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

[Jason Ekstrand]

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.


>
> - 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
> >
> > _______________________________________________
> > mesa-dev mailing list
> > mesa-dev at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
>
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