[PATCH v2 6/7] Documentation/gpu: split up mm, kms and kms-helpers from internals

Make the documents more manageable.

Signed-off-by: Jani Nikula jani.nikula@intel.com --- Documentation/gpu/drm-internals.rst | 1379 +-------------------------------- Documentation/gpu/drm-kms-helpers.rst | 260 +++++++ Documentation/gpu/drm-kms.rst | 656 ++++++++++++++++ Documentation/gpu/drm-mm.rst | 454 +++++++++++ Documentation/gpu/index.rst | 3 + 5 files changed, 1379 insertions(+), 1373 deletions(-) create mode 100644 Documentation/gpu/drm-kms-helpers.rst create mode 100644 Documentation/gpu/drm-kms.rst create mode 100644 Documentation/gpu/drm-mm.rst

diff --git a/Documentation/gpu/drm-internals.rst b/Documentation/gpu/drm-internals.rst index a7f117653033..4f7176576feb 100644 --- a/Documentation/gpu/drm-internals.rst +++ b/Documentation/gpu/drm-internals.rst @@ -40,7 +40,7 @@ Driver Information ------------------

Driver Features -^^^^^^^^^^^^^^^ +~~~~~~~~~~~~~~~

Drivers inform the DRM core about their requirements and supported features by setting appropriate flags in the driver_features field. @@ -96,7 +96,7 @@ DRIVER_ATOMIC modeset objects with driver specific properties.

Major, Minor and Patchlevel -^^^^^^^^^^^^^^^^^^^^^^^^^^^ +~~~~~~~~~~~~~~~~~~~~~~~~~~~

int major; int minor; int patchlevel; The DRM core identifies driver versions by a major, minor and patch @@ -114,7 +114,7 @@ return an error. Otherwise the driver's set_version() method will be called with the requested version.

Name, Description and Date -^^^^^^^^^^^^^^^^^^^^^^^^^^ +~~~~~~~~~~~~~~~~~~~~~~~~~~

char *name; char *desc; char *date; The driver name is printed to the kernel log at initialization time, @@ -144,7 +144,7 @@ Driver Load -----------

IRQ Registration -^^^^^^^^^^^^^^^^ +~~~~~~~~~~~~~~~~

The DRM core tries to facilitate IRQ handler registration and unregistration by providing :c:func:`drm_irq_install()` and @@ -198,7 +198,7 @@ registration of the IRQs, and clear it to 0 after unregistering the IRQs.

Memory Manager Initialization -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Every DRM driver requires a memory manager which must be initialized at load time. DRM currently contains two memory managers, the Translation @@ -207,7 +207,7 @@ document describes the use of the GEM memory manager only. See ? for details.

Miscellaneous Device Configuration -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Another task that may be necessary for PCI devices during configuration is mapping the video BIOS. On many devices, the VBIOS describes device @@ -236,1373 +236,6 @@ drivers. .. kernel-doc:: drivers/gpu/drm/drm_platform.c :export:

-Memory management -================= - -Modern Linux systems require large amount of graphics memory to store -frame buffers, textures, vertices and other graphics-related data. Given -the very dynamic nature of many of that data, managing graphics memory -efficiently is thus crucial for the graphics stack and plays a central -role in the DRM infrastructure. - -The DRM core includes two memory managers, namely Translation Table Maps -(TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory -manager to be developed and tried to be a one-size-fits-them all -solution. It provides a single userspace API to accommodate the need of -all hardware, supporting both Unified Memory Architecture (UMA) devices -and devices with dedicated video RAM (i.e. most discrete video cards). -This resulted in a large, complex piece of code that turned out to be -hard to use for driver development. - -GEM started as an Intel-sponsored project in reaction to TTM's -complexity. Its design philosophy is completely different: instead of -providing a solution to every graphics memory-related problems, GEM -identified common code between drivers and created a support library to -share it. GEM has simpler initialization and execution requirements than -TTM, but has no video RAM management capabilities and is thus limited to -UMA devices. - -The Translation Table Manager (TTM) ------------------------------------ - -TTM design background and information belongs here. - -TTM initialization -^^^^^^^^^^^^^^^^^^ - - **Warning** - - This section is outdated. - -Drivers wishing to support TTM must fill out a drm_bo_driver -structure. The structure contains several fields with function pointers -for initializing the TTM, allocating and freeing memory, waiting for -command completion and fence synchronization, and memory migration. See -the radeon_ttm.c file for an example of usage. - -The ttm_global_reference structure is made up of several fields: - -:: - - struct ttm_global_reference { - enum ttm_global_types global_type; - size_t size; - void *object; - int (*init) (struct ttm_global_reference *); - void (*release) (struct ttm_global_reference *); - }; - - -There should be one global reference structure for your memory manager -as a whole, and there will be others for each object created by the -memory manager at runtime. Your global TTM should have a type of -TTM_GLOBAL_TTM_MEM. The size field for the global object should be -sizeof(struct ttm_mem_global), and the init and release hooks should -point at your driver-specific init and release routines, which probably -eventually call ttm_mem_global_init and ttm_mem_global_release, -respectively. - -Once your global TTM accounting structure is set up and initialized by -calling ttm_global_item_ref() on it, you need to create a buffer -object TTM to provide a pool for buffer object allocation by clients and -the kernel itself. The type of this object should be -TTM_GLOBAL_TTM_BO, and its size should be sizeof(struct -ttm_bo_global). Again, driver-specific init and release functions may -be provided, likely eventually calling ttm_bo_global_init() and -ttm_bo_global_release(), respectively. Also, like the previous -object, ttm_global_item_ref() is used to create an initial reference -count for the TTM, which will call your initialization function. - -The Graphics Execution Manager (GEM) ------------------------------------- - -The GEM design approach has resulted in a memory manager that doesn't -provide full coverage of all (or even all common) use cases in its -userspace or kernel API. GEM exposes a set of standard memory-related -operations to userspace and a set of helper functions to drivers, and -let drivers implement hardware-specific operations with their own -private API. - -The GEM userspace API is described in the `GEM - the Graphics Execution -Manager http://lwn.net/Articles/283798/`__ article on LWN. While -slightly outdated, the document provides a good overview of the GEM API -principles. Buffer allocation and read and write operations, described -as part of the common GEM API, are currently implemented using -driver-specific ioctls. - -GEM is data-agnostic. It manages abstract buffer objects without knowing -what individual buffers contain. APIs that require knowledge of buffer -contents or purpose, such as buffer allocation or synchronization -primitives, are thus outside of the scope of GEM and must be implemented -using driver-specific ioctls. - -On a fundamental level, GEM involves several operations: - -- Memory allocation and freeing -- Command execution -- Aperture management at command execution time - -Buffer object allocation is relatively straightforward and largely -provided by Linux's shmem layer, which provides memory to back each -object. - -Device-specific operations, such as command execution, pinning, buffer -read & write, mapping, and domain ownership transfers are left to -driver-specific ioctls. - -GEM Initialization -^^^^^^^^^^^^^^^^^^ - -Drivers that use GEM must set the DRIVER_GEM bit in the struct -:c:type:`struct drm_driver <drm_driver>` driver_features -field. The DRM core will then automatically initialize the GEM core -before calling the load operation. Behind the scene, this will create a -DRM Memory Manager object which provides an address space pool for -object allocation. - -In a KMS configuration, drivers need to allocate and initialize a -command ring buffer following core GEM initialization if required by the -hardware. UMA devices usually have what is called a "stolen" memory -region, which provides space for the initial framebuffer and large, -contiguous memory regions required by the device. This space is -typically not managed by GEM, and must be initialized separately into -its own DRM MM object. - -GEM Objects Creation -^^^^^^^^^^^^^^^^^^^^ - -GEM splits creation of GEM objects and allocation of the memory that -backs them in two distinct operations. - -GEM objects are represented by an instance of struct :c:type:`struct -drm_gem_object <drm_gem_object>`. Drivers usually need to -extend GEM objects with private information and thus create a -driver-specific GEM object structure type that embeds an instance of -struct :c:type:`struct drm_gem_object <drm_gem_object>`. - -To create a GEM object, a driver allocates memory for an instance of its -specific GEM object type and initializes the embedded struct -:c:type:`struct drm_gem_object <drm_gem_object>` with a call -to :c:func:`drm_gem_object_init()`. The function takes a pointer -to the DRM device, a pointer to the GEM object and the buffer object -size in bytes. - -GEM uses shmem to allocate anonymous pageable memory. -:c:func:`drm_gem_object_init()` will create an shmfs file of the -requested size and store it into the struct :c:type:`struct -drm_gem_object <drm_gem_object>` filp field. The memory is -used as either main storage for the object when the graphics hardware -uses system memory directly or as a backing store otherwise. - -Drivers are responsible for the actual physical pages allocation by -calling :c:func:`shmem_read_mapping_page_gfp()` for each page. -Note that they can decide to allocate pages when initializing the GEM -object, or to delay allocation until the memory is needed (for instance -when a page fault occurs as a result of a userspace memory access or -when the driver needs to start a DMA transfer involving the memory). - -Anonymous pageable memory allocation is not always desired, for instance -when the hardware requires physically contiguous system memory as is -often the case in embedded devices. Drivers can create GEM objects with -no shmfs backing (called private GEM objects) by initializing them with -a call to :c:func:`drm_gem_private_object_init()` instead of -:c:func:`drm_gem_object_init()`. Storage for private GEM objects -must be managed by drivers. - -GEM Objects Lifetime -^^^^^^^^^^^^^^^^^^^^ - -All GEM objects are reference-counted by the GEM core. References can be -acquired and release by :c:func:`calling -drm_gem_object_reference()` and -:c:func:`drm_gem_object_unreference()` respectively. The caller -must hold the :c:type:`struct drm_device <drm_device>` -struct_mutex lock when calling -:c:func:`drm_gem_object_reference()`. As a convenience, GEM -provides :c:func:`drm_gem_object_unreference_unlocked()` -functions that can be called without holding the lock. - -When the last reference to a GEM object is released the GEM core calls -the :c:type:`struct drm_driver <drm_driver>` gem_free_object -operation. That operation is mandatory for GEM-enabled drivers and must -free the GEM object and all associated resources. - -void (*gem_free_object) (struct drm_gem_object *obj); Drivers are -responsible for freeing all GEM object resources. This includes the -resources created by the GEM core, which need to be released with -:c:func:`drm_gem_object_release()`. - -GEM Objects Naming -^^^^^^^^^^^^^^^^^^ - -Communication between userspace and the kernel refers to GEM objects -using local handles, global names or, more recently, file descriptors. -All of those are 32-bit integer values; the usual Linux kernel limits -apply to the file descriptors. - -GEM handles are local to a DRM file. Applications get a handle to a GEM -object through a driver-specific ioctl, and can use that handle to refer -to the GEM object in other standard or driver-specific ioctls. Closing a -DRM file handle frees all its GEM handles and dereferences the -associated GEM objects. - -To create a handle for a GEM object drivers call -:c:func:`drm_gem_handle_create()`. The function takes a pointer -to the DRM file and the GEM object and returns a locally unique handle. -When the handle is no longer needed drivers delete it with a call to -:c:func:`drm_gem_handle_delete()`. Finally the GEM object -associated with a handle can be retrieved by a call to -:c:func:`drm_gem_object_lookup()`. - -Handles don't take ownership of GEM objects, they only take a reference -to the object that will be dropped when the handle is destroyed. To -avoid leaking GEM objects, drivers must make sure they drop the -reference(s) they own (such as the initial reference taken at object -creation time) as appropriate, without any special consideration for the -handle. For example, in the particular case of combined GEM object and -handle creation in the implementation of the dumb_create operation, -drivers must drop the initial reference to the GEM object before -returning the handle. - -GEM names are similar in purpose to handles but are not local to DRM -files. They can be passed between processes to reference a GEM object -globally. Names can't be used directly to refer to objects in the DRM -API, applications must convert handles to names and names to handles -using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls -respectively. The conversion is handled by the DRM core without any -driver-specific support. - -GEM also supports buffer sharing with dma-buf file descriptors through -PRIME. GEM-based drivers must use the provided helpers functions to -implement the exporting and importing correctly. See ?. Since sharing -file descriptors is inherently more secure than the easily guessable and -global GEM names it is the preferred buffer sharing mechanism. Sharing -buffers through GEM names is only supported for legacy userspace. -Furthermore PRIME also allows cross-device buffer sharing since it is -based on dma-bufs. - -GEM Objects Mapping -^^^^^^^^^^^^^^^^^^^ - -Because mapping operations are fairly heavyweight GEM favours -read/write-like access to buffers, implemented through driver-specific -ioctls, over mapping buffers to userspace. However, when random access -to the buffer is needed (to perform software rendering for instance), -direct access to the object can be more efficient. - -The mmap system call can't be used directly to map GEM objects, as they -don't have their own file handle. Two alternative methods currently -co-exist to map GEM objects to userspace. The first method uses a -driver-specific ioctl to perform the mapping operation, calling -:c:func:`do_mmap()` under the hood. This is often considered -dubious, seems to be discouraged for new GEM-enabled drivers, and will -thus not be described here. - -The second method uses the mmap system call on the DRM file handle. void -*mmap(void *addr, size_t length, int prot, int flags, int fd, off_t -offset); DRM identifies the GEM object to be mapped by a fake offset -passed through the mmap offset argument. Prior to being mapped, a GEM -object must thus be associated with a fake offset. To do so, drivers -must call :c:func:`drm_gem_create_mmap_offset()` on the object. - -Once allocated, the fake offset value must be passed to the application -in a driver-specific way and can then be used as the mmap offset -argument. - -The GEM core provides a helper method :c:func:`drm_gem_mmap()` to -handle object mapping. The method can be set directly as the mmap file -operation handler. It will look up the GEM object based on the offset -value and set the VMA operations to the :c:type:`struct drm_driver -<drm_driver>` gem_vm_ops field. Note that -:c:func:`drm_gem_mmap()` doesn't map memory to userspace, but -relies on the driver-provided fault handler to map pages individually. - -To use :c:func:`drm_gem_mmap()`, drivers must fill the struct -:c:type:`struct drm_driver <drm_driver>` gem_vm_ops field -with a pointer to VM operations. - -struct vm_operations_struct *gem_vm_ops struct -vm_operations_struct { void (*open)(struct vm_area_struct * area); -void (*close)(struct vm_area_struct * area); int (*fault)(struct -vm_area_struct *vma, struct vm_fault *vmf); }; - -The open and close operations must update the GEM object reference -count. Drivers can use the :c:func:`drm_gem_vm_open()` and -:c:func:`drm_gem_vm_close()` helper functions directly as open -and close handlers. - -The fault operation handler is responsible for mapping individual pages -to userspace when a page fault occurs. Depending on the memory -allocation scheme, drivers can allocate pages at fault time, or can -decide to allocate memory for the GEM object at the time the object is -created. - -Drivers that want to map the GEM object upfront instead of handling page -faults can implement their own mmap file operation handler. - -Memory Coherency -^^^^^^^^^^^^^^^^ - -When mapped to the device or used in a command buffer, backing pages for -an object are flushed to memory and marked write combined so as to be -coherent with the GPU. Likewise, if the CPU accesses an object after the -GPU has finished rendering to the object, then the object must be made -coherent with the CPU's view of memory, usually involving GPU cache -flushing of various kinds. This core CPU<->GPU coherency management is -provided by a device-specific ioctl, which evaluates an object's current -domain and performs any necessary flushing or synchronization to put the -object into the desired coherency domain (note that the object may be -busy, i.e. an active render target; in that case, setting the domain -blocks the client and waits for rendering to complete before performing -any necessary flushing operations). - -Command Execution -^^^^^^^^^^^^^^^^^ - -Perhaps the most important GEM function for GPU devices is providing a -command execution interface to clients. Client programs construct -command buffers containing references to previously allocated memory -objects, and then submit them to GEM. At that point, GEM takes care to -bind all the objects into the GTT, execute the buffer, and provide -necessary synchronization between clients accessing the same buffers. -This often involves evicting some objects from the GTT and re-binding -others (a fairly expensive operation), and providing relocation support -which hides fixed GTT offsets from clients. Clients must take care not -to submit command buffers that reference more objects than can fit in -the GTT; otherwise, GEM will reject them and no rendering will occur. -Similarly, if several objects in the buffer require fence registers to -be allocated for correct rendering (e.g. 2D blits on pre-965 chips), -care must be taken not to require more fence registers than are -available to the client. Such resource management should be abstracted -from the client in libdrm. - -GEM Function Reference ----------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_gem.c - :export: - -.. kernel-doc:: include/drm/drm_gem.h - :internal: - -VMA Offset Manager ------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_vma_manager.c - :doc: vma offset manager - -.. kernel-doc:: drivers/gpu/drm/drm_vma_manager.c - :export: - -.. kernel-doc:: include/drm/drm_vma_manager.h - :internal: - -PRIME Buffer Sharing --------------------- - -PRIME is the cross device buffer sharing framework in drm, originally -created for the OPTIMUS range of multi-gpu platforms. To userspace PRIME -buffers are dma-buf based file descriptors. - -Overview and Driver Interface -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -Similar to GEM global names, PRIME file descriptors are also used to -share buffer objects across processes. They offer additional security: -as file descriptors must be explicitly sent over UNIX domain sockets to -be shared between applications, they can't be guessed like the globally -unique GEM names. - -Drivers that support the PRIME API must set the DRIVER_PRIME bit in the -struct :c:type:`struct drm_driver <drm_driver>` -driver_features field, and implement the prime_handle_to_fd and -prime_fd_to_handle operations. - -int (*prime_handle_to_fd)(struct drm_device *dev, struct drm_file -*file_priv, uint32_t handle, uint32_t flags, int *prime_fd); int -(*prime_fd_to_handle)(struct drm_device *dev, struct drm_file -*file_priv, int prime_fd, uint32_t *handle); Those two operations -convert a handle to a PRIME file descriptor and vice versa. Drivers must -use the kernel dma-buf buffer sharing framework to manage the PRIME file -descriptors. Similar to the mode setting API PRIME is agnostic to the -underlying buffer object manager, as long as handles are 32bit unsigned -integers. - -While non-GEM drivers must implement the operations themselves, GEM -drivers must use the :c:func:`drm_gem_prime_handle_to_fd()` and -:c:func:`drm_gem_prime_fd_to_handle()` helper functions. Those -helpers rely on the driver gem_prime_export and gem_prime_import -operations to create a dma-buf instance from a GEM object (dma-buf -exporter role) and to create a GEM object from a dma-buf instance -(dma-buf importer role). - -struct dma_buf * (*gem_prime_export)(struct drm_device *dev, -struct drm_gem_object *obj, int flags); struct drm_gem_object * -(*gem_prime_import)(struct drm_device *dev, struct dma_buf -*dma_buf); These two operations are mandatory for GEM drivers that -support PRIME. - -PRIME Helper Functions -^^^^^^^^^^^^^^^^^^^^^^ - -.. kernel-doc:: drivers/gpu/drm/drm_prime.c - :doc: PRIME Helpers - -PRIME Function References -------------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_prime.c - :export: - -DRM MM Range Allocator ----------------------- - -Overview -^^^^^^^^ - -.. kernel-doc:: drivers/gpu/drm/drm_mm.c - :doc: Overview - -LRU Scan/Eviction Support -^^^^^^^^^^^^^^^^^^^^^^^^^ - -.. kernel-doc:: drivers/gpu/drm/drm_mm.c - :doc: lru scan roaster - -DRM MM Range Allocator Function References ------------------------------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_mm.c - :export: - -.. kernel-doc:: include/drm/drm_mm.h - :internal: - -CMA Helper Functions Reference ------------------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_gem_cma_helper.c - :doc: cma helpers - -.. kernel-doc:: drivers/gpu/drm/drm_gem_cma_helper.c - :export: - -.. kernel-doc:: include/drm/drm_gem_cma_helper.h - :internal: - -Mode Setting -============ - -Drivers must initialize the mode setting core by calling -:c:func:`drm_mode_config_init()` on the DRM device. The function -initializes the :c:type:`struct drm_device <drm_device>` -mode_config field and never fails. Once done, mode configuration must -be setup by initializing the following fields. - -- int min_width, min_height; int max_width, max_height; - Minimum and maximum width and height of the frame buffers in pixel - units. - -- struct drm_mode_config_funcs *funcs; - Mode setting functions. - -Display Modes Function Reference --------------------------------- - -.. kernel-doc:: include/drm/drm_modes.h - :internal: - -.. kernel-doc:: drivers/gpu/drm/drm_modes.c - :export: - -Atomic Mode Setting Function Reference --------------------------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_atomic.c - :export: - -.. kernel-doc:: drivers/gpu/drm/drm_atomic.c - :internal: - -Frame Buffer Abstraction ------------------------- - -Frame buffers are abstract memory objects that provide a source of -pixels to scanout to a CRTC. Applications explicitly request the -creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls -and receive an opaque handle that can be passed to the KMS CRTC control, -plane configuration and page flip functions. - -Frame buffers rely on the underneath memory manager for low-level memory -operations. When creating a frame buffer applications pass a memory -handle (or a list of memory handles for multi-planar formats) through -the ``drm_mode_fb_cmd2`` argument. For drivers using GEM as their -userspace buffer management interface this would be a GEM handle. -Drivers are however free to use their own backing storage object -handles, e.g. vmwgfx directly exposes special TTM handles to userspace -and so expects TTM handles in the create ioctl and not GEM handles. - -The lifetime of a drm framebuffer is controlled with a reference count, -drivers can grab additional references with -:c:func:`drm_framebuffer_reference()`and drop them again with -:c:func:`drm_framebuffer_unreference()`. For driver-private -framebuffers for which the last reference is never dropped (e.g. for the -fbdev framebuffer when the struct :c:type:`struct drm_framebuffer -<drm_framebuffer>` is embedded into the fbdev helper struct) -drivers can manually clean up a framebuffer at module unload time with -:c:func:`drm_framebuffer_unregister_private()`. - -DRM Format Handling -------------------- - -.. kernel-doc:: include/drm/drm_fourcc.h - :internal: - -.. kernel-doc:: drivers/gpu/drm/drm_fourcc.c - :export: - -Dumb Buffer Objects -------------------- - -The KMS API doesn't standardize backing storage object creation and -leaves it to driver-specific ioctls. Furthermore actually creating a -buffer object even for GEM-based drivers is done through a -driver-specific ioctl - GEM only has a common userspace interface for -sharing and destroying objects. While not an issue for full-fledged -graphics stacks that include device-specific userspace components (in -libdrm for instance), this limit makes DRM-based early boot graphics -unnecessarily complex. - -Dumb objects partly alleviate the problem by providing a standard API to -create dumb buffers suitable for scanout, which can then be used to -create KMS frame buffers. - -To support dumb objects drivers must implement the dumb_create, -dumb_destroy and dumb_map_offset operations. - -- int (*dumb_create)(struct drm_file *file_priv, struct - drm_device *dev, struct drm_mode_create_dumb *args); - The dumb_create operation creates a driver object (GEM or TTM - handle) suitable for scanout based on the width, height and depth - from the struct :c:type:`struct drm_mode_create_dumb - <drm_mode_create_dumb>` argument. It fills the argument's - handle, pitch and size fields with a handle for the newly created - object and its line pitch and size in bytes. - -- int (*dumb_destroy)(struct drm_file *file_priv, struct - drm_device *dev, uint32_t handle); - The dumb_destroy operation destroys a dumb object created by - dumb_create. - -- int (*dumb_map_offset)(struct drm_file *file_priv, struct - drm_device *dev, uint32_t handle, uint64_t *offset); - The dumb_map_offset operation associates an mmap fake offset with - the object given by the handle and returns it. Drivers must use the - :c:func:`drm_gem_create_mmap_offset()` function to associate - the fake offset as described in ?. - -Note that dumb objects may not be used for gpu acceleration, as has been -attempted on some ARM embedded platforms. Such drivers really must have -a hardware-specific ioctl to allocate suitable buffer objects. - -Output Polling --------------- - -void (*output_poll_changed)(struct drm_device *dev); -This operation notifies the driver that the status of one or more -connectors has changed. Drivers that use the fb helper can just call the -:c:func:`drm_fb_helper_hotplug_event()` function to handle this -operation. - -KMS Initialization and Cleanup -============================== - -A KMS device is abstracted and exposed as a set of planes, CRTCs, -encoders and connectors. KMS drivers must thus create and initialize all -those objects at load time after initializing mode setting. - -CRTCs (:c:type:`struct drm_crtc <drm_crtc>`) --------------------------------------------- - -A CRTC is an abstraction representing a part of the chip that contains a -pointer to a scanout buffer. Therefore, the number of CRTCs available -determines how many independent scanout buffers can be active at any -given time. The CRTC structure contains several fields to support this: -a pointer to some video memory (abstracted as a frame buffer object), a -display mode, and an (x, y) offset into the video memory to support -panning or configurations where one piece of video memory spans multiple -CRTCs. - -CRTC Initialization -^^^^^^^^^^^^^^^^^^^ - -A KMS device must create and register at least one struct -:c:type:`struct drm_crtc <drm_crtc>` instance. The instance is -allocated and zeroed by the driver, possibly as part of a larger -structure, and registered with a call to :c:func:`drm_crtc_init()` -with a pointer to CRTC functions. - -Planes (:c:type:`struct drm_plane <drm_plane>`) ------------------------------------------------ - -A plane represents an image source that can be blended with or overlayed -on top of a CRTC during the scanout process. Planes are associated with -a frame buffer to crop a portion of the image memory (source) and -optionally scale it to a destination size. The result is then blended -with or overlayed on top of a CRTC. - -The DRM core recognizes three types of planes: - -- DRM_PLANE_TYPE_PRIMARY represents a "main" plane for a CRTC. - Primary planes are the planes operated upon by CRTC modesetting and - flipping operations described in the page_flip hook in - :c:type:`struct drm_crtc_funcs <drm_crtc_funcs>`. -- DRM_PLANE_TYPE_CURSOR represents a "cursor" plane for a CRTC. - Cursor planes are the planes operated upon by the - DRM_IOCTL_MODE_CURSOR and DRM_IOCTL_MODE_CURSOR2 ioctls. -- DRM_PLANE_TYPE_OVERLAY represents all non-primary, non-cursor - planes. Some drivers refer to these types of planes as "sprites" - internally. - -For compatibility with legacy userspace, only overlay planes are made -available to userspace by default. Userspace clients may set the -DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate -that they wish to receive a universal plane list containing all plane -types. - -Plane Initialization -^^^^^^^^^^^^^^^^^^^^ - -To create a plane, a KMS drivers allocates and zeroes an instances of -:c:type:`struct drm_plane <drm_plane>` (possibly as part of a -larger structure) and registers it with a call to -:c:func:`drm_universal_plane_init()`. The function takes a -bitmask of the CRTCs that can be associated with the plane, a pointer to -the plane functions, a list of format supported formats, and the type of -plane (primary, cursor, or overlay) being initialized. - -Cursor and overlay planes are optional. All drivers should provide one -primary plane per CRTC (although this requirement may change in the -future); drivers that do not wish to provide special handling for -primary planes may make use of the helper functions described in ? to -create and register a primary plane with standard capabilities. - -Encoders (:c:type:`struct drm_encoder <drm_encoder>`) ------------------------------------------------------ - -An encoder takes pixel data from a CRTC and converts it to a format -suitable for any attached connectors. On some devices, it may be -possible to have a CRTC send data to more than one encoder. In that -case, both encoders would receive data from the same scanout buffer, -resulting in a "cloned" display configuration across the connectors -attached to each encoder. - -Encoder Initialization -^^^^^^^^^^^^^^^^^^^^^^ - -As for CRTCs, a KMS driver must create, initialize and register at least -one :c:type:`struct drm_encoder <drm_encoder>` instance. The -instance is allocated and zeroed by the driver, possibly as part of a -larger structure. - -Drivers must initialize the :c:type:`struct drm_encoder -<drm_encoder>` possible_crtcs and possible_clones fields before -registering the encoder. Both fields are bitmasks of respectively the -CRTCs that the encoder can be connected to, and sibling encoders -candidate for cloning. - -After being initialized, the encoder must be registered with a call to -:c:func:`drm_encoder_init()`. The function takes a pointer to the -encoder functions and an encoder type. Supported types are - -- DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A -- DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort -- DRM_MODE_ENCODER_LVDS for display panels -- DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, - Component, SCART) -- DRM_MODE_ENCODER_VIRTUAL for virtual machine displays - -Encoders must be attached to a CRTC to be used. DRM drivers leave -encoders unattached at initialization time. Applications (or the fbdev -compatibility layer when implemented) are responsible for attaching the -encoders they want to use to a CRTC. - -Connectors (:c:type:`struct drm_connector <drm_connector>`) ------------------------------------------------------------ - -A connector is the final destination for pixel data on a device, and -usually connects directly to an external display device like a monitor -or laptop panel. A connector can only be attached to one encoder at a -time. The connector is also the structure where information about the -attached display is kept, so it contains fields for display data, EDID -data, DPMS & connection status, and information about modes supported on -the attached displays. - -Connector Initialization -^^^^^^^^^^^^^^^^^^^^^^^^ - -Finally a KMS driver must create, initialize, register and attach at -least one :c:type:`struct drm_connector <drm_connector>` -instance. The instance is created as other KMS objects and initialized -by setting the following fields. - -interlace_allowed - Whether the connector can handle interlaced modes. - -doublescan_allowed - Whether the connector can handle doublescan. - -display_info - Display information is filled from EDID information when a display - is detected. For non hot-pluggable displays such as flat panels in - embedded systems, the driver should initialize the - display_info.width_mm and display_info.height_mm fields with the - physical size of the display. - -polled - Connector polling mode, a combination of - - DRM_CONNECTOR_POLL_HPD - The connector generates hotplug events and doesn't need to be - periodically polled. The CONNECT and DISCONNECT flags must not - be set together with the HPD flag. - - DRM_CONNECTOR_POLL_CONNECT - Periodically poll the connector for connection. - - DRM_CONNECTOR_POLL_DISCONNECT - Periodically poll the connector for disconnection. - - Set to 0 for connectors that don't support connection status - discovery. - -The connector is then registered with a call to -:c:func:`drm_connector_init()` with a pointer to the connector -functions and a connector type, and exposed through sysfs with a call to -:c:func:`drm_connector_register()`. - -Supported connector types are - -- DRM_MODE_CONNECTOR_VGA -- DRM_MODE_CONNECTOR_DVII -- DRM_MODE_CONNECTOR_DVID -- DRM_MODE_CONNECTOR_DVIA -- DRM_MODE_CONNECTOR_Composite -- DRM_MODE_CONNECTOR_SVIDEO -- DRM_MODE_CONNECTOR_LVDS -- DRM_MODE_CONNECTOR_Component -- DRM_MODE_CONNECTOR_9PinDIN -- DRM_MODE_CONNECTOR_DisplayPort -- DRM_MODE_CONNECTOR_HDMIA -- DRM_MODE_CONNECTOR_HDMIB -- DRM_MODE_CONNECTOR_TV -- DRM_MODE_CONNECTOR_eDP -- DRM_MODE_CONNECTOR_VIRTUAL - -Connectors must be attached to an encoder to be used. For devices that -map connectors to encoders 1:1, the connector should be attached at -initialization time with a call to -:c:func:`drm_mode_connector_attach_encoder()`. The driver must -also set the :c:type:`struct drm_connector <drm_connector>` -encoder field to point to the attached encoder. - -Finally, drivers must initialize the connectors state change detection -with a call to :c:func:`drm_kms_helper_poll_init()`. If at least -one connector is pollable but can't generate hotplug interrupts -(indicated by the DRM_CONNECTOR_POLL_CONNECT and -DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will -automatically be queued to periodically poll for changes. Connectors -that can generate hotplug interrupts must be marked with the -DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must -call :c:func:`drm_helper_hpd_irq_event()`. The function will -queue a delayed work to check the state of all connectors, but no -periodic polling will be done. - -Connector Operations -^^^^^^^^^^^^^^^^^^^^ - - **Note** - - Unless otherwise state, all operations are mandatory. - -DPMS -'''' - -void (*dpms)(struct drm_connector *connector, int mode); -The DPMS operation sets the power state of a connector. The mode -argument is one of - -- DRM_MODE_DPMS_ON - -- DRM_MODE_DPMS_STANDBY - -- DRM_MODE_DPMS_SUSPEND - -- DRM_MODE_DPMS_OFF - -In all but DPMS_ON mode the encoder to which the connector is attached -should put the display in low-power mode by driving its signals -appropriately. If more than one connector is attached to the encoder -care should be taken not to change the power state of other displays as -a side effect. Low-power mode should be propagated to the encoders and -CRTCs when all related connectors are put in low-power mode. - -Modes -''''' - -int (*fill_modes)(struct drm_connector *connector, uint32_t -max_width, uint32_t max_height); -Fill the mode list with all supported modes for the connector. If the -``max_width`` and ``max_height`` arguments are non-zero, the -implementation must ignore all modes wider than ``max_width`` or higher -than ``max_height``. - -The connector must also fill in this operation its display_info -width_mm and height_mm fields with the connected display physical size -in millimeters. The fields should be set to 0 if the value isn't known -or is not applicable (for instance for projector devices). - -Connection Status -''''''''''''''''' - -The connection status is updated through polling or hotplug events when -supported (see ?). The status value is reported to userspace through -ioctls and must not be used inside the driver, as it only gets -initialized by a call to :c:func:`drm_mode_getconnector()` from -userspace. - -enum drm_connector_status (*detect)(struct drm_connector -*connector, bool force); -Check to see if anything is attached to the connector. The ``force`` -parameter is set to false whilst polling or to true when checking the -connector due to user request. ``force`` can be used by the driver to -avoid expensive, destructive operations during automated probing. - -Return connector_status_connected if something is connected to the -connector, connector_status_disconnected if nothing is connected and -connector_status_unknown if the connection state isn't known. - -Drivers should only return connector_status_connected if the -connection status has really been probed as connected. Connectors that -can't detect the connection status, or failed connection status probes, -should return connector_status_unknown. - -Cleanup -------- - -The DRM core manages its objects' lifetime. When an object is not needed -anymore the core calls its destroy function, which must clean up and -free every resource allocated for the object. Every -:c:func:`drm_*_init()` call must be matched with a corresponding -:c:func:`drm_*_cleanup()` call to cleanup CRTCs -(:c:func:`drm_crtc_cleanup()`), planes -(:c:func:`drm_plane_cleanup()`), encoders -(:c:func:`drm_encoder_cleanup()`) and connectors -(:c:func:`drm_connector_cleanup()`). Furthermore, connectors that -have been added to sysfs must be removed by a call to -:c:func:`drm_connector_unregister()` before calling -:c:func:`drm_connector_cleanup()`. - -Connectors state change detection must be cleanup up with a call to -:c:func:`drm_kms_helper_poll_fini()`. - -Output discovery and initialization example -------------------------------------------- - -:: - - void intel_crt_init(struct drm_device *dev) - { - struct drm_connector *connector; - struct intel_output *intel_output; - - intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL); - if (!intel_output) - return; - - connector = &intel_output->base; - drm_connector_init(dev, &intel_output->base, - &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA); - - drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs, - DRM_MODE_ENCODER_DAC); - - drm_mode_connector_attach_encoder(&intel_output->base, - &intel_output->enc); - - /* Set up the DDC bus. */ - intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A"); - if (!intel_output->ddc_bus) { - dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration " - "failed.\n"); - return; - } - - intel_output->type = INTEL_OUTPUT_ANALOG; - connector->interlace_allowed = 0; - connector->doublescan_allowed = 0; - - drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs); - drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs); - - drm_connector_register(connector); - } - -In the example above (taken from the i915 driver), a CRTC, connector and -encoder combination is created. A device-specific i2c bus is also -created for fetching EDID data and performing monitor detection. Once -the process is complete, the new connector is registered with sysfs to -make its properties available to applications. - -KMS API Functions ------------------ - -.. kernel-doc:: drivers/gpu/drm/drm_crtc.c - :export: - -KMS Data Structures -------------------- - -.. kernel-doc:: include/drm/drm_crtc.h - :internal: - -KMS Locking ------------ - -.. kernel-doc:: drivers/gpu/drm/drm_modeset_lock.c - :doc: kms locking - -.. kernel-doc:: include/drm/drm_modeset_lock.h - :internal: - -.. kernel-doc:: drivers/gpu/drm/drm_modeset_lock.c - :export: - -Mode Setting Helper Functions -============================= - -The plane, CRTC, encoder and connector functions provided by the drivers -implement the DRM API. They're called by the DRM core and ioctl handlers -to handle device state changes and configuration request. As -implementing those functions often requires logic not specific to -drivers, mid-layer helper functions are available to avoid duplicating -boilerplate code. - -The DRM core contains one mid-layer implementation. The mid-layer -provides implementations of several plane, CRTC, encoder and connector -functions (called from the top of the mid-layer) that pre-process -requests and call lower-level functions provided by the driver (at the -bottom of the mid-layer). For instance, the -:c:func:`drm_crtc_helper_set_config()` function can be used to -fill the :c:type:`struct drm_crtc_funcs <drm_crtc_funcs>` -set_config field. When called, it will split the set_config operation -in smaller, simpler operations and call the driver to handle them. - -To use the mid-layer, drivers call -:c:func:`drm_crtc_helper_add()`, -:c:func:`drm_encoder_helper_add()` and -:c:func:`drm_connector_helper_add()` functions to install their -mid-layer bottom operations handlers, and fill the :c:type:`struct -drm_crtc_funcs <drm_crtc_funcs>`, :c:type:`struct -drm_encoder_funcs <drm_encoder_funcs>` and :c:type:`struct -drm_connector_funcs <drm_connector_funcs>` structures with -pointers to the mid-layer top API functions. Installing the mid-layer -bottom operation handlers is best done right after registering the -corresponding KMS object. - -The mid-layer is not split between CRTC, encoder and connector -operations. To use it, a driver must provide bottom functions for all of -the three KMS entities. - -Atomic Modeset Helper Functions Reference ------------------------------------------ - -Overview -^^^^^^^^ - -.. kernel-doc:: drivers/gpu/drm/drm_atomic_helper.c - :doc: overview - -Implementing Asynchronous Atomic Commit -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -.. kernel-doc:: drivers/gpu/drm/drm_atomic_helper.c - :doc: implementing nonblocking commit - -Atomic State Reset and Initialization -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -.. kernel-doc:: drivers/gpu/drm/drm_atomic_helper.c - :doc: atomic state reset and initialization - -.. kernel-doc:: include/drm/drm_atomic_helper.h - :internal: - -.. kernel-doc:: drivers/gpu/drm/drm_atomic_helper.c - :export: - -Modeset Helper Reference for Common Vtables -------------------------------------------- - -.. kernel-doc:: include/drm/drm_modeset_helper_vtables.h - :internal: - -.. kernel-doc:: include/drm/drm_modeset_helper_vtables.h - :doc: overview - -Legacy CRTC/Modeset Helper Functions Reference ----------------------------------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_crtc_helper.c - :export: - -.. kernel-doc:: drivers/gpu/drm/drm_crtc_helper.c - :doc: overview - -Output Probing Helper Functions Reference ------------------------------------------ - -.. kernel-doc:: drivers/gpu/drm/drm_probe_helper.c - :doc: output probing helper overview - -.. kernel-doc:: drivers/gpu/drm/drm_probe_helper.c - :export: - -fbdev Helper Functions Reference --------------------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_fb_helper.c - :doc: fbdev helpers - -.. kernel-doc:: drivers/gpu/drm/drm_fb_helper.c - :export: - -.. kernel-doc:: include/drm/drm_fb_helper.h - :internal: - -Framebuffer CMA Helper Functions Reference ------------------------------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_fb_cma_helper.c - :doc: framebuffer cma helper functions - -.. kernel-doc:: drivers/gpu/drm/drm_fb_cma_helper.c - :export: - -Display Port Helper Functions Reference ---------------------------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_dp_helper.c - :doc: dp helpers - -.. kernel-doc:: include/drm/drm_dp_helper.h - :internal: - -.. kernel-doc:: drivers/gpu/drm/drm_dp_helper.c - :export: - -Display Port Dual Mode Adaptor Helper Functions Reference ---------------------------------------------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_dp_dual_mode_helper.c - :doc: dp dual mode helpers - -.. kernel-doc:: include/drm/drm_dp_dual_mode_helper.h - :internal: - -.. kernel-doc:: drivers/gpu/drm/drm_dp_dual_mode_helper.c - :export: - -Display Port MST Helper Functions Reference -------------------------------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_dp_mst_topology.c - :doc: dp mst helper - -.. kernel-doc:: include/drm/drm_dp_mst_helper.h - :internal: - -.. kernel-doc:: drivers/gpu/drm/drm_dp_mst_topology.c - :export: - -MIPI DSI Helper Functions Reference ------------------------------------ - -.. kernel-doc:: drivers/gpu/drm/drm_mipi_dsi.c - :doc: dsi helpers - -.. kernel-doc:: include/drm/drm_mipi_dsi.h - :internal: - -.. kernel-doc:: drivers/gpu/drm/drm_mipi_dsi.c - :export: - -EDID Helper Functions Reference -------------------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_edid.c - :export: - -Rectangle Utilities Reference ------------------------------ - -.. kernel-doc:: include/drm/drm_rect.h - :doc: rect utils - -.. kernel-doc:: include/drm/drm_rect.h - :internal: - -.. kernel-doc:: drivers/gpu/drm/drm_rect.c - :export: - -Flip-work Helper Reference --------------------------- - -.. kernel-doc:: include/drm/drm_flip_work.h - :doc: flip utils - -.. kernel-doc:: include/drm/drm_flip_work.h - :internal: - -.. kernel-doc:: drivers/gpu/drm/drm_flip_work.c - :export: - -HDMI Infoframes Helper Reference --------------------------------- - -Strictly speaking this is not a DRM helper library but generally useable -by any driver interfacing with HDMI outputs like v4l or alsa drivers. -But it nicely fits into the overall topic of mode setting helper -libraries and hence is also included here. - -.. kernel-doc:: include/linux/hdmi.h - :internal: - -.. kernel-doc:: drivers/video/hdmi.c - :export: - -Plane Helper Reference ----------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_plane_helper.c - :export: - -.. kernel-doc:: drivers/gpu/drm/drm_plane_helper.c - :doc: overview - -Tile group ----------- - -.. kernel-doc:: drivers/gpu/drm/drm_crtc.c - :doc: Tile group - -Bridges -------- - -Overview -^^^^^^^^ - -.. kernel-doc:: drivers/gpu/drm/drm_bridge.c - :doc: overview - -Default bridge callback sequence -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -.. kernel-doc:: drivers/gpu/drm/drm_bridge.c - :doc: bridge callbacks - -.. kernel-doc:: drivers/gpu/drm/drm_bridge.c - :export: - -Panel Helper Reference ----------------------- - -.. kernel-doc:: include/drm/drm_panel.h - :internal: - -.. kernel-doc:: drivers/gpu/drm/drm_panel.c - :export: - -.. kernel-doc:: drivers/gpu/drm/drm_panel.c - :doc: drm panel - -Simple KMS Helper Reference ---------------------------- - -.. kernel-doc:: include/drm/drm_simple_kms_helper.h - :internal: - -.. kernel-doc:: drivers/gpu/drm/drm_simple_kms_helper.c - :export: - -.. kernel-doc:: drivers/gpu/drm/drm_simple_kms_helper.c - :doc: overview - -KMS Properties -============== - -Drivers may need to expose additional parameters to applications than -those described in the previous sections. KMS supports attaching -properties to CRTCs, connectors and planes and offers a userspace API to -list, get and set the property values. - -Properties are identified by a name that uniquely defines the property -purpose, and store an associated value. For all property types except -blob properties the value is a 64-bit unsigned integer. - -KMS differentiates between properties and property instances. Drivers -first create properties and then create and associate individual -instances of those properties to objects. A property can be instantiated -multiple times and associated with different objects. Values are stored -in property instances, and all other property information are stored in -the property and shared between all instances of the property. - -Every property is created with a type that influences how the KMS core -handles the property. Supported property types are - -DRM_MODE_PROP_RANGE - Range properties report their minimum and maximum admissible values. - The KMS core verifies that values set by application fit in that - range. - -DRM_MODE_PROP_ENUM - Enumerated properties take a numerical value that ranges from 0 to - the number of enumerated values defined by the property minus one, - and associate a free-formed string name to each value. Applications - can retrieve the list of defined value-name pairs and use the - numerical value to get and set property instance values. - -DRM_MODE_PROP_BITMASK - Bitmask properties are enumeration properties that additionally - restrict all enumerated values to the 0..63 range. Bitmask property - instance values combine one or more of the enumerated bits defined - by the property. - -DRM_MODE_PROP_BLOB - Blob properties store a binary blob without any format restriction. - The binary blobs are created as KMS standalone objects, and blob - property instance values store the ID of their associated blob - object. - - Blob properties are only used for the connector EDID property and - cannot be created by drivers. - -To create a property drivers call one of the following functions -depending on the property type. All property creation functions take -property flags and name, as well as type-specific arguments. - -- struct drm_property *drm_property_create_range(struct - drm_device *dev, int flags, const char *name, uint64_t min, - uint64_t max); - Create a range property with the given minimum and maximum values. - -- struct drm_property *drm_property_create_enum(struct drm_device - *dev, int flags, const char *name, const struct - drm_prop_enum_list *props, int num_values); - Create an enumerated property. The ``props`` argument points to an - array of ``num_values`` value-name pairs. - -- struct drm_property *drm_property_create_bitmask(struct - drm_device *dev, int flags, const char *name, const struct - drm_prop_enum_list *props, int num_values); - Create a bitmask property. The ``props`` argument points to an array - of ``num_values`` value-name pairs. - -Properties can additionally be created as immutable, in which case they -will be read-only for applications but can be modified by the driver. To -create an immutable property drivers must set the -DRM_MODE_PROP_IMMUTABLE flag at property creation time. - -When no array of value-name pairs is readily available at property -creation time for enumerated or range properties, drivers can create the -property using the :c:func:`drm_property_create()` function and -manually add enumeration value-name pairs by calling the -:c:func:`drm_property_add_enum()` function. Care must be taken to -properly specify the property type through the ``flags`` argument. - -After creating properties drivers can attach property instances to CRTC, -connector and plane objects by calling the -:c:func:`drm_object_attach_property()`. The function takes a -pointer to the target object, a pointer to the previously created -property and an initial instance value. - -Existing KMS Properties ------------------------ - -The following table gives description of drm properties exposed by -various modules/drivers. - -.. csv-table:: - :header-rows: 1 - :file: kms-properties.csv - -Vertical Blanking -================= - -Vertical blanking plays a major role in graphics rendering. To achieve -tear-free display, users must synchronize page flips and/or rendering to -vertical blanking. The DRM API offers ioctls to perform page flips -synchronized to vertical blanking and wait for vertical blanking. - -The DRM core handles most of the vertical blanking management logic, -which involves filtering out spurious interrupts, keeping race-free -blanking counters, coping with counter wrap-around and resets and -keeping use counts. It relies on the driver to generate vertical -blanking interrupts and optionally provide a hardware vertical blanking -counter. Drivers must implement the following operations. - -- int (*enable_vblank) (struct drm_device *dev, int crtc); void - (*disable_vblank) (struct drm_device *dev, int crtc); - Enable or disable vertical blanking interrupts for the given CRTC. - -- u32 (*get_vblank_counter) (struct drm_device *dev, int crtc); - Retrieve the value of the vertical blanking counter for the given - CRTC. If the hardware maintains a vertical blanking counter its value - should be returned. Otherwise drivers can use the - :c:func:`drm_vblank_count()` helper function to handle this - operation. - -Drivers must initialize the vertical blanking handling core with a call -to :c:func:`drm_vblank_init()` in their load operation. - -Vertical blanking interrupts can be enabled by the DRM core or by -drivers themselves (for instance to handle page flipping operations). -The DRM core maintains a vertical blanking use count to ensure that the -interrupts are not disabled while a user still needs them. To increment -the use count, drivers call :c:func:`drm_vblank_get()`. Upon -return vertical blanking interrupts are guaranteed to be enabled. - -To decrement the use count drivers call -:c:func:`drm_vblank_put()`. Only when the use count drops to zero -will the DRM core disable the vertical blanking interrupts after a delay -by scheduling a timer. The delay is accessible through the -vblankoffdelay module parameter or the ``drm_vblank_offdelay`` global -variable and expressed in milliseconds. Its default value is 5000 ms. -Zero means never disable, and a negative value means disable -immediately. Drivers may override the behaviour by setting the -:c:type:`struct drm_device <drm_device>` -vblank_disable_immediate flag, which when set causes vblank interrupts -to be disabled immediately regardless of the drm_vblank_offdelay -value. The flag should only be set if there's a properly working -hardware vblank counter present. - -When a vertical blanking interrupt occurs drivers only need to call the -:c:func:`drm_handle_vblank()` function to account for the -interrupt. - -Resources allocated by :c:func:`drm_vblank_init()` must be freed -with a call to :c:func:`drm_vblank_cleanup()` in the driver unload -operation handler. - -Vertical Blanking and Interrupt Handling Functions Reference ------------------------------------------------------------- - -.. kernel-doc:: drivers/gpu/drm/drm_irq.c - :export: - -.. kernel-doc:: include/drm/drmP.h - :functions: drm_crtc_vblank_waitqueue - Open/Close, File Operations and IOCTLs ======================================

diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst new file mode 100644 index 000000000000..0b302fedf1af --- /dev/null +++ b/Documentation/gpu/drm-kms-helpers.rst @@ -0,0 +1,260 @@ +============================= +Mode Setting Helper Functions +============================= + +The plane, CRTC, encoder and connector functions provided by the drivers +implement the DRM API. They're called by the DRM core and ioctl handlers +to handle device state changes and configuration request. As +implementing those functions often requires logic not specific to +drivers, mid-layer helper functions are available to avoid duplicating +boilerplate code. + +The DRM core contains one mid-layer implementation. The mid-layer +provides implementations of several plane, CRTC, encoder and connector +functions (called from the top of the mid-layer) that pre-process +requests and call lower-level functions provided by the driver (at the +bottom of the mid-layer). For instance, the +:c:func:`drm_crtc_helper_set_config()` function can be used to +fill the :c:type:`struct drm_crtc_funcs <drm_crtc_funcs>` +set_config field. When called, it will split the set_config operation +in smaller, simpler operations and call the driver to handle them. + +To use the mid-layer, drivers call +:c:func:`drm_crtc_helper_add()`, +:c:func:`drm_encoder_helper_add()` and +:c:func:`drm_connector_helper_add()` functions to install their +mid-layer bottom operations handlers, and fill the :c:type:`struct +drm_crtc_funcs <drm_crtc_funcs>`, :c:type:`struct +drm_encoder_funcs <drm_encoder_funcs>` and :c:type:`struct +drm_connector_funcs <drm_connector_funcs>` structures with +pointers to the mid-layer top API functions. Installing the mid-layer +bottom operation handlers is best done right after registering the +corresponding KMS object. + +The mid-layer is not split between CRTC, encoder and connector +operations. To use it, a driver must provide bottom functions for all of +the three KMS entities. + +Atomic Modeset Helper Functions Reference +========================================= + +Overview +-------- + +.. kernel-doc:: drivers/gpu/drm/drm_atomic_helper.c + :doc: overview + +Implementing Asynchronous Atomic Commit +--------------------------------------- + +.. kernel-doc:: drivers/gpu/drm/drm_atomic_helper.c + :doc: implementing nonblocking commit + +Atomic State Reset and Initialization +------------------------------------- + +.. kernel-doc:: drivers/gpu/drm/drm_atomic_helper.c + :doc: atomic state reset and initialization + +.. kernel-doc:: include/drm/drm_atomic_helper.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_atomic_helper.c + :export: + +Modeset Helper Reference for Common Vtables +=========================================== + +.. kernel-doc:: include/drm/drm_modeset_helper_vtables.h + :internal: + +.. kernel-doc:: include/drm/drm_modeset_helper_vtables.h + :doc: overview + +Legacy CRTC/Modeset Helper Functions Reference +============================================== + +.. kernel-doc:: drivers/gpu/drm/drm_crtc_helper.c + :export: + +.. kernel-doc:: drivers/gpu/drm/drm_crtc_helper.c + :doc: overview + +Output Probing Helper Functions Reference +========================================= + +.. kernel-doc:: drivers/gpu/drm/drm_probe_helper.c + :doc: output probing helper overview + +.. kernel-doc:: drivers/gpu/drm/drm_probe_helper.c + :export: + +fbdev Helper Functions Reference +================================ + +.. kernel-doc:: drivers/gpu/drm/drm_fb_helper.c + :doc: fbdev helpers + +.. kernel-doc:: drivers/gpu/drm/drm_fb_helper.c + :export: + +.. kernel-doc:: include/drm/drm_fb_helper.h + :internal: + +Framebuffer CMA Helper Functions Reference +========================================== + +.. kernel-doc:: drivers/gpu/drm/drm_fb_cma_helper.c + :doc: framebuffer cma helper functions + +.. kernel-doc:: drivers/gpu/drm/drm_fb_cma_helper.c + :export: + +Display Port Helper Functions Reference +======================================= + +.. kernel-doc:: drivers/gpu/drm/drm_dp_helper.c + :doc: dp helpers + +.. kernel-doc:: include/drm/drm_dp_helper.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_dp_helper.c + :export: + +Display Port Dual Mode Adaptor Helper Functions Reference +========================================================= + +.. kernel-doc:: drivers/gpu/drm/drm_dp_dual_mode_helper.c + :doc: dp dual mode helpers + +.. kernel-doc:: include/drm/drm_dp_dual_mode_helper.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_dp_dual_mode_helper.c + :export: + +Display Port MST Helper Functions Reference +=========================================== + +.. kernel-doc:: drivers/gpu/drm/drm_dp_mst_topology.c + :doc: dp mst helper + +.. kernel-doc:: include/drm/drm_dp_mst_helper.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_dp_mst_topology.c + :export: + +MIPI DSI Helper Functions Reference +=================================== + +.. kernel-doc:: drivers/gpu/drm/drm_mipi_dsi.c + :doc: dsi helpers + +.. kernel-doc:: include/drm/drm_mipi_dsi.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_mipi_dsi.c + :export: + +EDID Helper Functions Reference +=============================== + +.. kernel-doc:: drivers/gpu/drm/drm_edid.c + :export: + +Rectangle Utilities Reference +============================= + +.. kernel-doc:: include/drm/drm_rect.h + :doc: rect utils + +.. kernel-doc:: include/drm/drm_rect.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_rect.c + :export: + +Flip-work Helper Reference +========================== + +.. kernel-doc:: include/drm/drm_flip_work.h + :doc: flip utils + +.. kernel-doc:: include/drm/drm_flip_work.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_flip_work.c + :export: + +HDMI Infoframes Helper Reference +================================ + +Strictly speaking this is not a DRM helper library but generally useable +by any driver interfacing with HDMI outputs like v4l or alsa drivers. +But it nicely fits into the overall topic of mode setting helper +libraries and hence is also included here. + +.. kernel-doc:: include/linux/hdmi.h + :internal: + +.. kernel-doc:: drivers/video/hdmi.c + :export: + +Plane Helper Reference +====================== + +.. kernel-doc:: drivers/gpu/drm/drm_plane_helper.c + :export: + +.. kernel-doc:: drivers/gpu/drm/drm_plane_helper.c + :doc: overview + +Tile group +---------- + +.. kernel-doc:: drivers/gpu/drm/drm_crtc.c + :doc: Tile group + +Bridges +======= + +Overview +-------- + +.. kernel-doc:: drivers/gpu/drm/drm_bridge.c + :doc: overview + +Default bridge callback sequence +-------------------------------- + +.. kernel-doc:: drivers/gpu/drm/drm_bridge.c + :doc: bridge callbacks + +.. kernel-doc:: drivers/gpu/drm/drm_bridge.c + :export: + +Panel Helper Reference +====================== + +.. kernel-doc:: include/drm/drm_panel.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_panel.c + :export: + +.. kernel-doc:: drivers/gpu/drm/drm_panel.c + :doc: drm panel + +Simple KMS Helper Reference +=========================== + +.. kernel-doc:: include/drm/drm_simple_kms_helper.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_simple_kms_helper.c + :export: + +.. kernel-doc:: drivers/gpu/drm/drm_simple_kms_helper.c + :doc: overview diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst new file mode 100644 index 000000000000..0e1c80436c1d --- /dev/null +++ b/Documentation/gpu/drm-kms.rst @@ -0,0 +1,656 @@ +========================= +Kernel Mode Setting (KMS) +========================= + +Mode Setting +============ + +Drivers must initialize the mode setting core by calling +:c:func:`drm_mode_config_init()` on the DRM device. The function +initializes the :c:type:`struct drm_device <drm_device>` +mode_config field and never fails. Once done, mode configuration must +be setup by initializing the following fields. + +- int min_width, min_height; int max_width, max_height; + Minimum and maximum width and height of the frame buffers in pixel + units. + +- struct drm_mode_config_funcs *funcs; + Mode setting functions. + +Display Modes Function Reference +-------------------------------- + +.. kernel-doc:: include/drm/drm_modes.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_modes.c + :export: + +Atomic Mode Setting Function Reference +-------------------------------------- + +.. kernel-doc:: drivers/gpu/drm/drm_atomic.c + :export: + +.. kernel-doc:: drivers/gpu/drm/drm_atomic.c + :internal: + +Frame Buffer Abstraction +------------------------ + +Frame buffers are abstract memory objects that provide a source of +pixels to scanout to a CRTC. Applications explicitly request the +creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls +and receive an opaque handle that can be passed to the KMS CRTC control, +plane configuration and page flip functions. + +Frame buffers rely on the underneath memory manager for low-level memory +operations. When creating a frame buffer applications pass a memory +handle (or a list of memory handles for multi-planar formats) through +the ``drm_mode_fb_cmd2`` argument. For drivers using GEM as their +userspace buffer management interface this would be a GEM handle. +Drivers are however free to use their own backing storage object +handles, e.g. vmwgfx directly exposes special TTM handles to userspace +and so expects TTM handles in the create ioctl and not GEM handles. + +The lifetime of a drm framebuffer is controlled with a reference count, +drivers can grab additional references with +:c:func:`drm_framebuffer_reference()`and drop them again with +:c:func:`drm_framebuffer_unreference()`. For driver-private +framebuffers for which the last reference is never dropped (e.g. for the +fbdev framebuffer when the struct :c:type:`struct drm_framebuffer +<drm_framebuffer>` is embedded into the fbdev helper struct) +drivers can manually clean up a framebuffer at module unload time with +:c:func:`drm_framebuffer_unregister_private()`. + +DRM Format Handling +------------------- + +.. kernel-doc:: include/drm/drm_fourcc.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_fourcc.c + :export: + +Dumb Buffer Objects +------------------- + +The KMS API doesn't standardize backing storage object creation and +leaves it to driver-specific ioctls. Furthermore actually creating a +buffer object even for GEM-based drivers is done through a +driver-specific ioctl - GEM only has a common userspace interface for +sharing and destroying objects. While not an issue for full-fledged +graphics stacks that include device-specific userspace components (in +libdrm for instance), this limit makes DRM-based early boot graphics +unnecessarily complex. + +Dumb objects partly alleviate the problem by providing a standard API to +create dumb buffers suitable for scanout, which can then be used to +create KMS frame buffers. + +To support dumb objects drivers must implement the dumb_create, +dumb_destroy and dumb_map_offset operations. + +- int (*dumb_create)(struct drm_file *file_priv, struct + drm_device *dev, struct drm_mode_create_dumb *args); + The dumb_create operation creates a driver object (GEM or TTM + handle) suitable for scanout based on the width, height and depth + from the struct :c:type:`struct drm_mode_create_dumb + <drm_mode_create_dumb>` argument. It fills the argument's + handle, pitch and size fields with a handle for the newly created + object and its line pitch and size in bytes. + +- int (*dumb_destroy)(struct drm_file *file_priv, struct + drm_device *dev, uint32_t handle); + The dumb_destroy operation destroys a dumb object created by + dumb_create. + +- int (*dumb_map_offset)(struct drm_file *file_priv, struct + drm_device *dev, uint32_t handle, uint64_t *offset); + The dumb_map_offset operation associates an mmap fake offset with + the object given by the handle and returns it. Drivers must use the + :c:func:`drm_gem_create_mmap_offset()` function to associate + the fake offset as described in ?. + +Note that dumb objects may not be used for gpu acceleration, as has been +attempted on some ARM embedded platforms. Such drivers really must have +a hardware-specific ioctl to allocate suitable buffer objects. + +Output Polling +-------------- + +void (*output_poll_changed)(struct drm_device *dev); +This operation notifies the driver that the status of one or more +connectors has changed. Drivers that use the fb helper can just call the +:c:func:`drm_fb_helper_hotplug_event()` function to handle this +operation. + +KMS Initialization and Cleanup +============================== + +A KMS device is abstracted and exposed as a set of planes, CRTCs, +encoders and connectors. KMS drivers must thus create and initialize all +those objects at load time after initializing mode setting. + +CRTCs (:c:type:`struct drm_crtc <drm_crtc>`) +-------------------------------------------- + +A CRTC is an abstraction representing a part of the chip that contains a +pointer to a scanout buffer. Therefore, the number of CRTCs available +determines how many independent scanout buffers can be active at any +given time. The CRTC structure contains several fields to support this: +a pointer to some video memory (abstracted as a frame buffer object), a +display mode, and an (x, y) offset into the video memory to support +panning or configurations where one piece of video memory spans multiple +CRTCs. + +CRTC Initialization +~~~~~~~~~~~~~~~~~~~ + +A KMS device must create and register at least one struct +:c:type:`struct drm_crtc <drm_crtc>` instance. The instance is +allocated and zeroed by the driver, possibly as part of a larger +structure, and registered with a call to :c:func:`drm_crtc_init()` +with a pointer to CRTC functions. + +Planes (:c:type:`struct drm_plane <drm_plane>`) +----------------------------------------------- + +A plane represents an image source that can be blended with or overlayed +on top of a CRTC during the scanout process. Planes are associated with +a frame buffer to crop a portion of the image memory (source) and +optionally scale it to a destination size. The result is then blended +with or overlayed on top of a CRTC. + +The DRM core recognizes three types of planes: + +- DRM_PLANE_TYPE_PRIMARY represents a "main" plane for a CRTC. + Primary planes are the planes operated upon by CRTC modesetting and + flipping operations described in the page_flip hook in + :c:type:`struct drm_crtc_funcs <drm_crtc_funcs>`. +- DRM_PLANE_TYPE_CURSOR represents a "cursor" plane for a CRTC. + Cursor planes are the planes operated upon by the + DRM_IOCTL_MODE_CURSOR and DRM_IOCTL_MODE_CURSOR2 ioctls. +- DRM_PLANE_TYPE_OVERLAY represents all non-primary, non-cursor + planes. Some drivers refer to these types of planes as "sprites" + internally. + +For compatibility with legacy userspace, only overlay planes are made +available to userspace by default. Userspace clients may set the +DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate +that they wish to receive a universal plane list containing all plane +types. + +Plane Initialization +~~~~~~~~~~~~~~~~~~~~ + +To create a plane, a KMS drivers allocates and zeroes an instances of +:c:type:`struct drm_plane <drm_plane>` (possibly as part of a +larger structure) and registers it with a call to +:c:func:`drm_universal_plane_init()`. The function takes a +bitmask of the CRTCs that can be associated with the plane, a pointer to +the plane functions, a list of format supported formats, and the type of +plane (primary, cursor, or overlay) being initialized. + +Cursor and overlay planes are optional. All drivers should provide one +primary plane per CRTC (although this requirement may change in the +future); drivers that do not wish to provide special handling for +primary planes may make use of the helper functions described in ? to +create and register a primary plane with standard capabilities. + +Encoders (:c:type:`struct drm_encoder <drm_encoder>`) +----------------------------------------------------- + +An encoder takes pixel data from a CRTC and converts it to a format +suitable for any attached connectors. On some devices, it may be +possible to have a CRTC send data to more than one encoder. In that +case, both encoders would receive data from the same scanout buffer, +resulting in a "cloned" display configuration across the connectors +attached to each encoder. + +Encoder Initialization +~~~~~~~~~~~~~~~~~~~~~~ + +As for CRTCs, a KMS driver must create, initialize and register at least +one :c:type:`struct drm_encoder <drm_encoder>` instance. The +instance is allocated and zeroed by the driver, possibly as part of a +larger structure. + +Drivers must initialize the :c:type:`struct drm_encoder +<drm_encoder>` possible_crtcs and possible_clones fields before +registering the encoder. Both fields are bitmasks of respectively the +CRTCs that the encoder can be connected to, and sibling encoders +candidate for cloning. + +After being initialized, the encoder must be registered with a call to +:c:func:`drm_encoder_init()`. The function takes a pointer to the +encoder functions and an encoder type. Supported types are + +- DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A +- DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort +- DRM_MODE_ENCODER_LVDS for display panels +- DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, + Component, SCART) +- DRM_MODE_ENCODER_VIRTUAL for virtual machine displays + +Encoders must be attached to a CRTC to be used. DRM drivers leave +encoders unattached at initialization time. Applications (or the fbdev +compatibility layer when implemented) are responsible for attaching the +encoders they want to use to a CRTC. + +Connectors (:c:type:`struct drm_connector <drm_connector>`) +----------------------------------------------------------- + +A connector is the final destination for pixel data on a device, and +usually connects directly to an external display device like a monitor +or laptop panel. A connector can only be attached to one encoder at a +time. The connector is also the structure where information about the +attached display is kept, so it contains fields for display data, EDID +data, DPMS & connection status, and information about modes supported on +the attached displays. + +Connector Initialization +~~~~~~~~~~~~~~~~~~~~~~~~ + +Finally a KMS driver must create, initialize, register and attach at +least one :c:type:`struct drm_connector <drm_connector>` +instance. The instance is created as other KMS objects and initialized +by setting the following fields. + +interlace_allowed + Whether the connector can handle interlaced modes. + +doublescan_allowed + Whether the connector can handle doublescan. + +display_info + Display information is filled from EDID information when a display + is detected. For non hot-pluggable displays such as flat panels in + embedded systems, the driver should initialize the + display_info.width_mm and display_info.height_mm fields with the + physical size of the display. + +polled + Connector polling mode, a combination of + + DRM_CONNECTOR_POLL_HPD + The connector generates hotplug events and doesn't need to be + periodically polled. The CONNECT and DISCONNECT flags must not + be set together with the HPD flag. + + DRM_CONNECTOR_POLL_CONNECT + Periodically poll the connector for connection. + + DRM_CONNECTOR_POLL_DISCONNECT + Periodically poll the connector for disconnection. + + Set to 0 for connectors that don't support connection status + discovery. + +The connector is then registered with a call to +:c:func:`drm_connector_init()` with a pointer to the connector +functions and a connector type, and exposed through sysfs with a call to +:c:func:`drm_connector_register()`. + +Supported connector types are + +- DRM_MODE_CONNECTOR_VGA +- DRM_MODE_CONNECTOR_DVII +- DRM_MODE_CONNECTOR_DVID +- DRM_MODE_CONNECTOR_DVIA +- DRM_MODE_CONNECTOR_Composite +- DRM_MODE_CONNECTOR_SVIDEO +- DRM_MODE_CONNECTOR_LVDS +- DRM_MODE_CONNECTOR_Component +- DRM_MODE_CONNECTOR_9PinDIN +- DRM_MODE_CONNECTOR_DisplayPort +- DRM_MODE_CONNECTOR_HDMIA +- DRM_MODE_CONNECTOR_HDMIB +- DRM_MODE_CONNECTOR_TV +- DRM_MODE_CONNECTOR_eDP +- DRM_MODE_CONNECTOR_VIRTUAL + +Connectors must be attached to an encoder to be used. For devices that +map connectors to encoders 1:1, the connector should be attached at +initialization time with a call to +:c:func:`drm_mode_connector_attach_encoder()`. The driver must +also set the :c:type:`struct drm_connector <drm_connector>` +encoder field to point to the attached encoder. + +Finally, drivers must initialize the connectors state change detection +with a call to :c:func:`drm_kms_helper_poll_init()`. If at least +one connector is pollable but can't generate hotplug interrupts +(indicated by the DRM_CONNECTOR_POLL_CONNECT and +DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will +automatically be queued to periodically poll for changes. Connectors +that can generate hotplug interrupts must be marked with the +DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must +call :c:func:`drm_helper_hpd_irq_event()`. The function will +queue a delayed work to check the state of all connectors, but no +periodic polling will be done. + +Connector Operations +~~~~~~~~~~~~~~~~~~~~ + + **Note** + + Unless otherwise state, all operations are mandatory. + +DPMS +'''' + +void (*dpms)(struct drm_connector *connector, int mode); +The DPMS operation sets the power state of a connector. The mode +argument is one of + +- DRM_MODE_DPMS_ON + +- DRM_MODE_DPMS_STANDBY + +- DRM_MODE_DPMS_SUSPEND + +- DRM_MODE_DPMS_OFF + +In all but DPMS_ON mode the encoder to which the connector is attached +should put the display in low-power mode by driving its signals +appropriately. If more than one connector is attached to the encoder +care should be taken not to change the power state of other displays as +a side effect. Low-power mode should be propagated to the encoders and +CRTCs when all related connectors are put in low-power mode. + +Modes +''''' + +int (*fill_modes)(struct drm_connector *connector, uint32_t +max_width, uint32_t max_height); +Fill the mode list with all supported modes for the connector. If the +``max_width`` and ``max_height`` arguments are non-zero, the +implementation must ignore all modes wider than ``max_width`` or higher +than ``max_height``. + +The connector must also fill in this operation its display_info +width_mm and height_mm fields with the connected display physical size +in millimeters. The fields should be set to 0 if the value isn't known +or is not applicable (for instance for projector devices). + +Connection Status +''''''''''''''''' + +The connection status is updated through polling or hotplug events when +supported (see ?). The status value is reported to userspace through +ioctls and must not be used inside the driver, as it only gets +initialized by a call to :c:func:`drm_mode_getconnector()` from +userspace. + +enum drm_connector_status (*detect)(struct drm_connector +*connector, bool force); +Check to see if anything is attached to the connector. The ``force`` +parameter is set to false whilst polling or to true when checking the +connector due to user request. ``force`` can be used by the driver to +avoid expensive, destructive operations during automated probing. + +Return connector_status_connected if something is connected to the +connector, connector_status_disconnected if nothing is connected and +connector_status_unknown if the connection state isn't known. + +Drivers should only return connector_status_connected if the +connection status has really been probed as connected. Connectors that +can't detect the connection status, or failed connection status probes, +should return connector_status_unknown. + +Cleanup +------- + +The DRM core manages its objects' lifetime. When an object is not needed +anymore the core calls its destroy function, which must clean up and +free every resource allocated for the object. Every +:c:func:`drm_*_init()` call must be matched with a corresponding +:c:func:`drm_*_cleanup()` call to cleanup CRTCs +(:c:func:`drm_crtc_cleanup()`), planes +(:c:func:`drm_plane_cleanup()`), encoders +(:c:func:`drm_encoder_cleanup()`) and connectors +(:c:func:`drm_connector_cleanup()`). Furthermore, connectors that +have been added to sysfs must be removed by a call to +:c:func:`drm_connector_unregister()` before calling +:c:func:`drm_connector_cleanup()`. + +Connectors state change detection must be cleanup up with a call to +:c:func:`drm_kms_helper_poll_fini()`. + +Output discovery and initialization example +------------------------------------------- + +:: + + void intel_crt_init(struct drm_device *dev) + { + struct drm_connector *connector; + struct intel_output *intel_output; + + intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL); + if (!intel_output) + return; + + connector = &intel_output->base; + drm_connector_init(dev, &intel_output->base, + &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA); + + drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs, + DRM_MODE_ENCODER_DAC); + + drm_mode_connector_attach_encoder(&intel_output->base, + &intel_output->enc); + + /* Set up the DDC bus. */ + intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A"); + if (!intel_output->ddc_bus) { + dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration " + "failed.\n"); + return; + } + + intel_output->type = INTEL_OUTPUT_ANALOG; + connector->interlace_allowed = 0; + connector->doublescan_allowed = 0; + + drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs); + drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs); + + drm_connector_register(connector); + } + +In the example above (taken from the i915 driver), a CRTC, connector and +encoder combination is created. A device-specific i2c bus is also +created for fetching EDID data and performing monitor detection. Once +the process is complete, the new connector is registered with sysfs to +make its properties available to applications. + +KMS API Functions +----------------- + +.. kernel-doc:: drivers/gpu/drm/drm_crtc.c + :export: + +KMS Data Structures +------------------- + +.. kernel-doc:: include/drm/drm_crtc.h + :internal: + +KMS Locking +----------- + +.. kernel-doc:: drivers/gpu/drm/drm_modeset_lock.c + :doc: kms locking + +.. kernel-doc:: include/drm/drm_modeset_lock.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_modeset_lock.c + :export: + +KMS Properties +============== + +Drivers may need to expose additional parameters to applications than +those described in the previous sections. KMS supports attaching +properties to CRTCs, connectors and planes and offers a userspace API to +list, get and set the property values. + +Properties are identified by a name that uniquely defines the property +purpose, and store an associated value. For all property types except +blob properties the value is a 64-bit unsigned integer. + +KMS differentiates between properties and property instances. Drivers +first create properties and then create and associate individual +instances of those properties to objects. A property can be instantiated +multiple times and associated with different objects. Values are stored +in property instances, and all other property information are stored in +the property and shared between all instances of the property. + +Every property is created with a type that influences how the KMS core +handles the property. Supported property types are + +DRM_MODE_PROP_RANGE + Range properties report their minimum and maximum admissible values. + The KMS core verifies that values set by application fit in that + range. + +DRM_MODE_PROP_ENUM + Enumerated properties take a numerical value that ranges from 0 to + the number of enumerated values defined by the property minus one, + and associate a free-formed string name to each value. Applications + can retrieve the list of defined value-name pairs and use the + numerical value to get and set property instance values. + +DRM_MODE_PROP_BITMASK + Bitmask properties are enumeration properties that additionally + restrict all enumerated values to the 0..63 range. Bitmask property + instance values combine one or more of the enumerated bits defined + by the property. + +DRM_MODE_PROP_BLOB + Blob properties store a binary blob without any format restriction. + The binary blobs are created as KMS standalone objects, and blob + property instance values store the ID of their associated blob + object. + + Blob properties are only used for the connector EDID property and + cannot be created by drivers. + +To create a property drivers call one of the following functions +depending on the property type. All property creation functions take +property flags and name, as well as type-specific arguments. + +- struct drm_property *drm_property_create_range(struct + drm_device *dev, int flags, const char *name, uint64_t min, + uint64_t max); + Create a range property with the given minimum and maximum values. + +- struct drm_property *drm_property_create_enum(struct drm_device + *dev, int flags, const char *name, const struct + drm_prop_enum_list *props, int num_values); + Create an enumerated property. The ``props`` argument points to an + array of ``num_values`` value-name pairs. + +- struct drm_property *drm_property_create_bitmask(struct + drm_device *dev, int flags, const char *name, const struct + drm_prop_enum_list *props, int num_values); + Create a bitmask property. The ``props`` argument points to an array + of ``num_values`` value-name pairs. + +Properties can additionally be created as immutable, in which case they +will be read-only for applications but can be modified by the driver. To +create an immutable property drivers must set the +DRM_MODE_PROP_IMMUTABLE flag at property creation time. + +When no array of value-name pairs is readily available at property +creation time for enumerated or range properties, drivers can create the +property using the :c:func:`drm_property_create()` function and +manually add enumeration value-name pairs by calling the +:c:func:`drm_property_add_enum()` function. Care must be taken to +properly specify the property type through the ``flags`` argument. + +After creating properties drivers can attach property instances to CRTC, +connector and plane objects by calling the +:c:func:`drm_object_attach_property()`. The function takes a +pointer to the target object, a pointer to the previously created +property and an initial instance value. + +Existing KMS Properties +----------------------- + +The following table gives description of drm properties exposed by +various modules/drivers. + +.. csv-table:: + :header-rows: 1 + :file: kms-properties.csv + +Vertical Blanking +================= + +Vertical blanking plays a major role in graphics rendering. To achieve +tear-free display, users must synchronize page flips and/or rendering to +vertical blanking. The DRM API offers ioctls to perform page flips +synchronized to vertical blanking and wait for vertical blanking. + +The DRM core handles most of the vertical blanking management logic, +which involves filtering out spurious interrupts, keeping race-free +blanking counters, coping with counter wrap-around and resets and +keeping use counts. It relies on the driver to generate vertical +blanking interrupts and optionally provide a hardware vertical blanking +counter. Drivers must implement the following operations. + +- int (*enable_vblank) (struct drm_device *dev, int crtc); void + (*disable_vblank) (struct drm_device *dev, int crtc); + Enable or disable vertical blanking interrupts for the given CRTC. + +- u32 (*get_vblank_counter) (struct drm_device *dev, int crtc); + Retrieve the value of the vertical blanking counter for the given + CRTC. If the hardware maintains a vertical blanking counter its value + should be returned. Otherwise drivers can use the + :c:func:`drm_vblank_count()` helper function to handle this + operation. + +Drivers must initialize the vertical blanking handling core with a call +to :c:func:`drm_vblank_init()` in their load operation. + +Vertical blanking interrupts can be enabled by the DRM core or by +drivers themselves (for instance to handle page flipping operations). +The DRM core maintains a vertical blanking use count to ensure that the +interrupts are not disabled while a user still needs them. To increment +the use count, drivers call :c:func:`drm_vblank_get()`. Upon +return vertical blanking interrupts are guaranteed to be enabled. + +To decrement the use count drivers call +:c:func:`drm_vblank_put()`. Only when the use count drops to zero +will the DRM core disable the vertical blanking interrupts after a delay +by scheduling a timer. The delay is accessible through the +vblankoffdelay module parameter or the ``drm_vblank_offdelay`` global +variable and expressed in milliseconds. Its default value is 5000 ms. +Zero means never disable, and a negative value means disable +immediately. Drivers may override the behaviour by setting the +:c:type:`struct drm_device <drm_device>` +vblank_disable_immediate flag, which when set causes vblank interrupts +to be disabled immediately regardless of the drm_vblank_offdelay +value. The flag should only be set if there's a properly working +hardware vblank counter present. + +When a vertical blanking interrupt occurs drivers only need to call the +:c:func:`drm_handle_vblank()` function to account for the +interrupt. + +Resources allocated by :c:func:`drm_vblank_init()` must be freed +with a call to :c:func:`drm_vblank_cleanup()` in the driver unload +operation handler. + +Vertical Blanking and Interrupt Handling Functions Reference +------------------------------------------------------------ + +.. kernel-doc:: drivers/gpu/drm/drm_irq.c + :export: + +.. kernel-doc:: include/drm/drmP.h + :functions: drm_crtc_vblank_waitqueue diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst new file mode 100644 index 000000000000..59f9822fecd0 --- /dev/null +++ b/Documentation/gpu/drm-mm.rst @@ -0,0 +1,454 @@ +===================== +DRM Memory Management +===================== + +Modern Linux systems require large amount of graphics memory to store +frame buffers, textures, vertices and other graphics-related data. Given +the very dynamic nature of many of that data, managing graphics memory +efficiently is thus crucial for the graphics stack and plays a central +role in the DRM infrastructure. + +The DRM core includes two memory managers, namely Translation Table Maps +(TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory +manager to be developed and tried to be a one-size-fits-them all +solution. It provides a single userspace API to accommodate the need of +all hardware, supporting both Unified Memory Architecture (UMA) devices +and devices with dedicated video RAM (i.e. most discrete video cards). +This resulted in a large, complex piece of code that turned out to be +hard to use for driver development. + +GEM started as an Intel-sponsored project in reaction to TTM's +complexity. Its design philosophy is completely different: instead of +providing a solution to every graphics memory-related problems, GEM +identified common code between drivers and created a support library to +share it. GEM has simpler initialization and execution requirements than +TTM, but has no video RAM management capabilities and is thus limited to +UMA devices. + +The Translation Table Manager (TTM) +----------------------------------- + +TTM design background and information belongs here. + +TTM initialization +~~~~~~~~~~~~~~~~~~ + + **Warning** + + This section is outdated. + +Drivers wishing to support TTM must fill out a drm_bo_driver +structure. The structure contains several fields with function pointers +for initializing the TTM, allocating and freeing memory, waiting for +command completion and fence synchronization, and memory migration. See +the radeon_ttm.c file for an example of usage. + +The ttm_global_reference structure is made up of several fields: + +:: + + struct ttm_global_reference { + enum ttm_global_types global_type; + size_t size; + void *object; + int (*init) (struct ttm_global_reference *); + void (*release) (struct ttm_global_reference *); + }; + + +There should be one global reference structure for your memory manager +as a whole, and there will be others for each object created by the +memory manager at runtime. Your global TTM should have a type of +TTM_GLOBAL_TTM_MEM. The size field for the global object should be +sizeof(struct ttm_mem_global), and the init and release hooks should +point at your driver-specific init and release routines, which probably +eventually call ttm_mem_global_init and ttm_mem_global_release, +respectively. + +Once your global TTM accounting structure is set up and initialized by +calling ttm_global_item_ref() on it, you need to create a buffer +object TTM to provide a pool for buffer object allocation by clients and +the kernel itself. The type of this object should be +TTM_GLOBAL_TTM_BO, and its size should be sizeof(struct +ttm_bo_global). Again, driver-specific init and release functions may +be provided, likely eventually calling ttm_bo_global_init() and +ttm_bo_global_release(), respectively. Also, like the previous +object, ttm_global_item_ref() is used to create an initial reference +count for the TTM, which will call your initialization function. + +The Graphics Execution Manager (GEM) +------------------------------------ + +The GEM design approach has resulted in a memory manager that doesn't +provide full coverage of all (or even all common) use cases in its +userspace or kernel API. GEM exposes a set of standard memory-related +operations to userspace and a set of helper functions to drivers, and +let drivers implement hardware-specific operations with their own +private API. + +The GEM userspace API is described in the `GEM - the Graphics Execution +Manager http://lwn.net/Articles/283798/`__ article on LWN. While +slightly outdated, the document provides a good overview of the GEM API +principles. Buffer allocation and read and write operations, described +as part of the common GEM API, are currently implemented using +driver-specific ioctls. + +GEM is data-agnostic. It manages abstract buffer objects without knowing +what individual buffers contain. APIs that require knowledge of buffer +contents or purpose, such as buffer allocation or synchronization +primitives, are thus outside of the scope of GEM and must be implemented +using driver-specific ioctls. + +On a fundamental level, GEM involves several operations: + +- Memory allocation and freeing +- Command execution +- Aperture management at command execution time + +Buffer object allocation is relatively straightforward and largely +provided by Linux's shmem layer, which provides memory to back each +object. + +Device-specific operations, such as command execution, pinning, buffer +read & write, mapping, and domain ownership transfers are left to +driver-specific ioctls. + +GEM Initialization +~~~~~~~~~~~~~~~~~~ + +Drivers that use GEM must set the DRIVER_GEM bit in the struct +:c:type:`struct drm_driver <drm_driver>` driver_features +field. The DRM core will then automatically initialize the GEM core +before calling the load operation. Behind the scene, this will create a +DRM Memory Manager object which provides an address space pool for +object allocation. + +In a KMS configuration, drivers need to allocate and initialize a +command ring buffer following core GEM initialization if required by the +hardware. UMA devices usually have what is called a "stolen" memory +region, which provides space for the initial framebuffer and large, +contiguous memory regions required by the device. This space is +typically not managed by GEM, and must be initialized separately into +its own DRM MM object. + +GEM Objects Creation +~~~~~~~~~~~~~~~~~~~~ + +GEM splits creation of GEM objects and allocation of the memory that +backs them in two distinct operations. + +GEM objects are represented by an instance of struct :c:type:`struct +drm_gem_object <drm_gem_object>`. Drivers usually need to +extend GEM objects with private information and thus create a +driver-specific GEM object structure type that embeds an instance of +struct :c:type:`struct drm_gem_object <drm_gem_object>`. + +To create a GEM object, a driver allocates memory for an instance of its +specific GEM object type and initializes the embedded struct +:c:type:`struct drm_gem_object <drm_gem_object>` with a call +to :c:func:`drm_gem_object_init()`. The function takes a pointer +to the DRM device, a pointer to the GEM object and the buffer object +size in bytes. + +GEM uses shmem to allocate anonymous pageable memory. +:c:func:`drm_gem_object_init()` will create an shmfs file of the +requested size and store it into the struct :c:type:`struct +drm_gem_object <drm_gem_object>` filp field. The memory is +used as either main storage for the object when the graphics hardware +uses system memory directly or as a backing store otherwise. + +Drivers are responsible for the actual physical pages allocation by +calling :c:func:`shmem_read_mapping_page_gfp()` for each page. +Note that they can decide to allocate pages when initializing the GEM +object, or to delay allocation until the memory is needed (for instance +when a page fault occurs as a result of a userspace memory access or +when the driver needs to start a DMA transfer involving the memory). + +Anonymous pageable memory allocation is not always desired, for instance +when the hardware requires physically contiguous system memory as is +often the case in embedded devices. Drivers can create GEM objects with +no shmfs backing (called private GEM objects) by initializing them with +a call to :c:func:`drm_gem_private_object_init()` instead of +:c:func:`drm_gem_object_init()`. Storage for private GEM objects +must be managed by drivers. + +GEM Objects Lifetime +~~~~~~~~~~~~~~~~~~~~ + +All GEM objects are reference-counted by the GEM core. References can be +acquired and release by :c:func:`calling +drm_gem_object_reference()` and +:c:func:`drm_gem_object_unreference()` respectively. The caller +must hold the :c:type:`struct drm_device <drm_device>` +struct_mutex lock when calling +:c:func:`drm_gem_object_reference()`. As a convenience, GEM +provides :c:func:`drm_gem_object_unreference_unlocked()` +functions that can be called without holding the lock. + +When the last reference to a GEM object is released the GEM core calls +the :c:type:`struct drm_driver <drm_driver>` gem_free_object +operation. That operation is mandatory for GEM-enabled drivers and must +free the GEM object and all associated resources. + +void (*gem_free_object) (struct drm_gem_object *obj); Drivers are +responsible for freeing all GEM object resources. This includes the +resources created by the GEM core, which need to be released with +:c:func:`drm_gem_object_release()`. + +GEM Objects Naming +~~~~~~~~~~~~~~~~~~ + +Communication between userspace and the kernel refers to GEM objects +using local handles, global names or, more recently, file descriptors. +All of those are 32-bit integer values; the usual Linux kernel limits +apply to the file descriptors. + +GEM handles are local to a DRM file. Applications get a handle to a GEM +object through a driver-specific ioctl, and can use that handle to refer +to the GEM object in other standard or driver-specific ioctls. Closing a +DRM file handle frees all its GEM handles and dereferences the +associated GEM objects. + +To create a handle for a GEM object drivers call +:c:func:`drm_gem_handle_create()`. The function takes a pointer +to the DRM file and the GEM object and returns a locally unique handle. +When the handle is no longer needed drivers delete it with a call to +:c:func:`drm_gem_handle_delete()`. Finally the GEM object +associated with a handle can be retrieved by a call to +:c:func:`drm_gem_object_lookup()`. + +Handles don't take ownership of GEM objects, they only take a reference +to the object that will be dropped when the handle is destroyed. To +avoid leaking GEM objects, drivers must make sure they drop the +reference(s) they own (such as the initial reference taken at object +creation time) as appropriate, without any special consideration for the +handle. For example, in the particular case of combined GEM object and +handle creation in the implementation of the dumb_create operation, +drivers must drop the initial reference to the GEM object before +returning the handle. + +GEM names are similar in purpose to handles but are not local to DRM +files. They can be passed between processes to reference a GEM object +globally. Names can't be used directly to refer to objects in the DRM +API, applications must convert handles to names and names to handles +using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls +respectively. The conversion is handled by the DRM core without any +driver-specific support. + +GEM also supports buffer sharing with dma-buf file descriptors through +PRIME. GEM-based drivers must use the provided helpers functions to +implement the exporting and importing correctly. See ?. Since sharing +file descriptors is inherently more secure than the easily guessable and +global GEM names it is the preferred buffer sharing mechanism. Sharing +buffers through GEM names is only supported for legacy userspace. +Furthermore PRIME also allows cross-device buffer sharing since it is +based on dma-bufs. + +GEM Objects Mapping +~~~~~~~~~~~~~~~~~~~ + +Because mapping operations are fairly heavyweight GEM favours +read/write-like access to buffers, implemented through driver-specific +ioctls, over mapping buffers to userspace. However, when random access +to the buffer is needed (to perform software rendering for instance), +direct access to the object can be more efficient. + +The mmap system call can't be used directly to map GEM objects, as they +don't have their own file handle. Two alternative methods currently +co-exist to map GEM objects to userspace. The first method uses a +driver-specific ioctl to perform the mapping operation, calling +:c:func:`do_mmap()` under the hood. This is often considered +dubious, seems to be discouraged for new GEM-enabled drivers, and will +thus not be described here. + +The second method uses the mmap system call on the DRM file handle. void +*mmap(void *addr, size_t length, int prot, int flags, int fd, off_t +offset); DRM identifies the GEM object to be mapped by a fake offset +passed through the mmap offset argument. Prior to being mapped, a GEM +object must thus be associated with a fake offset. To do so, drivers +must call :c:func:`drm_gem_create_mmap_offset()` on the object. + +Once allocated, the fake offset value must be passed to the application +in a driver-specific way and can then be used as the mmap offset +argument. + +The GEM core provides a helper method :c:func:`drm_gem_mmap()` to +handle object mapping. The method can be set directly as the mmap file +operation handler. It will look up the GEM object based on the offset +value and set the VMA operations to the :c:type:`struct drm_driver +<drm_driver>` gem_vm_ops field. Note that +:c:func:`drm_gem_mmap()` doesn't map memory to userspace, but +relies on the driver-provided fault handler to map pages individually. + +To use :c:func:`drm_gem_mmap()`, drivers must fill the struct +:c:type:`struct drm_driver <drm_driver>` gem_vm_ops field +with a pointer to VM operations. + +struct vm_operations_struct *gem_vm_ops struct +vm_operations_struct { void (*open)(struct vm_area_struct * area); +void (*close)(struct vm_area_struct * area); int (*fault)(struct +vm_area_struct *vma, struct vm_fault *vmf); }; + +The open and close operations must update the GEM object reference +count. Drivers can use the :c:func:`drm_gem_vm_open()` and +:c:func:`drm_gem_vm_close()` helper functions directly as open +and close handlers. + +The fault operation handler is responsible for mapping individual pages +to userspace when a page fault occurs. Depending on the memory +allocation scheme, drivers can allocate pages at fault time, or can +decide to allocate memory for the GEM object at the time the object is +created. + +Drivers that want to map the GEM object upfront instead of handling page +faults can implement their own mmap file operation handler. + +Memory Coherency +~~~~~~~~~~~~~~~~ + +When mapped to the device or used in a command buffer, backing pages for +an object are flushed to memory and marked write combined so as to be +coherent with the GPU. Likewise, if the CPU accesses an object after the +GPU has finished rendering to the object, then the object must be made +coherent with the CPU's view of memory, usually involving GPU cache +flushing of various kinds. This core CPU<->GPU coherency management is +provided by a device-specific ioctl, which evaluates an object's current +domain and performs any necessary flushing or synchronization to put the +object into the desired coherency domain (note that the object may be +busy, i.e. an active render target; in that case, setting the domain +blocks the client and waits for rendering to complete before performing +any necessary flushing operations). + +Command Execution +~~~~~~~~~~~~~~~~~ + +Perhaps the most important GEM function for GPU devices is providing a +command execution interface to clients. Client programs construct +command buffers containing references to previously allocated memory +objects, and then submit them to GEM. At that point, GEM takes care to +bind all the objects into the GTT, execute the buffer, and provide +necessary synchronization between clients accessing the same buffers. +This often involves evicting some objects from the GTT and re-binding +others (a fairly expensive operation), and providing relocation support +which hides fixed GTT offsets from clients. Clients must take care not +to submit command buffers that reference more objects than can fit in +the GTT; otherwise, GEM will reject them and no rendering will occur. +Similarly, if several objects in the buffer require fence registers to +be allocated for correct rendering (e.g. 2D blits on pre-965 chips), +care must be taken not to require more fence registers than are +available to the client. Such resource management should be abstracted +from the client in libdrm. + +GEM Function Reference +---------------------- + +.. kernel-doc:: drivers/gpu/drm/drm_gem.c + :export: + +.. kernel-doc:: include/drm/drm_gem.h + :internal: + +VMA Offset Manager +------------------ + +.. kernel-doc:: drivers/gpu/drm/drm_vma_manager.c + :doc: vma offset manager + +.. kernel-doc:: drivers/gpu/drm/drm_vma_manager.c + :export: + +.. kernel-doc:: include/drm/drm_vma_manager.h + :internal: + +PRIME Buffer Sharing +-------------------- + +PRIME is the cross device buffer sharing framework in drm, originally +created for the OPTIMUS range of multi-gpu platforms. To userspace PRIME +buffers are dma-buf based file descriptors. + +Overview and Driver Interface +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Similar to GEM global names, PRIME file descriptors are also used to +share buffer objects across processes. They offer additional security: +as file descriptors must be explicitly sent over UNIX domain sockets to +be shared between applications, they can't be guessed like the globally +unique GEM names. + +Drivers that support the PRIME API must set the DRIVER_PRIME bit in the +struct :c:type:`struct drm_driver <drm_driver>` +driver_features field, and implement the prime_handle_to_fd and +prime_fd_to_handle operations. + +int (*prime_handle_to_fd)(struct drm_device *dev, struct drm_file +*file_priv, uint32_t handle, uint32_t flags, int *prime_fd); int +(*prime_fd_to_handle)(struct drm_device *dev, struct drm_file +*file_priv, int prime_fd, uint32_t *handle); Those two operations +convert a handle to a PRIME file descriptor and vice versa. Drivers must +use the kernel dma-buf buffer sharing framework to manage the PRIME file +descriptors. Similar to the mode setting API PRIME is agnostic to the +underlying buffer object manager, as long as handles are 32bit unsigned +integers. + +While non-GEM drivers must implement the operations themselves, GEM +drivers must use the :c:func:`drm_gem_prime_handle_to_fd()` and +:c:func:`drm_gem_prime_fd_to_handle()` helper functions. Those +helpers rely on the driver gem_prime_export and gem_prime_import +operations to create a dma-buf instance from a GEM object (dma-buf +exporter role) and to create a GEM object from a dma-buf instance +(dma-buf importer role). + +struct dma_buf * (*gem_prime_export)(struct drm_device *dev, +struct drm_gem_object *obj, int flags); struct drm_gem_object * +(*gem_prime_import)(struct drm_device *dev, struct dma_buf +*dma_buf); These two operations are mandatory for GEM drivers that +support PRIME. + +PRIME Helper Functions +~~~~~~~~~~~~~~~~~~~~~~ + +.. kernel-doc:: drivers/gpu/drm/drm_prime.c + :doc: PRIME Helpers + +PRIME Function References +------------------------- + +.. kernel-doc:: drivers/gpu/drm/drm_prime.c + :export: + +DRM MM Range Allocator +---------------------- + +Overview +~~~~~~~~ + +.. kernel-doc:: drivers/gpu/drm/drm_mm.c + :doc: Overview + +LRU Scan/Eviction Support +~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. kernel-doc:: drivers/gpu/drm/drm_mm.c + :doc: lru scan roaster + +DRM MM Range Allocator Function References +------------------------------------------ + +.. kernel-doc:: drivers/gpu/drm/drm_mm.c + :export: + +.. kernel-doc:: include/drm/drm_mm.h + :internal: + +CMA Helper Functions Reference +------------------------------ + +.. kernel-doc:: drivers/gpu/drm/drm_gem_cma_helper.c + :doc: cma helpers + +.. kernel-doc:: drivers/gpu/drm/drm_gem_cma_helper.c + :export: + +.. kernel-doc:: include/drm/drm_gem_cma_helper.h + :internal: diff --git a/Documentation/gpu/index.rst b/Documentation/gpu/index.rst index e6b38e8e57c9..fcac0fa72056 100644 --- a/Documentation/gpu/index.rst +++ b/Documentation/gpu/index.rst @@ -6,6 +6,9 @@ Linux GPU Driver Developer's Guide

introduction drm-internals + drm-mm + drm-kms + drm-kms-helpers drm-uapi i915 vga-switcheroo