From 51342cc021400841b461cc579f76db24cdb482fc Mon Sep 17 00:00:00 2001 From: Sean Paul Date: Tue, 3 Jan 2023 15:27:38 +0000 Subject: [PATCH] drm/docs: Explicitly document default CRTC background behavior 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. Reviewed-by: Simon Ser Signed-off-by: Sean Paul Link: https://patchwork.freedesktop.org/patch/msgid/20230103152738.1213785-1-sean@poorly.run --- drivers/gpu/drm/drm_plane.c | 5 +++++ 1 file changed, 5 insertions(+) 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().