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path: root/drivers/gpu/drm/drm_plane.c
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Diffstat (limited to 'drivers/gpu/drm/drm_plane.c')
-rw-r--r--drivers/gpu/drm/drm_plane.c5
1 files changed, 5 insertions, 0 deletions
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().