[Mesa-dev] Disagreement between ChooseTextureFormat and QuerySamplesForFormat

[Marek Olšák]

On Sun, Jul 12, 2015 at 7:30 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> I asked this on IRC, but figured I'd get wider distribution for the
> question. The situation is that nv50 doesn't support RGBA32 MS8
> textures. However QuerySamplesForFormat will try its hardest to find
> supported sample counts, which means it'll go down st/mesa's fallback
> format list, which includes RGBA16, which can handle MS8 just fine. So
> the teximage.c code thinks that the # of samples is OK.
>
> However when it selects the teximage format, ChooseTextureFormat,
> which does not take a sample count, will return RGBA32 (which is
> supported for MS1, MS2, MS4 on nv50). When later it attempts to
> AllocTextureStorage, it will again attempt to do so using RGBA32 with
> MS8, which will fail. The core code handles this case (since texture
> storage allocation can happen for a wide variety of reasons), but I
> think this is suboptimal.
>
> Should ChooseTextureFormat take a sample count? This would allow the
> driver to provide the "correct" TexFormat for that format / sample
> count combo.

Yes. If your hardware has such limitations, ChooseTextureFormat needs
to be updated to reflect that.

Marek