From 42770cbf18aefbe632f34e4097c872f1dca0ec4a Mon Sep 17 00:00:00 2001
From: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Fri, 6 Sep 2019 16:44:59 +0200
Subject: drm/blend: Define the direction of Z position values
Git-commit: 42770cbf18aefbe632f34e4097c872f1dca0ec4a
Patch-mainline: v5.5-rc1
References: bsc#1152489
We forgot that.
Proof is the one igt testcase we have:
https://gitlab.freedesktop.org/drm/igt-gpu-tools/blob/master/tests/kms_atomic.c#L280
While at it also document that we have immutable zpos properties in
some cases.
Reported-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Cc: Pekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Cc: Ilia Mirkin <imirkin@alum.mit.edu>
Acked-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190906144459.16025-1-daniel.vetter@ffwll.ch
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
drivers/gpu/drm/drm_blend.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
index 37ac168fcb60..d02709dd2d4a 100644
--- a/drivers/gpu/drm/drm_blend.c
+++ b/drivers/gpu/drm/drm_blend.c
@@ -130,7 +130,12 @@
* Z position is set up with drm_plane_create_zpos_immutable_property() and
* drm_plane_create_zpos_property(). It controls the visibility of overlapping
* planes. Without this property the primary plane is always below the cursor
- * plane, and ordering between all other planes is undefined.
+ * 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().
*
* pixel blend mode:
* Pixel blend mode is set up with drm_plane_create_blend_mode_property().
--
2.28.0