On Tuesday, September 10, 2019 1:38 PM, Pekka Paalanen <ppaalanen@xxxxxxxxx> wrote: > On Tue, 10 Sep 2019 10:09:55 +0000 > Simon Ser contact@xxxxxxxxxxx wrote: > > > Currently the property docs don't specify whether it's okay for two planes to > > have the same zpos value and what user-space should expect in this case. > > The rule mentionned in the past was to disambiguate with object IDs. However > > some drivers break this rule (that's why the ordering is documented as > > unspecified in case the zpos property is missing). Additionally it doesn't > > really make sense for a driver to user identical zpos values if it knows their > > relative position: the driver can just pick different values instead. > > So two solutions would make sense: either disallow completely identical zpos > > values for two different planes, either make the ordering unspecified. To allow > > drivers that don't know the relative ordering between two planes to still > > expose the zpos property, choose the latter solution. > > > > Signed-off-by: Simon Ser contact@xxxxxxxxxxx > > > > --------------------------------------------- > > > > Err, I'm sorry about the double-post. I sent this to intel-gfx by mistake. > > drivers/gpu/drm/drm_blend.c | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c > > index d02709dd2d4a..51bd5454e50a 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 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(). > > Hi, > > this seems to contradict what the docs say in another place: Except this comment is about drm_plane_state.zpos, an internal DRM property. This is not about the zpos property itself. The comment was introduced in v2 of [1], although the motivation for the change isn't documented. [1]: https://patchwork.freedesktop.org/series/13528/#rev2 > 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. > > See drm_plane_create_zpos_property() and > drm_plane_create_zpos_immutable_property() for more details. > > from https://01.org/linuxgraphics/gfx-docs/drm/gpu/drm-kms.html#plane-functions-reference > > Thanks, > pq _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
