diff options
| -rw-r--r-- | drivers/gpu/drm/drm_blend.c | 8 | ||||
| -rw-r--r-- | include/drm/drm_plane.h | 9 |
2 files changed, 9 insertions, 8 deletions
diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c index d02709dd2d4a..121481f6aa71 100644 --- a/drivers/gpu/drm/drm_blend.c +++ b/drivers/gpu/drm/drm_blend.c @@ -132,10 +132,10 @@ * planes. Without this property the primary plane is always below the cursor * plane, and ordering between all other planes is undefined. The positive * Z axis points towards the user, i.e. planes with lower Z position values - * are underneath planes with higher Z position values. Note that the Z - * position value can also be immutable, to inform userspace about the - * hard-coded stacking of overlay planes, see - * drm_plane_create_zpos_immutable_property(). + * are underneath planes with higher Z position values. Two planes with the + * same Z position value have undefined ordering. Note that the Z position + * value can also be immutable, to inform userspace about the hard-coded + * stacking of planes, see drm_plane_create_zpos_immutable_property(). * * pixel blend mode: * Pixel blend mode is set up with drm_plane_create_blend_mode_property(). diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h index cd5903ad33f7..328773690851 100644 --- a/include/drm/drm_plane.h +++ b/include/drm/drm_plane.h @@ -140,10 +140,11 @@ struct drm_plane_state { * @zpos: * Priority of the given plane on crtc (optional). * - * Note that multiple active planes on the same crtc can have an - * identical zpos value. The rule to solving the conflict is to compare - * the plane object IDs; the plane with a higher ID must be stacked on - * top of a plane with a lower ID. + * User-space may set mutable zpos properties so that multiple active + * planes on the same CRTC have identical zpos values. This is a + * user-space bug, but drivers can solve the conflict by comparing the + * plane object IDs; the plane with a higher ID is stacked on top of a + * plane with a lower ID. * * See drm_plane_create_zpos_property() and * drm_plane_create_zpos_immutable_property() for more details. |