diff options
Diffstat (limited to 'Documentation/gpu/todo.rst')
| -rw-r--r-- | Documentation/gpu/todo.rst | 97 |
1 files changed, 37 insertions, 60 deletions
diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst index 40ccac61137e..7ff9fac10d8b 100644 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -459,52 +459,6 @@ 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 - Use struct dma_buf_map throughout codebase ------------------------------------------ @@ -596,23 +550,48 @@ Contact: Daniel Vetter Level: Intermediate -KMS cleanups ------------- +Object lifetime fixes +--------------------- + +There's two related issues here -Some of these date from the very introduction of KMS in 2008 ... +- Cleanup up the various ->destroy callbacks, which often are all the same + simple code. -- 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. +- 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. -- 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. +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 ============== @@ -645,8 +624,6 @@ 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 @@ -700,7 +677,7 @@ Outside DRM Convert fbdev drivers to DRM ---------------------------- -There are plenty of fbdev drivers for older hardware. Some hwardware has +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. |