Bug 97379

Summary: Wayland buffer synchronisation is undocumented
Product: Wayland Reporter: Tomek Bury <tomek.bury>
Component: waylandAssignee: Wayland bug list <wayland-bugs>
Status: RESOLVED MOVED QA Contact:
Severity: normal    
Priority: medium CC: dancol, daniel
Version: unspecified   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:

Description Tomek Bury 2016-08-17 10:25:29 UTC 
Wayland silently assumes implicit cross-process fencing on shared buffers. This assumption goes beyond EGL/GLES core spec and any Wayland extension but is not specified anywhere.

It would be much easier for driver or compositor authors to have very clearly spelled out requirements and guarantrees, especially around shared resources.

Current mechanism, as far as I understand it, looks rather weird: EGL is responsible for handing a buffer over from client to compositor, but EGL is not involved (and completely unaware) of handing buffer back to client.

As it's pretty much guaranteed that drivers and compositors will come from completely unrelated parties and can be mixed and matched, implicit assumptions in this area must lead to interoperability issues and a lot of confusion as to what is valid or invalid behaviour.

Could you clearly document responsibilities and guarantees of both driver and compositor in buffer management, including CPU-GPU synchronisation please?
Comment 1 Tomek Bury 2016-08-17 10:27:05 UTC 
See bug 97353 for initial discussion.
Comment 2 Daniel Stone 2016-08-17 14:03:32 UTC 
This is something I expect we'll discuss a lot more at XDC in Helsinki, at the end of September.
Comment 3 Daniel Stone 2016-08-17 14:04:15 UTC 
(In reply to Daniel Stone from comment #2)
> This is something I expect we'll discuss a lot more at XDC in Helsinki, at
> the end of September.

Argh, wrong bug - that was meant for #97380. This one is not blocked on XDC.
Comment 4 Daniel Stone 2018-06-04 06:57:06 UTC 
I submitted a protocol implementing this, as well as support for Mutter and Mesa:
https://lists.freedesktop.org/archives/wayland-devel/2017-September/035080.html
Comment 5 Daniel Stone 2018-06-04 06:58:01 UTC 
Wrong bug again, sorry Tomek. :\
Comment 6 GitLab Migration User 2018-06-08 23:49:29 UTC 
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