Re: [PATCH v7 4/6] drm: Refuse to async flip with atomic prop changes

[Simon Ser]

On Monday, October 23rd, 2023 at 10:42, Michel Dänzer <michel.daenzer@xxxxxxxxxxx> wrote:

> On 10/23/23 10:27, Simon Ser wrote:
> 
> > On Sunday, October 22nd, 2023 at 12:12, Michel Dänzer michel.daenzer@xxxxxxxxxxx wrote:
> > 
> > > On 10/17/23 14:16, Simon Ser wrote:
> > > 
> > > > After discussing with André it seems like we missed a plane type check
> > > > here. We need to make sure FB_ID changes are only allowed on primary
> > > > planes.
> > > 
> > > Can you elaborate why that's needed?
> > 
> > Current drivers are in general not prepared to perform async page-flips
> > on planes other than primary. For instance I don't think i915 has logic
> > to perform async page-flip on an overlay plane FB_ID change.
> 
> 
> That should be handled in the driver's atomic_check then?
> 
> Async flips of overlay planes would be useful e.g. for presenting a windowed application with tearing, while the rest of the desktop is tear-free.

Yes, that would be useful, but requires more work. Small steps: first
expose what the legacy uAPI can do in atomic, then later extend that in
some drivers.