[Mesa-dev] [PATCH] mesa: Match MESA_FORMAT_B5G6R5 for a shallow pixel format of GL_RGB

[Chris Wilson]

On Wed, Sep 09, 2015 at 11:11:59AM +0200, Erik Faye-Lund wrote:
> On Thu, Sep 3, 2015 at 6:05 PM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > If the user supplies a pixel format of GL_RGB + GL_UNSIGNED_SHORT_5_6_5
> > and specifies a generic unsized GL_RGB internal format, match that to a
> > texture format of MESA_FORMAT_B5G6R5 if supported by the hardware.
> >
> > Noticed while playing with mesa-demos/teximage:
> >
> >   TexImage(RGB/565 256 x 256): 79.8 images/sec, 10.0 MB/sec
> >   TexSubImage(RGB/565 256 x 256): 3804.9 images/sec, 475.6 MB/sec
> >   GetTexImage(RGB/565 256 x 256): 99.5 images/sec, 12.4 MB/sec
> >
> > becomes
> >
> >   TexImage(RGB/565 256 x 256): 3439.1 images/sec, 429.9 MB/sec
> >   TexSubImage(RGB/565 256 x 256): 3744.1 images/sec, 468.0 MB/sec
> >   GetTexImage(RGB/565 256 x 256): 4713.5 images/sec, 589.2 MB/sec
> >
> > on a puny Baytrail which is still far from what it is capable of. The
> > reason for the disparity is that the teximage demo uses a busy texture
> > which is performs an accelerated pixel conversion from the user's B5G6R5
> > into the native X8B8G8R8. After the patch, no conversion is required
> > allowing use of the blitter and memcpy fast paths.
> >
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >  src/mesa/main/texformat.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/src/mesa/main/texformat.c b/src/mesa/main/texformat.c
> > index fd9f335..866c7b3 100644
> > --- a/src/mesa/main/texformat.c
> > +++ b/src/mesa/main/texformat.c
> > @@ -114,6 +114,8 @@ _mesa_choose_tex_format(struct gl_context *ctx, GLenum target,
> >     case GL_RGB:
> >        if (type == GL_UNSIGNED_INT_2_10_10_10_REV) {
> >           RETURN_IF_SUPPORTED(MESA_FORMAT_B10G10R10A2_UNORM);
> > +      } else if (type == GL_UNSIGNED_SHORT_5_6_5) {
> > +         RETURN_IF_SUPPORTED(MESA_FORMAT_B5G6R5_UNORM);
> 
> Shouldn't this be MESA_FORMAT_R5G6B5_UNORM? AFAICT, the reason for
> using BGR above, is the _REV suffix on the type...

No, it's the first line that's "wrong" since the B10G10R10A2 matches
GL_BGRA + GL_UNSIGNED_INT_2_10_10_10_REV, GL_RGB implies that the
incoming data only has 3 channels (no alpha at all).

i965 know how to do B5G6R5 and not R5G6B5, but for completeness we could
also add RETURN_IF_SUPPORTED(MESA_FORMAT_R5G6B5_UNORM);
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre