On Sun, 29 Sep 2019 20:30:44 +0000 Simon Ser <contact@xxxxxxxxxxx> wrote: > Hi, > > > On Mon, Sep 23, 2019 at 12:39:20PM +0000, Simon Ser 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. > > > > Some Arm's usage cases about two planes with same zpos. > > > > - "Smart layer" > > which can accepts 4 different fbs with different src/display rect, > > but this smart layer has one restriction: > > > > 4 display rects must have no overlaps in V direction > > (A optimization for android window like Toolbar/Navigation bar) > > > > So when map this Smart-layer to drm world, it might be 4 different > > drm-planes, but with same zorder to indicate that these 4 planes are > > smart-laye planes. > > > > - "VR-Layer" > > One VR-layer comprises two different viewports which can be configured > > with totoally different fbs, src/display rect. > > we use two differernt drm-planes to drive on HW "VR-Layer", and these > > two drm-planes must be configured with same zpos. > > Thanks a lot for your feedback James, that's exactly what I was looking for. > Both of these use-cases make sense to me. > > I think user-space should be prepared to handle identical immutable zpos values. > Pekka and Daniel, thoughts? Hi, given those explained use cases, sure, I agree. > In any case, this doesn't change the patch itself. Probably something worth > mentionning in the commit message. Yes, recording these use cases would be very nice. Thanks, pq
Attachment:
pgpZHQgiaftaA.pgp
Description: OpenPGP digital signature
_______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
