[PATCH v2 1/2] drm/dumb-buffers: reference the ioctl interface for its constraints

[Icenowy Zheng]

The current design of the DRM_IOCTL_MODE_CREATE_DUMB interface can only
promise linear RGB buffers to be properly working.

Add a reference to the interface from the document snippet for dumb
objects (which is included by drm-kms.rst document and will end up in
the built kernel documentation).

Signed-off-by: Icenowy Zheng <zhengxingda@xxxxxxxxxxx>
Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
Changes in v2:
- Reword modifier to framebuffer layout.
- Added Thomas's R-b.

 drivers/gpu/drm/drm_dumb_buffers.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dumb_buffers.c b/drivers/gpu/drm/drm_dumb_buffers.c
index e2b62e5fb891b..4538517a8cdcc 100644
--- a/drivers/gpu/drm/drm_dumb_buffers.c
+++ b/drivers/gpu/drm/drm_dumb_buffers.c
@@ -57,7 +57,10 @@
  *
  * Note that dumb objects may not be used for gpu acceleration, as has been
  * attempted on some ARM embedded platforms. Such drivers really must have
- * a hardware-specific ioctl to allocate suitable buffer objects.
+ * a hardware-specific ioctl to allocate suitable buffer objects. The current
+ * userspace API also includes some constraints on the pixel format and
+ * framebuffer layout to be used with buffers backed by dumb objects, see
+ * &struct drm_mode_create_dumb for more details.
  */
 
 static int drm_mode_align_dumb(struct drm_mode_create_dumb *args,
-- 
2.52.0