Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 677 insertions, 0 deletions

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
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+.. _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.
+
+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+implementation (there's lots of outdated locking leftovers in various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.
+
+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_free_object_unlocked`` 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
+
+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. Current generic fbdev emulation
+expects the framebuffer in system memory (or system-like memory).
+
+Contact: Maintainer of the driver you plan to convert
+
+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
+
+Clean up mmap forwarding
+------------------------
+
+A lot of drivers forward gem mmap calls to dma-buf mmap for imported buffers.
+And also a lot of them forward dma-buf mmap to the gem mmap implementations.
+There's drm_gem_prime_mmap() for this now, but still needs to be rolled out.
+
+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 and drivers can be moved over.
+
+We also need a 2nd version of the CMA define that doesn't require the
+vmapping to be present (different hook for prime importing). Plus this needs to
+be rolled out to all drivers using their own implementations, too.
+
+Level: Intermediate
+
+Use DRM_MODESET_LOCK_ALL_* helpers instead of boilerplate
+---------------------------------------------------------
+
+For cases where drivers are attempting to grab the modeset locks with a local
+acquire context. Replace the boilerplate code surrounding
+drm_modeset_lock_all_ctx() with DRM_MODESET_LOCK_ALL_BEGIN() and
+DRM_MODESET_LOCK_ALL_END() instead.
+
+This should also be done for all places where drm_modeset_lock_all() is still
+used.
+
+As a reference, take a look at the conversions already completed in drm core.
+
+Contact: Sean Paul, respective driver maintainers
+
+Level: Starter
+
+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
+
+Plumb drm_atomic_state all over
+-------------------------------
+
+Currently various atomic functions take just a single or a handful of
+object states (eg. plane state). While that single object state can
+suffice for some simple cases, we often have to dig out additional
+object states for dealing with various dependencies between the individual
+objects or the hardware they represent. The process of digging out the
+additional states is rather non-intuitive and error prone.
+
+To fix that most functions should rather take the overall
+drm_atomic_state as one of their parameters. The other parameters
+would generally be the object(s) we mainly want to interact with.
+
+For example, instead of
+
+.. code-block:: c
+
+   int (*atomic_check)(struct drm_plane *plane, struct drm_plane_state *state);
+
+we would have something like
+
+.. code-block:: c
+
+   int (*atomic_check)(struct drm_plane *plane, struct drm_atomic_state *state);
+
+The implementation can then trivially gain access to any required object
+state(s) via drm_atomic_get_plane_state(), drm_atomic_get_new_plane_state(),
+drm_atomic_get_old_plane_state(), and their equivalents for
+other object types.
+
+Additionally many drivers currently access the object->state pointer
+directly in their commit functions. That is not going to work if we
+eg. want to allow deeper commit pipelines as those pointers could
+then point to the states corresponding to a future commit instead of
+the current commit we're trying to process. Also non-blocking commits
+execute locklessly so there are serious concerns with dereferencing
+the object->state pointers without holding the locks that protect them.
+Use of drm_atomic_get_new_plane_state(), drm_atomic_get_old_plane_state(),
+etc. avoids these problems as well since they relate to a specific
+commit via the passed in drm_atomic_state.
+
+Contact: Ville Syrjälä, Daniel Vetter
+
+Level: Intermediate
+
+
+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 have one, but on top of that the fbcon code itself also has one. We
+  need to make sure that they stop fighting over each another.
+
+* ``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.
+
+* For the above locking troubles reasons it's pretty much impossible to
+  attempt a synchronous modeset from panic handlers. The only thing we could
+  try to achive is an atomic ``set_base`` of the primary plane, and hope that
+  it shows up. Everything else probably needs to be delayed to some worker or
+  something else which happens later on. Otherwise it just kills the box
+  harder, prevent the panic from going out on e.g. netconsole.
+
+* There's also proposal for a simplied DRM console instead of the full-blown
+  fbcon and DRM fbdev emulation. Any kind of panic handling tricks should
+  obviously work for both console, in case we ever get kmslog merged.
+
+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.
+
+- Drop the return code and error checking from all debugfs functions. Greg KH is
+  working on this already.
+
+Contact: Daniel Vetter
+
+Level: Intermediate
+
+KMS cleanups
+------------
+
+Some of these date from the very introduction of KMS in 2008 ...
+
+- Make ->funcs and ->helper_private vtables optional. There's a bunch of empty
+  function tables in drivers, but before we can remove them we need to make sure
+  that all the users in helpers and drivers do correctly check for a NULL
+  vtable.
+
+- Cleanup up the various ->destroy callbacks. A lot of them just wrapt the
+  drm_*_cleanup implementations and can be removed. Some tack a kfree() at the
+  end, for which we could add drm_*_cleanup_kfree(). And then there's the (for
+  historical reasons) misnamed drm_primary_helper_destroy() function.
+
+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
+==============
+
+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.
+
+Contact: Daniel Vetter
+
+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
+
+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://lkml.org/lkml/2017/12/13/764
+
+Contact: Sam Ravnborg
+
+Level: Advanced
+
+Outside DRM
+===========
+
+Convert fbdev drivers to DRM
+----------------------------
+
+There are plenty of fbdev drivers for older hardware. Some hwardware 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