[Mesa-dev] [PATCH] egl: dri2: Use present extension. (Was: Re: [RFC] egl: Add DRI3 support to the EGL backend.)

[Joonas Lahtinen]

This is still awaiting for comments.

I'd rather hear what are the desirable modifications than try guessing.

On ma, 2014-11-10 at 15:18 +0200, Joonas Lahtinen wrote:
> Hi,
> 
> On pe, 2014-11-07 at 17:40 -0800, Eric Anholt wrote:
> > Ian Romanick <idr at freedesktop.org> writes:
> > 
> > > On 11/06/2014 06:16 PM, Michel Dänzer wrote:
> > >> On 06.11.2014 19:18, Joonas Lahtinen wrote:
> > >>> On to, 2014-11-06 at 18:12 +0900, Michel Dänzer wrote:
> > >>>> On 05.11.2014 20:14, Joonas Lahtinen wrote:
> > >>>>>
> > >>>>> Modified not refer to DRI3, just uses the present extension to get rid
> > >>>>> of the excess buffer invalidations.
> > >>>>
> > >>>> AFAICT there's no fallback from your changes to the current behaviour if
> > >>>> the X server doesn't support the Present extension. There probably needs
> > >>>> to be such a fallback.
> > >>>
> > >>> It gets rid of such nasty hack (the intel_viewport one), that I thought
> > >>> there is no point making fallback. Because without this, the egl dri2
> > >>> backend is fundamentally broken anyway.
> > >> 
> > >> Well, AFAICT your code uses Present extension functionality
> > >> unconditionally, without checking that the X server supports Present. I
> > >> can't see how that could possibly work on an X server which doesn't
> > >> support Present, but I think it would be better to keep it working at
> > >> least as badly as it does now in that case. :)
> > >
> > > I was going to say pretty much the same thing.  Aren't there (non-Intel)
> > > drivers that don't do Present?  If I'm not mistaken, some parts of DRI3
> > > (not sure about Present) are even disabled in the Intel driver when SNA
> > > is in use... or at least that was the case at one point.
> > 
> > They actually get a fallback implementation if there's no driver
> > support, which would be sufficient for this code.
> > 
> > However, Present is too new for Mesa to be unconditionally relying on in
> > my opinion.
> 
> Based on above discussion, I would bring back the dynamic detection like
> in the original patch. But for present extension instead of DRI3.
> Technically it would be very much the same, different naming
> conventions. And also, re-use the USE_INVALIDATE extension instead of
> adding DRI3 extension.
> 
> Would that be an acceptable solution?
> 
> Regards, Joonas
> 
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