diff options
Diffstat (limited to 'Documentation/gpu')
| -rw-r--r-- | Documentation/gpu/drm-internals.rst | 1379 | ||||
| -rw-r--r-- | Documentation/gpu/drm-kms-helpers.rst | 260 | ||||
| -rw-r--r-- | Documentation/gpu/drm-kms.rst | 656 | ||||
| -rw-r--r-- | Documentation/gpu/drm-mm.rst | 454 | ||||
| -rw-r--r-- | Documentation/gpu/index.rst | 3 |
5 files changed, 1379 insertions, 1373 deletions
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 - |