[PATCH] drm: two planes with the same zpos have undefined ordering

[Pekka Paalanen]

On Thu, 19 Sep 2019 10:18:04 +0200
Daniel Vetter <daniel.vetter at ffwll.ch> wrote:

> On Thu, Sep 19, 2019 at 9:18 AM Pekka Paalanen <ppaalanen at gmail.com> wrote:
> >

...

> > Right, and we are suffering from that confusion already. Should
> > userspace use ID order if zpos property is not there or not? I have no
> > idea.  
> 
> Nope. I think the only options for this case are:
> - file bug against upstream driver so they add zpos
> - you magically know how planes work on that hw
> - you don't overlap planes at all
> - cursor is above primary, that much we can guarantee
> 
> Yes it's kinda uapi fail we didn't add zpos from the start :-/

Good. Weston does the last two. The confusion did not last long
enough to let us add code using the object ID to infer stacking order.

Although, Weston does have the assumption that overlays are in unknown
order between primary and cursor, which now seems false.


Thanks,
pq
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 833 bytes
Desc: OpenPGP digital signature
URL: <https://lists.freedesktop.org/archives/dri-devel/attachments/20190919/f9e5054d/attachment.sig>