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

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Message-ID: <20231123221315.3579454-6-javierm@redhat.com>
Date:   Thu, 23 Nov 2023 23:13:04 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Maxime Ripard <mripard@...nel.org>, Zack Rusin <zackr@...are.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Pekka Paalanen <pekka.paalanen@...labora.com>,
        Bilal Elmoussaoui <belmouss@...hat.com>,
        Simon Ser <contact@...rsion.fr>,
        Erico Nunes <nunes.erico@...il.com>,
        Sima Vetter <daniel.vetter@...ll.ch>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        dri-devel@...ts.freedesktop.org, linux-doc@...r.kernel.org
Subject: [PATCH v4 5/5] drm/todo: Add entry about implementing buffer age for damage tracking

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@...rsion.fr>
Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
Reviewed-by: Simon Ser <contact@...rsion.fr>
Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
Reviewed-by: Zack Rusin <zackr@...are.com>
Acked-by: Sima Vetter <daniel.vetter@...ll.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@...hat.com>
+
+Level: Advanced
+
 Outside DRM
 ===========
 
-- 
2.41.0