[PATCH v4 5/5] drm/todo: Add entry about implementing buffer age for damage tracking

[Javier Martinez Canillas <javierm@redhat.com>]

Currently, only damage tracking for frame damage is supported. If a driver
needs to do buffer damage (e.g: the framebuffer attached to plane's state
has changed since the last page-flip), the damage helpers just fallback to
a full plane update.

Add en entry in the TODO about implementing buffer age or any other damage
accumulation algorithm for buffer damage handling.

Suggested-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Zack Rusin <zackr@vmware.com>
Acked-by: Sima Vetter <daniel.vetter@ffwll.ch>
---

Changes in v4:
- Reference the &drm_plane_state.ignore_damage_clips and the damage helpers
  in the buffer damage TODO entry (Sima Vetter).

 Documentation/gpu/todo.rst | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index b62c7fa0c2bc..503d57c75215 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -782,6 +782,29 @@ Contact: Hans de Goede
 
 Level: Advanced
 
+Buffer age or other damage accumulation algorithm for buffer damage
+===================================================================
+
+Drivers that do per-buffer uploads, need a buffer damage handling (rather than
+frame damage like drivers that do per-plane or per-CRTC uploads), but there is
+no support to get the buffer age or any other damage accumulation algorithm.
+
+For this reason, the damage helpers just fallback to a full plane update if the
+framebuffer attached to a plane has changed since the last page-flip. Drivers
+set &drm_plane_state.ignore_damage_clips to true as indication to
+drm_atomic_helper_damage_iter_init() and drm_atomic_helper_damage_iter_next()
+helpers that the damage clips should be ignored.
+
+This should be improved to get damage tracking properly working on drivers that
+do per-buffer uploads.
+
+More information about damage tracking and references to learning materials can
+be found in :ref:`damage_tracking_properties`.
+
+Contact: Javier Martinez Canillas <javierm@redhat.com>
+
+Level: Advanced
+
 Outside DRM
 ===========
 
-- 
2.41.0