[PATCH 3/3] drm/doc: Document legacy_cursor_update better

[Daniel Vetter]

It's the horror and shouldn't be used. Realized we're not clear on
this in a discussion with Rob about what msm is doing to better
support async commits.

v2: Refine existing todo item to include this (Thomas)

Cc: Sean Paul <sean at poorly.run>
Cc: Rob Clark <robdclark at gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: David Airlie <airlied at linux.ie>
Cc: Daniel Vetter <daniel at ffwll.ch>
---
 Documentation/gpu/todo.rst |  4 ++++
 include/drm/drm_atomic.h   | 12 +++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 700637e25ecd..6b224ef14455 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -105,6 +105,10 @@ converted over to the new infrastructure.
 One issue with the helpers is that they require that drivers handle completion
 events for atomic commits correctly. But fixing these bugs is good anyway.
 
+Somewhat related is the legacy_cursor_update hack, which should be replaced with
+the new atomic_async_check/commit functionality in the helpers in drivers that
+still look at that flag.
+
 Contact: Daniel Vetter, respective driver maintainers
 
 Level: Advanced
diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
index d07c851d255b..413fd0ca56a8 100644
--- a/include/drm/drm_atomic.h
+++ b/include/drm/drm_atomic.h
@@ -308,7 +308,6 @@ struct __drm_private_objs_state {
  * struct drm_atomic_state - the global state object for atomic updates
  * @ref: count of all references to this state (will not be freed until zero)
  * @dev: parent DRM device
- * @legacy_cursor_update: hint to enforce legacy cursor IOCTL semantics
  * @async_update: hint for asynchronous plane update
  * @planes: pointer to array of structures with per-plane data
  * @crtcs: pointer to array of CRTC pointers
@@ -336,6 +335,17 @@ struct drm_atomic_state {
 	 * drm_atomic_crtc_needs_modeset().
 	 */
 	bool allow_modeset : 1;
+	/**
+	 * @legacy_cursor_update:
+	 *
+	 * Hint to enforce legacy cursor IOCTL semantics.
+	 *
+	 * WARNING: This is thoroughly broken and pretty much impossible to
+	 * implement correctly. Drivers must ignore this and should instead
+	 * implement &drm_plane_helper_funcs.atomic_async_check and
+	 * &drm_plane_helper_funcs.atomic_async_commit hooks. New users of this
+	 * flag are not allowed.
+	 */
 	bool legacy_cursor_update : 1;
 	bool async_update : 1;
 	/**
-- 
2.28.0