diff mbox series

drm/docs: Explicitly document default CRTC background behavior

Message ID 20230103152738.1213785-1-sean@poorly.run (mailing list archive)
State New, archived
Headers show
Series drm/docs: Explicitly document default CRTC background behavior | expand

Commit Message

Sean Paul Jan. 3, 2023, 3:27 p.m. UTC 
From: Sean Paul <seanpaul@chromium.org>

Add a paragraph explaining that the default behavior for areas which
are not covered by planes or where planes are blending with the CRTC
background, is black.

This is alluded to in the "pixel blend mode" property docs, but not
called out explicitly.

Signed-off-by: Sean Paul <seanpaul@chromium.org>
---
 drivers/gpu/drm/drm_plane.c | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Simon Ser Jan. 3, 2023, 6:32 p.m. UTC | #1 
Nice!

Reviewed-by: Simon Ser <contact@emersion.fr>
Sean Paul Jan. 4, 2023, 4:15 p.m. UTC | #2 
On Tue, Jan 03, 2023 at 06:32:58PM +0000, Simon Ser wrote:
> Nice!
> 
> Reviewed-by: Simon Ser <contact@emersion.fr>

Thanks for the review, Simon! Applied to drm-misc-next.
diff mbox series

Patch

diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
index 33357629a7f5..24e7998d1731 100644
--- a/drivers/gpu/drm/drm_plane.c
+++ b/drivers/gpu/drm/drm_plane.c
@@ -46,6 +46,11 @@ 
  * properties that specify how the pixels are positioned and blended, like
  * rotation or Z-position. All these properties are stored in &drm_plane_state.
  *
+ * Unless explicitly specified (via CRTC property or otherwise), the active area
+ * of a CRTC will be black by default. This means portions of the active area
+ * which are not covered by a plane will be black, and alpha blending of any
+ * planes with the CRTC background will blend with black at the lowest zpos.
+ *
  * To create a plane, a KMS drivers allocates and zeroes an instances of
  * &struct drm_plane (possibly as part of a larger structure) and registers it
  * with a call to drm_universal_plane_init().