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Diffstat (limited to 'Documentation/gpu/todo.rst')
| -rw-r--r-- | Documentation/gpu/todo.rst | 164 |
1 files changed, 111 insertions, 53 deletions
diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst index 77c2b3c25565..159a4aba49e6 100644 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -28,22 +28,16 @@ them, but also all the virtual ones used by KVM, so everyone qualifies). Contact: Daniel Vetter, Thierry Reding, respective driver maintainers -Switch from reference/unreference to get/put --------------------------------------------- - -For some reason DRM core uses ``reference``/``unreference`` suffixes for -refcounting functions, but kernel uses ``get``/``put`` (e.g. -``kref_get``/``put()``). It would be good to switch over for consistency, and -it's shorter. Needs to be done in 3 steps for each pair of functions: -* Create new ``get``/``put`` functions, define the old names as compatibility - wrappers -* Switch over each file/driver using a cocci-generated spatch. -* Once all users of the old names are gone, remove them. +Remove custom dumb_map_offset implementations +--------------------------------------------- -This way drivers/patches in the progress of getting merged won't break. +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 +Audit each individual driver, make sure it'll work with the generic +implementation (there's lots of outdated locking leftovers in various +implementations), and then remove it.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 +Contact: Daniel Vetter, respective driver maintainers Convert existing KMS drivers to atomic modesetting -------------------------------------------------- @@ -88,30 +82,6 @@ events for atomic commits correctly. But fixing these bugs is good anyway. Contact: Daniel Vetter, respective driver maintainers -Better manual-upload support for atomic ---------------------------------------- - -This would be especially useful for tinydrm: - -- Add a struct drm_rect dirty_clip to drm_crtc_state. When duplicating the - crtc state, clear that to the max values, x/y = 0 and w/h = MAX_INT, in - __drm_atomic_helper_crtc_duplicate_state(). - -- Move tinydrm_merge_clips into drm_framebuffer.c, dropping the tinydrm\_ - prefix ofc and using drm_fb\_. drm_framebuffer.c makes sense since this - is a function useful to implement the fb->dirty function. - -- Create a new drm_fb_dirty function which does essentially what e.g. - mipi_dbi_fb_dirty does. You can use e.g. drm_atomic_helper_update_plane as the - template. But instead of doing a simple full-screen plane update, this new - helper also sets crtc_state->dirty_clip to the right coordinates. And of - course it needs to check whether the fb is actually active (and maybe where), - so there's some book-keeping involved. There's also some good fun involved in - scaling things appropriately. For that case we might simply give up and - declare the entire area covered by the plane as dirty. - -Contact: Noralf Trønnes, Daniel Vetter - Fallout from atomic KMS ----------------------- @@ -215,6 +185,36 @@ Would be great to refactor this all into a set of small common helpers. Contact: Daniel Vetter +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. Which prevents +us from using the generic fbdev emulation code everywhere. The main issue is +that it uses some fields in struct page itself, which breaks shmem gem objects +(and other things). + +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 + Put a reservation_object into drm_gem_object -------------------------------------------- @@ -234,6 +234,72 @@ efficient. Contact: Daniel Vetter +Defaults for .gem_prime_import and export +----------------------------------------- + +Most drivers don't need to set drm_driver->gem_prime_import and +->gem_prime_export now that drm_gem_prime_import() and drm_gem_prime_export() +are the default. + +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. + +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_modest_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 + +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 + +Convert direct mode.vrefresh accesses to use drm_mode_vrefresh() +---------------------------------------------------------------- + +drm_display_mode.vrefresh isn't guaranteed to be populated. As such, using it +is risky and has been known to cause div-by-zero bugs. Fortunately, drm core +has helper which will use mode.vrefresh if it's !0 and will calculate it from +the timings when it's 0. + +Use simple search/replace, or (more fun) cocci to replace instances of direct +vrefresh access with a call to the helper. Check out +https://lists.freedesktop.org/archives/dri-devel/2019-January/205186.html for +inspiration. + +Once all instances of vrefresh have been converted, remove vrefresh from +drm_display_mode to avoid future use. + +Contact: Sean Paul + +Remove drm_display_mode.hsync +----------------------------- + +We have drm_mode_hsync() to calculate this from hsync_start/end, since drivers +shouldn't/don't use this, remove this member to avoid any temptations to use it +in the future. If there is any debug code using drm_display_mode.hsync, convert +it to use drm_mode_hsync() instead. + +Contact: Sean Paul + Core refactorings ================= @@ -332,12 +398,15 @@ KMS cleanups Some of these date from the very introduction of KMS in 2008 ... -- drm_mode_config.crtc_idr is misnamed, since it contains all KMS object. Should - be renamed to drm_mode_config.object_idr. +- 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. -- drm_display_mode doesn't need to be derived from drm_mode_object. That's - leftovers from older (never merged into upstream) KMS designs where modes - where set using their ID, including support to add/remove modes. +- 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. Better Testing ============== @@ -400,21 +469,10 @@ those drivers as simple as possible, so lots of room for refactoring: one of the ideas for having a shared dsi/dbi helper, abstracting away the transport details more. -- tinydrm_gem_cma_prime_import_sg_table should probably go into the cma - helpers, as a _vmapped variant (since not every driver needs the vmap). - And tinydrm_gem_cma_free_object could the be merged into - drm_gem_cma_free_object(). - -- tinydrm_fb_create we could move into drm_simple_pipe, only need to add - the fb_create hook to drm_simple_pipe_funcs, which would again simplify a - bunch of things (since it gives you a one-stop vfunc for simple drivers). - - Quick aside: The unregister devm stuff is kinda getting the lifetimes of a drm_device wrong. Doesn't matter, since everyone else gets it wrong too :-) -- also rework the drm_framebuffer_funcs->dirty hook wire-up, see above. - Contact: Noralf Trønnes, Daniel Vetter AMD DC Display Driver |