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.
245 <title>Major, Minor and Patchlevel</title>
248 int patchlevel;</synopsis>
250 The DRM core identifies driver versions by a major, minor and patch
251 level triplet. The information is printed to the kernel log at
252 initialization time and passed to userspace through the
253 DRM_IOCTL_VERSION ioctl.
256 The major and minor numbers are also used to verify the requested driver
257 API version passed to DRM_IOCTL_SET_VERSION. When the driver API changes
258 between minor versions, applications can call DRM_IOCTL_SET_VERSION to
259 select a specific version of the API. If the requested major isn't equal
260 to the driver major, or the requested minor is larger than the driver
261 minor, the DRM_IOCTL_SET_VERSION call will return an error. Otherwise
262 the driver's set_version() method will be called with the requested
267 <title>Name, Description and Date</title>
268 <synopsis>char *name;
270 char *date;</synopsis>
272 The driver name is printed to the kernel log at initialization time,
273 used for IRQ registration and passed to userspace through
277 The driver description is a purely informative string passed to
278 userspace through the DRM_IOCTL_VERSION ioctl and otherwise unused by
282 The driver date, formatted as YYYYMMDD, is meant to identify the date of
283 the latest modification to the driver. However, as most drivers fail to
284 update it, its value is mostly useless. The DRM core prints it to the
285 kernel log at initialization time and passes it to userspace through the
286 DRM_IOCTL_VERSION ioctl.
291 <title>Device Registration</title>
293 A number of functions are provided to help with device registration.
294 The functions deal with PCI and platform devices, respectively.
296 !Edrivers/gpu/drm/drm_pci.c
297 !Edrivers/gpu/drm/drm_platform.c
299 New drivers that no longer rely on the services provided by the
300 <structname>drm_bus</structname> structure can call the low-level
301 device registration functions directly. The
302 <function>drm_dev_alloc()</function> function can be used to allocate
303 and initialize a new <structname>drm_device</structname> structure.
304 Drivers will typically want to perform some additional setup on this
305 structure, such as allocating driver-specific data and storing a
306 pointer to it in the DRM device's <structfield>dev_private</structfield>
307 field. Drivers should also set the device's unique name using the
308 <function>drm_dev_set_unique()</function> function. After it has been
309 set up a device can be registered with the DRM subsystem by calling
310 <function>drm_dev_register()</function>. This will cause the device to
311 be exposed to userspace and will call the driver's
312 <structfield>.load()</structfield> implementation. When a device is
313 removed, the DRM device can safely be unregistered and freed by calling
314 <function>drm_dev_unregister()</function> followed by a call to
315 <function>drm_dev_unref()</function>.
317 !Edrivers/gpu/drm/drm_drv.c
320 <title>Driver Load</title>
322 The <methodname>load</methodname> method is the driver and device
323 initialization entry point. The method is responsible for allocating and
324 initializing driver private data, performing resource allocation and
325 mapping (e.g. acquiring
326 clocks, mapping registers or allocating command buffers), initializing
327 the memory manager (<xref linkend="drm-memory-management"/>), installing
328 the IRQ handler (<xref linkend="drm-irq-registration"/>), setting up
329 vertical blanking handling (<xref linkend="drm-vertical-blank"/>), mode
330 setting (<xref linkend="drm-mode-setting"/>) and initial output
331 configuration (<xref linkend="drm-kms-init"/>).
334 If compatibility is a concern (e.g. with drivers converted over from
335 User Mode Setting to Kernel Mode Setting), care must be taken to prevent
336 device initialization and control that is incompatible with currently
337 active userspace drivers. For instance, if user level mode setting
338 drivers are in use, it would be problematic to perform output discovery
339 & configuration at load time. Likewise, if user-level drivers
340 unaware of memory management are in use, memory management and command
341 buffer setup may need to be omitted. These requirements are
342 driver-specific, and care needs to be taken to keep both old and new
343 applications and libraries working.
345 <synopsis>int (*load) (struct drm_device *, unsigned long flags);</synopsis>
347 The method takes two arguments, a pointer to the newly created
348 <structname>drm_device</structname> and flags. The flags are used to
349 pass the <structfield>driver_data</structfield> field of the device id
350 corresponding to the device passed to <function>drm_*_init()</function>.
351 Only PCI devices currently use this, USB and platform DRM drivers have
352 their <methodname>load</methodname> method called with flags to 0.
355 <title>Driver Private Data</title>
357 The driver private hangs off the main
358 <structname>drm_device</structname> structure and can be used for
359 tracking various device-specific bits of information, like register
360 offsets, command buffer status, register state for suspend/resume, etc.
361 At load time, a driver may simply allocate one and set
362 <structname>drm_device</structname>.<structfield>dev_priv</structfield>
363 appropriately; it should be freed and
364 <structname>drm_device</structname>.<structfield>dev_priv</structfield>
365 set to NULL when the driver is unloaded.
368 <sect3 id="drm-irq-registration">
369 <title>IRQ Registration</title>
371 The DRM core tries to facilitate IRQ handler registration and
372 unregistration by providing <function>drm_irq_install</function> and
373 <function>drm_irq_uninstall</function> functions. Those functions only
374 support a single interrupt per device, devices that use more than one
375 IRQs need to be handled manually.
378 <title>Managed IRQ Registration</title>
380 <function>drm_irq_install</function> starts by calling the
381 <methodname>irq_preinstall</methodname> driver operation. The operation
382 is optional and must make sure that the interrupt will not get fired by
383 clearing all pending interrupt flags or disabling the interrupt.
386 The passed-in IRQ will then be requested by a call to
387 <function>request_irq</function>. If the DRIVER_IRQ_SHARED driver
388 feature flag is set, a shared (IRQF_SHARED) IRQ handler will be
392 The IRQ handler function must be provided as the mandatory irq_handler
393 driver operation. It will get passed directly to
394 <function>request_irq</function> and thus has the same prototype as all
395 IRQ handlers. It will get called with a pointer to the DRM device as the
399 Finally the function calls the optional
400 <methodname>irq_postinstall</methodname> driver operation. The operation
401 usually enables interrupts (excluding the vblank interrupt, which is
402 enabled separately), but drivers may choose to enable/disable interrupts
406 <function>drm_irq_uninstall</function> is similarly used to uninstall an
407 IRQ handler. It starts by waking up all processes waiting on a vblank
408 interrupt to make sure they don't hang, and then calls the optional
409 <methodname>irq_uninstall</methodname> driver operation. The operation
410 must disable all hardware interrupts. Finally the function frees the IRQ
411 by calling <function>free_irq</function>.
415 <title>Manual IRQ Registration</title>
417 Drivers that require multiple interrupt handlers can't use the managed
418 IRQ registration functions. In that case IRQs must be registered and
419 unregistered manually (usually with the <function>request_irq</function>
420 and <function>free_irq</function> functions, or their devm_* equivalent).
423 When manually registering IRQs, drivers must not set the DRIVER_HAVE_IRQ
424 driver feature flag, and must not provide the
425 <methodname>irq_handler</methodname> driver operation. They must set the
426 <structname>drm_device</structname> <structfield>irq_enabled</structfield>
427 field to 1 upon registration of the IRQs, and clear it to 0 after
428 unregistering the IRQs.
433 <title>Memory Manager Initialization</title>
435 Every DRM driver requires a memory manager which must be initialized at
436 load time. DRM currently contains two memory managers, the Translation
437 Table Manager (TTM) and the Graphics Execution Manager (GEM).
438 This document describes the use of the GEM memory manager only. See
439 <xref linkend="drm-memory-management"/> for details.
443 <title>Miscellaneous Device Configuration</title>
445 Another task that may be necessary for PCI devices during configuration
446 is mapping the video BIOS. On many devices, the VBIOS describes device
447 configuration, LCD panel timings (if any), and contains flags indicating
448 device state. Mapping the BIOS can be done using the pci_map_rom() call,
449 a convenience function that takes care of mapping the actual ROM,
450 whether it has been shadowed into memory (typically at address 0xc0000)
451 or exists on the PCI device in the ROM BAR. Note that after the ROM has
452 been mapped and any necessary information has been extracted, it should
453 be unmapped; on many devices, the ROM address decoder is shared with
454 other BARs, so leaving it mapped could cause undesired behaviour like
455 hangs or memory corruption.
456 <!--!Fdrivers/pci/rom.c pci_map_rom-->
462 <!-- Internals: memory management -->
464 <sect1 id="drm-memory-management">
465 <title>Memory management</title>
467 Modern Linux systems require large amount of graphics memory to store
468 frame buffers, textures, vertices and other graphics-related data. Given
469 the very dynamic nature of many of that data, managing graphics memory
470 efficiently is thus crucial for the graphics stack and plays a central
471 role in the DRM infrastructure.
474 The DRM core includes two memory managers, namely Translation Table Maps
475 (TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory
476 manager to be developed and tried to be a one-size-fits-them all
477 solution. It provides a single userspace API to accommodate the need of
478 all hardware, supporting both Unified Memory Architecture (UMA) devices
479 and devices with dedicated video RAM (i.e. most discrete video cards).
480 This resulted in a large, complex piece of code that turned out to be
481 hard to use for driver development.
484 GEM started as an Intel-sponsored project in reaction to TTM's
485 complexity. Its design philosophy is completely different: instead of
486 providing a solution to every graphics memory-related problems, GEM
487 identified common code between drivers and created a support library to
488 share it. GEM has simpler initialization and execution requirements than
489 TTM, but has no video RAM management capabilities and is thus limited to
493 <title>The Translation Table Manager (TTM)</title>
495 TTM design background and information belongs here.
498 <title>TTM initialization</title>
499 <warning><para>This section is outdated.</para></warning>
501 Drivers wishing to support TTM must fill out a drm_bo_driver
502 structure. The structure contains several fields with function
503 pointers for initializing the TTM, allocating and freeing memory,
504 waiting for command completion and fence synchronization, and memory
505 migration. See the radeon_ttm.c file for an example of usage.
508 The ttm_global_reference structure is made up of several fields:
511 struct ttm_global_reference {
512 enum ttm_global_types global_type;
515 int (*init) (struct ttm_global_reference *);
516 void (*release) (struct ttm_global_reference *);
520 There should be one global reference structure for your memory
521 manager as a whole, and there will be others for each object
522 created by the memory manager at runtime. Your global TTM should
523 have a type of TTM_GLOBAL_TTM_MEM. The size field for the global
524 object should be sizeof(struct ttm_mem_global), and the init and
525 release hooks should point at your driver-specific init and
526 release routines, which probably eventually call
527 ttm_mem_global_init and ttm_mem_global_release, respectively.
530 Once your global TTM accounting structure is set up and initialized
531 by calling ttm_global_item_ref() on it,
532 you need to create a buffer object TTM to
533 provide a pool for buffer object allocation by clients and the
534 kernel itself. The type of this object should be TTM_GLOBAL_TTM_BO,
535 and its size should be sizeof(struct ttm_bo_global). Again,
536 driver-specific init and release functions may be provided,
537 likely eventually calling ttm_bo_global_init() and
538 ttm_bo_global_release(), respectively. Also, like the previous
539 object, ttm_global_item_ref() is used to create an initial reference
540 count for the TTM, which will call your initialization function.
545 <title>The Graphics Execution Manager (GEM)</title>
547 The GEM design approach has resulted in a memory manager that doesn't
548 provide full coverage of all (or even all common) use cases in its
549 userspace or kernel API. GEM exposes a set of standard memory-related
550 operations to userspace and a set of helper functions to drivers, and let
551 drivers implement hardware-specific operations with their own private API.
554 The GEM userspace API is described in the
555 <ulink url="http://lwn.net/Articles/283798/"><citetitle>GEM - the Graphics
556 Execution Manager</citetitle></ulink> article on LWN. While slightly
557 outdated, the document provides a good overview of the GEM API principles.
558 Buffer allocation and read and write operations, described as part of the
559 common GEM API, are currently implemented using driver-specific ioctls.
562 GEM is data-agnostic. It manages abstract buffer objects without knowing
563 what individual buffers contain. APIs that require knowledge of buffer
564 contents or purpose, such as buffer allocation or synchronization
565 primitives, are thus outside of the scope of GEM and must be implemented
566 using driver-specific ioctls.
569 On a fundamental level, GEM involves several operations:
571 <listitem>Memory allocation and freeing</listitem>
572 <listitem>Command execution</listitem>
573 <listitem>Aperture management at command execution time</listitem>
575 Buffer object allocation is relatively straightforward and largely
576 provided by Linux's shmem layer, which provides memory to back each
580 Device-specific operations, such as command execution, pinning, buffer
581 read & write, mapping, and domain ownership transfers are left to
582 driver-specific ioctls.
585 <title>GEM Initialization</title>
587 Drivers that use GEM must set the DRIVER_GEM bit in the struct
588 <structname>drm_driver</structname>
589 <structfield>driver_features</structfield> field. The DRM core will
590 then automatically initialize the GEM core before calling the
591 <methodname>load</methodname> operation. Behind the scene, this will
592 create a DRM Memory Manager object which provides an address space
593 pool for object allocation.
596 In a KMS configuration, drivers need to allocate and initialize a
597 command ring buffer following core GEM initialization if required by
598 the hardware. UMA devices usually have what is called a "stolen"
599 memory region, which provides space for the initial framebuffer and
600 large, contiguous memory regions required by the device. This space is
601 typically not managed by GEM, and must be initialized separately into
602 its own DRM MM object.
606 <title>GEM Objects Creation</title>
608 GEM splits creation of GEM objects and allocation of the memory that
609 backs them in two distinct operations.
612 GEM objects are represented by an instance of struct
613 <structname>drm_gem_object</structname>. Drivers usually need to extend
614 GEM objects with private information and thus create a driver-specific
615 GEM object structure type that embeds an instance of struct
616 <structname>drm_gem_object</structname>.
619 To create a GEM object, a driver allocates memory for an instance of its
620 specific GEM object type and initializes the embedded struct
621 <structname>drm_gem_object</structname> with a call to
622 <function>drm_gem_object_init</function>. The function takes a pointer to
623 the DRM device, a pointer to the GEM object and the buffer object size
627 GEM uses shmem to allocate anonymous pageable memory.
628 <function>drm_gem_object_init</function> will create an shmfs file of
629 the requested size and store it into the struct
630 <structname>drm_gem_object</structname> <structfield>filp</structfield>
631 field. The memory is used as either main storage for the object when the
632 graphics hardware uses system memory directly or as a backing store
636 Drivers are responsible for the actual physical pages allocation by
637 calling <function>shmem_read_mapping_page_gfp</function> for each page.
638 Note that they can decide to allocate pages when initializing the GEM
639 object, or to delay allocation until the memory is needed (for instance
640 when a page fault occurs as a result of a userspace memory access or
641 when the driver needs to start a DMA transfer involving the memory).
644 Anonymous pageable memory allocation is not always desired, for instance
645 when the hardware requires physically contiguous system memory as is
646 often the case in embedded devices. Drivers can create GEM objects with
647 no shmfs backing (called private GEM objects) by initializing them with
648 a call to <function>drm_gem_private_object_init</function> instead of
649 <function>drm_gem_object_init</function>. Storage for private GEM
650 objects must be managed by drivers.
653 Drivers that do not need to extend GEM objects with private information
654 can call the <function>drm_gem_object_alloc</function> function to
655 allocate and initialize a struct <structname>drm_gem_object</structname>
656 instance. The GEM core will call the optional driver
657 <methodname>gem_init_object</methodname> operation after initializing
658 the GEM object with <function>drm_gem_object_init</function>.
659 <synopsis>int (*gem_init_object) (struct drm_gem_object *obj);</synopsis>
662 No alloc-and-init function exists for private GEM objects.
666 <title>GEM Objects Lifetime</title>
668 All GEM objects are reference-counted by the GEM core. References can be
669 acquired and release by <function>calling drm_gem_object_reference</function>
670 and <function>drm_gem_object_unreference</function> respectively. The
671 caller must hold the <structname>drm_device</structname>
672 <structfield>struct_mutex</structfield> lock. As a convenience, GEM
673 provides the <function>drm_gem_object_reference_unlocked</function> and
674 <function>drm_gem_object_unreference_unlocked</function> functions that
675 can be called without holding the lock.
678 When the last reference to a GEM object is released the GEM core calls
679 the <structname>drm_driver</structname>
680 <methodname>gem_free_object</methodname> operation. That operation is
681 mandatory for GEM-enabled drivers and must free the GEM object and all
682 associated resources.
685 <synopsis>void (*gem_free_object) (struct drm_gem_object *obj);</synopsis>
686 Drivers are responsible for freeing all GEM object resources, including
687 the resources created by the GEM core. If an mmap offset has been
688 created for the object (in which case
689 <structname>drm_gem_object</structname>::<structfield>map_list</structfield>::<structfield>map</structfield>
690 is not NULL) it must be freed by a call to
691 <function>drm_gem_free_mmap_offset</function>. The shmfs backing store
692 must be released by calling <function>drm_gem_object_release</function>
693 (that function can safely be called if no shmfs backing store has been
698 <title>GEM Objects Naming</title>
700 Communication between userspace and the kernel refers to GEM objects
701 using local handles, global names or, more recently, file descriptors.
702 All of those are 32-bit integer values; the usual Linux kernel limits
703 apply to the file descriptors.
706 GEM handles are local to a DRM file. Applications get a handle to a GEM
707 object through a driver-specific ioctl, and can use that handle to refer
708 to the GEM object in other standard or driver-specific ioctls. Closing a
709 DRM file handle frees all its GEM handles and dereferences the
710 associated GEM objects.
713 To create a handle for a GEM object drivers call
714 <function>drm_gem_handle_create</function>. The function takes a pointer
715 to the DRM file and the GEM object and returns a locally unique handle.
716 When the handle is no longer needed drivers delete it with a call to
717 <function>drm_gem_handle_delete</function>. Finally the GEM object
718 associated with a handle can be retrieved by a call to
719 <function>drm_gem_object_lookup</function>.
722 Handles don't take ownership of GEM objects, they only take a reference
723 to the object that will be dropped when the handle is destroyed. To
724 avoid leaking GEM objects, drivers must make sure they drop the
725 reference(s) they own (such as the initial reference taken at object
726 creation time) as appropriate, without any special consideration for the
727 handle. For example, in the particular case of combined GEM object and
728 handle creation in the implementation of the
729 <methodname>dumb_create</methodname> operation, drivers must drop the
730 initial reference to the GEM object before returning the handle.
733 GEM names are similar in purpose to handles but are not local to DRM
734 files. They can be passed between processes to reference a GEM object
735 globally. Names can't be used directly to refer to objects in the DRM
736 API, applications must convert handles to names and names to handles
737 using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls
738 respectively. The conversion is handled by the DRM core without any
739 driver-specific support.
742 GEM also supports buffer sharing with dma-buf file descriptors through
743 PRIME. GEM-based drivers must use the provided helpers functions to
744 implement the exporting and importing correctly. See <xref linkend="drm-prime-support" />.
745 Since sharing file descriptors is inherently more secure than the
746 easily guessable and global GEM names it is the preferred buffer
747 sharing mechanism. Sharing buffers through GEM names is only supported
748 for legacy userspace. Furthermore PRIME also allows cross-device
749 buffer sharing since it is based on dma-bufs.
752 <sect3 id="drm-gem-objects-mapping">
753 <title>GEM Objects Mapping</title>
755 Because mapping operations are fairly heavyweight GEM favours
756 read/write-like access to buffers, implemented through driver-specific
757 ioctls, over mapping buffers to userspace. However, when random access
758 to the buffer is needed (to perform software rendering for instance),
759 direct access to the object can be more efficient.
762 The mmap system call can't be used directly to map GEM objects, as they
763 don't have their own file handle. Two alternative methods currently
764 co-exist to map GEM objects to userspace. The first method uses a
765 driver-specific ioctl to perform the mapping operation, calling
766 <function>do_mmap</function> under the hood. This is often considered
767 dubious, seems to be discouraged for new GEM-enabled drivers, and will
768 thus not be described here.
771 The second method uses the mmap system call on the DRM file handle.
772 <synopsis>void *mmap(void *addr, size_t length, int prot, int flags, int fd,
773 off_t offset);</synopsis>
774 DRM identifies the GEM object to be mapped by a fake offset passed
775 through the mmap offset argument. Prior to being mapped, a GEM object
776 must thus be associated with a fake offset. To do so, drivers must call
777 <function>drm_gem_create_mmap_offset</function> on the object. The
778 function allocates a fake offset range from a pool and stores the
779 offset divided by PAGE_SIZE in
780 <literal>obj->map_list.hash.key</literal>. Care must be taken not to
781 call <function>drm_gem_create_mmap_offset</function> if a fake offset
782 has already been allocated for the object. This can be tested by
783 <literal>obj->map_list.map</literal> being non-NULL.
786 Once allocated, the fake offset value
787 (<literal>obj->map_list.hash.key << PAGE_SHIFT</literal>)
788 must be passed to the application in a driver-specific way and can then
789 be used as the mmap offset argument.
792 The GEM core provides a helper method <function>drm_gem_mmap</function>
793 to handle object mapping. The method can be set directly as the mmap
794 file operation handler. It will look up the GEM object based on the
795 offset value and set the VMA operations to the
796 <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
797 field. Note that <function>drm_gem_mmap</function> doesn't map memory to
798 userspace, but relies on the driver-provided fault handler to map pages
802 To use <function>drm_gem_mmap</function>, drivers must fill the struct
803 <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
804 field with a pointer to VM operations.
807 <synopsis>struct vm_operations_struct *gem_vm_ops
809 struct vm_operations_struct {
810 void (*open)(struct vm_area_struct * area);
811 void (*close)(struct vm_area_struct * area);
812 int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf);
816 The <methodname>open</methodname> and <methodname>close</methodname>
817 operations must update the GEM object reference count. Drivers can use
818 the <function>drm_gem_vm_open</function> and
819 <function>drm_gem_vm_close</function> helper functions directly as open
823 The fault operation handler is responsible for mapping individual pages
824 to userspace when a page fault occurs. Depending on the memory
825 allocation scheme, drivers can allocate pages at fault time, or can
826 decide to allocate memory for the GEM object at the time the object is
830 Drivers that want to map the GEM object upfront instead of handling page
831 faults can implement their own mmap file operation handler.
835 <title>Memory Coherency</title>
837 When mapped to the device or used in a command buffer, backing pages
838 for an object are flushed to memory and marked write combined so as to
839 be coherent with the GPU. Likewise, if the CPU accesses an object
840 after the GPU has finished rendering to the object, then the object
841 must be made coherent with the CPU's view of memory, usually involving
842 GPU cache flushing of various kinds. This core CPU<->GPU
843 coherency management is provided by a device-specific ioctl, which
844 evaluates an object's current domain and performs any necessary
845 flushing or synchronization to put the object into the desired
846 coherency domain (note that the object may be busy, i.e. an active
847 render target; in that case, setting the domain blocks the client and
848 waits for rendering to complete before performing any necessary
849 flushing operations).
853 <title>Command Execution</title>
855 Perhaps the most important GEM function for GPU devices is providing a
856 command execution interface to clients. Client programs construct
857 command buffers containing references to previously allocated memory
858 objects, and then submit them to GEM. At that point, GEM takes care to
859 bind all the objects into the GTT, execute the buffer, and provide
860 necessary synchronization between clients accessing the same buffers.
861 This often involves evicting some objects from the GTT and re-binding
862 others (a fairly expensive operation), and providing relocation
863 support which hides fixed GTT offsets from clients. Clients must take
864 care not to submit command buffers that reference more objects than
865 can fit in the GTT; otherwise, GEM will reject them and no rendering
866 will occur. Similarly, if several objects in the buffer require fence
867 registers to be allocated for correct rendering (e.g. 2D blits on
868 pre-965 chips), care must be taken not to require more fence registers
869 than are available to the client. Such resource management should be
870 abstracted from the client in libdrm.
874 <title>GEM Function Reference</title>
875 !Edrivers/gpu/drm/drm_gem.c
879 <title>VMA Offset Manager</title>
880 !Pdrivers/gpu/drm/drm_vma_manager.c vma offset manager
881 !Edrivers/gpu/drm/drm_vma_manager.c
882 !Iinclude/drm/drm_vma_manager.h
884 <sect2 id="drm-prime-support">
885 <title>PRIME Buffer Sharing</title>
887 PRIME is the cross device buffer sharing framework in drm, originally
888 created for the OPTIMUS range of multi-gpu platforms. To userspace
889 PRIME buffers are dma-buf based file descriptors.
892 <title>Overview and Driver Interface</title>
894 Similar to GEM global names, PRIME file descriptors are
895 also used to share buffer objects across processes. They offer
896 additional security: as file descriptors must be explicitly sent over
897 UNIX domain sockets to be shared between applications, they can't be
898 guessed like the globally unique GEM names.
901 Drivers that support the PRIME
902 API must set the DRIVER_PRIME bit in the struct
903 <structname>drm_driver</structname>
904 <structfield>driver_features</structfield> field, and implement the
905 <methodname>prime_handle_to_fd</methodname> and
906 <methodname>prime_fd_to_handle</methodname> operations.
909 <synopsis>int (*prime_handle_to_fd)(struct drm_device *dev,
910 struct drm_file *file_priv, uint32_t handle,
911 uint32_t flags, int *prime_fd);
912 int (*prime_fd_to_handle)(struct drm_device *dev,
913 struct drm_file *file_priv, int prime_fd,
914 uint32_t *handle);</synopsis>
915 Those two operations convert a handle to a PRIME file descriptor and
916 vice versa. Drivers must use the kernel dma-buf buffer sharing framework
917 to manage the PRIME file descriptors. Similar to the mode setting
918 API PRIME is agnostic to the underlying buffer object manager, as
919 long as handles are 32bit unsigned integers.
922 While non-GEM drivers must implement the operations themselves, GEM
923 drivers must use the <function>drm_gem_prime_handle_to_fd</function>
924 and <function>drm_gem_prime_fd_to_handle</function> helper functions.
925 Those helpers rely on the driver
926 <methodname>gem_prime_export</methodname> and
927 <methodname>gem_prime_import</methodname> operations to create a dma-buf
928 instance from a GEM object (dma-buf exporter role) and to create a GEM
929 object from a dma-buf instance (dma-buf importer role).
932 <synopsis>struct dma_buf * (*gem_prime_export)(struct drm_device *dev,
933 struct drm_gem_object *obj,
935 struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev,
936 struct dma_buf *dma_buf);</synopsis>
937 These two operations are mandatory for GEM drivers that support
942 <title>PRIME Helper Functions</title>
943 !Pdrivers/gpu/drm/drm_prime.c PRIME Helpers
947 <title>PRIME Function References</title>
948 !Edrivers/gpu/drm/drm_prime.c
951 <title>DRM MM Range Allocator</title>
953 <title>Overview</title>
954 !Pdrivers/gpu/drm/drm_mm.c Overview
957 <title>LRU Scan/Eviction Support</title>
958 !Pdrivers/gpu/drm/drm_mm.c lru scan roaster
962 <title>DRM MM Range Allocator Function References</title>
963 !Edrivers/gpu/drm/drm_mm.c
964 !Iinclude/drm/drm_mm.h
968 <!-- Internals: mode setting -->
970 <sect1 id="drm-mode-setting">
971 <title>Mode Setting</title>
973 Drivers must initialize the mode setting core by calling
974 <function>drm_mode_config_init</function> on the DRM device. The function
975 initializes the <structname>drm_device</structname>
976 <structfield>mode_config</structfield> field and never fails. Once done,
977 mode configuration must be setup by initializing the following fields.
981 <synopsis>int min_width, min_height;
982 int max_width, max_height;</synopsis>
984 Minimum and maximum width and height of the frame buffers in pixel
989 <synopsis>struct drm_mode_config_funcs *funcs;</synopsis>
990 <para>Mode setting functions.</para>
994 <title>Display Modes Function Reference</title>
995 !Iinclude/drm/drm_modes.h
996 !Edrivers/gpu/drm/drm_modes.c
999 <title>Frame Buffer Creation</title>
1000 <synopsis>struct drm_framebuffer *(*fb_create)(struct drm_device *dev,
1001 struct drm_file *file_priv,
1002 struct drm_mode_fb_cmd2 *mode_cmd);</synopsis>
1004 Frame buffers are abstract memory objects that provide a source of
1005 pixels to scanout to a CRTC. Applications explicitly request the
1006 creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls and
1007 receive an opaque handle that can be passed to the KMS CRTC control,
1008 plane configuration and page flip functions.
1011 Frame buffers rely on the underneath memory manager for low-level memory
1012 operations. When creating a frame buffer applications pass a memory
1013 handle (or a list of memory handles for multi-planar formats) through
1014 the <parameter>drm_mode_fb_cmd2</parameter> argument. For drivers using
1015 GEM as their userspace buffer management interface this would be a GEM
1016 handle. Drivers are however free to use their own backing storage object
1017 handles, e.g. vmwgfx directly exposes special TTM handles to userspace
1018 and so expects TTM handles in the create ioctl and not GEM handles.
1021 Drivers must first validate the requested frame buffer parameters passed
1022 through the mode_cmd argument. In particular this is where invalid
1023 sizes, pixel formats or pitches can be caught.
1026 If the parameters are deemed valid, drivers then create, initialize and
1027 return an instance of struct <structname>drm_framebuffer</structname>.
1028 If desired the instance can be embedded in a larger driver-specific
1029 structure. Drivers must fill its <structfield>width</structfield>,
1030 <structfield>height</structfield>, <structfield>pitches</structfield>,
1031 <structfield>offsets</structfield>, <structfield>depth</structfield>,
1032 <structfield>bits_per_pixel</structfield> and
1033 <structfield>pixel_format</structfield> fields from the values passed
1034 through the <parameter>drm_mode_fb_cmd2</parameter> argument. They
1035 should call the <function>drm_helper_mode_fill_fb_struct</function>
1036 helper function to do so.
1040 The initialization of the new framebuffer instance is finalized with a
1041 call to <function>drm_framebuffer_init</function> which takes a pointer
1042 to DRM frame buffer operations (struct
1043 <structname>drm_framebuffer_funcs</structname>). Note that this function
1044 publishes the framebuffer and so from this point on it can be accessed
1045 concurrently from other threads. Hence it must be the last step in the
1046 driver's framebuffer initialization sequence. Frame buffer operations
1050 <synopsis>int (*create_handle)(struct drm_framebuffer *fb,
1051 struct drm_file *file_priv, unsigned int *handle);</synopsis>
1053 Create a handle to the frame buffer underlying memory object. If
1054 the frame buffer uses a multi-plane format, the handle will
1055 reference the memory object associated with the first plane.
1058 Drivers call <function>drm_gem_handle_create</function> to create
1063 <synopsis>void (*destroy)(struct drm_framebuffer *framebuffer);</synopsis>
1065 Destroy the frame buffer object and frees all associated
1066 resources. Drivers must call
1067 <function>drm_framebuffer_cleanup</function> to free resources
1068 allocated by the DRM core for the frame buffer object, and must
1069 make sure to unreference all memory objects associated with the
1070 frame buffer. Handles created by the
1071 <methodname>create_handle</methodname> operation are released by
1076 <synopsis>int (*dirty)(struct drm_framebuffer *framebuffer,
1077 struct drm_file *file_priv, unsigned flags, unsigned color,
1078 struct drm_clip_rect *clips, unsigned num_clips);</synopsis>
1080 This optional operation notifies the driver that a region of the
1081 frame buffer has changed in response to a DRM_IOCTL_MODE_DIRTYFB
1088 The lifetime of a drm framebuffer is controlled with a reference count,
1089 drivers can grab additional references with
1090 <function>drm_framebuffer_reference</function>and drop them
1091 again with <function>drm_framebuffer_unreference</function>. For
1092 driver-private framebuffers for which the last reference is never
1093 dropped (e.g. for the fbdev framebuffer when the struct
1094 <structname>drm_framebuffer</structname> is embedded into the fbdev
1095 helper struct) drivers can manually clean up a framebuffer at module
1097 <function>drm_framebuffer_unregister_private</function>.
1101 <title>Dumb Buffer Objects</title>
1103 The KMS API doesn't standardize backing storage object creation and
1104 leaves it to driver-specific ioctls. Furthermore actually creating a
1105 buffer object even for GEM-based drivers is done through a
1106 driver-specific ioctl - GEM only has a common userspace interface for
1107 sharing and destroying objects. While not an issue for full-fledged
1108 graphics stacks that include device-specific userspace components (in
1109 libdrm for instance), this limit makes DRM-based early boot graphics
1110 unnecessarily complex.
1113 Dumb objects partly alleviate the problem by providing a standard
1114 API to create dumb buffers suitable for scanout, which can then be used
1115 to create KMS frame buffers.
1118 To support dumb objects drivers must implement the
1119 <methodname>dumb_create</methodname>,
1120 <methodname>dumb_destroy</methodname> and
1121 <methodname>dumb_map_offset</methodname> operations.
1125 <synopsis>int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev,
1126 struct drm_mode_create_dumb *args);</synopsis>
1128 The <methodname>dumb_create</methodname> operation creates a driver
1129 object (GEM or TTM handle) suitable for scanout based on the
1130 width, height and depth from the struct
1131 <structname>drm_mode_create_dumb</structname> argument. It fills the
1132 argument's <structfield>handle</structfield>,
1133 <structfield>pitch</structfield> and <structfield>size</structfield>
1134 fields with a handle for the newly created object and its line
1135 pitch and size in bytes.
1139 <synopsis>int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev,
1140 uint32_t handle);</synopsis>
1142 The <methodname>dumb_destroy</methodname> operation destroys a dumb
1143 object created by <methodname>dumb_create</methodname>.
1147 <synopsis>int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev,
1148 uint32_t handle, uint64_t *offset);</synopsis>
1150 The <methodname>dumb_map_offset</methodname> operation associates an
1151 mmap fake offset with the object given by the handle and returns
1152 it. Drivers must use the
1153 <function>drm_gem_create_mmap_offset</function> function to
1154 associate the fake offset as described in
1155 <xref linkend="drm-gem-objects-mapping"/>.
1160 Note that dumb objects may not be used for gpu acceleration, as has been
1161 attempted on some ARM embedded platforms. Such drivers really must have
1162 a hardware-specific ioctl to allocate suitable buffer objects.
1166 <title>Output Polling</title>
1167 <synopsis>void (*output_poll_changed)(struct drm_device *dev);</synopsis>
1169 This operation notifies the driver that the status of one or more
1170 connectors has changed. Drivers that use the fb helper can just call the
1171 <function>drm_fb_helper_hotplug_event</function> function to handle this
1176 <title>Locking</title>
1178 Beside some lookup structures with their own locking (which is hidden
1179 behind the interface functions) most of the modeset state is protected
1180 by the <code>dev-<mode_config.lock</code> mutex and additionally
1181 per-crtc locks to allow cursor updates, pageflips and similar operations
1182 to occur concurrently with background tasks like output detection.
1183 Operations which cross domains like a full modeset always grab all
1184 locks. Drivers there need to protect resources shared between crtcs with
1185 additional locking. They also need to be careful to always grab the
1186 relevant crtc locks if a modset functions touches crtc state, e.g. for
1187 load detection (which does only grab the <code>mode_config.lock</code>
1188 to allow concurrent screen updates on live crtcs).
1193 <!-- Internals: kms initialization and cleanup -->
1195 <sect1 id="drm-kms-init">
1196 <title>KMS Initialization and Cleanup</title>
1198 A KMS device is abstracted and exposed as a set of planes, CRTCs, encoders
1199 and connectors. KMS drivers must thus create and initialize all those
1200 objects at load time after initializing mode setting.
1203 <title>CRTCs (struct <structname>drm_crtc</structname>)</title>
1205 A CRTC is an abstraction representing a part of the chip that contains a
1206 pointer to a scanout buffer. Therefore, the number of CRTCs available
1207 determines how many independent scanout buffers can be active at any
1208 given time. The CRTC structure contains several fields to support this:
1209 a pointer to some video memory (abstracted as a frame buffer object), a
1210 display mode, and an (x, y) offset into the video memory to support
1211 panning or configurations where one piece of video memory spans multiple
1215 <title>CRTC Initialization</title>
1217 A KMS device must create and register at least one struct
1218 <structname>drm_crtc</structname> instance. The instance is allocated
1219 and zeroed by the driver, possibly as part of a larger structure, and
1220 registered with a call to <function>drm_crtc_init</function> with a
1221 pointer to CRTC functions.
1224 <sect3 id="drm-kms-crtcops">
1225 <title>CRTC Operations</title>
1227 <title>Set Configuration</title>
1228 <synopsis>int (*set_config)(struct drm_mode_set *set);</synopsis>
1230 Apply a new CRTC configuration to the device. The configuration
1231 specifies a CRTC, a frame buffer to scan out from, a (x,y) position in
1232 the frame buffer, a display mode and an array of connectors to drive
1233 with the CRTC if possible.
1236 If the frame buffer specified in the configuration is NULL, the driver
1237 must detach all encoders connected to the CRTC and all connectors
1238 attached to those encoders and disable them.
1241 This operation is called with the mode config lock held.
1244 Note that the drm core has no notion of restoring the mode setting
1245 state after resume, since all resume handling is in the full
1246 responsibility of the driver. The common mode setting helper library
1247 though provides a helper which can be used for this:
1248 <function>drm_helper_resume_force_mode</function>.
1252 <title>Page Flipping</title>
1253 <synopsis>int (*page_flip)(struct drm_crtc *crtc, struct drm_framebuffer *fb,
1254 struct drm_pending_vblank_event *event);</synopsis>
1256 Schedule a page flip to the given frame buffer for the CRTC. This
1257 operation is called with the mode config mutex held.
1260 Page flipping is a synchronization mechanism that replaces the frame
1261 buffer being scanned out by the CRTC with a new frame buffer during
1262 vertical blanking, avoiding tearing. When an application requests a page
1263 flip the DRM core verifies that the new frame buffer is large enough to
1264 be scanned out by the CRTC in the currently configured mode and then
1265 calls the CRTC <methodname>page_flip</methodname> operation with a
1266 pointer to the new frame buffer.
1269 The <methodname>page_flip</methodname> operation schedules a page flip.
1270 Once any pending rendering targeting the new frame buffer has
1271 completed, the CRTC will be reprogrammed to display that frame buffer
1272 after the next vertical refresh. The operation must return immediately
1273 without waiting for rendering or page flip to complete and must block
1274 any new rendering to the frame buffer until the page flip completes.
1277 If a page flip can be successfully scheduled the driver must set the
1278 <code>drm_crtc-<fb</code> field to the new framebuffer pointed to
1279 by <code>fb</code>. This is important so that the reference counting
1280 on framebuffers stays balanced.
1283 If a page flip is already pending, the
1284 <methodname>page_flip</methodname> operation must return
1285 -<errorname>EBUSY</errorname>.
1288 To synchronize page flip to vertical blanking the driver will likely
1289 need to enable vertical blanking interrupts. It should call
1290 <function>drm_vblank_get</function> for that purpose, and call
1291 <function>drm_vblank_put</function> after the page flip completes.
1294 If the application has requested to be notified when page flip completes
1295 the <methodname>page_flip</methodname> operation will be called with a
1296 non-NULL <parameter>event</parameter> argument pointing to a
1297 <structname>drm_pending_vblank_event</structname> instance. Upon page
1298 flip completion the driver must call <methodname>drm_send_vblank_event</methodname>
1299 to fill in the event and send to wake up any waiting processes.
1300 This can be performed with
1301 <programlisting><![CDATA[
1302 spin_lock_irqsave(&dev->event_lock, flags);
1304 drm_send_vblank_event(dev, pipe, event);
1305 spin_unlock_irqrestore(&dev->event_lock, flags);
1306 ]]></programlisting>
1309 FIXME: Could drivers that don't need to wait for rendering to complete
1310 just add the event to <literal>dev->vblank_event_list</literal> and
1311 let the DRM core handle everything, as for "normal" vertical blanking
1315 While waiting for the page flip to complete, the
1316 <literal>event->base.link</literal> list head can be used freely by
1317 the driver to store the pending event in a driver-specific list.
1320 If the file handle is closed before the event is signaled, drivers must
1321 take care to destroy the event in their
1322 <methodname>preclose</methodname> operation (and, if needed, call
1323 <function>drm_vblank_put</function>).
1327 <title>Miscellaneous</title>
1330 <synopsis>void (*set_property)(struct drm_crtc *crtc,
1331 struct drm_property *property, uint64_t value);</synopsis>
1333 Set the value of the given CRTC property to
1334 <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1335 for more information about properties.
1339 <synopsis>void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b,
1340 uint32_t start, uint32_t size);</synopsis>
1342 Apply a gamma table to the device. The operation is optional.
1346 <synopsis>void (*destroy)(struct drm_crtc *crtc);</synopsis>
1348 Destroy the CRTC when not needed anymore. See
1349 <xref linkend="drm-kms-init"/>.
1357 <title>Planes (struct <structname>drm_plane</structname>)</title>
1359 A plane represents an image source that can be blended with or overlayed
1360 on top of a CRTC during the scanout process. Planes are associated with
1361 a frame buffer to crop a portion of the image memory (source) and
1362 optionally scale it to a destination size. The result is then blended
1363 with or overlayed on top of a CRTC.
1366 The DRM core recognizes three types of planes:
1369 DRM_PLANE_TYPE_PRIMARY represents a "main" plane for a CRTC. Primary
1370 planes are the planes operated upon by by CRTC modesetting and flipping
1371 operations described in <xref linkend="drm-kms-crtcops"/>.
1374 DRM_PLANE_TYPE_CURSOR represents a "cursor" plane for a CRTC. Cursor
1375 planes are the planes operated upon by the DRM_IOCTL_MODE_CURSOR and
1376 DRM_IOCTL_MODE_CURSOR2 ioctls.
1379 DRM_PLANE_TYPE_OVERLAY represents all non-primary, non-cursor planes.
1380 Some drivers refer to these types of planes as "sprites" internally.
1383 For compatibility with legacy userspace, only overlay planes are made
1384 available to userspace by default. Userspace clients may set the
1385 DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate that
1386 they wish to receive a universal plane list containing all plane types.
1389 <title>Plane Initialization</title>
1391 To create a plane, a KMS drivers allocates and
1392 zeroes an instances of struct <structname>drm_plane</structname>
1393 (possibly as part of a larger structure) and registers it with a call
1394 to <function>drm_universal_plane_init</function>. The function takes a bitmask
1395 of the CRTCs that can be associated with the plane, a pointer to the
1396 plane functions, a list of format supported formats, and the type of
1397 plane (primary, cursor, or overlay) being initialized.
1400 Cursor and overlay planes are optional. All drivers should provide
1401 one primary plane per CRTC (although this requirement may change in
1402 the future); drivers that do not wish to provide special handling for
1403 primary planes may make use of the helper functions described in
1404 <xref linkend="drm-kms-planehelpers"/> to create and register a
1405 primary plane with standard capabilities.
1409 <title>Plane Operations</title>
1412 <synopsis>int (*update_plane)(struct drm_plane *plane, struct drm_crtc *crtc,
1413 struct drm_framebuffer *fb, int crtc_x, int crtc_y,
1414 unsigned int crtc_w, unsigned int crtc_h,
1415 uint32_t src_x, uint32_t src_y,
1416 uint32_t src_w, uint32_t src_h);</synopsis>
1418 Enable and configure the plane to use the given CRTC and frame buffer.
1421 The source rectangle in frame buffer memory coordinates is given by
1422 the <parameter>src_x</parameter>, <parameter>src_y</parameter>,
1423 <parameter>src_w</parameter> and <parameter>src_h</parameter>
1424 parameters (as 16.16 fixed point values). Devices that don't support
1425 subpixel plane coordinates can ignore the fractional part.
1428 The destination rectangle in CRTC coordinates is given by the
1429 <parameter>crtc_x</parameter>, <parameter>crtc_y</parameter>,
1430 <parameter>crtc_w</parameter> and <parameter>crtc_h</parameter>
1431 parameters (as integer values). Devices scale the source rectangle to
1432 the destination rectangle. If scaling is not supported, and the source
1433 rectangle size doesn't match the destination rectangle size, the
1434 driver must return a -<errorname>EINVAL</errorname> error.
1438 <synopsis>int (*disable_plane)(struct drm_plane *plane);</synopsis>
1440 Disable the plane. The DRM core calls this method in response to a
1441 DRM_IOCTL_MODE_SETPLANE ioctl call with the frame buffer ID set to 0.
1442 Disabled planes must not be processed by the CRTC.
1446 <synopsis>void (*destroy)(struct drm_plane *plane);</synopsis>
1448 Destroy the plane when not needed anymore. See
1449 <xref linkend="drm-kms-init"/>.
1456 <title>Encoders (struct <structname>drm_encoder</structname>)</title>
1458 An encoder takes pixel data from a CRTC and converts it to a format
1459 suitable for any attached connectors. On some devices, it may be
1460 possible to have a CRTC send data to more than one encoder. In that
1461 case, both encoders would receive data from the same scanout buffer,
1462 resulting in a "cloned" display configuration across the connectors
1463 attached to each encoder.
1466 <title>Encoder Initialization</title>
1468 As for CRTCs, a KMS driver must create, initialize and register at
1469 least one struct <structname>drm_encoder</structname> instance. The
1470 instance is allocated and zeroed by the driver, possibly as part of a
1474 Drivers must initialize the struct <structname>drm_encoder</structname>
1475 <structfield>possible_crtcs</structfield> and
1476 <structfield>possible_clones</structfield> fields before registering the
1477 encoder. Both fields are bitmasks of respectively the CRTCs that the
1478 encoder can be connected to, and sibling encoders candidate for cloning.
1481 After being initialized, the encoder must be registered with a call to
1482 <function>drm_encoder_init</function>. The function takes a pointer to
1483 the encoder functions and an encoder type. Supported types are
1486 DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A
1489 DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort
1492 DRM_MODE_ENCODER_LVDS for display panels
1495 DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, Component,
1499 DRM_MODE_ENCODER_VIRTUAL for virtual machine displays
1504 Encoders must be attached to a CRTC to be used. DRM drivers leave
1505 encoders unattached at initialization time. Applications (or the fbdev
1506 compatibility layer when implemented) are responsible for attaching the
1507 encoders they want to use to a CRTC.
1511 <title>Encoder Operations</title>
1514 <synopsis>void (*destroy)(struct drm_encoder *encoder);</synopsis>
1516 Called to destroy the encoder when not needed anymore. See
1517 <xref linkend="drm-kms-init"/>.
1521 <synopsis>void (*set_property)(struct drm_plane *plane,
1522 struct drm_property *property, uint64_t value);</synopsis>
1524 Set the value of the given plane property to
1525 <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1526 for more information about properties.
1533 <title>Connectors (struct <structname>drm_connector</structname>)</title>
1535 A connector is the final destination for pixel data on a device, and
1536 usually connects directly to an external display device like a monitor
1537 or laptop panel. A connector can only be attached to one encoder at a
1538 time. The connector is also the structure where information about the
1539 attached display is kept, so it contains fields for display data, EDID
1540 data, DPMS & connection status, and information about modes
1541 supported on the attached displays.
1544 <title>Connector Initialization</title>
1546 Finally a KMS driver must create, initialize, register and attach at
1547 least one struct <structname>drm_connector</structname> instance. The
1548 instance is created as other KMS objects and initialized by setting the
1553 <term><structfield>interlace_allowed</structfield></term>
1555 Whether the connector can handle interlaced modes.
1559 <term><structfield>doublescan_allowed</structfield></term>
1561 Whether the connector can handle doublescan.
1565 <term><structfield>display_info
1566 </structfield></term>
1568 Display information is filled from EDID information when a display
1569 is detected. For non hot-pluggable displays such as flat panels in
1570 embedded systems, the driver should initialize the
1571 <structfield>display_info</structfield>.<structfield>width_mm</structfield>
1573 <structfield>display_info</structfield>.<structfield>height_mm</structfield>
1574 fields with the physical size of the display.
1578 <term id="drm-kms-connector-polled"><structfield>polled</structfield></term>
1580 Connector polling mode, a combination of
1583 <term>DRM_CONNECTOR_POLL_HPD</term>
1585 The connector generates hotplug events and doesn't need to be
1586 periodically polled. The CONNECT and DISCONNECT flags must not
1587 be set together with the HPD flag.
1591 <term>DRM_CONNECTOR_POLL_CONNECT</term>
1593 Periodically poll the connector for connection.
1597 <term>DRM_CONNECTOR_POLL_DISCONNECT</term>
1599 Periodically poll the connector for disconnection.
1603 Set to 0 for connectors that don't support connection status
1609 The connector is then registered with a call to
1610 <function>drm_connector_init</function> with a pointer to the connector
1611 functions and a connector type, and exposed through sysfs with a call to
1612 <function>drm_connector_register</function>.
1615 Supported connector types are
1617 <listitem>DRM_MODE_CONNECTOR_VGA</listitem>
1618 <listitem>DRM_MODE_CONNECTOR_DVII</listitem>
1619 <listitem>DRM_MODE_CONNECTOR_DVID</listitem>
1620 <listitem>DRM_MODE_CONNECTOR_DVIA</listitem>
1621 <listitem>DRM_MODE_CONNECTOR_Composite</listitem>
1622 <listitem>DRM_MODE_CONNECTOR_SVIDEO</listitem>
1623 <listitem>DRM_MODE_CONNECTOR_LVDS</listitem>
1624 <listitem>DRM_MODE_CONNECTOR_Component</listitem>
1625 <listitem>DRM_MODE_CONNECTOR_9PinDIN</listitem>
1626 <listitem>DRM_MODE_CONNECTOR_DisplayPort</listitem>
1627 <listitem>DRM_MODE_CONNECTOR_HDMIA</listitem>
1628 <listitem>DRM_MODE_CONNECTOR_HDMIB</listitem>
1629 <listitem>DRM_MODE_CONNECTOR_TV</listitem>
1630 <listitem>DRM_MODE_CONNECTOR_eDP</listitem>
1631 <listitem>DRM_MODE_CONNECTOR_VIRTUAL</listitem>
1635 Connectors must be attached to an encoder to be used. For devices that
1636 map connectors to encoders 1:1, the connector should be attached at
1637 initialization time with a call to
1638 <function>drm_mode_connector_attach_encoder</function>. The driver must
1639 also set the <structname>drm_connector</structname>
1640 <structfield>encoder</structfield> field to point to the attached
1644 Finally, drivers must initialize the connectors state change detection
1645 with a call to <function>drm_kms_helper_poll_init</function>. If at
1646 least one connector is pollable but can't generate hotplug interrupts
1647 (indicated by the DRM_CONNECTOR_POLL_CONNECT and
1648 DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will
1649 automatically be queued to periodically poll for changes. Connectors
1650 that can generate hotplug interrupts must be marked with the
1651 DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must
1652 call <function>drm_helper_hpd_irq_event</function>. The function will
1653 queue a delayed work to check the state of all connectors, but no
1654 periodic polling will be done.
1658 <title>Connector Operations</title>
1660 Unless otherwise state, all operations are mandatory.
1664 <synopsis>void (*dpms)(struct drm_connector *connector, int mode);</synopsis>
1666 The DPMS operation sets the power state of a connector. The mode
1669 <listitem><para>DRM_MODE_DPMS_ON</para></listitem>
1670 <listitem><para>DRM_MODE_DPMS_STANDBY</para></listitem>
1671 <listitem><para>DRM_MODE_DPMS_SUSPEND</para></listitem>
1672 <listitem><para>DRM_MODE_DPMS_OFF</para></listitem>
1676 In all but DPMS_ON mode the encoder to which the connector is attached
1677 should put the display in low-power mode by driving its signals
1678 appropriately. If more than one connector is attached to the encoder
1679 care should be taken not to change the power state of other displays as
1680 a side effect. Low-power mode should be propagated to the encoders and
1681 CRTCs when all related connectors are put in low-power mode.
1685 <title>Modes</title>
1686 <synopsis>int (*fill_modes)(struct drm_connector *connector, uint32_t max_width,
1687 uint32_t max_height);</synopsis>
1689 Fill the mode list with all supported modes for the connector. If the
1690 <parameter>max_width</parameter> and <parameter>max_height</parameter>
1691 arguments are non-zero, the implementation must ignore all modes wider
1692 than <parameter>max_width</parameter> or higher than
1693 <parameter>max_height</parameter>.
1696 The connector must also fill in this operation its
1697 <structfield>display_info</structfield>
1698 <structfield>width_mm</structfield> and
1699 <structfield>height_mm</structfield> fields with the connected display
1700 physical size in millimeters. The fields should be set to 0 if the value
1701 isn't known or is not applicable (for instance for projector devices).
1705 <title>Connection Status</title>
1707 The connection status is updated through polling or hotplug events when
1708 supported (see <xref linkend="drm-kms-connector-polled"/>). The status
1709 value is reported to userspace through ioctls and must not be used
1710 inside the driver, as it only gets initialized by a call to
1711 <function>drm_mode_getconnector</function> from userspace.
1713 <synopsis>enum drm_connector_status (*detect)(struct drm_connector *connector,
1714 bool force);</synopsis>
1716 Check to see if anything is attached to the connector. The
1717 <parameter>force</parameter> parameter is set to false whilst polling or
1718 to true when checking the connector due to user request.
1719 <parameter>force</parameter> can be used by the driver to avoid
1720 expensive, destructive operations during automated probing.
1723 Return connector_status_connected if something is connected to the
1724 connector, connector_status_disconnected if nothing is connected and
1725 connector_status_unknown if the connection state isn't known.
1728 Drivers should only return connector_status_connected if the connection
1729 status has really been probed as connected. Connectors that can't detect
1730 the connection status, or failed connection status probes, should return
1731 connector_status_unknown.
1735 <title>Miscellaneous</title>
1738 <synopsis>void (*set_property)(struct drm_connector *connector,
1739 struct drm_property *property, uint64_t value);</synopsis>
1741 Set the value of the given connector property to
1742 <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1743 for more information about properties.
1747 <synopsis>void (*destroy)(struct drm_connector *connector);</synopsis>
1749 Destroy the connector when not needed anymore. See
1750 <xref linkend="drm-kms-init"/>.
1758 <title>Cleanup</title>
1760 The DRM core manages its objects' lifetime. When an object is not needed
1761 anymore the core calls its destroy function, which must clean up and
1762 free every resource allocated for the object. Every
1763 <function>drm_*_init</function> call must be matched with a
1764 corresponding <function>drm_*_cleanup</function> call to cleanup CRTCs
1765 (<function>drm_crtc_cleanup</function>), planes
1766 (<function>drm_plane_cleanup</function>), encoders
1767 (<function>drm_encoder_cleanup</function>) and connectors
1768 (<function>drm_connector_cleanup</function>). Furthermore, connectors
1769 that have been added to sysfs must be removed by a call to
1770 <function>drm_connector_unregister</function> before calling
1771 <function>drm_connector_cleanup</function>.
1774 Connectors state change detection must be cleanup up with a call to
1775 <function>drm_kms_helper_poll_fini</function>.
1779 <title>Output discovery and initialization example</title>
1780 <programlisting><![CDATA[
1781 void intel_crt_init(struct drm_device *dev)
1783 struct drm_connector *connector;
1784 struct intel_output *intel_output;
1786 intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL);
1790 connector = &intel_output->base;
1791 drm_connector_init(dev, &intel_output->base,
1792 &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA);
1794 drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs,
1795 DRM_MODE_ENCODER_DAC);
1797 drm_mode_connector_attach_encoder(&intel_output->base,
1798 &intel_output->enc);
1800 /* Set up the DDC bus. */
1801 intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A");
1802 if (!intel_output->ddc_bus) {
1803 dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration "
1808 intel_output->type = INTEL_OUTPUT_ANALOG;
1809 connector->interlace_allowed = 0;
1810 connector->doublescan_allowed = 0;
1812 drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs);
1813 drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs);
1815 drm_connector_register(connector);
1816 }]]></programlisting>
1818 In the example above (taken from the i915 driver), a CRTC, connector and
1819 encoder combination is created. A device-specific i2c bus is also
1820 created for fetching EDID data and performing monitor detection. Once
1821 the process is complete, the new connector is registered with sysfs to
1822 make its properties available to applications.
1826 <title>KMS API Functions</title>
1827 !Edrivers/gpu/drm/drm_crtc.c
1830 <title>KMS Locking</title>
1831 !Pdrivers/gpu/drm/drm_modeset_lock.c kms locking
1832 !Iinclude/drm/drm_modeset_lock.h
1833 !Edrivers/gpu/drm/drm_modeset_lock.c
1837 <!-- Internals: kms helper functions -->
1840 <title>Mode Setting Helper Functions</title>
1842 The plane, CRTC, encoder and connector functions provided by the drivers
1843 implement the DRM API. They're called by the DRM core and ioctl handlers
1844 to handle device state changes and configuration request. As implementing
1845 those functions often requires logic not specific to drivers, mid-layer
1846 helper functions are available to avoid duplicating boilerplate code.
1849 The DRM core contains one mid-layer implementation. The mid-layer provides
1850 implementations of several plane, CRTC, encoder and connector functions
1851 (called from the top of the mid-layer) that pre-process requests and call
1852 lower-level functions provided by the driver (at the bottom of the
1853 mid-layer). For instance, the
1854 <function>drm_crtc_helper_set_config</function> function can be used to
1855 fill the struct <structname>drm_crtc_funcs</structname>
1856 <structfield>set_config</structfield> field. When called, it will split
1857 the <methodname>set_config</methodname> operation in smaller, simpler
1858 operations and call the driver to handle them.
1861 To use the mid-layer, drivers call <function>drm_crtc_helper_add</function>,
1862 <function>drm_encoder_helper_add</function> and
1863 <function>drm_connector_helper_add</function> functions to install their
1864 mid-layer bottom operations handlers, and fill the
1865 <structname>drm_crtc_funcs</structname>,
1866 <structname>drm_encoder_funcs</structname> and
1867 <structname>drm_connector_funcs</structname> structures with pointers to
1868 the mid-layer top API functions. Installing the mid-layer bottom operation
1869 handlers is best done right after registering the corresponding KMS object.
1872 The mid-layer is not split between CRTC, encoder and connector operations.
1873 To use it, a driver must provide bottom functions for all of the three KMS
1877 <title>Helper Functions</title>
1880 <synopsis>int drm_crtc_helper_set_config(struct drm_mode_set *set);</synopsis>
1882 The <function>drm_crtc_helper_set_config</function> helper function
1883 is a CRTC <methodname>set_config</methodname> implementation. It
1884 first tries to locate the best encoder for each connector by calling
1885 the connector <methodname>best_encoder</methodname> helper
1889 After locating the appropriate encoders, the helper function will
1890 call the <methodname>mode_fixup</methodname> encoder and CRTC helper
1891 operations to adjust the requested mode, or reject it completely in
1892 which case an error will be returned to the application. If the new
1893 configuration after mode adjustment is identical to the current
1894 configuration the helper function will return without performing any
1898 If the adjusted mode is identical to the current mode but changes to
1899 the frame buffer need to be applied, the
1900 <function>drm_crtc_helper_set_config</function> function will call
1901 the CRTC <methodname>mode_set_base</methodname> helper operation. If
1902 the adjusted mode differs from the current mode, or if the
1903 <methodname>mode_set_base</methodname> helper operation is not
1904 provided, the helper function performs a full mode set sequence by
1905 calling the <methodname>prepare</methodname>,
1906 <methodname>mode_set</methodname> and
1907 <methodname>commit</methodname> CRTC and encoder helper operations,
1912 <synopsis>void drm_helper_connector_dpms(struct drm_connector *connector, int mode);</synopsis>
1914 The <function>drm_helper_connector_dpms</function> helper function
1915 is a connector <methodname>dpms</methodname> implementation that
1916 tracks power state of connectors. To use the function, drivers must
1917 provide <methodname>dpms</methodname> helper operations for CRTCs
1918 and encoders to apply the DPMS state to the device.
1921 The mid-layer doesn't track the power state of CRTCs and encoders.
1922 The <methodname>dpms</methodname> helper operations can thus be
1923 called with a mode identical to the currently active mode.
1927 <synopsis>int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
1928 uint32_t maxX, uint32_t maxY);</synopsis>
1930 The <function>drm_helper_probe_single_connector_modes</function> helper
1931 function is a connector <methodname>fill_modes</methodname>
1932 implementation that updates the connection status for the connector
1933 and then retrieves a list of modes by calling the connector
1934 <methodname>get_modes</methodname> helper operation.
1937 The function filters out modes larger than
1938 <parameter>max_width</parameter> and <parameter>max_height</parameter>
1939 if specified. It then calls the optional connector
1940 <methodname>mode_valid</methodname> helper operation for each mode in
1941 the probed list to check whether the mode is valid for the connector.
1947 <title>CRTC Helper Operations</title>
1949 <listitem id="drm-helper-crtc-mode-fixup">
1950 <synopsis>bool (*mode_fixup)(struct drm_crtc *crtc,
1951 const struct drm_display_mode *mode,
1952 struct drm_display_mode *adjusted_mode);</synopsis>
1954 Let CRTCs adjust the requested mode or reject it completely. This
1955 operation returns true if the mode is accepted (possibly after being
1956 adjusted) or false if it is rejected.
1959 The <methodname>mode_fixup</methodname> operation should reject the
1960 mode if it can't reasonably use it. The definition of "reasonable"
1961 is currently fuzzy in this context. One possible behaviour would be
1962 to set the adjusted mode to the panel timings when a fixed-mode
1963 panel is used with hardware capable of scaling. Another behaviour
1964 would be to accept any input mode and adjust it to the closest mode
1965 supported by the hardware (FIXME: This needs to be clarified).
1969 <synopsis>int (*mode_set_base)(struct drm_crtc *crtc, int x, int y,
1970 struct drm_framebuffer *old_fb)</synopsis>
1972 Move the CRTC on the current frame buffer (stored in
1973 <literal>crtc->fb</literal>) to position (x,y). Any of the frame
1974 buffer, x position or y position may have been modified.
1977 This helper operation is optional. If not provided, the
1978 <function>drm_crtc_helper_set_config</function> function will fall
1979 back to the <methodname>mode_set</methodname> helper operation.
1982 FIXME: Why are x and y passed as arguments, as they can be accessed
1983 through <literal>crtc->x</literal> and
1984 <literal>crtc->y</literal>?
1988 <synopsis>void (*prepare)(struct drm_crtc *crtc);</synopsis>
1990 Prepare the CRTC for mode setting. This operation is called after
1991 validating the requested mode. Drivers use it to perform
1992 device-specific operations required before setting the new mode.
1996 <synopsis>int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,
1997 struct drm_display_mode *adjusted_mode, int x, int y,
1998 struct drm_framebuffer *old_fb);</synopsis>
2000 Set a new mode, position and frame buffer. Depending on the device
2001 requirements, the mode can be stored internally by the driver and
2002 applied in the <methodname>commit</methodname> operation, or
2003 programmed to the hardware immediately.
2006 The <methodname>mode_set</methodname> operation returns 0 on success
2007 or a negative error code if an error occurs.
2011 <synopsis>void (*commit)(struct drm_crtc *crtc);</synopsis>
2013 Commit a mode. This operation is called after setting the new mode.
2014 Upon return the device must use the new mode and be fully
2021 <title>Encoder Helper Operations</title>
2024 <synopsis>bool (*mode_fixup)(struct drm_encoder *encoder,
2025 const struct drm_display_mode *mode,
2026 struct drm_display_mode *adjusted_mode);</synopsis>
2028 Let encoders adjust the requested mode or reject it completely. This
2029 operation returns true if the mode is accepted (possibly after being
2030 adjusted) or false if it is rejected. See the
2031 <link linkend="drm-helper-crtc-mode-fixup">mode_fixup CRTC helper
2032 operation</link> for an explanation of the allowed adjustments.
2036 <synopsis>void (*prepare)(struct drm_encoder *encoder);</synopsis>
2038 Prepare the encoder for mode setting. This operation is called after
2039 validating the requested mode. Drivers use it to perform
2040 device-specific operations required before setting the new mode.
2044 <synopsis>void (*mode_set)(struct drm_encoder *encoder,
2045 struct drm_display_mode *mode,
2046 struct drm_display_mode *adjusted_mode);</synopsis>
2048 Set a new mode. Depending on the device requirements, the mode can
2049 be stored internally by the driver and applied in the
2050 <methodname>commit</methodname> operation, or programmed to the
2051 hardware immediately.
2055 <synopsis>void (*commit)(struct drm_encoder *encoder);</synopsis>
2057 Commit a mode. This operation is called after setting the new mode.
2058 Upon return the device must use the new mode and be fully
2065 <title>Connector Helper Operations</title>
2068 <synopsis>struct drm_encoder *(*best_encoder)(struct drm_connector *connector);</synopsis>
2070 Return a pointer to the best encoder for the connecter. Device that
2071 map connectors to encoders 1:1 simply return the pointer to the
2072 associated encoder. This operation is mandatory.
2076 <synopsis>int (*get_modes)(struct drm_connector *connector);</synopsis>
2078 Fill the connector's <structfield>probed_modes</structfield> list
2079 by parsing EDID data with <function>drm_add_edid_modes</function> or
2080 calling <function>drm_mode_probed_add</function> directly for every
2081 supported mode and return the number of modes it has detected. This
2082 operation is mandatory.
2085 When adding modes manually the driver creates each mode with a call to
2086 <function>drm_mode_create</function> and must fill the following fields.
2089 <synopsis>__u32 type;</synopsis>
2091 Mode type bitmask, a combination of
2094 <term>DRM_MODE_TYPE_BUILTIN</term>
2095 <listitem><para>not used?</para></listitem>
2098 <term>DRM_MODE_TYPE_CLOCK_C</term>
2099 <listitem><para>not used?</para></listitem>
2102 <term>DRM_MODE_TYPE_CRTC_C</term>
2103 <listitem><para>not used?</para></listitem>
2107 DRM_MODE_TYPE_PREFERRED - The preferred mode for the connector
2110 <para>not used?</para>
2114 <term>DRM_MODE_TYPE_DEFAULT</term>
2115 <listitem><para>not used?</para></listitem>
2118 <term>DRM_MODE_TYPE_USERDEF</term>
2119 <listitem><para>not used?</para></listitem>
2122 <term>DRM_MODE_TYPE_DRIVER</term>
2125 The mode has been created by the driver (as opposed to
2126 to user-created modes).
2131 Drivers must set the DRM_MODE_TYPE_DRIVER bit for all modes they
2132 create, and set the DRM_MODE_TYPE_PREFERRED bit for the preferred
2137 <synopsis>__u32 clock;</synopsis>
2138 <para>Pixel clock frequency in kHz unit</para>
2141 <synopsis>__u16 hdisplay, hsync_start, hsync_end, htotal;
2142 __u16 vdisplay, vsync_start, vsync_end, vtotal;</synopsis>
2143 <para>Horizontal and vertical timing information</para>
2145 Active Front Sync Back
2147 <-----------------------><----------------><-------------><-------------->
2149 //////////////////////|
2150 ////////////////////// |
2151 ////////////////////// |.................. ................
2154 <----- [hv]display ----->
2155 <------------- [hv]sync_start ------------>
2156 <--------------------- [hv]sync_end --------------------->
2157 <-------------------------------- [hv]total ----------------------------->
2161 <synopsis>__u16 hskew;
2162 __u16 vscan;</synopsis>
2163 <para>Unknown</para>
2166 <synopsis>__u32 flags;</synopsis>
2168 Mode flags, a combination of
2171 <term>DRM_MODE_FLAG_PHSYNC</term>
2173 Horizontal sync is active high
2177 <term>DRM_MODE_FLAG_NHSYNC</term>
2179 Horizontal sync is active low
2183 <term>DRM_MODE_FLAG_PVSYNC</term>
2185 Vertical sync is active high
2189 <term>DRM_MODE_FLAG_NVSYNC</term>
2191 Vertical sync is active low
2195 <term>DRM_MODE_FLAG_INTERLACE</term>
2201 <term>DRM_MODE_FLAG_DBLSCAN</term>
2203 Mode uses doublescan
2207 <term>DRM_MODE_FLAG_CSYNC</term>
2209 Mode uses composite sync
2213 <term>DRM_MODE_FLAG_PCSYNC</term>
2215 Composite sync is active high
2219 <term>DRM_MODE_FLAG_NCSYNC</term>
2221 Composite sync is active low
2225 <term>DRM_MODE_FLAG_HSKEW</term>
2227 hskew provided (not used?)
2231 <term>DRM_MODE_FLAG_BCAST</term>
2237 <term>DRM_MODE_FLAG_PIXMUX</term>
2243 <term>DRM_MODE_FLAG_DBLCLK</term>
2249 <term>DRM_MODE_FLAG_CLKDIV2</term>
2257 Note that modes marked with the INTERLACE or DBLSCAN flags will be
2259 <function>drm_helper_probe_single_connector_modes</function> if
2260 the connector's <structfield>interlace_allowed</structfield> or
2261 <structfield>doublescan_allowed</structfield> field is set to 0.
2265 <synopsis>char name[DRM_DISPLAY_MODE_LEN];</synopsis>
2267 Mode name. The driver must call
2268 <function>drm_mode_set_name</function> to fill the mode name from
2269 <structfield>hdisplay</structfield>,
2270 <structfield>vdisplay</structfield> and interlace flag after
2271 filling the corresponding fields.
2277 The <structfield>vrefresh</structfield> value is computed by
2278 <function>drm_helper_probe_single_connector_modes</function>.
2281 When parsing EDID data, <function>drm_add_edid_modes</function> fill the
2282 connector <structfield>display_info</structfield>
2283 <structfield>width_mm</structfield> and
2284 <structfield>height_mm</structfield> fields. When creating modes
2285 manually the <methodname>get_modes</methodname> helper operation must
2286 set the <structfield>display_info</structfield>
2287 <structfield>width_mm</structfield> and
2288 <structfield>height_mm</structfield> fields if they haven't been set
2289 already (for instance at initialization time when a fixed-size panel is
2290 attached to the connector). The mode <structfield>width_mm</structfield>
2291 and <structfield>height_mm</structfield> fields are only used internally
2292 during EDID parsing and should not be set when creating modes manually.
2296 <synopsis>int (*mode_valid)(struct drm_connector *connector,
2297 struct drm_display_mode *mode);</synopsis>
2299 Verify whether a mode is valid for the connector. Return MODE_OK for
2300 supported modes and one of the enum drm_mode_status values (MODE_*)
2301 for unsupported modes. This operation is optional.
2304 As the mode rejection reason is currently not used beside for
2305 immediately removing the unsupported mode, an implementation can
2306 return MODE_BAD regardless of the exact reason why the mode is not
2310 Note that the <methodname>mode_valid</methodname> helper operation is
2311 only called for modes detected by the device, and
2312 <emphasis>not</emphasis> for modes set by the user through the CRTC
2313 <methodname>set_config</methodname> operation.
2319 <title>Modeset Helper Functions Reference</title>
2320 !Edrivers/gpu/drm/drm_crtc_helper.c
2323 <title>Output Probing Helper Functions Reference</title>
2324 !Pdrivers/gpu/drm/drm_probe_helper.c output probing helper overview
2325 !Edrivers/gpu/drm/drm_probe_helper.c
2328 <title>fbdev Helper Functions Reference</title>
2329 !Pdrivers/gpu/drm/drm_fb_helper.c fbdev helpers
2330 !Edrivers/gpu/drm/drm_fb_helper.c
2331 !Iinclude/drm/drm_fb_helper.h
2334 <title>Display Port Helper Functions Reference</title>
2335 !Pdrivers/gpu/drm/drm_dp_helper.c dp helpers
2336 !Iinclude/drm/drm_dp_helper.h
2337 !Edrivers/gpu/drm/drm_dp_helper.c
2340 <title>Display Port MST Helper Functions Reference</title>
2341 !Pdrivers/gpu/drm/drm_dp_mst_topology.c dp mst helper
2342 !Iinclude/drm/drm_dp_mst_helper.h
2343 !Edrivers/gpu/drm/drm_dp_mst_topology.c
2346 <title>EDID Helper Functions Reference</title>
2347 !Edrivers/gpu/drm/drm_edid.c
2350 <title>Rectangle Utilities Reference</title>
2351 !Pinclude/drm/drm_rect.h rect utils
2352 !Iinclude/drm/drm_rect.h
2353 !Edrivers/gpu/drm/drm_rect.c
2356 <title>Flip-work Helper Reference</title>
2357 !Pinclude/drm/drm_flip_work.h flip utils
2358 !Iinclude/drm/drm_flip_work.h
2359 !Edrivers/gpu/drm/drm_flip_work.c
2362 <title>HDMI Infoframes Helper Reference</title>
2364 Strictly speaking this is not a DRM helper library but generally useable
2365 by any driver interfacing with HDMI outputs like v4l or alsa drivers.
2366 But it nicely fits into the overall topic of mode setting helper
2367 libraries and hence is also included here.
2369 !Iinclude/linux/hdmi.h
2370 !Edrivers/video/hdmi.c
2373 <title id="drm-kms-planehelpers">Plane Helper Reference</title>
2374 !Edrivers/gpu/drm/drm_plane_helper.c Plane Helpers
2378 <!-- Internals: kms properties -->
2380 <sect1 id="drm-kms-properties">
2381 <title>KMS Properties</title>
2383 Drivers may need to expose additional parameters to applications than
2384 those described in the previous sections. KMS supports attaching
2385 properties to CRTCs, connectors and planes and offers a userspace API to
2386 list, get and set the property values.
2389 Properties are identified by a name that uniquely defines the property
2390 purpose, and store an associated value. For all property types except blob
2391 properties the value is a 64-bit unsigned integer.
2394 KMS differentiates between properties and property instances. Drivers
2395 first create properties and then create and associate individual instances
2396 of those properties to objects. A property can be instantiated multiple
2397 times and associated with different objects. Values are stored in property
2398 instances, and all other property information are stored in the property
2399 and shared between all instances of the property.
2402 Every property is created with a type that influences how the KMS core
2403 handles the property. Supported property types are
2406 <term>DRM_MODE_PROP_RANGE</term>
2407 <listitem><para>Range properties report their minimum and maximum
2408 admissible values. The KMS core verifies that values set by
2409 application fit in that range.</para></listitem>
2412 <term>DRM_MODE_PROP_ENUM</term>
2413 <listitem><para>Enumerated properties take a numerical value that
2414 ranges from 0 to the number of enumerated values defined by the
2415 property minus one, and associate a free-formed string name to each
2416 value. Applications can retrieve the list of defined value-name pairs
2417 and use the numerical value to get and set property instance values.
2421 <term>DRM_MODE_PROP_BITMASK</term>
2422 <listitem><para>Bitmask properties are enumeration properties that
2423 additionally restrict all enumerated values to the 0..63 range.
2424 Bitmask property instance values combine one or more of the
2425 enumerated bits defined by the property.</para></listitem>
2428 <term>DRM_MODE_PROP_BLOB</term>
2429 <listitem><para>Blob properties store a binary blob without any format
2430 restriction. The binary blobs are created as KMS standalone objects,
2431 and blob property instance values store the ID of their associated
2433 <para>Blob properties are only used for the connector EDID property
2434 and cannot be created by drivers.</para></listitem>
2439 To create a property drivers call one of the following functions depending
2440 on the property type. All property creation functions take property flags
2441 and name, as well as type-specific arguments.
2444 <synopsis>struct drm_property *drm_property_create_range(struct drm_device *dev, int flags,
2446 uint64_t min, uint64_t max);</synopsis>
2447 <para>Create a range property with the given minimum and maximum
2451 <synopsis>struct drm_property *drm_property_create_enum(struct drm_device *dev, int flags,
2453 const struct drm_prop_enum_list *props,
2454 int num_values);</synopsis>
2455 <para>Create an enumerated property. The <parameter>props</parameter>
2456 argument points to an array of <parameter>num_values</parameter>
2457 value-name pairs.</para>
2460 <synopsis>struct drm_property *drm_property_create_bitmask(struct drm_device *dev,
2461 int flags, const char *name,
2462 const struct drm_prop_enum_list *props,
2463 int num_values);</synopsis>
2464 <para>Create a bitmask property. The <parameter>props</parameter>
2465 argument points to an array of <parameter>num_values</parameter>
2466 value-name pairs.</para>
2471 Properties can additionally be created as immutable, in which case they
2472 will be read-only for applications but can be modified by the driver. To
2473 create an immutable property drivers must set the DRM_MODE_PROP_IMMUTABLE
2474 flag at property creation time.
2477 When no array of value-name pairs is readily available at property
2478 creation time for enumerated or range properties, drivers can create
2479 the property using the <function>drm_property_create</function> function
2480 and manually add enumeration value-name pairs by calling the
2481 <function>drm_property_add_enum</function> function. Care must be taken to
2482 properly specify the property type through the <parameter>flags</parameter>
2486 After creating properties drivers can attach property instances to CRTC,
2487 connector and plane objects by calling the
2488 <function>drm_object_attach_property</function>. The function takes a
2489 pointer to the target object, a pointer to the previously created property
2490 and an initial instance value.
2493 <title>Existing KMS Properties</title>
2495 The following table gives description of drm properties exposed by various
2498 <table border="1" cellpadding="0" cellspacing="0">
2500 <tr style="font-weight: bold;">
2501 <td valign="top" >Owner Module/Drivers</td>
2502 <td valign="top" >Group</td>
2503 <td valign="top" >Property Name</td>
2504 <td valign="top" >Type</td>
2505 <td valign="top" >Property Values</td>
2506 <td valign="top" >Object attached</td>
2507 <td valign="top" >Description/Restrictions</td>
2510 <td rowspan="21" valign="top" >DRM</td>
2511 <td rowspan="2" valign="top" >Generic</td>
2512 <td valign="top" >“EDID”</td>
2513 <td valign="top" >BLOB | IMMUTABLE</td>
2514 <td valign="top" >0</td>
2515 <td valign="top" >Connector</td>
2516 <td valign="top" >Contains id of edid blob ptr object.</td>
2519 <td valign="top" >“DPMS”</td>
2520 <td valign="top" >ENUM</td>
2521 <td valign="top" >{ “On”, “Standby”, “Suspend”, “Off” }</td>
2522 <td valign="top" >Connector</td>
2523 <td valign="top" >Contains DPMS operation mode value.</td>
2526 <td rowspan="1" valign="top" >Plane</td>
2527 <td valign="top" >“type”</td>
2528 <td valign="top" >ENUM | IMMUTABLE</td>
2529 <td valign="top" >{ "Overlay", "Primary", "Cursor" }</td>
2530 <td valign="top" >Plane</td>
2531 <td valign="top" >Plane type</td>
2534 <td rowspan="2" valign="top" >DVI-I</td>
2535 <td valign="top" >“subconnector”</td>
2536 <td valign="top" >ENUM</td>
2537 <td valign="top" >{ “Unknown”, “DVI-D”, “DVI-A” }</td>
2538 <td valign="top" >Connector</td>
2539 <td valign="top" >TBD</td>
2542 <td valign="top" >“select subconnector”</td>
2543 <td valign="top" >ENUM</td>
2544 <td valign="top" >{ “Automatic”, “DVI-D”, “DVI-A” }</td>
2545 <td valign="top" >Connector</td>
2546 <td valign="top" >TBD</td>
2549 <td rowspan="13" valign="top" >TV</td>
2550 <td valign="top" >“subconnector”</td>
2551 <td valign="top" >ENUM</td>
2552 <td valign="top" >{ "Unknown", "Composite", "SVIDEO", "Component", "SCART" }</td>
2553 <td valign="top" >Connector</td>
2554 <td valign="top" >TBD</td>
2557 <td valign="top" >“select subconnector”</td>
2558 <td valign="top" >ENUM</td>
2559 <td valign="top" >{ "Automatic", "Composite", "SVIDEO", "Component", "SCART" }</td>
2560 <td valign="top" >Connector</td>
2561 <td valign="top" >TBD</td>
2564 <td valign="top" >“mode”</td>
2565 <td valign="top" >ENUM</td>
2566 <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2567 <td valign="top" >Connector</td>
2568 <td valign="top" >TBD</td>
2571 <td valign="top" >“left margin”</td>
2572 <td valign="top" >RANGE</td>
2573 <td valign="top" >Min=0, Max=100</td>
2574 <td valign="top" >Connector</td>
2575 <td valign="top" >TBD</td>
2578 <td valign="top" >“right margin”</td>
2579 <td valign="top" >RANGE</td>
2580 <td valign="top" >Min=0, Max=100</td>
2581 <td valign="top" >Connector</td>
2582 <td valign="top" >TBD</td>
2585 <td valign="top" >“top margin”</td>
2586 <td valign="top" >RANGE</td>
2587 <td valign="top" >Min=0, Max=100</td>
2588 <td valign="top" >Connector</td>
2589 <td valign="top" >TBD</td>
2592 <td valign="top" >“bottom margin”</td>
2593 <td valign="top" >RANGE</td>
2594 <td valign="top" >Min=0, Max=100</td>
2595 <td valign="top" >Connector</td>
2596 <td valign="top" >TBD</td>
2599 <td valign="top" >“brightness”</td>
2600 <td valign="top" >RANGE</td>
2601 <td valign="top" >Min=0, Max=100</td>
2602 <td valign="top" >Connector</td>
2603 <td valign="top" >TBD</td>
2606 <td valign="top" >“contrast”</td>
2607 <td valign="top" >RANGE</td>
2608 <td valign="top" >Min=0, Max=100</td>
2609 <td valign="top" >Connector</td>
2610 <td valign="top" >TBD</td>
2613 <td valign="top" >“flicker reduction”</td>
2614 <td valign="top" >RANGE</td>
2615 <td valign="top" >Min=0, Max=100</td>
2616 <td valign="top" >Connector</td>
2617 <td valign="top" >TBD</td>
2620 <td valign="top" >“overscan”</td>
2621 <td valign="top" >RANGE</td>
2622 <td valign="top" >Min=0, Max=100</td>
2623 <td valign="top" >Connector</td>
2624 <td valign="top" >TBD</td>
2627 <td valign="top" >“saturation”</td>
2628 <td valign="top" >RANGE</td>
2629 <td valign="top" >Min=0, Max=100</td>
2630 <td valign="top" >Connector</td>
2631 <td valign="top" >TBD</td>
2634 <td valign="top" >“hue”</td>
2635 <td valign="top" >RANGE</td>
2636 <td valign="top" >Min=0, Max=100</td>
2637 <td valign="top" >Connector</td>
2638 <td valign="top" >TBD</td>
2641 <td rowspan="3" valign="top" >Optional</td>
2642 <td valign="top" >“scaling mode”</td>
2643 <td valign="top" >ENUM</td>
2644 <td valign="top" >{ "None", "Full", "Center", "Full aspect" }</td>
2645 <td valign="top" >Connector</td>
2646 <td valign="top" >TBD</td>
2649 <td valign="top" >"aspect ratio"</td>
2650 <td valign="top" >ENUM</td>
2651 <td valign="top" >{ "None", "4:3", "16:9" }</td>
2652 <td valign="top" >Connector</td>
2653 <td valign="top" >DRM property to set aspect ratio from user space app.
2654 This enum is made generic to allow addition of custom aspect
2658 <td valign="top" >“dirty”</td>
2659 <td valign="top" >ENUM | IMMUTABLE</td>
2660 <td valign="top" >{ "Off", "On", "Annotate" }</td>
2661 <td valign="top" >Connector</td>
2662 <td valign="top" >TBD</td>
2665 <td rowspan="21" valign="top" >i915</td>
2666 <td rowspan="2" valign="top" >Generic</td>
2667 <td valign="top" >"Broadcast RGB"</td>
2668 <td valign="top" >ENUM</td>
2669 <td valign="top" >{ "Automatic", "Full", "Limited 16:235" }</td>
2670 <td valign="top" >Connector</td>
2671 <td valign="top" >TBD</td>
2674 <td valign="top" >“audio”</td>
2675 <td valign="top" >ENUM</td>
2676 <td valign="top" >{ "force-dvi", "off", "auto", "on" }</td>
2677 <td valign="top" >Connector</td>
2678 <td valign="top" >TBD</td>
2681 <td rowspan="1" valign="top" >Plane</td>
2682 <td valign="top" >“rotation”</td>
2683 <td valign="top" >BITMASK</td>
2684 <td valign="top" >{ 0, "rotate-0" }, { 2, "rotate-180" }</td>
2685 <td valign="top" >Plane</td>
2686 <td valign="top" >TBD</td>
2689 <td rowspan="17" valign="top" >SDVO-TV</td>
2690 <td valign="top" >“mode”</td>
2691 <td valign="top" >ENUM</td>
2692 <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2693 <td valign="top" >Connector</td>
2694 <td valign="top" >TBD</td>
2697 <td valign="top" >"left_margin"</td>
2698 <td valign="top" >RANGE</td>
2699 <td valign="top" >Min=0, Max= SDVO dependent</td>
2700 <td valign="top" >Connector</td>
2701 <td valign="top" >TBD</td>
2704 <td valign="top" >"right_margin"</td>
2705 <td valign="top" >RANGE</td>
2706 <td valign="top" >Min=0, Max= SDVO dependent</td>
2707 <td valign="top" >Connector</td>
2708 <td valign="top" >TBD</td>
2711 <td valign="top" >"top_margin"</td>
2712 <td valign="top" >RANGE</td>
2713 <td valign="top" >Min=0, Max= SDVO dependent</td>
2714 <td valign="top" >Connector</td>
2715 <td valign="top" >TBD</td>
2718 <td valign="top" >"bottom_margin"</td>
2719 <td valign="top" >RANGE</td>
2720 <td valign="top" >Min=0, Max= SDVO dependent</td>
2721 <td valign="top" >Connector</td>
2722 <td valign="top" >TBD</td>
2725 <td valign="top" >“hpos”</td>
2726 <td valign="top" >RANGE</td>
2727 <td valign="top" >Min=0, Max= SDVO dependent</td>
2728 <td valign="top" >Connector</td>
2729 <td valign="top" >TBD</td>
2732 <td valign="top" >“vpos”</td>
2733 <td valign="top" >RANGE</td>
2734 <td valign="top" >Min=0, Max= SDVO dependent</td>
2735 <td valign="top" >Connector</td>
2736 <td valign="top" >TBD</td>
2739 <td valign="top" >“contrast”</td>
2740 <td valign="top" >RANGE</td>
2741 <td valign="top" >Min=0, Max= SDVO dependent</td>
2742 <td valign="top" >Connector</td>
2743 <td valign="top" >TBD</td>
2746 <td valign="top" >“saturation”</td>
2747 <td valign="top" >RANGE</td>
2748 <td valign="top" >Min=0, Max= SDVO dependent</td>
2749 <td valign="top" >Connector</td>
2750 <td valign="top" >TBD</td>
2753 <td valign="top" >“hue”</td>
2754 <td valign="top" >RANGE</td>
2755 <td valign="top" >Min=0, Max= SDVO dependent</td>
2756 <td valign="top" >Connector</td>
2757 <td valign="top" >TBD</td>
2760 <td valign="top" >“sharpness”</td>
2761 <td valign="top" >RANGE</td>
2762 <td valign="top" >Min=0, Max= SDVO dependent</td>
2763 <td valign="top" >Connector</td>
2764 <td valign="top" >TBD</td>
2767 <td valign="top" >“flicker_filter”</td>
2768 <td valign="top" >RANGE</td>
2769 <td valign="top" >Min=0, Max= SDVO dependent</td>
2770 <td valign="top" >Connector</td>
2771 <td valign="top" >TBD</td>
2774 <td valign="top" >“flicker_filter_adaptive”</td>
2775 <td valign="top" >RANGE</td>
2776 <td valign="top" >Min=0, Max= SDVO dependent</td>
2777 <td valign="top" >Connector</td>
2778 <td valign="top" >TBD</td>
2781 <td valign="top" >“flicker_filter_2d”</td>
2782 <td valign="top" >RANGE</td>
2783 <td valign="top" >Min=0, Max= SDVO dependent</td>
2784 <td valign="top" >Connector</td>
2785 <td valign="top" >TBD</td>
2788 <td valign="top" >“tv_chroma_filter”</td>
2789 <td valign="top" >RANGE</td>
2790 <td valign="top" >Min=0, Max= SDVO dependent</td>
2791 <td valign="top" >Connector</td>
2792 <td valign="top" >TBD</td>
2795 <td valign="top" >“tv_luma_filter”</td>
2796 <td valign="top" >RANGE</td>
2797 <td valign="top" >Min=0, Max= SDVO dependent</td>
2798 <td valign="top" >Connector</td>
2799 <td valign="top" >TBD</td>
2802 <td valign="top" >“dot_crawl”</td>
2803 <td valign="top" >RANGE</td>
2804 <td valign="top" >Min=0, Max=1</td>
2805 <td valign="top" >Connector</td>
2806 <td valign="top" >TBD</td>
2809 <td valign="top" >SDVO-TV/LVDS</td>
2810 <td valign="top" >“brightness”</td>
2811 <td valign="top" >RANGE</td>
2812 <td valign="top" >Min=0, Max= SDVO dependent</td>
2813 <td valign="top" >Connector</td>
2814 <td valign="top" >TBD</td>
2817 <td rowspan="2" valign="top" >CDV gma-500</td>
2818 <td rowspan="2" valign="top" >Generic</td>
2819 <td valign="top" >"Broadcast RGB"</td>
2820 <td valign="top" >ENUM</td>
2821 <td valign="top" >{ “Full”, “Limited 16:235” }</td>
2822 <td valign="top" >Connector</td>
2823 <td valign="top" >TBD</td>
2826 <td valign="top" >"Broadcast RGB"</td>
2827 <td valign="top" >ENUM</td>
2828 <td valign="top" >{ “off”, “auto”, “on” }</td>
2829 <td valign="top" >Connector</td>
2830 <td valign="top" >TBD</td>
2833 <td rowspan="19" valign="top" >Poulsbo</td>
2834 <td rowspan="1" valign="top" >Generic</td>
2835 <td valign="top" >“backlight”</td>
2836 <td valign="top" >RANGE</td>
2837 <td valign="top" >Min=0, Max=100</td>
2838 <td valign="top" >Connector</td>
2839 <td valign="top" >TBD</td>
2842 <td rowspan="17" valign="top" >SDVO-TV</td>
2843 <td valign="top" >“mode”</td>
2844 <td valign="top" >ENUM</td>
2845 <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2846 <td valign="top" >Connector</td>
2847 <td valign="top" >TBD</td>
2850 <td valign="top" >"left_margin"</td>
2851 <td valign="top" >RANGE</td>
2852 <td valign="top" >Min=0, Max= SDVO dependent</td>
2853 <td valign="top" >Connector</td>
2854 <td valign="top" >TBD</td>
2857 <td valign="top" >"right_margin"</td>
2858 <td valign="top" >RANGE</td>
2859 <td valign="top" >Min=0, Max= SDVO dependent</td>
2860 <td valign="top" >Connector</td>
2861 <td valign="top" >TBD</td>
2864 <td valign="top" >"top_margin"</td>
2865 <td valign="top" >RANGE</td>
2866 <td valign="top" >Min=0, Max= SDVO dependent</td>
2867 <td valign="top" >Connector</td>
2868 <td valign="top" >TBD</td>
2871 <td valign="top" >"bottom_margin"</td>
2872 <td valign="top" >RANGE</td>
2873 <td valign="top" >Min=0, Max= SDVO dependent</td>
2874 <td valign="top" >Connector</td>
2875 <td valign="top" >TBD</td>
2878 <td valign="top" >“hpos”</td>
2879 <td valign="top" >RANGE</td>
2880 <td valign="top" >Min=0, Max= SDVO dependent</td>
2881 <td valign="top" >Connector</td>
2882 <td valign="top" >TBD</td>
2885 <td valign="top" >“vpos”</td>
2886 <td valign="top" >RANGE</td>
2887 <td valign="top" >Min=0, Max= SDVO dependent</td>
2888 <td valign="top" >Connector</td>
2889 <td valign="top" >TBD</td>
2892 <td valign="top" >“contrast”</td>
2893 <td valign="top" >RANGE</td>
2894 <td valign="top" >Min=0, Max= SDVO dependent</td>
2895 <td valign="top" >Connector</td>
2896 <td valign="top" >TBD</td>
2899 <td valign="top" >“saturation”</td>
2900 <td valign="top" >RANGE</td>
2901 <td valign="top" >Min=0, Max= SDVO dependent</td>
2902 <td valign="top" >Connector</td>
2903 <td valign="top" >TBD</td>
2906 <td valign="top" >“hue”</td>
2907 <td valign="top" >RANGE</td>
2908 <td valign="top" >Min=0, Max= SDVO dependent</td>
2909 <td valign="top" >Connector</td>
2910 <td valign="top" >TBD</td>
2913 <td valign="top" >“sharpness”</td>
2914 <td valign="top" >RANGE</td>
2915 <td valign="top" >Min=0, Max= SDVO dependent</td>
2916 <td valign="top" >Connector</td>
2917 <td valign="top" >TBD</td>
2920 <td valign="top" >“flicker_filter”</td>
2921 <td valign="top" >RANGE</td>
2922 <td valign="top" >Min=0, Max= SDVO dependent</td>
2923 <td valign="top" >Connector</td>
2924 <td valign="top" >TBD</td>
2927 <td valign="top" >“flicker_filter_adaptive”</td>
2928 <td valign="top" >RANGE</td>
2929 <td valign="top" >Min=0, Max= SDVO dependent</td>
2930 <td valign="top" >Connector</td>
2931 <td valign="top" >TBD</td>
2934 <td valign="top" >“flicker_filter_2d”</td>
2935 <td valign="top" >RANGE</td>
2936 <td valign="top" >Min=0, Max= SDVO dependent</td>
2937 <td valign="top" >Connector</td>
2938 <td valign="top" >TBD</td>
2941 <td valign="top" >“tv_chroma_filter”</td>
2942 <td valign="top" >RANGE</td>
2943 <td valign="top" >Min=0, Max= SDVO dependent</td>
2944 <td valign="top" >Connector</td>
2945 <td valign="top" >TBD</td>
2948 <td valign="top" >“tv_luma_filter”</td>
2949 <td valign="top" >RANGE</td>
2950 <td valign="top" >Min=0, Max= SDVO dependent</td>
2951 <td valign="top" >Connector</td>
2952 <td valign="top" >TBD</td>
2955 <td valign="top" >“dot_crawl”</td>
2956 <td valign="top" >RANGE</td>
2957 <td valign="top" >Min=0, Max=1</td>
2958 <td valign="top" >Connector</td>
2959 <td valign="top" >TBD</td>
2962 <td valign="top" >SDVO-TV/LVDS</td>
2963 <td valign="top" >“brightness”</td>
2964 <td valign="top" >RANGE</td>
2965 <td valign="top" >Min=0, Max= SDVO dependent</td>
2966 <td valign="top" >Connector</td>
2967 <td valign="top" >TBD</td>
2970 <td rowspan="11" valign="top" >armada</td>
2971 <td rowspan="2" valign="top" >CRTC</td>
2972 <td valign="top" >"CSC_YUV"</td>
2973 <td valign="top" >ENUM</td>
2974 <td valign="top" >{ "Auto" , "CCIR601", "CCIR709" }</td>
2975 <td valign="top" >CRTC</td>
2976 <td valign="top" >TBD</td>
2979 <td valign="top" >"CSC_RGB"</td>
2980 <td valign="top" >ENUM</td>
2981 <td valign="top" >{ "Auto", "Computer system", "Studio" }</td>
2982 <td valign="top" >CRTC</td>
2983 <td valign="top" >TBD</td>
2986 <td rowspan="9" valign="top" >Overlay</td>
2987 <td valign="top" >"colorkey"</td>
2988 <td valign="top" >RANGE</td>
2989 <td valign="top" >Min=0, Max=0xffffff</td>
2990 <td valign="top" >Plane</td>
2991 <td valign="top" >TBD</td>
2994 <td valign="top" >"colorkey_min"</td>
2995 <td valign="top" >RANGE</td>
2996 <td valign="top" >Min=0, Max=0xffffff</td>
2997 <td valign="top" >Plane</td>
2998 <td valign="top" >TBD</td>
3001 <td valign="top" >"colorkey_max"</td>
3002 <td valign="top" >RANGE</td>
3003 <td valign="top" >Min=0, Max=0xffffff</td>
3004 <td valign="top" >Plane</td>
3005 <td valign="top" >TBD</td>
3008 <td valign="top" >"colorkey_val"</td>
3009 <td valign="top" >RANGE</td>
3010 <td valign="top" >Min=0, Max=0xffffff</td>
3011 <td valign="top" >Plane</td>
3012 <td valign="top" >TBD</td>
3015 <td valign="top" >"colorkey_alpha"</td>
3016 <td valign="top" >RANGE</td>
3017 <td valign="top" >Min=0, Max=0xffffff</td>
3018 <td valign="top" >Plane</td>
3019 <td valign="top" >TBD</td>
3022 <td valign="top" >"colorkey_mode"</td>
3023 <td valign="top" >ENUM</td>
3024 <td valign="top" >{ "disabled", "Y component", "U component"
3025 , "V component", "RGB", “R component", "G component", "B component" }</td>
3026 <td valign="top" >Plane</td>
3027 <td valign="top" >TBD</td>
3030 <td valign="top" >"brightness"</td>
3031 <td valign="top" >RANGE</td>
3032 <td valign="top" >Min=0, Max=256 + 255</td>
3033 <td valign="top" >Plane</td>
3034 <td valign="top" >TBD</td>
3037 <td valign="top" >"contrast"</td>
3038 <td valign="top" >RANGE</td>
3039 <td valign="top" >Min=0, Max=0x7fff</td>
3040 <td valign="top" >Plane</td>
3041 <td valign="top" >TBD</td>
3044 <td valign="top" >"saturation"</td>
3045 <td valign="top" >RANGE</td>
3046 <td valign="top" >Min=0, Max=0x7fff</td>
3047 <td valign="top" >Plane</td>
3048 <td valign="top" >TBD</td>
3051 <td rowspan="2" valign="top" >exynos</td>
3052 <td valign="top" >CRTC</td>
3053 <td valign="top" >“mode”</td>
3054 <td valign="top" >ENUM</td>
3055 <td valign="top" >{ "normal", "blank" }</td>
3056 <td valign="top" >CRTC</td>
3057 <td valign="top" >TBD</td>
3060 <td valign="top" >Overlay</td>
3061 <td valign="top" >“zpos”</td>
3062 <td valign="top" >RANGE</td>
3063 <td valign="top" >Min=0, Max=MAX_PLANE-1</td>
3064 <td valign="top" >Plane</td>
3065 <td valign="top" >TBD</td>
3068 <td rowspan="2" valign="top" >i2c/ch7006_drv</td>
3069 <td valign="top" >Generic</td>
3070 <td valign="top" >“scale”</td>
3071 <td valign="top" >RANGE</td>
3072 <td valign="top" >Min=0, Max=2</td>
3073 <td valign="top" >Connector</td>
3074 <td valign="top" >TBD</td>
3077 <td rowspan="1" valign="top" >TV</td>
3078 <td valign="top" >“mode”</td>
3079 <td valign="top" >ENUM</td>
3080 <td valign="top" >{ "PAL", "PAL-M","PAL-N"}, ”PAL-Nc"
3081 , "PAL-60", "NTSC-M", "NTSC-J" }</td>
3082 <td valign="top" >Connector</td>
3083 <td valign="top" >TBD</td>
3086 <td rowspan="15" valign="top" >nouveau</td>
3087 <td rowspan="6" valign="top" >NV10 Overlay</td>
3088 <td valign="top" >"colorkey"</td>
3089 <td valign="top" >RANGE</td>
3090 <td valign="top" >Min=0, Max=0x01ffffff</td>
3091 <td valign="top" >Plane</td>
3092 <td valign="top" >TBD</td>
3095 <td valign="top" >“contrast”</td>
3096 <td valign="top" >RANGE</td>
3097 <td valign="top" >Min=0, Max=8192-1</td>
3098 <td valign="top" >Plane</td>
3099 <td valign="top" >TBD</td>
3102 <td valign="top" >“brightness”</td>
3103 <td valign="top" >RANGE</td>
3104 <td valign="top" >Min=0, Max=1024</td>
3105 <td valign="top" >Plane</td>
3106 <td valign="top" >TBD</td>
3109 <td valign="top" >“hue”</td>
3110 <td valign="top" >RANGE</td>
3111 <td valign="top" >Min=0, Max=359</td>
3112 <td valign="top" >Plane</td>
3113 <td valign="top" >TBD</td>
3116 <td valign="top" >“saturation”</td>
3117 <td valign="top" >RANGE</td>
3118 <td valign="top" >Min=0, Max=8192-1</td>
3119 <td valign="top" >Plane</td>
3120 <td valign="top" >TBD</td>
3123 <td valign="top" >“iturbt_709”</td>
3124 <td valign="top" >RANGE</td>
3125 <td valign="top" >Min=0, Max=1</td>
3126 <td valign="top" >Plane</td>
3127 <td valign="top" >TBD</td>
3130 <td rowspan="2" valign="top" >Nv04 Overlay</td>
3131 <td valign="top" >“colorkey”</td>
3132 <td valign="top" >RANGE</td>
3133 <td valign="top" >Min=0, Max=0x01ffffff</td>
3134 <td valign="top" >Plane</td>
3135 <td valign="top" >TBD</td>
3138 <td valign="top" >“brightness”</td>
3139 <td valign="top" >RANGE</td>
3140 <td valign="top" >Min=0, Max=1024</td>
3141 <td valign="top" >Plane</td>
3142 <td valign="top" >TBD</td>
3145 <td rowspan="7" valign="top" >Display</td>
3146 <td valign="top" >“dithering mode”</td>
3147 <td valign="top" >ENUM</td>
3148 <td valign="top" >{ "auto", "off", "on" }</td>
3149 <td valign="top" >Connector</td>
3150 <td valign="top" >TBD</td>
3153 <td valign="top" >“dithering depth”</td>
3154 <td valign="top" >ENUM</td>
3155 <td valign="top" >{ "auto", "off", "on", "static 2x2", "dynamic 2x2", "temporal" }</td>
3156 <td valign="top" >Connector</td>
3157 <td valign="top" >TBD</td>
3160 <td valign="top" >“underscan”</td>
3161 <td valign="top" >ENUM</td>
3162 <td valign="top" >{ "auto", "6 bpc", "8 bpc" }</td>
3163 <td valign="top" >Connector</td>
3164 <td valign="top" >TBD</td>
3167 <td valign="top" >“underscan hborder”</td>
3168 <td valign="top" >RANGE</td>
3169 <td valign="top" >Min=0, Max=128</td>
3170 <td valign="top" >Connector</td>
3171 <td valign="top" >TBD</td>
3174 <td valign="top" >“underscan vborder”</td>
3175 <td valign="top" >RANGE</td>
3176 <td valign="top" >Min=0, Max=128</td>
3177 <td valign="top" >Connector</td>
3178 <td valign="top" >TBD</td>
3181 <td valign="top" >“vibrant hue”</td>
3182 <td valign="top" >RANGE</td>
3183 <td valign="top" >Min=0, Max=180</td>
3184 <td valign="top" >Connector</td>
3185 <td valign="top" >TBD</td>
3188 <td valign="top" >“color vibrance”</td>
3189 <td valign="top" >RANGE</td>
3190 <td valign="top" >Min=0, Max=200</td>
3191 <td valign="top" >Connector</td>
3192 <td valign="top" >TBD</td>
3195 <td rowspan="2" valign="top" >omap</td>
3196 <td rowspan="2" valign="top" >Generic</td>
3197 <td valign="top" >“rotation”</td>
3198 <td valign="top" >BITMASK</td>
3199 <td valign="top" >{ 0, "rotate-0" },
3201 { 2, "rotate-180" },
3202 { 3, "rotate-270" },
3204 { 5, "reflect-y" }</td>
3205 <td valign="top" >CRTC, Plane</td>
3206 <td valign="top" >TBD</td>
3209 <td valign="top" >“zorder”</td>
3210 <td valign="top" >RANGE</td>
3211 <td valign="top" >Min=0, Max=3</td>
3212 <td valign="top" >CRTC, Plane</td>
3213 <td valign="top" >TBD</td>
3216 <td valign="top" >qxl</td>
3217 <td valign="top" >Generic</td>
3218 <td valign="top" >“hotplug_mode_update"</td>
3219 <td valign="top" >RANGE</td>
3220 <td valign="top" >Min=0, Max=1</td>
3221 <td valign="top" >Connector</td>
3222 <td valign="top" >TBD</td>
3225 <td rowspan="9" valign="top" >radeon</td>
3226 <td valign="top" >DVI-I</td>
3227 <td valign="top" >“coherent”</td>
3228 <td valign="top" >RANGE</td>
3229 <td valign="top" >Min=0, Max=1</td>
3230 <td valign="top" >Connector</td>
3231 <td valign="top" >TBD</td>
3234 <td valign="top" >DAC enable load detect</td>
3235 <td valign="top" >“load detection”</td>
3236 <td valign="top" >RANGE</td>
3237 <td valign="top" >Min=0, Max=1</td>
3238 <td valign="top" >Connector</td>
3239 <td valign="top" >TBD</td>
3242 <td valign="top" >TV Standard</td>
3243 <td valign="top" >"tv standard"</td>
3244 <td valign="top" >ENUM</td>
3245 <td valign="top" >{ "ntsc", "pal", "pal-m", "pal-60", "ntsc-j"
3246 , "scart-pal", "pal-cn", "secam" }</td>
3247 <td valign="top" >Connector</td>
3248 <td valign="top" >TBD</td>
3251 <td valign="top" >legacy TMDS PLL detect</td>
3252 <td valign="top" >"tmds_pll"</td>
3253 <td valign="top" >ENUM</td>
3254 <td valign="top" >{ "driver", "bios" }</td>
3255 <td valign="top" >-</td>
3256 <td valign="top" >TBD</td>
3259 <td rowspan="3" valign="top" >Underscan</td>
3260 <td valign="top" >"underscan"</td>
3261 <td valign="top" >ENUM</td>
3262 <td valign="top" >{ "off", "on", "auto" }</td>
3263 <td valign="top" >Connector</td>
3264 <td valign="top" >TBD</td>
3267 <td valign="top" >"underscan hborder"</td>
3268 <td valign="top" >RANGE</td>
3269 <td valign="top" >Min=0, Max=128</td>
3270 <td valign="top" >Connector</td>
3271 <td valign="top" >TBD</td>
3274 <td valign="top" >"underscan vborder"</td>
3275 <td valign="top" >RANGE</td>
3276 <td valign="top" >Min=0, Max=128</td>
3277 <td valign="top" >Connector</td>
3278 <td valign="top" >TBD</td>
3281 <td valign="top" >Audio</td>
3282 <td valign="top" >“audio”</td>
3283 <td valign="top" >ENUM</td>
3284 <td valign="top" >{ "off", "on", "auto" }</td>
3285 <td valign="top" >Connector</td>
3286 <td valign="top" >TBD</td>
3289 <td valign="top" >FMT Dithering</td>
3290 <td valign="top" >“dither”</td>
3291 <td valign="top" >ENUM</td>
3292 <td valign="top" >{ "off", "on" }</td>
3293 <td valign="top" >Connector</td>
3294 <td valign="top" >TBD</td>
3297 <td rowspan="3" valign="top" >rcar-du</td>
3298 <td rowspan="3" valign="top" >Generic</td>
3299 <td valign="top" >"alpha"</td>
3300 <td valign="top" >RANGE</td>
3301 <td valign="top" >Min=0, Max=255</td>
3302 <td valign="top" >Plane</td>
3303 <td valign="top" >TBD</td>
3306 <td valign="top" >"colorkey"</td>
3307 <td valign="top" >RANGE</td>
3308 <td valign="top" >Min=0, Max=0x01ffffff</td>
3309 <td valign="top" >Plane</td>
3310 <td valign="top" >TBD</td>
3313 <td valign="top" >"zpos"</td>
3314 <td valign="top" >RANGE</td>
3315 <td valign="top" >Min=1, Max=7</td>
3316 <td valign="top" >Plane</td>
3317 <td valign="top" >TBD</td>
3324 <!-- Internals: vertical blanking -->
3326 <sect1 id="drm-vertical-blank">
3327 <title>Vertical Blanking</title>
3329 Vertical blanking plays a major role in graphics rendering. To achieve
3330 tear-free display, users must synchronize page flips and/or rendering to
3331 vertical blanking. The DRM API offers ioctls to perform page flips
3332 synchronized to vertical blanking and wait for vertical blanking.
3335 The DRM core handles most of the vertical blanking management logic, which
3336 involves filtering out spurious interrupts, keeping race-free blanking
3337 counters, coping with counter wrap-around and resets and keeping use
3338 counts. It relies on the driver to generate vertical blanking interrupts
3339 and optionally provide a hardware vertical blanking counter. Drivers must
3340 implement the following operations.
3344 <synopsis>int (*enable_vblank) (struct drm_device *dev, int crtc);
3345 void (*disable_vblank) (struct drm_device *dev, int crtc);</synopsis>
3347 Enable or disable vertical blanking interrupts for the given CRTC.
3351 <synopsis>u32 (*get_vblank_counter) (struct drm_device *dev, int crtc);</synopsis>
3353 Retrieve the value of the vertical blanking counter for the given
3354 CRTC. If the hardware maintains a vertical blanking counter its value
3355 should be returned. Otherwise drivers can use the
3356 <function>drm_vblank_count</function> helper function to handle this
3362 Drivers must initialize the vertical blanking handling core with a call to
3363 <function>drm_vblank_init</function> in their
3364 <methodname>load</methodname> operation. The function will set the struct
3365 <structname>drm_device</structname>
3366 <structfield>vblank_disable_allowed</structfield> field to 0. This will
3367 keep vertical blanking interrupts enabled permanently until the first mode
3368 set operation, where <structfield>vblank_disable_allowed</structfield> is
3369 set to 1. The reason behind this is not clear. Drivers can set the field
3370 to 1 after <function>calling drm_vblank_init</function> to make vertical
3371 blanking interrupts dynamically managed from the beginning.
3374 Vertical blanking interrupts can be enabled by the DRM core or by drivers
3375 themselves (for instance to handle page flipping operations). The DRM core
3376 maintains a vertical blanking use count to ensure that the interrupts are
3377 not disabled while a user still needs them. To increment the use count,
3378 drivers call <function>drm_vblank_get</function>. Upon return vertical
3379 blanking interrupts are guaranteed to be enabled.
3382 To decrement the use count drivers call
3383 <function>drm_vblank_put</function>. Only when the use count drops to zero
3384 will the DRM core disable the vertical blanking interrupts after a delay
3385 by scheduling a timer. The delay is accessible through the vblankoffdelay
3386 module parameter or the <varname>drm_vblank_offdelay</varname> global
3387 variable and expressed in milliseconds. Its default value is 5000 ms.
3388 Zero means never disable, and a negative value means disable immediately.
3389 Drivers may override the behaviour by setting the
3390 <structname>drm_device</structname>
3391 <structfield>vblank_disable_immediate</structfield> flag, which when set
3392 causes vblank interrupts to be disabled immediately regardless of the
3393 drm_vblank_offdelay value. The flag should only be set if there's a
3394 properly working hardware vblank counter present.
3397 When a vertical blanking interrupt occurs drivers only need to call the
3398 <function>drm_handle_vblank</function> function to account for the
3402 Resources allocated by <function>drm_vblank_init</function> must be freed
3403 with a call to <function>drm_vblank_cleanup</function> in the driver
3404 <methodname>unload</methodname> operation handler.
3407 <title>Vertical Blanking and Interrupt Handling Functions Reference</title>
3408 !Edrivers/gpu/drm/drm_irq.c
3409 !Finclude/drm/drmP.h drm_crtc_vblank_waitqueue
3413 <!-- Internals: open/close, file operations and ioctls -->
3416 <title>Open/Close, File Operations and IOCTLs</title>
3418 <title>Open and Close</title>
3419 <synopsis>int (*firstopen) (struct drm_device *);
3420 void (*lastclose) (struct drm_device *);
3421 int (*open) (struct drm_device *, struct drm_file *);
3422 void (*preclose) (struct drm_device *, struct drm_file *);
3423 void (*postclose) (struct drm_device *, struct drm_file *);</synopsis>
3424 <abstract>Open and close handlers. None of those methods are mandatory.
3427 The <methodname>firstopen</methodname> method is called by the DRM core
3428 for legacy UMS (User Mode Setting) drivers only when an application
3429 opens a device that has no other opened file handle. UMS drivers can
3430 implement it to acquire device resources. KMS drivers can't use the
3431 method and must acquire resources in the <methodname>load</methodname>
3435 Similarly the <methodname>lastclose</methodname> method is called when
3436 the last application holding a file handle opened on the device closes
3437 it, for both UMS and KMS drivers. Additionally, the method is also
3438 called at module unload time or, for hot-pluggable devices, when the
3439 device is unplugged. The <methodname>firstopen</methodname> and
3440 <methodname>lastclose</methodname> calls can thus be unbalanced.
3443 The <methodname>open</methodname> method is called every time the device
3444 is opened by an application. Drivers can allocate per-file private data
3445 in this method and store them in the struct
3446 <structname>drm_file</structname> <structfield>driver_priv</structfield>
3447 field. Note that the <methodname>open</methodname> method is called
3448 before <methodname>firstopen</methodname>.
3451 The close operation is split into <methodname>preclose</methodname> and
3452 <methodname>postclose</methodname> methods. Drivers must stop and
3453 cleanup all per-file operations in the <methodname>preclose</methodname>
3454 method. For instance pending vertical blanking and page flip events must
3455 be cancelled. No per-file operation is allowed on the file handle after
3456 returning from the <methodname>preclose</methodname> method.
3459 Finally the <methodname>postclose</methodname> method is called as the
3460 last step of the close operation, right before calling the
3461 <methodname>lastclose</methodname> method if no other open file handle
3462 exists for the device. Drivers that have allocated per-file private data
3463 in the <methodname>open</methodname> method should free it here.
3466 The <methodname>lastclose</methodname> method should restore CRTC and
3467 plane properties to default value, so that a subsequent open of the
3468 device will not inherit state from the previous user. It can also be
3469 used to execute delayed power switching state changes, e.g. in
3470 conjunction with the vga-switcheroo infrastructure. Beyond that KMS
3471 drivers should not do any further cleanup. Only legacy UMS drivers might
3472 need to clean up device state so that the vga console or an independent
3473 fbdev driver could take over.
3477 <title>File Operations</title>
3478 <synopsis>const struct file_operations *fops</synopsis>
3479 <abstract>File operations for the DRM device node.</abstract>
3481 Drivers must define the file operations structure that forms the DRM
3482 userspace API entry point, even though most of those operations are
3483 implemented in the DRM core. The <methodname>open</methodname>,
3484 <methodname>release</methodname> and <methodname>ioctl</methodname>
3485 operations are handled by
3487 .owner = THIS_MODULE,
3489 .release = drm_release,
3490 .unlocked_ioctl = drm_ioctl,
3491 #ifdef CONFIG_COMPAT
3492 .compat_ioctl = drm_compat_ioctl,
3497 Drivers that implement private ioctls that requires 32/64bit
3498 compatibility support must provide their own
3499 <methodname>compat_ioctl</methodname> handler that processes private
3500 ioctls and calls <function>drm_compat_ioctl</function> for core ioctls.
3503 The <methodname>read</methodname> and <methodname>poll</methodname>
3504 operations provide support for reading DRM events and polling them. They
3509 .llseek = no_llseek,
3513 The memory mapping implementation varies depending on how the driver
3514 manages memory. Pre-GEM drivers will use <function>drm_mmap</function>,
3515 while GEM-aware drivers will use <function>drm_gem_mmap</function>. See
3516 <xref linkend="drm-gem"/>.
3518 .mmap = drm_gem_mmap,
3522 No other file operation is supported by the DRM API.
3526 <title>IOCTLs</title>
3527 <synopsis>struct drm_ioctl_desc *ioctls;
3528 int num_ioctls;</synopsis>
3529 <abstract>Driver-specific ioctls descriptors table.</abstract>
3531 Driver-specific ioctls numbers start at DRM_COMMAND_BASE. The ioctls
3532 descriptors table is indexed by the ioctl number offset from the base
3533 value. Drivers can use the DRM_IOCTL_DEF_DRV() macro to initialize the
3537 <programlisting>DRM_IOCTL_DEF_DRV(ioctl, func, flags)</programlisting>
3539 <parameter>ioctl</parameter> is the ioctl name. Drivers must define
3540 the DRM_##ioctl and DRM_IOCTL_##ioctl macros to the ioctl number
3541 offset from DRM_COMMAND_BASE and the ioctl number respectively. The
3542 first macro is private to the device while the second must be exposed
3543 to userspace in a public header.
3546 <parameter>func</parameter> is a pointer to the ioctl handler function
3547 compatible with the <type>drm_ioctl_t</type> type.
3548 <programlisting>typedef int drm_ioctl_t(struct drm_device *dev, void *data,
3549 struct drm_file *file_priv);</programlisting>
3552 <parameter>flags</parameter> is a bitmask combination of the following
3553 values. It restricts how the ioctl is allowed to be called.
3556 DRM_AUTH - Only authenticated callers allowed
3559 DRM_MASTER - The ioctl can only be called on the master file
3563 DRM_ROOT_ONLY - Only callers with the SYSADMIN capability allowed
3566 DRM_CONTROL_ALLOW - The ioctl can only be called on a control
3570 DRM_UNLOCKED - The ioctl handler will be called without locking
3571 the DRM global mutex
3579 <title>Legacy Support Code</title>
3581 The section very briefly covers some of the old legacy support code which
3582 is only used by old DRM drivers which have done a so-called shadow-attach
3583 to the underlying device instead of registering as a real driver. This
3584 also includes some of the old generic buffer management and command
3585 submission code. Do not use any of this in new and modern drivers.
3589 <title>Legacy Suspend/Resume</title>
3591 The DRM core provides some suspend/resume code, but drivers wanting full
3592 suspend/resume support should provide save() and restore() functions.
3593 These are called at suspend, hibernate, or resume time, and should perform
3594 any state save or restore required by your device across suspend or
3597 <synopsis>int (*suspend) (struct drm_device *, pm_message_t state);
3598 int (*resume) (struct drm_device *);</synopsis>
3600 Those are legacy suspend and resume methods which
3601 <emphasis>only</emphasis> work with the legacy shadow-attach driver
3602 registration functions. New driver should use the power management
3603 interface provided by their bus type (usually through
3604 the struct <structname>device_driver</structname> dev_pm_ops) and set
3605 these methods to NULL.
3610 <title>Legacy DMA Services</title>
3612 This should cover how DMA mapping etc. is supported by the core.
3613 These functions are deprecated and should not be used.
3622 - Document the struct_mutex catch-all lock
3623 - Document connector properties
3625 - Why is the load method optional?
3626 - What are drivers supposed to set the initial display state to, and how?
3627 Connector's DPMS states are not initialized and are thus equal to
3628 DRM_MODE_DPMS_ON. The fbcon compatibility layer calls
3629 drm_helper_disable_unused_functions(), which disables unused encoders and
3630 CRTCs, but doesn't touch the connectors' DPMS state, and
3631 drm_helper_connector_dpms() in reaction to fbdev blanking events. Do drivers
3632 that don't implement (or just don't use) fbcon compatibility need to call
3633 those functions themselves?
3634 - KMS drivers must call drm_vblank_pre_modeset() and drm_vblank_post_modeset()
3635 around mode setting. Should this be done in the DRM core?
3636 - vblank_disable_allowed is set to 1 in the first drm_vblank_post_modeset()
3637 call and never set back to 0. It seems to be safe to permanently set it to 1
3638 in drm_vblank_init() for KMS driver, and it might be safe for UMS drivers as
3639 well. This should be investigated.
3640 - crtc and connector .save and .restore operations are only used internally in
3641 drivers, should they be removed from the core?
3642 - encoder mid-layer .save and .restore operations are only used internally in
3643 drivers, should they be removed from the core?
3644 - encoder mid-layer .detect operation is only used internally in drivers,
3645 should it be removed from the core?
3648 <!-- External interfaces -->
3650 <chapter id="drmExternals">
3651 <title>Userland interfaces</title>
3653 The DRM core exports several interfaces to applications,
3654 generally intended to be used through corresponding libdrm
3655 wrapper functions. In addition, drivers export device-specific
3656 interfaces for use by userspace drivers & device-aware
3657 applications through ioctls and sysfs files.
3660 External interfaces include: memory mapping, context management,
3661 DMA operations, AGP management, vblank control, fence
3662 management, memory management, and output management.
3665 Cover generic ioctls and sysfs layout here. We only need high-level
3666 info, since man pages should cover the rest.
3669 <!-- External: render nodes -->
3672 <title>Render nodes</title>
3674 DRM core provides multiple character-devices for user-space to use.
3675 Depending on which device is opened, user-space can perform a different
3676 set of operations (mainly ioctls). The primary node is always created
3677 and called card<num>. Additionally, a currently
3678 unused control node, called controlD<num> is also
3679 created. The primary node provides all legacy operations and
3680 historically was the only interface used by userspace. With KMS, the
3681 control node was introduced. However, the planned KMS control interface
3682 has never been written and so the control node stays unused to date.
3685 With the increased use of offscreen renderers and GPGPU applications,
3686 clients no longer require running compositors or graphics servers to
3687 make use of a GPU. But the DRM API required unprivileged clients to
3688 authenticate to a DRM-Master prior to getting GPU access. To avoid this
3689 step and to grant clients GPU access without authenticating, render
3690 nodes were introduced. Render nodes solely serve render clients, that
3691 is, no modesetting or privileged ioctls can be issued on render nodes.
3692 Only non-global rendering commands are allowed. If a driver supports
3693 render nodes, it must advertise it via the DRIVER_RENDER
3694 DRM driver capability. If not supported, the primary node must be used
3695 for render clients together with the legacy drmAuth authentication
3699 If a driver advertises render node support, DRM core will create a
3700 separate render node called renderD<num>. There will
3701 be one render node per device. No ioctls except PRIME-related ioctls
3702 will be allowed on this node. Especially GEM_OPEN will be
3703 explicitly prohibited. Render nodes are designed to avoid the
3704 buffer-leaks, which occur if clients guess the flink names or mmap
3705 offsets on the legacy interface. Additionally to this basic interface,
3706 drivers must mark their driver-dependent render-only ioctls as
3707 DRM_RENDER_ALLOW so render clients can use them. Driver
3708 authors must be careful not to allow any privileged ioctls on render
3712 With render nodes, user-space can now control access to the render node
3713 via basic file-system access-modes. A running graphics server which
3714 authenticates clients on the privileged primary/legacy node is no longer
3715 required. Instead, a client can open the render node and is immediately
3716 granted GPU access. Communication between clients (or servers) is done
3717 via PRIME. FLINK from render node to legacy node is not supported. New
3718 clients must not use the insecure FLINK interface.
3721 Besides dropping all modeset/global ioctls, render nodes also drop the
3722 DRM-Master concept. There is no reason to associate render clients with
3723 a DRM-Master as they are independent of any graphics server. Besides,
3724 they must work without any running master, anyway.
3725 Drivers must be able to run without a master object if they support
3726 render nodes. If, on the other hand, a driver requires shared state
3727 between clients which is visible to user-space and accessible beyond
3728 open-file boundaries, they cannot support render nodes.
3732 <!-- External: vblank handling -->
3735 <title>VBlank event handling</title>
3737 The DRM core exposes two vertical blank related ioctls:
3740 <term>DRM_IOCTL_WAIT_VBLANK</term>
3743 This takes a struct drm_wait_vblank structure as its argument,
3744 and it is used to block or request a signal when a specified
3745 vblank event occurs.
3750 <term>DRM_IOCTL_MODESET_CTL</term>
3753 This was only used for user-mode-settind drivers around
3754 modesetting changes to allow the kernel to update the vblank
3755 interrupt after mode setting, since on many devices the vertical
3756 blank counter is reset to 0 at some point during modeset. Modern
3757 drivers should not call this any more since with kernel mode
3758 setting it is a no-op.
3768 <part id="drmDrivers">
3769 <title>DRM Drivers</title>
3773 This second part of the DRM Developer's Guide documents driver code,
3774 implementation details and also all the driver-specific userspace
3775 interfaces. Especially since all hardware-acceleration interfaces to
3776 userspace are driver specific for efficiency and other reasons these
3777 interfaces can be rather substantial. Hence every driver has its own
3782 <chapter id="drmI915">
3783 <title>drm/i915 Intel GFX Driver</title>
3785 The drm/i915 driver supports all (with the exception of some very early
3786 models) integrated GFX chipsets with both Intel display and rendering
3787 blocks. This excludes a set of SoC platforms with an SGX rendering unit,
3788 those have basic support through the gma500 drm driver.
3791 <title>Display Hardware Handling</title>
3793 This section covers everything related to the display hardware including
3794 the mode setting infrastructure, plane, sprite and cursor handling and
3795 display, output probing and related topics.
3798 <title>Mode Setting Infrastructure</title>
3800 The i915 driver is thus far the only DRM driver which doesn't use the
3801 common DRM helper code to implement mode setting sequences. Thus it
3802 has its own tailor-made infrastructure for executing a display
3803 configuration change.
3807 <title>Plane Configuration</title>
3809 This section covers plane configuration and composition with the
3810 primary plane, sprites, cursors and overlays. This includes the
3811 infrastructure to do atomic vsync'ed updates of all this state and
3812 also tightly coupled topics like watermark setup and computation,
3813 framebuffer compression and panel self refresh.
3817 <title>Output Probing</title>
3819 This section covers output probing and related infrastructure like the
3820 hotplug interrupt storm detection and mitigation code. Note that the
3821 i915 driver still uses most of the common DRM helper code for output
3822 probing, so those sections fully apply.
3827 !Pdrivers/gpu/drm/i915/i915_reg.h DPIO
3829 <title>Dual channel PHY (VLV/CHV)</title>
3831 <colspec colname="c0" />
3832 <colspec colname="c1" />
3833 <colspec colname="c2" />
3834 <colspec colname="c3" />
3835 <colspec colname="c4" />
3836 <colspec colname="c5" />
3837 <colspec colname="c6" />
3838 <colspec colname="c7" />
3839 <spanspec spanname="ch0" namest="c0" nameend="c3" />
3840 <spanspec spanname="ch1" namest="c4" nameend="c7" />
3841 <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
3842 <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
3843 <spanspec spanname="ch1pcs01" namest="c4" nameend="c5" />
3844 <spanspec spanname="ch1pcs23" namest="c6" nameend="c7" />
3847 <entry spanname="ch0">CH0</entry>
3848 <entry spanname="ch1">CH1</entry>
3851 <tbody valign="top" align="center">
3853 <entry spanname="ch0">CMN/PLL/REF</entry>
3854 <entry spanname="ch1">CMN/PLL/REF</entry>
3857 <entry spanname="ch0pcs01">PCS01</entry>
3858 <entry spanname="ch0pcs23">PCS23</entry>
3859 <entry spanname="ch1pcs01">PCS01</entry>
3860 <entry spanname="ch1pcs23">PCS23</entry>
3873 <entry spanname="ch0">DDI0</entry>
3874 <entry spanname="ch1">DDI1</entry>
3880 <title>Single channel PHY (CHV)</title>
3882 <colspec colname="c0" />
3883 <colspec colname="c1" />
3884 <colspec colname="c2" />
3885 <colspec colname="c3" />
3886 <spanspec spanname="ch0" namest="c0" nameend="c3" />
3887 <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
3888 <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
3891 <entry spanname="ch0">CH0</entry>
3894 <tbody valign="top" align="center">
3896 <entry spanname="ch0">CMN/PLL/REF</entry>
3899 <entry spanname="ch0pcs01">PCS01</entry>
3900 <entry spanname="ch0pcs23">PCS23</entry>
3909 <entry spanname="ch0">DDI2</entry>
3918 <title>Memory Management and Command Submission</title>
3920 This sections covers all things related to the GEM implementation in the
3924 <title>Batchbuffer Parsing</title>
3925 !Pdrivers/gpu/drm/i915/i915_cmd_parser.c batch buffer command parser
3926 !Idrivers/gpu/drm/i915/i915_cmd_parser.c
3929 <title>Logical Rings, Logical Ring Contexts and Execlists</title>
3930 !Pdrivers/gpu/drm/i915/intel_lrc.c Logical Rings, Logical Ring Contexts and Execlists
3931 !Idrivers/gpu/drm/i915/intel_lrc.c
git.samba.org / sfrench / cifs-2.6.git / blob