[Mesa-dev] [PATCH] st/mesa: Override blend factors involving alpha if it doesn't exist.

Kenneth Graunke kenneth at whitecape.org
Tue Aug 28 05:36:39 UTC 2018

On Monday, August 27, 2018 6:18:21 PM PDT Marek Olšák wrote:
> On Mon, Aug 27, 2018 at 5:55 PM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> > On Monday, August 27, 2018 11:05:19 AM PDT Marek Olšák wrote:
> >> Yeah, this will be more complicated because it's per RT.
> >>
> >> I suggest adding a PIPE_CAP for the hw capability to force DST_ALPHA
> >> to 0, and applying this workaround only if the PIPE_CAP is 0.
> >>
> >> Marek
> >
> > I was thinking of applying this hack based on PIPE_CAP_INDEP_BLEND_FUNC.
> >
> > Ilia seemed to think that it was unsupportable on older Nouveau (without
> > independent alpha blending), but harmless either way on modern Nouveau.
> > (Supposedly Freedreno does this workaround in the driver...)
> >
> > Would you prefer not to have this triggered?
> Yes. I think it would be unnecessary overhead for us.
> Marek

Okay, cool, thanks for the feedback.  Let's shelve this for now.

I'm thinking of reworking how I handle RGBX -> RGBA stuff anyway,
and may need to handle it in the driver in the end.  I'll see how
things look and either handle it myself or come up with a version
of this patch which makes the hack optional.
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