OSCL-LXR linux-6.0.1/​Documentation/​gpu/​todo.rst	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 .. _todo:
 
 =========
 TODO list
 =========
 
 This section contains a list of smaller janitorial tasks in the kernel DRM
 graphics subsystem useful as newbie projects. Or for slow rainy days.
 
 Difficulty
 ----------
 
 To make it easier task are categorized into different levels:
 
 Starter: Good tasks to get started with the DRM subsystem.
 
 Intermediate: Tasks which need some experience with working in the DRM
 subsystem, or some specific GPU/display graphics knowledge. For debugging issue
 it's good to have the relevant hardware (or a virtual driver set up) available
 for testing.
 
 Advanced: Tricky tasks that need fairly good understanding of the DRM subsystem
 and graphics topics. Generally need the relevant hardware for development and
 testing.
 
 Expert: Only attempt these if you've successfully completed some tricky
 refactorings already and are an expert in the specific area
 
 Subsystem-wide refactorings
 ===========================
 
 Remove custom dumb_map_offset implementations
 ---------------------------------------------
 
 All GEM based drivers should be using drm_gem_create_mmap_offset() instead.
 Audit each individual driver, make sure it'll work with the generic
 implementation (there's lots of outdated locking leftovers in various
 implementations), and then remove it.
 
 Contact: Daniel Vetter, respective driver maintainers
 
 Level: Intermediate
 
 Convert existing KMS drivers to atomic modesetting
 --------------------------------------------------
 
 3.19 has the atomic modeset interfaces and helpers, so drivers can now be
 converted over. Modern compositors like Wayland or Surfaceflinger on Android
 really want an atomic modeset interface, so this is all about the bright
 future.
 
 There is a conversion guide for atomic and all you need is a GPU for a
 non-converted driver (again virtual HW drivers for KVM are still all
 suitable).
 
 As part of this drivers also need to convert to universal plane (which means
 exposing primary & cursor as proper plane objects). But that's much easier to
 do by directly using the new atomic helper driver callbacks.
 
 Contact: Daniel Vetter, respective driver maintainers
 
 Level: Advanced
 
 Clean up the clipped coordination confusion around planes
 ---------------------------------------------------------
 
 We have a helper to get this right with drm_plane_helper_check_update(), but
 it's not consistently used. This should be fixed, preferrably in the atomic
 helpers (and drivers then moved over to clipped coordinates). Probably the
 helper should also be moved from drm_plane_helper.c to the atomic helpers, to
 avoid confusion - the other helpers in that file are all deprecated legacy
 helpers.
 
 Contact: Ville Syrjälä, Daniel Vetter, driver maintainers
 
 Level: Advanced
 
 Improve plane atomic_check helpers
 ----------------------------------
 
 Aside from the clipped coordinates right above there's a few suboptimal things
 with the current helpers:
 
 - drm_plane_helper_funcs->atomic_check gets called for enabled or disabled
   planes. At best this seems to confuse drivers, worst it means they blow up
   when the plane is disabled without the CRTC. The only special handling is
   resetting values in the plane state structures, which instead should be moved
   into the drm_plane_funcs->atomic_duplicate_state functions.
 
 - Once that's done, helpers could stop calling ->atomic_check for disabled
   planes.
 
 - Then we could go through all the drivers and remove the more-or-less confused
   checks for plane_state->fb and plane_state->crtc.
 
 Contact: Daniel Vetter
 
 Level: Advanced
 
 Convert early atomic drivers to async commit helpers
 ----------------------------------------------------
 
 For the first year the atomic modeset helpers didn't support asynchronous /
 nonblocking commits, and every driver had to hand-roll them. This is fixed
 now, but there's still a pile of existing drivers that easily could be
 converted over to the new infrastructure.
 
 One issue with the helpers is that they require that drivers handle completion
 events for atomic commits correctly. But fixing these bugs is good anyway.
 
 Somewhat related is the legacy_cursor_update hack, which should be replaced with
 the new atomic_async_check/commit functionality in the helpers in drivers that
 still look at that flag.
 
 Contact: Daniel Vetter, respective driver maintainers
 
 Level: Advanced
 
 Fallout from atomic KMS
 -----------------------
 
 ``drm_atomic_helper.c`` provides a batch of functions which implement legacy
 IOCTLs on top of the new atomic driver interface. Which is really nice for
 gradual conversion of drivers, but unfortunately the semantic mismatches are
 a bit too severe. So there's some follow-up work to adjust the function
 interfaces to fix these issues:
 
 * atomic needs the lock acquire context. At the moment that's passed around
   implicitly with some horrible hacks, and it's also allocate with
   ``GFP_NOFAIL`` behind the scenes. All legacy paths need to start allocating
   the acquire context explicitly on stack and then also pass it down into
   drivers explicitly so that the legacy-on-atomic functions can use them.
 
   Except for some driver code this is done. This task should be finished by
   adding WARN_ON(!drm_drv_uses_atomic_modeset) in drm_modeset_lock_all().
 
 * A bunch of the vtable hooks are now in the wrong place: DRM has a split
   between core vfunc tables (named ``drm_foo_funcs``), which are used to
   implement the userspace ABI. And then there's the optional hooks for the
   helper libraries (name ``drm_foo_helper_funcs``), which are purely for
   internal use. Some of these hooks should be move from ``_funcs`` to
   ``_helper_funcs`` since they are not part of the core ABI. There's a
   ``FIXME`` comment in the kerneldoc for each such case in ``drm_crtc.h``.
 
 Contact: Daniel Vetter
 
 Level: Intermediate
 
 Get rid of dev->struct_mutex from GEM drivers
 ---------------------------------------------
 
 ``dev->struct_mutex`` is the Big DRM Lock from legacy days and infested
 everything. Nowadays in modern drivers the only bit where it's mandatory is
 serializing GEM buffer object destruction. Which unfortunately means drivers
 have to keep track of that lock and either call ``unreference`` or
 ``unreference_locked`` depending upon context.
 
 Core GEM doesn't have a need for ``struct_mutex`` any more since kernel 4.8,
 and there's a GEM object ``free`` callback for any drivers which are
 entirely ``struct_mutex`` free.
 
 For drivers that need ``struct_mutex`` it should be replaced with a driver-
 private lock. The tricky part is the BO free functions, since those can't
 reliably take that lock any more. Instead state needs to be protected with
 suitable subordinate locks or some cleanup work pushed to a worker thread. For
 performance-critical drivers it might also be better to go with a more
 fine-grained per-buffer object and per-context lockings scheme. Currently only
 the ``msm`` and `i915` drivers use ``struct_mutex``.
 
 Contact: Daniel Vetter, respective driver maintainers
 
 Level: Advanced
 
 Move Buffer Object Locking to dma_resv_lock()
 ---------------------------------------------
 
 Many drivers have their own per-object locking scheme, usually using
 mutex_lock(). This causes all kinds of trouble for buffer sharing, since
 depending which driver is the exporter and importer, the locking hierarchy is
 reversed.
 
 To solve this we need one standard per-object locking mechanism, which is
 dma_resv_lock(). This lock needs to be called as the outermost lock, with all
 other driver specific per-object locks removed. The problem is tha rolling out
 the actual change to the locking contract is a flag day, due to struct dma_buf
 buffer sharing.
 
 Level: Expert
 
 Convert logging to drm_* functions with drm_device paramater
 ------------------------------------------------------------
 
 For drivers which could have multiple instances, it is necessary to
 differentiate between which is which in the logs. Since DRM_INFO/WARN/ERROR
 don't do this, drivers used dev_info/warn/err to make this differentiation. We
 now have drm_* variants of the drm print functions, so we can start to convert
 those drivers back to using drm-formatted specific log messages.
 
 Before you start this conversion please contact the relevant maintainers to make
 sure your work will be merged - not everyone agrees that the DRM dmesg macros
 are better.
 
 Contact: Sean Paul, Maintainer of the driver you plan to convert
 
 Level: Starter
 
 Convert drivers to use simple modeset suspend/resume
 ----------------------------------------------------
 
 Most drivers (except i915 and nouveau) that use
 drm_atomic_helper_suspend/resume() can probably be converted to use
 drm_mode_config_helper_suspend/resume(). Also there's still open-coded version
 of the atomic suspend/resume code in older atomic modeset drivers.
 
 Contact: Maintainer of the driver you plan to convert
 
 Level: Intermediate
 
 Convert drivers to use drm_fbdev_generic_setup()
 ------------------------------------------------
 
 Most drivers can use drm_fbdev_generic_setup(). Driver have to implement
 atomic modesetting and GEM vmap support. Historically, generic fbdev emulation
 expected the framebuffer in system memory or system-like memory. By employing
 struct iosys_map, drivers with frambuffers in I/O memory can be supported
 as well.
 
 Contact: Maintainer of the driver you plan to convert
 
 Level: Intermediate
 
 Reimplement functions in drm_fbdev_fb_ops without fbdev
 -------------------------------------------------------
 
 A number of callback functions in drm_fbdev_fb_ops could benefit from
 being rewritten without dependencies on the fbdev module. Some of the
 helpers could further benefit from using struct iosys_map instead of
 raw pointers.
 
 Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter
 
 Level: Advanced
 
 Benchmark and optimize blitting and format-conversion function
 --------------------------------------------------------------
 
 Drawing to dispay memory quickly is crucial for many applications'
 performance.
 
 On at least x86-64, sys_imageblit() is significantly slower than
 cfb_imageblit(), even though both use the same blitting algorithm and
 the latter is written for I/O memory. It turns out that cfb_imageblit()
 uses movl instructions, while sys_imageblit apparently does not. This
 seems to be a problem with gcc's optimizer. DRM's format-conversion
 helpers might be subject to similar issues.
 
 Benchmark and optimize fbdev's sys_() helpers and DRM's format-conversion
 helpers. In cases that can be further optimized, maybe implement a different
 algorithm. For micro-optimizations, use movl/movq instructions explicitly.
 That might possibly require architecture-specific helpers (e.g., storel()
 storeq()).
 
 Contact: Thomas Zimmermann <tzimmermann@suse.de>
 
 Level: Intermediate
 
 drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup
 -----------------------------------------------------------------
 
 A lot more drivers could be switched over to the drm_gem_framebuffer helpers.
 Various hold-ups:
 
 - Need to switch over to the generic dirty tracking code using
   drm_atomic_helper_dirtyfb first (e.g. qxl).
 
 - Need to switch to drm_fbdev_generic_setup(), otherwise a lot of the custom fb
   setup code can't be deleted.
 
 - Many drivers wrap drm_gem_fb_create() only to check for valid formats. For
   atomic drivers we could check for valid formats by calling
   drm_plane_check_pixel_format() against all planes, and pass if any plane
   supports the format. For non-atomic that's not possible since like the format
   list for the primary plane is fake and we'd therefor reject valid formats.
 
 - Many drivers subclass drm_framebuffer, we'd need a embedding compatible
   version of the varios drm_gem_fb_create functions. Maybe called
   drm_gem_fb_create/_with_dirty/_with_funcs as needed.
 
 Contact: Daniel Vetter
 
 Level: Intermediate
 
 Generic fbdev defio support
 ---------------------------
 
 The defio support code in the fbdev core has some very specific requirements,
 which means drivers need to have a special framebuffer for fbdev. The main
 issue is that it uses some fields in struct page itself, which breaks shmem
 gem objects (and other things). To support defio, affected drivers require
 the use of a shadow buffer, which may add CPU and memory overhead.
 
 Possible solution would be to write our own defio mmap code in the drm fbdev
 emulation. It would need to fully wrap the existing mmap ops, forwarding
 everything after it has done the write-protect/mkwrite trickery:
 
 - In the drm_fbdev_fb_mmap helper, if we need defio, change the
   default page prots to write-protected with something like this::
 
       vma->vm_page_prot = pgprot_wrprotect(vma->vm_page_prot);
 
 - Set the mkwrite and fsync callbacks with similar implementions to the core
   fbdev defio stuff. These should all work on plain ptes, they don't actually
   require a struct page.  uff. These should all work on plain ptes, they don't
   actually require a struct page.
 
 - Track the dirty pages in a separate structure (bitfield with one bit per page
   should work) to avoid clobbering struct page.
 
 Might be good to also have some igt testcases for this.
 
 Contact: Daniel Vetter, Noralf Tronnes
 
 Level: Advanced
 
 idr_init_base()
 ---------------
 
 DRM core&drivers uses a lot of idr (integer lookup directories) for mapping
 userspace IDs to internal objects, and in most places ID=0 means NULL and hence
 is never used. Switching to idr_init_base() for these would make the idr more
 efficient.
 
 Contact: Daniel Vetter
 
 Level: Starter
 
 struct drm_gem_object_funcs
 ---------------------------
 
 GEM objects can now have a function table instead of having the callbacks on the
 DRM driver struct. This is now the preferred way. Callbacks in drivers have been
 converted, except for struct drm_driver.gem_prime_mmap.
 
 Level: Intermediate
 
 Rename CMA helpers to DMA helpers
 ---------------------------------
 
 CMA (standing for contiguous memory allocator) is really a bit an accident of
 what these were used for first, a much better name would be DMA helpers. In the
 text these should even be called coherent DMA memory helpers (so maybe CDM, but
 no one knows what that means) since underneath they just use dma_alloc_coherent.
 
 Contact: Laurent Pinchart, Daniel Vetter
 
 Level: Intermediate (mostly because it is a huge tasks without good partial
 milestones, not technically itself that challenging)
 
 connector register/unregister fixes
 -----------------------------------
 
 - For most connectors it's a no-op to call drm_connector_register/unregister
   directly from driver code, drm_dev_register/unregister take care of this
   already. We can remove all of them.
 
 - For dp drivers it's a bit more a mess, since we need the connector to be
   registered when calling drm_dp_aux_register. Fix this by instead calling
   drm_dp_aux_init, and moving the actual registering into a late_register
   callback as recommended in the kerneldoc.
 
 Level: Intermediate
 
 Remove load/unload callbacks from all non-DRIVER_LEGACY drivers
 ---------------------------------------------------------------
 
 The load/unload callbacks in struct &drm_driver are very much midlayers, plus
 for historical reasons they get the ordering wrong (and we can't fix that)
 between setting up the &drm_driver structure and calling drm_dev_register().
 
 - Rework drivers to no longer use the load/unload callbacks, directly coding the
   load/unload sequence into the driver's probe function.
 
 - Once all non-DRIVER_LEGACY drivers are converted, disallow the load/unload
   callbacks for all modern drivers.
 
 Contact: Daniel Vetter
 
 Level: Intermediate
 
 Replace drm_detect_hdmi_monitor() with drm_display_info.is_hdmi
 ---------------------------------------------------------------
 
 Once EDID is parsed, the monitor HDMI support information is available through
 drm_display_info.is_hdmi. Many drivers still call drm_detect_hdmi_monitor() to
 retrieve the same information, which is less efficient.
 
 Audit each individual driver calling drm_detect_hdmi_monitor() and switch to
 drm_display_info.is_hdmi if applicable.
 
 Contact: Laurent Pinchart, respective driver maintainers
 
 Level: Intermediate
 
 Consolidate custom driver modeset properties
 --------------------------------------------
 
 Before atomic modeset took place, many drivers where creating their own
 properties. Among other things, atomic brought the requirement that custom,
 driver specific properties should not be used.
 
 For this task, we aim to introduce core helpers or reuse the existing ones
 if available:
 
 A quick, unconfirmed, examples list.
 
 Introduce core helpers:
 - audio (amdgpu, intel, gma500, radeon)
 - brightness, contrast, etc (armada, nouveau) - overlay only (?)
 - broadcast rgb (gma500, intel)
 - colorkey (armada, nouveau, rcar) - overlay only (?)
 - dither (amdgpu, nouveau, radeon) - varies across drivers
 - underscan family (amdgpu, radeon, nouveau)
 
 Already in core:
 - colorspace (sti)
 - tv format names, enhancements (gma500, intel)
 - tv overscan, margins, etc. (gma500, intel)
 - zorder (omapdrm) - same as zpos (?)
 
 
 Contact: Emil Velikov, respective driver maintainers
 
 Level: Intermediate
 
 Use struct iosys_map throughout codebase
 ----------------------------------------
 
 Pointers to shared device memory are stored in struct iosys_map. Each
 instance knows whether it refers to system or I/O memory. Most of the DRM-wide
 interface have been converted to use struct iosys_map, but implementations
 often still use raw pointers.
 
 The task is to use struct iosys_map where it makes sense.
 
 * Memory managers should use struct iosys_map for dma-buf-imported buffers.
 * TTM might benefit from using struct iosys_map internally.
 * Framebuffer copying and blitting helpers should operate on struct iosys_map.
 
 Contact: Thomas Zimmermann <tzimmermann@suse.de>, Christian König, Daniel Vetter
 
 Level: Intermediate
 
 Review all drivers for setting struct drm_mode_config.{max_width,max_height} correctly
 --------------------------------------------------------------------------------------
 
 The values in struct drm_mode_config.{max_width,max_height} describe the
 maximum supported framebuffer size. It's the virtual screen size, but many
 drivers treat it like limitations of the physical resolution.
 
 The maximum width depends on the hardware's maximum scanline pitch. The
 maximum height depends on the amount of addressable video memory. Review all
 drivers to initialize the fields to the correct values.
 
 Contact: Thomas Zimmermann <tzimmermann@suse.de>
 
 Level: Intermediate
 
 Request memory regions in all drivers
 -------------------------------------
 
 Go through all drivers and add code to request the memory regions that the
 driver uses. This requires adding calls to request_mem_region(),
 pci_request_region() or similar functions. Use helpers for managed cleanup
 where possible.
 
 Drivers are pretty bad at doing this and there used to be conflicts among
 DRM and fbdev drivers. Still, it's the correct thing to do.
 
 Contact: Thomas Zimmermann <tzimmermann@suse.de>
 
 Level: Starter
 
 
 Core refactorings
 =================
 
 Make panic handling work
 ------------------------
 
 This is a really varied tasks with lots of little bits and pieces:
 
 * The panic path can't be tested currently, leading to constant breaking. The
   main issue here is that panics can be triggered from hardirq contexts and
   hence all panic related callback can run in hardirq context. It would be
   awesome if we could test at least the fbdev helper code and driver code by
   e.g. trigger calls through drm debugfs files. hardirq context could be
   achieved by using an IPI to the local processor.
 
 * There's a massive confusion of different panic handlers. DRM fbdev emulation
   helpers had their own (long removed), but on top of that the fbcon code itself
   also has one. We need to make sure that they stop fighting over each other.
   This is worked around by checking ``oops_in_progress`` at various entry points
   into the DRM fbdev emulation helpers. A much cleaner approach here would be to
   switch fbcon to the `threaded printk support
   <https://lwn.net/Articles/800946/>`_.
 
 * ``drm_can_sleep()`` is a mess. It hides real bugs in normal operations and
   isn't a full solution for panic paths. We need to make sure that it only
   returns true if there's a panic going on for real, and fix up all the
   fallout.
 
 * The panic handler must never sleep, which also means it can't ever
   ``mutex_lock()``. Also it can't grab any other lock unconditionally, not
   even spinlocks (because NMI and hardirq can panic too). We need to either
   make sure to not call such paths, or trylock everything. Really tricky.
 
 * A clean solution would be an entirely separate panic output support in KMS,
   bypassing the current fbcon support. See `[PATCH v2 0/3] drm: Add panic handling
   <https://lore.kernel.org/dri-devel/20190311174218.51899-1-noralf@tronnes.org/>`_.
 
 * Encoding the actual oops and preceding dmesg in a QR might help with the
   dread "important stuff scrolled away" problem. See `[RFC][PATCH] Oops messages
   transfer using QR codes
   <https://lore.kernel.org/lkml/1446217392-11981-1-git-send-email-alexandru.murtaza@intel.com/>`_
   for some example code that could be reused.
 
 Contact: Daniel Vetter
 
 Level: Advanced
 
 Clean up the debugfs support
 ----------------------------
 
 There's a bunch of issues with it:
 
 - The drm_info_list ->show() function doesn't even bother to cast to the drm
   structure for you. This is lazy.
 
 - We probably want to have some support for debugfs files on crtc/connectors and
   maybe other kms objects directly in core. There's even drm_print support in
   the funcs for these objects to dump kms state, so it's all there. And then the
   ->show() functions should obviously give you a pointer to the right object.
 
 - The drm_info_list stuff is centered on drm_minor instead of drm_device. For
   anything we want to print drm_device (or maybe drm_file) is the right thing.
 
 - The drm_driver->debugfs_init hooks we have is just an artifact of the old
   midlayered load sequence. DRM debugfs should work more like sysfs, where you
   can create properties/files for an object anytime you want, and the core
   takes care of publishing/unpuplishing all the files at register/unregister
   time. Drivers shouldn't need to worry about these technicalities, and fixing
   this (together with the drm_minor->drm_device move) would allow us to remove
   debugfs_init.
 
 Previous RFC that hasn't landed yet: https://lore.kernel.org/dri-devel/20200513114130.28641-2-wambui.karugax@gmail.com/
 
 Contact: Daniel Vetter
 
 Level: Intermediate
 
 Object lifetime fixes
 ---------------------
 
 There's two related issues here
 
 - Cleanup up the various ->destroy callbacks, which often are all the same
   simple code.
 
 - Lots of drivers erroneously allocate DRM modeset objects using devm_kzalloc,
   which results in use-after free issues on driver unload. This can be serious
   trouble even for drivers for hardware integrated on the SoC due to
   EPROBE_DEFERRED backoff.
 
 Both these problems can be solved by switching over to drmm_kzalloc(), and the
 various convenience wrappers provided, e.g. drmm_crtc_alloc_with_planes(),
 drmm_universal_plane_alloc(), ... and so on.
 
 Contact: Daniel Vetter
 
 Level: Intermediate
 
 Remove automatic page mapping from dma-buf importing
 ----------------------------------------------------
 
 When importing dma-bufs, the dma-buf and PRIME frameworks automatically map
 imported pages into the importer's DMA area. drm_gem_prime_fd_to_handle() and
 drm_gem_prime_handle_to_fd() require that importers call dma_buf_attach()
 even if they never do actual device DMA, but only CPU access through
 dma_buf_vmap(). This is a problem for USB devices, which do not support DMA
 operations.
 
 To fix the issue, automatic page mappings should be removed from the
 buffer-sharing code. Fixing this is a bit more involved, since the import/export
 cache is also tied to &drm_gem_object.import_attach. Meanwhile we paper over
 this problem for USB devices by fishing out the USB host controller device, as
 long as that supports DMA. Otherwise importing can still needlessly fail.
 
 Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter
 
 Level: Advanced
 
 
 Better Testing
 ==============
 
 Add unit tests using the Kernel Unit Testing (KUnit) framework
 --------------------------------------------------------------
 
 The `KUnit <https://www.kernel.org/doc/html/latest/dev-tools/kunit/index.html>`_
 provides a common framework for unit tests within the Linux kernel. Having a
 test suite would allow to identify regressions earlier.
 
 A good candidate for the first unit tests are the format-conversion helpers in
 ``drm_format_helper.c``.
 
 Contact: Javier Martinez Canillas <javierm@redhat.com>
 
 Level: Intermediate
 
 Convert Kernel Selftests (kselftest) to KUnit tests when appropriate
 --------------------------------------------------------------------
 
 Many of the `Kselftest <https://www.kernel.org/doc/html/latest/dev-tools/kselftest.html>`_
 tests in DRM could be converted to Kunit tests instead, since that framework
 is more suitable for unit testing.
 
 Contact: Javier Martinez Canillas <javierm@redhat.com>
 
 Level: Starter
 
 Enable trinity for DRM
 ----------------------
 
 And fix up the fallout. Should be really interesting ...
 
 Level: Advanced
 
 Make KMS tests in i-g-t generic
 -------------------------------
 
 The i915 driver team maintains an extensive testsuite for the i915 DRM driver,
 including tons of testcases for corner-cases in the modesetting API. It would
 be awesome if those tests (at least the ones not relying on Intel-specific GEM
 features) could be made to run on any KMS driver.
 
 Basic work to run i-g-t tests on non-i915 is done, what's now missing is mass-
 converting things over. For modeset tests we also first need a bit of
 infrastructure to use dumb buffers for untiled buffers, to be able to run all
 the non-i915 specific modeset tests.
 
 Level: Advanced
 
 Extend virtual test driver (VKMS)
 ---------------------------------
 
 See the documentation of :ref:`VKMS <vkms>` for more details. This is an ideal
 internship task, since it only requires a virtual machine and can be sized to
 fit the available time.
 
 Level: See details
 
 Backlight Refactoring
 ---------------------
 
 Backlight drivers have a triple enable/disable state, which is a bit overkill.
 Plan to fix this:
 
 1. Roll out backlight_enable() and backlight_disable() helpers everywhere. This
    has started already.
 2. In all, only look at one of the three status bits set by the above helpers.
 3. Remove the other two status bits.
 
 Contact: Daniel Vetter
 
 Level: Intermediate
 
 Driver Specific
 ===============
 
 AMD DC Display Driver
 ---------------------
 
 AMD DC is the display driver for AMD devices starting with Vega. There has been
 a bunch of progress cleaning it up but there's still plenty of work to be done.
 
 See drivers/gpu/drm/amd/display/TODO for tasks.
 
 Contact: Harry Wentland, Alex Deucher
 
 vmwgfx: Replace hashtable with Linux' implementation
 ----------------------------------------------------
 
 The vmwgfx driver uses its own hashtable implementation. Replace the
 code with Linux' implementation and update the callers. It's mostly a
 refactoring task, but the interfaces are different.
 
 Contact: Zack Rusin, Thomas Zimmermann <tzimmermann@suse.de>
 
 Level: Intermediate
 
 Bootsplash
 ==========
 
 There is support in place now for writing internal DRM clients making it
 possible to pick up the bootsplash work that was rejected because it was written
 for fbdev.
 
 - [v6,8/8] drm/client: Hack: Add bootsplash example
   https://patchwork.freedesktop.org/patch/306579/
 
 - [RFC PATCH v2 00/13] Kernel based bootsplash
   https://lore.kernel.org/r/20171213194755.3409-1-mstaudt@suse.de
 
 Contact: Sam Ravnborg
 
 Level: Advanced
 
 Outside DRM
 ===========
 
 Convert fbdev drivers to DRM
 ----------------------------
 
 There are plenty of fbdev drivers for older hardware. Some hardware has
 become obsolete, but some still provides good(-enough) framebuffers. The
 drivers that are still useful should be converted to DRM and afterwards
 removed from fbdev.
 
 Very simple fbdev drivers can best be converted by starting with a new
 DRM driver. Simple KMS helpers and SHMEM should be able to handle any
 existing hardware. The new driver's call-back functions are filled from
 existing fbdev code.
 
 More complex fbdev drivers can be refactored step-by-step into a DRM
 driver with the help of the DRM fbconv helpers. [1] These helpers provide
 the transition layer between the DRM core infrastructure and the fbdev
 driver interface. Create a new DRM driver on top of the fbconv helpers,
 copy over the fbdev driver, and hook it up to the DRM code. Examples for
 several fbdev drivers are available at [1] and a tutorial of this process
 available at [2]. The result is a primitive DRM driver that can run X11
 and Weston.
 
  - [1] https://gitlab.freedesktop.org/tzimmermann/linux/tree/fbconv
  - [2] https://gitlab.freedesktop.org/tzimmermann/linux/blob/fbconv/drivers/gpu/drm/drm_fbconv_helper.c
 
 Contact: Thomas Zimmermann <tzimmermann@suse.de>
 
 Level: Advanced

This page was automatically generated by the 2.1.0 LXR engine. The LXR team