Commit 42770cbf authored by Daniel Vetter's avatar Daniel Vetter

drm/blend: Define the direction of Z position values

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: default avatarPekka Paalanen <pekka.paalanen@collabora.com>
Cc: Pekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-by: default avatarPekka Paalanen <pekka.paalanen@collabora.com>
Cc: Ilia Mirkin <imirkin@alum.mit.edu>
Acked-by: default avatarIlia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: default avatarDaniel Stone <daniels@collabora.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190906144459.16025-1-daniel.vetter@ffwll.ch
parent c7581a41
......@@ -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().
......
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