Mesa (master): iris: Update comment about 3-component formats and buffer textures

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Module: Mesa
Branch: master
Commit: 016c19bc895ffaa85954aa864a9de969261f9922
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=016c19bc895ffaa85954aa864a9de969261f9922

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Mon Oct  7 16:03:14 2019 -0700

iris: Update comment about 3-component formats and buffer textures

You can't render to PIPE_BUFFER so there's no reason to prefer RGBX.
PBO upload would like to use proper RGB textures as source data.

---

 src/gallium/drivers/iris/iris_formats.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/gallium/drivers/iris/iris_formats.c b/src/gallium/drivers/iris/iris_formats.c
index 9daef41407a..94b89be84e0 100644
--- a/src/gallium/drivers/iris/iris_formats.c
+++ b/src/gallium/drivers/iris/iris_formats.c
@@ -479,12 +479,14 @@ iris_is_format_supported(struct pipe_screen *pscreen,
       if (!is_integer)
          supported &= isl_format_supports_filtering(devinfo, format);
 
-      /* Don't advertise 3-component RGB formats.  This ensures that they
-       * are renderable from an API perspective since the state tracker will
-       * fall back to RGBA or RGBX, which are renderable.  We want to render
-       * internally for copies and blits, even if the application doesn't.
+      /* Don't advertise 3-component RGB formats for non-buffer textures.
+       * This ensures that they are renderable from an API perspective since
+       * the state tracker will fall back to RGBA or RGBX, which are
+       * renderable.  We want to render internally for copies and blits,
+       * even if the application doesn't.
        *
-       * We do need to advertise 32-bit RGB for texture buffers though.
+       * Buffer textures don't need to be renderable, so we support real RGB.
+       * This is useful for PBO upload, and 32-bit RGB support is mandatory.
        */
       if (target != PIPE_BUFFER)
          supported &= fmtl->bpb != 24 && fmtl->bpb != 48 && fmtl->bpb != 96;