 !Pdrivers/gpu/drm/drm_plane_helper.c overview
2439 <title>Tile group</title>
2440 !Pdrivers/gpu/drm/drm_crtc.c Tile group
2444 <!-- Internals: kms properties -->
2446 <sect1 id="drm-kms-properties">
2447 <title>KMS Properties</title>
2449 Drivers may need to expose additional parameters to applications than
2450 those described in the previous sections. KMS supports attaching
2451 properties to CRTCs, connectors and planes and offers a userspace API to
2452 list, get and set the property values.
2455 Properties are identified by a name that uniquely defines the property
2456 purpose, and store an associated value. For all property types except blob
2457 properties the value is a 64-bit unsigned integer.
2460 KMS differentiates between properties and property instances. Drivers
2461 first create properties and then create and associate individual instances
2462 of those properties to objects. A property can be instantiated multiple
2463 times and associated with different objects. Values are stored in property
2464 instances, and all other property information are stored in the property
2465 and shared between all instances of the property.
2468 Every property is created with a type that influences how the KMS core
2469 handles the property. Supported property types are
2472 <term>DRM_MODE_PROP_RANGE</term>
2473 <listitem><para>Range properties report their minimum and maximum
2474 admissible values. The KMS core verifies that values set by
2475 application fit in that range.</para></listitem>
2478 <term>DRM_MODE_PROP_ENUM</term>
2479 <listitem><para>Enumerated properties take a numerical value that
2480 ranges from 0 to the number of enumerated values defined by the
2481 property minus one, and associate a free-formed string name to each
2482 value. Applications can retrieve the list of defined value-name pairs
2483 and use the numerical value to get and set property instance values.
2487 <term>DRM_MODE_PROP_BITMASK</term>
2488 <listitem><para>Bitmask properties are enumeration properties that
2489 additionally restrict all enumerated values to the 0..63 range.
2490 Bitmask property instance values combine one or more of the
2491 enumerated bits defined by the property.</para></listitem>
2494 <term>DRM_MODE_PROP_BLOB</term>
2495 <listitem><para>Blob properties store a binary blob without any format
2496 restriction. The binary blobs are created as KMS standalone objects,
2497 and blob property instance values store the ID of their associated
2499 <para>Blob properties are only used for the connector EDID property
2500 and cannot be created by drivers.</para></listitem>
2505 To create a property drivers call one of the following functions depending
2506 on the property type. All property creation functions take property flags
2507 and name, as well as type-specific arguments.
2510 <synopsis>struct drm_property *drm_property_create_range(struct drm_device *dev, int flags,
2512 uint64_t min, uint64_t max);</synopsis>
2513 <para>Create a range property with the given minimum and maximum
2517 <synopsis>struct drm_property *drm_property_create_enum(struct drm_device *dev, int flags,
2519 const struct drm_prop_enum_list *props,
2520 int num_values);</synopsis>
2521 <para>Create an enumerated property. The <parameter>props</parameter>
2522 argument points to an array of <parameter>num_values</parameter>
2523 value-name pairs.</para>
2526 <synopsis>struct drm_property *drm_property_create_bitmask(struct drm_device *dev,
2527 int flags, const char *name,
2528 const struct drm_prop_enum_list *props,
2529 int num_values);</synopsis>
2530 <para>Create a bitmask property. The <parameter>props</parameter>
2531 argument points to an array of <parameter>num_values</parameter>
2532 value-name pairs.</para>
2537 Properties can additionally be created as immutable, in which case they
2538 will be read-only for applications but can be modified by the driver. To
2539 create an immutable property drivers must set the DRM_MODE_PROP_IMMUTABLE
2540 flag at property creation time.
2543 When no array of value-name pairs is readily available at property
2544 creation time for enumerated or range properties, drivers can create
2545 the property using the <function>drm_property_create</function> function
2546 and manually add enumeration value-name pairs by calling the
2547 <function>drm_property_add_enum</function> function. Care must be taken to
2548 properly specify the property type through the <parameter>flags</parameter>
2552 After creating properties drivers can attach property instances to CRTC,
2553 connector and plane objects by calling the
2554 <function>drm_object_attach_property</function>. The function takes a
2555 pointer to the target object, a pointer to the previously created property
2556 and an initial instance value.
2559 <title>Existing KMS Properties</title>
2561 The following table gives description of drm properties exposed by various
2564 <table border="1" cellpadding="0" cellspacing="0">
2566 <tr style="font-weight: bold;">
2567 <td valign="top" >Owner Module/Drivers</td>
2568 <td valign="top" >Group</td>
2569 <td valign="top" >Property Name</td>
2570 <td valign="top" >Type</td>
2571 <td valign="top" >Property Values</td>
2572 <td valign="top" >Object attached</td>
2573 <td valign="top" >Description/Restrictions</td>
2576 <td rowspan="36" valign="top" >DRM</td>
2577 <td rowspan="5" valign="top" >Connector</td>
2578 <td valign="top" >“EDID”</td>
2579 <td valign="top" >BLOB | IMMUTABLE</td>
2580 <td valign="top" >0</td>
2581 <td valign="top" >Connector</td>
2582 <td valign="top" >Contains id of edid blob ptr object.</td>
2585 <td valign="top" >“DPMS”</td>
2586 <td valign="top" >ENUM</td>
2587 <td valign="top" >{ “On”, “Standby”, “Suspend”, “Off” }</td>
2588 <td valign="top" >Connector</td>
2589 <td valign="top" >Contains DPMS operation mode value.</td>
2592 <td valign="top" >“PATH”</td>
2593 <td valign="top" >BLOB | IMMUTABLE</td>
2594 <td valign="top" >0</td>
2595 <td valign="top" >Connector</td>
2596 <td valign="top" >Contains topology path to a connector.</td>
2599 <td valign="top" >“TILE”</td>
2600 <td valign="top" >BLOB | IMMUTABLE</td>
2601 <td valign="top" >0</td>
2602 <td valign="top" >Connector</td>
2603 <td valign="top" >Contains tiling information for a connector.</td>
2606 <td valign="top" >“CRTC_ID”</td>
2607 <td valign="top" >OBJECT</td>
2608 <td valign="top" >DRM_MODE_OBJECT_CRTC</td>
2609 <td valign="top" >Connector</td>
2610 <td valign="top" >CRTC that connector is attached to (atomic)</td>
2613 <td rowspan="11" valign="top" >Plane</td>
2614 <td valign="top" >“type”</td>
2615 <td valign="top" >ENUM | IMMUTABLE</td>
2616 <td valign="top" >{ "Overlay", "Primary", "Cursor" }</td>
2617 <td valign="top" >Plane</td>
2618 <td valign="top" >Plane type</td>
2621 <td valign="top" >“SRC_X”</td>
2622 <td valign="top" >RANGE</td>
2623 <td valign="top" >Min=0, Max=UINT_MAX</td>
2624 <td valign="top" >Plane</td>
2625 <td valign="top" >Scanout source x coordinate in 16.16 fixed point (atomic)</td>
2628 <td valign="top" >“SRC_Y”</td>
2629 <td valign="top" >RANGE</td>
2630 <td valign="top" >Min=0, Max=UINT_MAX</td>
2631 <td valign="top" >Plane</td>
2632 <td valign="top" >Scanout source y coordinate in 16.16 fixed point (atomic)</td>
2635 <td valign="top" >“SRC_W”</td>
2636 <td valign="top" >RANGE</td>
2637 <td valign="top" >Min=0, Max=UINT_MAX</td>
2638 <td valign="top" >Plane</td>
2639 <td valign="top" >Scanout source width in 16.16 fixed point (atomic)</td>
2642 <td valign="top" >“SRC_H”</td>
2643 <td valign="top" >RANGE</td>
2644 <td valign="top" >Min=0, Max=UINT_MAX</td>
2645 <td valign="top" >Plane</td>
2646 <td valign="top" >Scanout source height in 16.16 fixed point (atomic)</td>
2649 <td valign="top" >“CRTC_X”</td>
2650 <td valign="top" >SIGNED_RANGE</td>
2651 <td valign="top" >Min=INT_MIN, Max=INT_MAX</td>
2652 <td valign="top" >Plane</td>
2653 <td valign="top" >Scanout CRTC (destination) x coordinate (atomic)</td>
2656 <td valign="top" >“CRTC_Y”</td>
2657 <td valign="top" >SIGNED_RANGE</td>
2658 <td valign="top" >Min=INT_MIN, Max=INT_MAX</td>
2659 <td valign="top" >Plane</td>
2660 <td valign="top" >Scanout CRTC (destination) y coordinate (atomic)</td>
2663 <td valign="top" >“CRTC_W”</td>
2664 <td valign="top" >RANGE</td>
2665 <td valign="top" >Min=0, Max=UINT_MAX</td>
2666 <td valign="top" >Plane</td>
2667 <td valign="top" >Scanout CRTC (destination) width (atomic)</td>
2670 <td valign="top" >“CRTC_H”</td>
2671 <td valign="top" >RANGE</td>
2672 <td valign="top" >Min=0, Max=UINT_MAX</td>
2673 <td valign="top" >Plane</td>
2674 <td valign="top" >Scanout CRTC (destination) height (atomic)</td>
2677 <td valign="top" >“FB_ID”</td>
2678 <td valign="top" >OBJECT</td>
2679 <td valign="top" >DRM_MODE_OBJECT_FB</td>
2680 <td valign="top" >Plane</td>
2681 <td valign="top" >Scanout framebuffer (atomic)</td>
2684 <td valign="top" >“CRTC_ID”</td>
2685 <td valign="top" >OBJECT</td>
2686 <td valign="top" >DRM_MODE_OBJECT_CRTC</td>
2687 <td valign="top" >Plane</td>
2688 <td valign="top" >CRTC that plane is attached to (atomic)</td>
2691 <td rowspan="2" valign="top" >DVI-I</td>
2692 <td valign="top" >“subconnector”</td>
2693 <td valign="top" >ENUM</td>
2694 <td valign="top" >{ “Unknown”, “DVI-D”, “DVI-A” }</td>
2695 <td valign="top" >Connector</td>
2696 <td valign="top" >TBD</td>
2699 <td valign="top" >“select subconnector”</td>
2700 <td valign="top" >ENUM</td>
2701 <td valign="top" >{ “Automatic”, “DVI-D”, “DVI-A” }</td>
2702 <td valign="top" >Connector</td>
2703 <td valign="top" >TBD</td>
2706 <td rowspan="13" valign="top" >TV</td>
2707 <td valign="top" >“subconnector”</td>
2708 <td valign="top" >ENUM</td>
2709 <td valign="top" >{ "Unknown", "Composite", "SVIDEO", "Component", "SCART" }</td>
2710 <td valign="top" >Connector</td>
2711 <td valign="top" >TBD</td>
2714 <td valign="top" >“select subconnector”</td>
2715 <td valign="top" >ENUM</td>
2716 <td valign="top" >{ "Automatic", "Composite", "SVIDEO", "Component", "SCART" }</td>
2717 <td valign="top" >Connector</td>
2718 <td valign="top" >TBD</td>
2721 <td valign="top" >“mode”</td>
2722 <td valign="top" >ENUM</td>
2723 <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2724 <td valign="top" >Connector</td>
2725 <td valign="top" >TBD</td>
2728 <td valign="top" >“left margin”</td>
2729 <td valign="top" >RANGE</td>
2730 <td valign="top" >Min=0, Max=100</td>
2731 <td valign="top" >Connector</td>
2732 <td valign="top" >TBD</td>
2735 <td valign="top" >“right margin”</td>
2736 <td valign="top" >RANGE</td>
2737 <td valign="top" >Min=0, Max=100</td>
2738 <td valign="top" >Connector</td>
2739 <td valign="top" >TBD</td>
2742 <td valign="top" >“top margin”</td>
2743 <td valign="top" >RANGE</td>
2744 <td valign="top" >Min=0, Max=100</td>
2745 <td valign="top" >Connector</td>
2746 <td valign="top" >TBD</td>
2749 <td valign="top" >“bottom margin”</td>
2750 <td valign="top" >RANGE</td>
2751 <td valign="top" >Min=0, Max=100</td>
2752 <td valign="top" >Connector</td>
2753 <td valign="top" >TBD</td>
2756 <td valign="top" >“brightness”</td>
2757 <td valign="top" >RANGE</td>
2758 <td valign="top" >Min=0, Max=100</td>
2759 <td valign="top" >Connector</td>
2760 <td valign="top" >TBD</td>
2763 <td valign="top" >“contrast”</td>
2764 <td valign="top" >RANGE</td>
2765 <td valign="top" >Min=0, Max=100</td>
2766 <td valign="top" >Connector</td>
2767 <td valign="top" >TBD</td>
2770 <td valign="top" >“flicker reduction”</td>
2771 <td valign="top" >RANGE</td>
2772 <td valign="top" >Min=0, Max=100</td>
2773 <td valign="top" >Connector</td>
2774 <td valign="top" >TBD</td>
2777 <td valign="top" >“overscan”</td>
2778 <td valign="top" >RANGE</td>
2779 <td valign="top" >Min=0, Max=100</td>
2780 <td valign="top" >Connector</td>
2781 <td valign="top" >TBD</td>
2784 <td valign="top" >“saturation”</td>
2785 <td valign="top" >RANGE</td>
2786 <td valign="top" >Min=0, Max=100</td>
2787 <td valign="top" >Connector</td>
2788 <td valign="top" >TBD</td>
2791 <td valign="top" >“hue”</td>
2792 <td valign="top" >RANGE</td>
2793 <td valign="top" >Min=0, Max=100</td>
2794 <td valign="top" >Connector</td>
2795 <td valign="top" >TBD</td>
2798 <td rowspan="2" valign="top" >Virtual GPU</td>
2799 <td valign="top" >“suggested X”</td>
2800 <td valign="top" >RANGE</td>
2801 <td valign="top" >Min=0, Max=0xffffffff</td>
2802 <td valign="top" >Connector</td>
2803 <td valign="top" >property to suggest an X offset for a connector</td>
2806 <td valign="top" >“suggested Y”</td>
2807 <td valign="top" >RANGE</td>
2808 <td valign="top" >Min=0, Max=0xffffffff</td>
2809 <td valign="top" >Connector</td>
2810 <td valign="top" >property to suggest an Y offset for a connector</td>
2813 <td rowspan="3" valign="top" >Optional</td>
2814 <td valign="top" >“scaling mode”</td>
2815 <td valign="top" >ENUM</td>
2816 <td valign="top" >{ "None", "Full", "Center", "Full aspect" }</td>
2817 <td valign="top" >Connector</td>
2818 <td valign="top" >TBD</td>
2821 <td valign="top" >"aspect ratio"</td>
2822 <td valign="top" >ENUM</td>
2823 <td valign="top" >{ "None", "4:3", "16:9" }</td>
2824 <td valign="top" >Connector</td>
2825 <td valign="top" >DRM property to set aspect ratio from user space app.
2826 This enum is made generic to allow addition of custom aspect
2830 <td valign="top" >“dirty”</td>
2831 <td valign="top" >ENUM | IMMUTABLE</td>
2832 <td valign="top" >{ "Off", "On", "Annotate" }</td>
2833 <td valign="top" >Connector</td>
2834 <td valign="top" >TBD</td>
2837 <td rowspan="21" valign="top" >i915</td>
2838 <td rowspan="2" valign="top" >Generic</td>
2839 <td valign="top" >"Broadcast RGB"</td>
2840 <td valign="top" >ENUM</td>
2841 <td valign="top" >{ "Automatic", "Full", "Limited 16:235" }</td>
2842 <td valign="top" >Connector</td>
2843 <td valign="top" >TBD</td>
2846 <td valign="top" >“audio”</td>
2847 <td valign="top" >ENUM</td>
2848 <td valign="top" >{ "force-dvi", "off", "auto", "on" }</td>
2849 <td valign="top" >Connector</td>
2850 <td valign="top" >TBD</td>
2853 <td rowspan="1" valign="top" >Plane</td>
2854 <td valign="top" >“rotation”</td>
2855 <td valign="top" >BITMASK</td>
2856 <td valign="top" >{ 0, "rotate-0" }, { 2, "rotate-180" }</td>
2857 <td valign="top" >Plane</td>
2858 <td valign="top" >TBD</td>
2861 <td rowspan="17" valign="top" >SDVO-TV</td>
2862 <td valign="top" >“mode”</td>
2863 <td valign="top" >ENUM</td>
2864 <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2865 <td valign="top" >Connector</td>
2866 <td valign="top" >TBD</td>
2869 <td valign="top" >"left_margin"</td>
2870 <td valign="top" >RANGE</td>
2871 <td valign="top" >Min=0, Max= SDVO dependent</td>
2872 <td valign="top" >Connector</td>
2873 <td valign="top" >TBD</td>
2876 <td valign="top" >"right_margin"</td>
2877 <td valign="top" >RANGE</td>
2878 <td valign="top" >Min=0, Max= SDVO dependent</td>
2879 <td valign="top" >Connector</td>
2880 <td valign="top" >TBD</td>
2883 <td valign="top" >"top_margin"</td>
2884 <td valign="top" >RANGE</td>
2885 <td valign="top" >Min=0, Max= SDVO dependent</td>
2886 <td valign="top" >Connector</td>
2887 <td valign="top" >TBD</td>
2890 <td valign="top" >"bottom_margin"</td>
2891 <td valign="top" >RANGE</td>
2892 <td valign="top" >Min=0, Max= SDVO dependent</td>
2893 <td valign="top" >Connector</td>
2894 <td valign="top" >TBD</td>
2897 <td valign="top" >“hpos”</td>
2898 <td valign="top" >RANGE</td>
2899 <td valign="top" >Min=0, Max= SDVO dependent</td>
2900 <td valign="top" >Connector</td>
2901 <td valign="top" >TBD</td>
2904 <td valign="top" >“vpos”</td>
2905 <td valign="top" >RANGE</td>
2906 <td valign="top" >Min=0, Max= SDVO dependent</td>
2907 <td valign="top" >Connector</td>
2908 <td valign="top" >TBD</td>
2911 <td valign="top" >“contrast”</td>
2912 <td valign="top" >RANGE</td>
2913 <td valign="top" >Min=0, Max= SDVO dependent</td>
2914 <td valign="top" >Connector</td>
2915 <td valign="top" >TBD</td>
2918 <td valign="top" >“saturation”</td>
2919 <td valign="top" >RANGE</td>
2920 <td valign="top" >Min=0, Max= SDVO dependent</td>
2921 <td valign="top" >Connector</td>
2922 <td valign="top" >TBD</td>
2925 <td valign="top" >“hue”</td>
2926 <td valign="top" >RANGE</td>
2927 <td valign="top" >Min=0, Max= SDVO dependent</td>
2928 <td valign="top" >Connector</td>
2929 <td valign="top" >TBD</td>
2932 <td valign="top" >“sharpness”</td>
2933 <td valign="top" >RANGE</td>
2934 <td valign="top" >Min=0, Max= SDVO dependent</td>
2935 <td valign="top" >Connector</td>
2936 <td valign="top" >TBD</td>
2939 <td valign="top" >“flicker_filter”</td>
2940 <td valign="top" >RANGE</td>
2941 <td valign="top" >Min=0, Max= SDVO dependent</td>
2942 <td valign="top" >Connector</td>
2943 <td valign="top" >TBD</td>
2946 <td valign="top" >“flicker_filter_adaptive”</td>
2947 <td valign="top" >RANGE</td>
2948 <td valign="top" >Min=0, Max= SDVO dependent</td>
2949 <td valign="top" >Connector</td>
2950 <td valign="top" >TBD</td>
2953 <td valign="top" >“flicker_filter_2d”</td>
2954 <td valign="top" >RANGE</td>
2955 <td valign="top" >Min=0, Max= SDVO dependent</td>
2956 <td valign="top" >Connector</td>
2957 <td valign="top" >TBD</td>
2960 <td valign="top" >“tv_chroma_filter”</td>
2961 <td valign="top" >RANGE</td>
2962 <td valign="top" >Min=0, Max= SDVO dependent</td>
2963 <td valign="top" >Connector</td>
2964 <td valign="top" >TBD</td>
2967 <td valign="top" >“tv_luma_filter”</td>
2968 <td valign="top" >RANGE</td>
2969 <td valign="top" >Min=0, Max= SDVO dependent</td>
2970 <td valign="top" >Connector</td>
2971 <td valign="top" >TBD</td>
2974 <td valign="top" >“dot_crawl”</td>
2975 <td valign="top" >RANGE</td>
2976 <td valign="top" >Min=0, Max=1</td>
2977 <td valign="top" >Connector</td>
2978 <td valign="top" >TBD</td>
2981 <td valign="top" >SDVO-TV/LVDS</td>
2982 <td valign="top" >“brightness”</td>
2983 <td valign="top" >RANGE</td>
2984 <td valign="top" >Min=0, Max= SDVO dependent</td>
2985 <td valign="top" >Connector</td>
2986 <td valign="top" >TBD</td>
2989 <td rowspan="2" valign="top" >CDV gma-500</td>
2990 <td rowspan="2" valign="top" >Generic</td>
2991 <td valign="top" >"Broadcast RGB"</td>
2992 <td valign="top" >ENUM</td>
2993 <td valign="top" >{ “Full”, “Limited 16:235” }</td>
2994 <td valign="top" >Connector</td>
2995 <td valign="top" >TBD</td>
2998 <td valign="top" >"Broadcast RGB"</td>
2999 <td valign="top" >ENUM</td>
3000 <td valign="top" >{ “off”, “auto”, “on” }</td>
3001 <td valign="top" >Connector</td>
3002 <td valign="top" >TBD</td>
3005 <td rowspan="19" valign="top" >Poulsbo</td>
3006 <td rowspan="1" valign="top" >Generic</td>
3007 <td valign="top" >“backlight”</td>
3008 <td valign="top" >RANGE</td>
3009 <td valign="top" >Min=0, Max=100</td>
3010 <td valign="top" >Connector</td>
3011 <td valign="top" >TBD</td>
3014 <td rowspan="17" valign="top" >SDVO-TV</td>
3015 <td valign="top" >“mode”</td>
3016 <td valign="top" >ENUM</td>
3017 <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
3018 <td valign="top" >Connector</td>
3019 <td valign="top" >TBD</td>
3022 <td valign="top" >"left_margin"</td>
3023 <td valign="top" >RANGE</td>
3024 <td valign="top" >Min=0, Max= SDVO dependent</td>
3025 <td valign="top" >Connector</td>
3026 <td valign="top" >TBD</td>
3029 <td valign="top" >"right_margin"</td>
3030 <td valign="top" >RANGE</td>
3031 <td valign="top" >Min=0, Max= SDVO dependent</td>
3032 <td valign="top" >Connector</td>
3033 <td valign="top" >TBD</td>
3036 <td valign="top" >"top_margin"</td>
3037 <td valign="top" >RANGE</td>
3038 <td valign="top" >Min=0, Max= SDVO dependent</td>
3039 <td valign="top" >Connector</td>
3040 <td valign="top" >TBD</td>
3043 <td valign="top" >"bottom_margin"</td>
3044 <td valign="top" >RANGE</td>
3045 <td valign="top" >Min=0, Max= SDVO dependent</td>
3046 <td valign="top" >Connector</td>
3047 <td valign="top" >TBD</td>
3050 <td valign="top" >“hpos”</td>
3051 <td valign="top" >RANGE</td>
3052 <td valign="top" >Min=0, Max= SDVO dependent</td>
3053 <td valign="top" >Connector</td>
3054 <td valign="top" >TBD</td>
3057 <td valign="top" >“vpos”</td>
3058 <td valign="top" >RANGE</td>
3059 <td valign="top" >Min=0, Max= SDVO dependent</td>
3060 <td valign="top" >Connector</td>
3061 <td valign="top" >TBD</td>
3064 <td valign="top" >“contrast”</td>
3065 <td valign="top" >RANGE</td>
3066 <td valign="top" >Min=0, Max= SDVO dependent</td>
3067 <td valign="top" >Connector</td>
3068 <td valign="top" >TBD</td>
3071 <td valign="top" >“saturation”</td>
3072 <td valign="top" >RANGE</td>
3073 <td valign="top" >Min=0, Max= SDVO dependent</td>
3074 <td valign="top" >Connector</td>
3075 <td valign="top" >TBD</td>
3078 <td valign="top" >“hue”</td>
3079 <td valign="top" >RANGE</td>
3080 <td valign="top" >Min=0, Max= SDVO dependent</td>
3081 <td valign="top" >Connector</td>
3082 <td valign="top" >TBD</td>
3085 <td valign="top" >“sharpness”</td>
3086 <td valign="top" >RANGE</td>
3087 <td valign="top" >Min=0, Max= SDVO dependent</td>
3088 <td valign="top" >Connector</td>
3089 <td valign="top" >TBD</td>
3092 <td valign="top" >“flicker_filter”</td>
3093 <td valign="top" >RANGE</td>
3094 <td valign="top" >Min=0, Max= SDVO dependent</td>
3095 <td valign="top" >Connector</td>
3096 <td valign="top" >TBD</td>
3099 <td valign="top" >“flicker_filter_adaptive”</td>
3100 <td valign="top" >RANGE</td>
3101 <td valign="top" >Min=0, Max= SDVO dependent</td>
3102 <td valign="top" >Connector</td>
3103 <td valign="top" >TBD</td>
3106 <td valign="top" >“flicker_filter_2d”</td>
3107 <td valign="top" >RANGE</td>
3108 <td valign="top" >Min=0, Max= SDVO dependent</td>
3109 <td valign="top" >Connector</td>
3110 <td valign="top" >TBD</td>
3113 <td valign="top" >“tv_chroma_filter”</td>
3114 <td valign="top" >RANGE</td>
3115 <td valign="top" >Min=0, Max= SDVO dependent</td>
3116 <td valign="top" >Connector</td>
3117 <td valign="top" >TBD</td>
3120 <td valign="top" >“tv_luma_filter”</td>
3121 <td valign="top" >RANGE</td>
3122 <td valign="top" >Min=0, Max= SDVO dependent</td>
3123 <td valign="top" >Connector</td>
3124 <td valign="top" >TBD</td>
3127 <td valign="top" >“dot_crawl”</td>
3128 <td valign="top" >RANGE</td>
3129 <td valign="top" >Min=0, Max=1</td>
3130 <td valign="top" >Connector</td>
3131 <td valign="top" >TBD</td>
3134 <td valign="top" >SDVO-TV/LVDS</td>
3135 <td valign="top" >“brightness”</td>
3136 <td valign="top" >RANGE</td>
3137 <td valign="top" >Min=0, Max= SDVO dependent</td>
3138 <td valign="top" >Connector</td>
3139 <td valign="top" >TBD</td>
3142 <td rowspan="11" valign="top" >armada</td>
3143 <td rowspan="2" valign="top" >CRTC</td>
3144 <td valign="top" >"CSC_YUV"</td>
3145 <td valign="top" >ENUM</td>
3146 <td valign="top" >{ "Auto" , "CCIR601", "CCIR709" }</td>
3147 <td valign="top" >CRTC</td>
3148 <td valign="top" >TBD</td>
3151 <td valign="top" >"CSC_RGB"</td>
3152 <td valign="top" >ENUM</td>
3153 <td valign="top" >{ "Auto", "Computer system", "Studio" }</td>
3154 <td valign="top" >CRTC</td>
3155 <td valign="top" >TBD</td>
3158 <td rowspan="9" valign="top" >Overlay</td>
3159 <td valign="top" >"colorkey"</td>
3160 <td valign="top" >RANGE</td>
3161 <td valign="top" >Min=0, Max=0xffffff</td>
3162 <td valign="top" >Plane</td>
3163 <td valign="top" >TBD</td>
3166 <td valign="top" >"colorkey_min"</td>
3167 <td valign="top" >RANGE</td>
3168 <td valign="top" >Min=0, Max=0xffffff</td>
3169 <td valign="top" >Plane</td>
3170 <td valign="top" >TBD</td>
3173 <td valign="top" >"colorkey_max"</td>
3174 <td valign="top" >RANGE</td>
3175 <td valign="top" >Min=0, Max=0xffffff</td>
3176 <td valign="top" >Plane</td>
3177 <td valign="top" >TBD</td>
3180 <td valign="top" >"colorkey_val"</td>
3181 <td valign="top" >RANGE</td>
3182 <td valign="top" >Min=0, Max=0xffffff</td>
3183 <td valign="top" >Plane</td>
3184 <td valign="top" >TBD</td>
3187 <td valign="top" >"colorkey_alpha"</td>
3188 <td valign="top" >RANGE</td>
3189 <td valign="top" >Min=0, Max=0xffffff</td>
3190 <td valign="top" >Plane</td>
3191 <td valign="top" >TBD</td>
3194 <td valign="top" >"colorkey_mode"</td>
3195 <td valign="top" >ENUM</td>
3196 <td valign="top" >{ "disabled", "Y component", "U component"
3197 , "V component", "RGB", “R component", "G component", "B component" }</td>
3198 <td valign="top" >Plane</td>
3199 <td valign="top" >TBD</td>
3202 <td valign="top" >"brightness"</td>
3203 <td valign="top" >RANGE</td>
3204 <td valign="top" >Min=0, Max=256 + 255</td>
3205 <td valign="top" >Plane</td>
3206 <td valign="top" >TBD</td>
3209 <td valign="top" >"contrast"</td>
3210 <td valign="top" >RANGE</td>
3211 <td valign="top" >Min=0, Max=0x7fff</td>
3212 <td valign="top" >Plane</td>
3213 <td valign="top" >TBD</td>
3216 <td valign="top" >"saturation"</td>
3217 <td valign="top" >RANGE</td>
3218 <td valign="top" >Min=0, Max=0x7fff</td>
3219 <td valign="top" >Plane</td>
3220 <td valign="top" >TBD</td>
3223 <td rowspan="2" valign="top" >exynos</td>
3224 <td valign="top" >CRTC</td>
3225 <td valign="top" >“mode”</td>
3226 <td valign="top" >ENUM</td>
3227 <td valign="top" >{ "normal", "blank" }</td>
3228 <td valign="top" >CRTC</td>
3229 <td valign="top" >TBD</td>
3232 <td valign="top" >Overlay</td>
3233 <td valign="top" >“zpos”</td>
3234 <td valign="top" >RANGE</td>
3235 <td valign="top" >Min=0, Max=MAX_PLANE-1</td>
3236 <td valign="top" >Plane</td>
3237 <td valign="top" >TBD</td>
3240 <td rowspan="2" valign="top" >i2c/ch7006_drv</td>
3241 <td valign="top" >Generic</td>
3242 <td valign="top" >“scale”</td>
3243 <td valign="top" >RANGE</td>
3244 <td valign="top" >Min=0, Max=2</td>
3245 <td valign="top" >Connector</td>
3246 <td valign="top" >TBD</td>
3249 <td rowspan="1" valign="top" >TV</td>
3250 <td valign="top" >“mode”</td>
3251 <td valign="top" >ENUM</td>
3252 <td valign="top" >{ "PAL", "PAL-M","PAL-N"}, ”PAL-Nc"
3253 , "PAL-60", "NTSC-M", "NTSC-J" }</td>
3254 <td valign="top" >Connector</td>
3255 <td valign="top" >TBD</td>
3258 <td rowspan="15" valign="top" >nouveau</td>
3259 <td rowspan="6" valign="top" >NV10 Overlay</td>
3260 <td valign="top" >"colorkey"</td>
3261 <td valign="top" >RANGE</td>
3262 <td valign="top" >Min=0, Max=0x01ffffff</td>
3263 <td valign="top" >Plane</td>
3264 <td valign="top" >TBD</td>
3267 <td valign="top" >“contrast”</td>
3268 <td valign="top" >RANGE</td>
3269 <td valign="top" >Min=0, Max=8192-1</td>
3270 <td valign="top" >Plane</td>
3271 <td valign="top" >TBD</td>
3274 <td valign="top" >“brightness”</td>
3275 <td valign="top" >RANGE</td>
3276 <td valign="top" >Min=0, Max=1024</td>
3277 <td valign="top" >Plane</td>
3278 <td valign="top" >TBD</td>
3281 <td valign="top" >“hue”</td>
3282 <td valign="top" >RANGE</td>
3283 <td valign="top" >Min=0, Max=359</td>
3284 <td valign="top" >Plane</td>
3285 <td valign="top" >TBD</td>
3288 <td valign="top" >“saturation”</td>
3289 <td valign="top" >RANGE</td>
3290 <td valign="top" >Min=0, Max=8192-1</td>
3291 <td valign="top" >Plane</td>
3292 <td valign="top" >TBD</td>
3295 <td valign="top" >“iturbt_709”</td>
3296 <td valign="top" >RANGE</td>
3297 <td valign="top" >Min=0, Max=1</td>
3298 <td valign="top" >Plane</td>
3299 <td valign="top" >TBD</td>
3302 <td rowspan="2" valign="top" >Nv04 Overlay</td>
3303 <td valign="top" >“colorkey”</td>
3304 <td valign="top" >RANGE</td>
3305 <td valign="top" >Min=0, Max=0x01ffffff</td>
3306 <td valign="top" >Plane</td>
3307 <td valign="top" >TBD</td>
3310 <td valign="top" >“brightness”</td>
3311 <td valign="top" >RANGE</td>
3312 <td valign="top" >Min=0, Max=1024</td>
3313 <td valign="top" >Plane</td>
3314 <td valign="top" >TBD</td>
3317 <td rowspan="7" valign="top" >Display</td>
3318 <td valign="top" >“dithering mode”</td>
3319 <td valign="top" >ENUM</td>
3320 <td valign="top" >{ "auto", "off", "on" }</td>
3321 <td valign="top" >Connector</td>
3322 <td valign="top" >TBD</td>
3325 <td valign="top" >“dithering depth”</td>
3326 <td valign="top" >ENUM</td>
3327 <td valign="top" >{ "auto", "off", "on", "static 2x2", "dynamic 2x2", "temporal" }</td>
3328 <td valign="top" >Connector</td>
3329 <td valign="top" >TBD</td>
3332 <td valign="top" >“underscan”</td>
3333 <td valign="top" >ENUM</td>
3334 <td valign="top" >{ "auto", "6 bpc", "8 bpc" }</td>
3335 <td valign="top" >Connector</td>
3336 <td valign="top" >TBD</td>
3339 <td valign="top" >“underscan hborder”</td>
3340 <td valign="top" >RANGE</td>
3341 <td valign="top" >Min=0, Max=128</td>
3342 <td valign="top" >Connector</td>
3343 <td valign="top" >TBD</td>
3346 <td valign="top" >“underscan vborder”</td>
3347 <td valign="top" >RANGE</td>
3348 <td valign="top" >Min=0, Max=128</td>
3349 <td valign="top" >Connector</td>
3350 <td valign="top" >TBD</td>
3353 <td valign="top" >“vibrant hue”</td>
3354 <td valign="top" >RANGE</td>
3355 <td valign="top" >Min=0, Max=180</td>
3356 <td valign="top" >Connector</td>
3357 <td valign="top" >TBD</td>
3360 <td valign="top" >“color vibrance”</td>
3361 <td valign="top" >RANGE</td>
3362 <td valign="top" >Min=0, Max=200</td>
3363 <td valign="top" >Connector</td>
3364 <td valign="top" >TBD</td>
3367 <td rowspan="2" valign="top" >omap</td>
3368 <td rowspan="2" valign="top" >Generic</td>
3369 <td valign="top" >“rotation”</td>
3370 <td valign="top" >BITMASK</td>
3371 <td valign="top" >{ 0, "rotate-0" },
3373 { 2, "rotate-180" },
3374 { 3, "rotate-270" },
3376 { 5, "reflect-y" }</td>
3377 <td valign="top" >CRTC, Plane</td>
3378 <td valign="top" >TBD</td>
3381 <td valign="top" >“zorder”</td>
3382 <td valign="top" >RANGE</td>
3383 <td valign="top" >Min=0, Max=3</td>
3384 <td valign="top" >CRTC, Plane</td>
3385 <td valign="top" >TBD</td>
3388 <td valign="top" >qxl</td>
3389 <td valign="top" >Generic</td>
3390 <td valign="top" >“hotplug_mode_update"</td>
3391 <td valign="top" >RANGE</td>
3392 <td valign="top" >Min=0, Max=1</td>
3393 <td valign="top" >Connector</td>
3394 <td valign="top" >TBD</td>
3397 <td rowspan="9" valign="top" >radeon</td>
3398 <td valign="top" >DVI-I</td>
3399 <td valign="top" >“coherent”</td>
3400 <td valign="top" >RANGE</td>
3401 <td valign="top" >Min=0, Max=1</td>
3402 <td valign="top" >Connector</td>
3403 <td valign="top" >TBD</td>
3406 <td valign="top" >DAC enable load detect</td>
3407 <td valign="top" >“load detection”</td>
3408 <td valign="top" >RANGE</td>
3409 <td valign="top" >Min=0, Max=1</td>
3410 <td valign="top" >Connector</td>
3411 <td valign="top" >TBD</td>
3414 <td valign="top" >TV Standard</td>
3415 <td valign="top" >"tv standard"</td>
3416 <td valign="top" >ENUM</td>
3417 <td valign="top" >{ "ntsc", "pal", "pal-m", "pal-60", "ntsc-j"
3418 , "scart-pal", "pal-cn", "secam" }</td>
3419 <td valign="top" >Connector</td>
3420 <td valign="top" >TBD</td>
3423 <td valign="top" >legacy TMDS PLL detect</td>
3424 <td valign="top" >"tmds_pll"</td>
3425 <td valign="top" >ENUM</td>
3426 <td valign="top" >{ "driver", "bios" }</td>
3427 <td valign="top" >-</td>
3428 <td valign="top" >TBD</td>
3431 <td rowspan="3" valign="top" >Underscan</td>
3432 <td valign="top" >"underscan"</td>
3433 <td valign="top" >ENUM</td>
3434 <td valign="top" >{ "off", "on", "auto" }</td>
3435 <td valign="top" >Connector</td>
3436 <td valign="top" >TBD</td>
3439 <td valign="top" >"underscan hborder"</td>
3440 <td valign="top" >RANGE</td>
3441 <td valign="top" >Min=0, Max=128</td>
3442 <td valign="top" >Connector</td>
3443 <td valign="top" >TBD</td>
3446 <td valign="top" >"underscan vborder"</td>
3447 <td valign="top" >RANGE</td>
3448 <td valign="top" >Min=0, Max=128</td>
3449 <td valign="top" >Connector</td>
3450 <td valign="top" >TBD</td>
3453 <td valign="top" >Audio</td>
3454 <td valign="top" >“audio”</td>
3455 <td valign="top" >ENUM</td>
3456 <td valign="top" >{ "off", "on", "auto" }</td>
3457 <td valign="top" >Connector</td>
3458 <td valign="top" >TBD</td>
3461 <td valign="top" >FMT Dithering</td>
3462 <td valign="top" >“dither”</td>
3463 <td valign="top" >ENUM</td>
3464 <td valign="top" >{ "off", "on" }</td>
3465 <td valign="top" >Connector</td>
3466 <td valign="top" >TBD</td>
3469 <td rowspan="3" valign="top" >rcar-du</td>
3470 <td rowspan="3" valign="top" >Generic</td>
3471 <td valign="top" >"alpha"</td>
3472 <td valign="top" >RANGE</td>
3473 <td valign="top" >Min=0, Max=255</td>
3474 <td valign="top" >Plane</td>
3475 <td valign="top" >TBD</td>
3478 <td valign="top" >"colorkey"</td>
3479 <td valign="top" >RANGE</td>
3480 <td valign="top" >Min=0, Max=0x01ffffff</td>
3481 <td valign="top" >Plane</td>
3482 <td valign="top" >TBD</td>
3485 <td valign="top" >"zpos"</td>
3486 <td valign="top" >RANGE</td>
3487 <td valign="top" >Min=1, Max=7</td>
3488 <td valign="top" >Plane</td>
3489 <td valign="top" >TBD</td>
3496 <!-- Internals: vertical blanking -->
3498 <sect1 id="drm-vertical-blank">
3499 <title>Vertical Blanking</title>
3501 Vertical blanking plays a major role in graphics rendering. To achieve
3502 tear-free display, users must synchronize page flips and/or rendering to
3503 vertical blanking. The DRM API offers ioctls to perform page flips
3504 synchronized to vertical blanking and wait for vertical blanking.
3507 The DRM core handles most of the vertical blanking management logic, which
3508 involves filtering out spurious interrupts, keeping race-free blanking
3509 counters, coping with counter wrap-around and resets and keeping use
3510 counts. It relies on the driver to generate vertical blanking interrupts
3511 and optionally provide a hardware vertical blanking counter. Drivers must
3512 implement the following operations.
3516 <synopsis>int (*enable_vblank) (struct drm_device *dev, int crtc);
3517 void (*disable_vblank) (struct drm_device *dev, int crtc);</synopsis>
3519 Enable or disable vertical blanking interrupts for the given CRTC.
3523 <synopsis>u32 (*get_vblank_counter) (struct drm_device *dev, int crtc);</synopsis>
3525 Retrieve the value of the vertical blanking counter for the given
3526 CRTC. If the hardware maintains a vertical blanking counter its value
3527 should be returned. Otherwise drivers can use the
3528 <function>drm_vblank_count</function> helper function to handle this
3534 Drivers must initialize the vertical blanking handling core with a call to
3535 <function>drm_vblank_init</function> in their
3536 <methodname>load</methodname> operation. The function will set the struct
3537 <structname>drm_device</structname>
3538 <structfield>vblank_disable_allowed</structfield> field to 0. This will
3539 keep vertical blanking interrupts enabled permanently until the first mode
3540 set operation, where <structfield>vblank_disable_allowed</structfield> is
3541 set to 1. The reason behind this is not clear. Drivers can set the field
3542 to 1 after <function>calling drm_vblank_init</function> to make vertical
3543 blanking interrupts dynamically managed from the beginning.
3546 Vertical blanking interrupts can be enabled by the DRM core or by drivers
3547 themselves (for instance to handle page flipping operations). The DRM core
3548 maintains a vertical blanking use count to ensure that the interrupts are
3549 not disabled while a user still needs them. To increment the use count,
3550 drivers call <function>drm_vblank_get</function>. Upon return vertical
3551 blanking interrupts are guaranteed to be enabled.
3554 To decrement the use count drivers call
3555 <function>drm_vblank_put</function>. Only when the use count drops to zero
3556 will the DRM core disable the vertical blanking interrupts after a delay
3557 by scheduling a timer. The delay is accessible through the vblankoffdelay
3558 module parameter or the <varname>drm_vblank_offdelay</varname> global
3559 variable and expressed in milliseconds. Its default value is 5000 ms.
3560 Zero means never disable, and a negative value means disable immediately.
3561 Drivers may override the behaviour by setting the
3562 <structname>drm_device</structname>
3563 <structfield>vblank_disable_immediate</structfield> flag, which when set
3564 causes vblank interrupts to be disabled immediately regardless of the
3565 drm_vblank_offdelay value. The flag should only be set if there's a
3566 properly working hardware vblank counter present.
3569 When a vertical blanking interrupt occurs drivers only need to call the
3570 <function>drm_handle_vblank</function> function to account for the
3574 Resources allocated by <function>drm_vblank_init</function> must be freed
3575 with a call to <function>drm_vblank_cleanup</function> in the driver
3576 <methodname>unload</methodname> operation handler.
3579 <title>Vertical Blanking and Interrupt Handling Functions Reference</title>
3580 !Edrivers/gpu/drm/drm_irq.c
3581 !Finclude/drm/drmP.h drm_crtc_vblank_waitqueue
3585 <!-- Internals: open/close, file operations and ioctls -->
3588 <title>Open/Close, File Operations and IOCTLs</title>
3590 <title>Open and Close</title>
3591 <synopsis>int (*firstopen) (struct drm_device *);
3592 void (*lastclose) (struct drm_device *);
3593 int (*open) (struct drm_device *, struct drm_file *);
3594 void (*preclose) (struct drm_device *, struct drm_file *);
3595 void (*postclose) (struct drm_device *, struct drm_file *);</synopsis>
3596 <abstract>Open and close handlers. None of those methods are mandatory.
3599 The <methodname>firstopen</methodname> method is called by the DRM core
3600 for legacy UMS (User Mode Setting) drivers only when an application
3601 opens a device that has no other opened file handle. UMS drivers can
3602 implement it to acquire device resources. KMS drivers can't use the
3603 method and must acquire resources in the <methodname>load</methodname>
3607 Similarly the <methodname>lastclose</methodname> method is called when
3608 the last application holding a file handle opened on the device closes
3609 it, for both UMS and KMS drivers. Additionally, the method is also
3610 called at module unload time or, for hot-pluggable devices, when the
3611 device is unplugged. The <methodname>firstopen</methodname> and
3612 <methodname>lastclose</methodname> calls can thus be unbalanced.
3615 The <methodname>open</methodname> method is called every time the device
3616 is opened by an application. Drivers can allocate per-file private data
3617 in this method and store them in the struct
3618 <structname>drm_file</structname> <structfield>driver_priv</structfield>
3619 field. Note that the <methodname>open</methodname> method is called
3620 before <methodname>firstopen</methodname>.
3623 The close operation is split into <methodname>preclose</methodname> and
3624 <methodname>postclose</methodname> methods. Drivers must stop and
3625 cleanup all per-file operations in the <methodname>preclose</methodname>
3626 method. For instance pending vertical blanking and page flip events must
3627 be cancelled. No per-file operation is allowed on the file handle after
3628 returning from the <methodname>preclose</methodname> method.
3631 Finally the <methodname>postclose</methodname> method is called as the
3632 last step of the close operation, right before calling the
3633 <methodname>lastclose</methodname> method if no other open file handle
3634 exists for the device. Drivers that have allocated per-file private data
3635 in the <methodname>open</methodname> method should free it here.
3638 The <methodname>lastclose</methodname> method should restore CRTC and
3639 plane properties to default value, so that a subsequent open of the
3640 device will not inherit state from the previous user. It can also be
3641 used to execute delayed power switching state changes, e.g. in
3642 conjunction with the vga-switcheroo infrastructure. Beyond that KMS
3643 drivers should not do any further cleanup. Only legacy UMS drivers might
3644 need to clean up device state so that the vga console or an independent
3645 fbdev driver could take over.
3649 <title>File Operations</title>
3650 <synopsis>const struct file_operations *fops</synopsis>
3651 <abstract>File operations for the DRM device node.</abstract>
3653 Drivers must define the file operations structure that forms the DRM
3654 userspace API entry point, even though most of those operations are
3655 implemented in the DRM core. The <methodname>open</methodname>,
3656 <methodname>release</methodname> and <methodname>ioctl</methodname>
3657 operations are handled by
3659 .owner = THIS_MODULE,
3661 .release = drm_release,
3662 .unlocked_ioctl = drm_ioctl,
3663 #ifdef CONFIG_COMPAT
3664 .compat_ioctl = drm_compat_ioctl,
3669 Drivers that implement private ioctls that requires 32/64bit
3670 compatibility support must provide their own
3671 <methodname>compat_ioctl</methodname> handler that processes private
3672 ioctls and calls <function>drm_compat_ioctl</function> for core ioctls.
3675 The <methodname>read</methodname> and <methodname>poll</methodname>
3676 operations provide support for reading DRM events and polling them. They
3681 .llseek = no_llseek,
3685 The memory mapping implementation varies depending on how the driver
3686 manages memory. Pre-GEM drivers will use <function>drm_mmap</function>,
3687 while GEM-aware drivers will use <function>drm_gem_mmap</function>. See
3688 <xref linkend="drm-gem"/>.
3690 .mmap = drm_gem_mmap,
3694 No other file operation is supported by the DRM API.
3698 <title>IOCTLs</title>
3699 <synopsis>struct drm_ioctl_desc *ioctls;
3700 int num_ioctls;</synopsis>
3701 <abstract>Driver-specific ioctls descriptors table.</abstract>
3703 Driver-specific ioctls numbers start at DRM_COMMAND_BASE. The ioctls
3704 descriptors table is indexed by the ioctl number offset from the base
3705 value. Drivers can use the DRM_IOCTL_DEF_DRV() macro to initialize the
3709 <programlisting>DRM_IOCTL_DEF_DRV(ioctl, func, flags)</programlisting>
3711 <parameter>ioctl</parameter> is the ioctl name. Drivers must define
3712 the DRM_##ioctl and DRM_IOCTL_##ioctl macros to the ioctl number
3713 offset from DRM_COMMAND_BASE and the ioctl number respectively. The
3714 first macro is private to the device while the second must be exposed
3715 to userspace in a public header.
3718 <parameter>func</parameter> is a pointer to the ioctl handler function
3719 compatible with the <type>drm_ioctl_t</type> type.
3720 <programlisting>typedef int drm_ioctl_t(struct drm_device *dev, void *data,
3721 struct drm_file *file_priv);</programlisting>
3724 <parameter>flags</parameter> is a bitmask combination of the following
3725 values. It restricts how the ioctl is allowed to be called.
3728 DRM_AUTH - Only authenticated callers allowed
3731 DRM_MASTER - The ioctl can only be called on the master file
3735 DRM_ROOT_ONLY - Only callers with the SYSADMIN capability allowed
3738 DRM_CONTROL_ALLOW - The ioctl can only be called on a control
3742 DRM_UNLOCKED - The ioctl handler will be called without locking
3743 the DRM global mutex
3751 <title>Legacy Support Code</title>
3753 The section very briefly covers some of the old legacy support code which
3754 is only used by old DRM drivers which have done a so-called shadow-attach
3755 to the underlying device instead of registering as a real driver. This
3756 also includes some of the old generic buffer management and command
3757 submission code. Do not use any of this in new and modern drivers.
3761 <title>Legacy Suspend/Resume</title>
3763 The DRM core provides some suspend/resume code, but drivers wanting full
3764 suspend/resume support should provide save() and restore() functions.
3765 These are called at suspend, hibernate, or resume time, and should perform
3766 any state save or restore required by your device across suspend or
3769 <synopsis>int (*suspend) (struct drm_device *, pm_message_t state);
3770 int (*resume) (struct drm_device *);</synopsis>
3772 Those are legacy suspend and resume methods which
3773 <emphasis>only</emphasis> work with the legacy shadow-attach driver
3774 registration functions. New driver should use the power management
3775 interface provided by their bus type (usually through
3776 the struct <structname>device_driver</structname> dev_pm_ops) and set
3777 these methods to NULL.
3782 <title>Legacy DMA Services</title>
3784 This should cover how DMA mapping etc. is supported by the core.
3785 These functions are deprecated and should not be used.
3794 - Document the struct_mutex catch-all lock
3795 - Document connector properties
3797 - Why is the load method optional?
3798 - What are drivers supposed to set the initial display state to, and how?
3799 Connector's DPMS states are not initialized and are thus equal to
3800 DRM_MODE_DPMS_ON. The fbcon compatibility layer calls
3801 drm_helper_disable_unused_functions(), which disables unused encoders and
3802 CRTCs, but doesn't touch the connectors' DPMS state, and
3803 drm_helper_connector_dpms() in reaction to fbdev blanking events. Do drivers
3804 that don't implement (or just don't use) fbcon compatibility need to call
3805 those functions themselves?
3806 - KMS drivers must call drm_vblank_pre_modeset() and drm_vblank_post_modeset()
3807 around mode setting. Should this be done in the DRM core?
3808 - vblank_disable_allowed is set to 1 in the first drm_vblank_post_modeset()
3809 call and never set back to 0. It seems to be safe to permanently set it to 1
3810 in drm_vblank_init() for KMS driver, and it might be safe for UMS drivers as
3811 well. This should be investigated.
3812 - crtc and connector .save and .restore operations are only used internally in
3813 drivers, should they be removed from the core?
3814 - encoder mid-layer .save and .restore operations are only used internally in
3815 drivers, should they be removed from the core?
3816 - encoder mid-layer .detect operation is only used internally in drivers,
3817 should it be removed from the core?
3820 <!-- External interfaces -->
3822 <chapter id="drmExternals">
3823 <title>Userland interfaces</title>
3825 The DRM core exports several interfaces to applications,
3826 generally intended to be used through corresponding libdrm
3827 wrapper functions. In addition, drivers export device-specific
3828 interfaces for use by userspace drivers & device-aware
3829 applications through ioctls and sysfs files.
3832 External interfaces include: memory mapping, context management,
3833 DMA operations, AGP management, vblank control, fence
3834 management, memory management, and output management.
3837 Cover generic ioctls and sysfs layout here. We only need high-level
3838 info, since man pages should cover the rest.
3841 <!-- External: render nodes -->
3844 <title>Render nodes</title>
3846 DRM core provides multiple character-devices for user-space to use.
3847 Depending on which device is opened, user-space can perform a different
3848 set of operations (mainly ioctls). The primary node is always created
3849 and called card<num>. Additionally, a currently
3850 unused control node, called controlD<num> is also
3851 created. The primary node provides all legacy operations and
3852 historically was the only interface used by userspace. With KMS, the
3853 control node was introduced. However, the planned KMS control interface
3854 has never been written and so the control node stays unused to date.
3857 With the increased use of offscreen renderers and GPGPU applications,
3858 clients no longer require running compositors or graphics servers to
3859 make use of a GPU. But the DRM API required unprivileged clients to
3860 authenticate to a DRM-Master prior to getting GPU access. To avoid this
3861 step and to grant clients GPU access without authenticating, render
3862 nodes were introduced. Render nodes solely serve render clients, that
3863 is, no modesetting or privileged ioctls can be issued on render nodes.
3864 Only non-global rendering commands are allowed. If a driver supports
3865 render nodes, it must advertise it via the DRIVER_RENDER
3866 DRM driver capability. If not supported, the primary node must be used
3867 for render clients together with the legacy drmAuth authentication
3871 If a driver advertises render node support, DRM core will create a
3872 separate render node called renderD<num>. There will
3873 be one render node per device. No ioctls except PRIME-related ioctls
3874 will be allowed on this node. Especially GEM_OPEN will be
3875 explicitly prohibited. Render nodes are designed to avoid the
3876 buffer-leaks, which occur if clients guess the flink names or mmap
3877 offsets on the legacy interface. Additionally to this basic interface,
3878 drivers must mark their driver-dependent render-only ioctls as
3879 DRM_RENDER_ALLOW so render clients can use them. Driver
3880 authors must be careful not to allow any privileged ioctls on render
3884 With render nodes, user-space can now control access to the render node
3885 via basic file-system access-modes. A running graphics server which
3886 authenticates clients on the privileged primary/legacy node is no longer
3887 required. Instead, a client can open the render node and is immediately
3888 granted GPU access. Communication between clients (or servers) is done
3889 via PRIME. FLINK from render node to legacy node is not supported. New
3890 clients must not use the insecure FLINK interface.
3893 Besides dropping all modeset/global ioctls, render nodes also drop the
3894 DRM-Master concept. There is no reason to associate render clients with
3895 a DRM-Master as they are independent of any graphics server. Besides,
3896 they must work without any running master, anyway.
3897 Drivers must be able to run without a master object if they support
3898 render nodes. If, on the other hand, a driver requires shared state
3899 between clients which is visible to user-space and accessible beyond
3900 open-file boundaries, they cannot support render nodes.
3904 <!-- External: vblank handling -->
3907 <title>VBlank event handling</title>
3909 The DRM core exposes two vertical blank related ioctls:
3912 <term>DRM_IOCTL_WAIT_VBLANK</term>
3915 This takes a struct drm_wait_vblank structure as its argument,
3916 and it is used to block or request a signal when a specified
3917 vblank event occurs.
3922 <term>DRM_IOCTL_MODESET_CTL</term>
3925 This was only used for user-mode-settind drivers around
3926 modesetting changes to allow the kernel to update the vblank
3927 interrupt after mode setting, since on many devices the vertical
3928 blank counter is reset to 0 at some point during modeset. Modern
3929 drivers should not call this any more since with kernel mode
3930 setting it is a no-op.
3940 <part id="drmDrivers">
3941 <title>DRM Drivers</title>
3945 This second part of the DRM Developer's Guide documents driver code,
3946 implementation details and also all the driver-specific userspace
3947 interfaces. Especially since all hardware-acceleration interfaces to
3948 userspace are driver specific for efficiency and other reasons these
3949 interfaces can be rather substantial. Hence every driver has its own
3954 <chapter id="drmI915">
3955 <title>drm/i915 Intel GFX Driver</title>
3957 The drm/i915 driver supports all (with the exception of some very early
3958 models) integrated GFX chipsets with both Intel display and rendering
3959 blocks. This excludes a set of SoC platforms with an SGX rendering unit,
3960 those have basic support through the gma500 drm driver.
3963 <title>Core Driver Infrastructure</title>
3965 This section covers core driver infrastructure used by both the display
3966 and the GEM parts of the driver.
3969 <title>Runtime Power Management</title>
3970 !Pdrivers/gpu/drm/i915/intel_runtime_pm.c runtime pm
3971 !Idrivers/gpu/drm/i915/intel_runtime_pm.c
3972 !Idrivers/gpu/drm/i915/intel_uncore.c
3975 <title>Interrupt Handling</title>
3976 !Pdrivers/gpu/drm/i915/i915_irq.c interrupt handling
3977 !Fdrivers/gpu/drm/i915/i915_irq.c intel_irq_init intel_irq_init_hw intel_hpd_init
3978 !Fdrivers/gpu/drm/i915/i915_irq.c intel_irq_fini
3979 !Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_disable_interrupts
3980 !Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_enable_interrupts
3984 <title>Display Hardware Handling</title>
3986 This section covers everything related to the display hardware including
3987 the mode setting infrastructure, plane, sprite and cursor handling and
3988 display, output probing and related topics.
3991 <title>Mode Setting Infrastructure</title>
3993 The i915 driver is thus far the only DRM driver which doesn't use the
3994 common DRM helper code to implement mode setting sequences. Thus it
3995 has its own tailor-made infrastructure for executing a display
3996 configuration change.
4000 <title>Frontbuffer Tracking</title>
4001 !Pdrivers/gpu/drm/i915/intel_frontbuffer.c frontbuffer tracking
4002 !Idrivers/gpu/drm/i915/intel_frontbuffer.c
4003 !Fdrivers/gpu/drm/i915/intel_drv.h intel_frontbuffer_flip
4004 !Fdrivers/gpu/drm/i915/i915_gem.c i915_gem_track_fb
4007 <title>Display FIFO Underrun Reporting</title>
4008 !Pdrivers/gpu/drm/i915/intel_fifo_underrun.c fifo underrun handling
4009 !Idrivers/gpu/drm/i915/intel_fifo_underrun.c
4012 <title>Plane Configuration</title>
4014 This section covers plane configuration and composition with the
4015 primary plane, sprites, cursors and overlays. This includes the
4016 infrastructure to do atomic vsync'ed updates of all this state and
4017 also tightly coupled topics like watermark setup and computation,
4018 framebuffer compression and panel self refresh.
4022 <title>Atomic Plane Helpers</title>
4023 !Pdrivers/gpu/drm/i915/intel_atomic_plane.c atomic plane helpers
4024 !Idrivers/gpu/drm/i915/intel_atomic_plane.c
4027 <title>Output Probing</title>
4029 This section covers output probing and related infrastructure like the
4030 hotplug interrupt storm detection and mitigation code. Note that the
4031 i915 driver still uses most of the common DRM helper code for output
4032 probing, so those sections fully apply.
4036 <title>High Definition Audio</title>
4037 !Pdrivers/gpu/drm/i915/intel_audio.c High Definition Audio over HDMI and Display Port
4038 !Idrivers/gpu/drm/i915/intel_audio.c
4041 <title>Panel Self Refresh PSR (PSR/SRD)</title>
4042 !Pdrivers/gpu/drm/i915/intel_psr.c Panel Self Refresh (PSR/SRD)
4043 !Idrivers/gpu/drm/i915/intel_psr.c
4046 <title>Frame Buffer Compression (FBC)</title>
4047 !Pdrivers/gpu/drm/i915/intel_fbc.c Frame Buffer Compression (FBC)
4048 !Idrivers/gpu/drm/i915/intel_fbc.c
4052 !Pdrivers/gpu/drm/i915/i915_reg.h DPIO
4054 <title>Dual channel PHY (VLV/CHV)</title>
4056 <colspec colname="c0" />
4057 <colspec colname="c1" />
4058 <colspec colname="c2" />
4059 <colspec colname="c3" />
4060 <colspec colname="c4" />
4061 <colspec colname="c5" />
4062 <colspec colname="c6" />
4063 <colspec colname="c7" />
4064 <spanspec spanname="ch0" namest="c0" nameend="c3" />
4065 <spanspec spanname="ch1" namest="c4" nameend="c7" />
4066 <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
4067 <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
4068 <spanspec spanname="ch1pcs01" namest="c4" nameend="c5" />
4069 <spanspec spanname="ch1pcs23" namest="c6" nameend="c7" />
4072 <entry spanname="ch0">CH0</entry>
4073 <entry spanname="ch1">CH1</entry>
4076 <tbody valign="top" align="center">
4078 <entry spanname="ch0">CMN/PLL/REF</entry>
4079 <entry spanname="ch1">CMN/PLL/REF</entry>
4082 <entry spanname="ch0pcs01">PCS01</entry>
4083 <entry spanname="ch0pcs23">PCS23</entry>
4084 <entry spanname="ch1pcs01">PCS01</entry>
4085 <entry spanname="ch1pcs23">PCS23</entry>
4098 <entry spanname="ch0">DDI0</entry>
4099 <entry spanname="ch1">DDI1</entry>
4105 <title>Single channel PHY (CHV)</title>
4107 <colspec colname="c0" />
4108 <colspec colname="c1" />
4109 <colspec colname="c2" />
4110 <colspec colname="c3" />
4111 <spanspec spanname="ch0" namest="c0" nameend="c3" />
4112 <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
4113 <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
4116 <entry spanname="ch0">CH0</entry>
4119 <tbody valign="top" align="center">
4121 <entry spanname="ch0">CMN/PLL/REF</entry>
4124 <entry spanname="ch0pcs01">PCS01</entry>
4125 <entry spanname="ch0pcs23">PCS23</entry>
4134 <entry spanname="ch0">DDI2</entry>
4143 <title>Memory Management and Command Submission</title>
4145 This sections covers all things related to the GEM implementation in the
4149 <title>Batchbuffer Parsing</title>
4150 !Pdrivers/gpu/drm/i915/i915_cmd_parser.c batch buffer command parser
4151 !Idrivers/gpu/drm/i915/i915_cmd_parser.c
4154 <title>Batchbuffer Pools</title>
4155 !Pdrivers/gpu/drm/i915/i915_gem_batch_pool.c batch pool
4156 !Idrivers/gpu/drm/i915/i915_gem_batch_pool.c
4159 <title>Logical Rings, Logical Ring Contexts and Execlists</title>
4160 !Pdrivers/gpu/drm/i915/intel_lrc.c Logical Rings, Logical Ring Contexts and Execlists
4161 !Idrivers/gpu/drm/i915/intel_lrc.c
4164 <title>Global GTT views</title>
4165 !Pdrivers/gpu/drm/i915/i915_gem_gtt.c Global GTT views
4166 !Idrivers/gpu/drm/i915/i915_gem_gtt.c
4169 <title>Buffer Object Eviction</title>
4171 This section documents the interface function for evicting buffer
4172 objects to make space available in the virtual gpu address spaces.
4173 Note that this is mostly orthogonal to shrinking buffer objects
4174 caches, which has the goal to make main memory (shared with the gpu
4175 through the unified memory architecture) available.
4177 !Idrivers/gpu/drm/i915/i915_gem_evict.c
4182 <title> Tracing </title>
4184 This sections covers all things related to the tracepoints implemented in
4188 <title> i915_ppgtt_create and i915_ppgtt_release </title>
4189 !Pdrivers/gpu/drm/i915/i915_trace.h i915_ppgtt_create and i915_ppgtt_release tracepoints
4192 <title> i915_context_create and i915_context_free </title>
4193 !Pdrivers/gpu/drm/i915/i915_trace.h i915_context_create and i915_context_free tracepoints
4196 <title> switch_mm </title>
4197 !Pdrivers/gpu/drm/i915/i915_trace.h switch_mm tracepoint
4202 !Cdrivers/gpu/drm/i915/i915_irq.c
git.openpandora.org / pandora-kernel.git / blob