[Mesa-dev] [PATCH 1/5] i965/surface_formats: Don't advertise 8 or 16-bit RGB formats

[Nanley Chery]

On Thu, Aug 11, 2016 at 04:23:51PM -0700, Jason Ekstrand wrote:
> On Thu, Aug 11, 2016 at 11:26 AM, Nanley Chery <nanleychery at gmail.com>
> wrote:
> 
> > On Tue, Jul 26, 2016 at 10:04:22PM -0700, Jason Ekstrand wrote:
> > > We have implicitly been not advertising these formats since we had them
> > > turned off in the format capabilities table.  We are about to update that
> > > table and this prevents a change in behavior.  The only change in
> > behavior
> > > created by this patch is that we no longer advertise support for
> > > R16G16B16_FLOAT which means that it's now renderable which seems like a
> > > bonus.  Maybe someday we'll want to change things to start supporting
> >
> > I don't understand this sentence. Assuming "renderable" means that we can
> > render to a texture with such a format, why does preventing the user from
> > creating an R16G16B16_FLOAT texture mean that it's now renderable?
> >
> 
> Because mesa will fall back to R16G16B16A16_FLOAT and fake RGB.  That
> format is renderable.
> 

Got it. Thanks for the clarification.

- Nanley

> 
> >
> > - Nanley
> >
> > > 16-bit RGB formats natively but, at the moment, there's no need.
> > > ---
> > >  src/mesa/drivers/dri/i965/brw_surface_formats.c | 10 ++++++++++
> > >  1 file changed, 10 insertions(+)
> > >
> > > diff --git a/src/mesa/drivers/dri/i965/brw_surface_formats.c
> > b/src/mesa/drivers/dri/i965/brw_surface_formats.c
> > > index 2543f4b..69d3bd4 100644
> > > --- a/src/mesa/drivers/dri/i965/brw_surface_formats.c
> > > +++ b/src/mesa/drivers/dri/i965/brw_surface_formats.c
> > > @@ -311,6 +311,16 @@ brw_init_surface_formats(struct brw_context *brw)
> > >        if (texture == 0 && format != MESA_FORMAT_RGBA_FLOAT32)
> > >        continue;
> > >
> > > +      /* Don't advertisel 8 and 16-bit RGB formats to core mesa.  This
> > ensures
> > > +       * that they are renderable from an API perspective since core
> > mesa will
> > > +       * fall back to RGBA or RGBX (we can't render to non-power-of-two
> > > +       * formats).  For 8-bit, formats, this also keeps us from hitting
> > some
> > > +       * nasty corners in intel_miptree_map_blit if you ever try to map
> > one.
> > > +       */
> > > +      int format_size = _mesa_get_format_bytes(format);
> > > +      if (format_size == 3 || format_size == 6)
> > > +         continue;
> > > +
> > >        if (isl_format_supports_sampling(devinfo, texture) &&
> > >            (isl_format_supports_filtering(devinfo, texture) ||
> > is_integer))
> > >        ctx->TextureFormatSupported[format] = true;
> > > --
> > > 2.5.0.400.gff86faf
> > >
> > > _______________________________________________
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> > > mesa-dev at lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
> >