From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> Add a TODO for plumbing drm_atomic_state all over to ease the hurdles of accessing additional object states. Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> #irc Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> --- Documentation/gpu/todo.rst | 46 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst index 7969f106877d..b0ea17da8ff6 100644 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -403,6 +403,52 @@ 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 ================= -- 2.26.2 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
