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-rw-r--r--drivers/gpu/drm/drm_blend.c8
-rw-r--r--include/drm/drm_plane.h9
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.