util: Distinguish between the different compression formats.

In particular, all current uses of util_format_is_compressed() actually
mean s3tc.

src/gallium/auxiliary/util/u_format.csv

@@ -110,14 +110,18 @@ PIPE_FORMAT_UYVY                 , subsampled, 2, 1, x32 ,     ,     ,     , xyz
 PIPE_FORMAT_YUYV                 , subsampled, 2, 1, x32 ,     ,     ,     , xyz1, yuv
 
 # Compressed formats
-PIPE_FORMAT_DXT1_RGB              , compressed, 4, 4, x64 ,     ,     ,     , xyz1, rgb
-PIPE_FORMAT_DXT1_RGBA             , compressed, 4, 4, x64 ,     ,     ,     , xyzw, rgb
-PIPE_FORMAT_DXT3_RGBA             , compressed, 4, 4, x128,     ,     ,     , xyzw, rgb
-PIPE_FORMAT_DXT5_RGBA             , compressed, 4, 4, x128,     ,     ,     , xyzw, rgb
-PIPE_FORMAT_DXT1_SRGB             , compressed, 4, 4, x64 ,     ,     ,     , xyz1, srgb
-PIPE_FORMAT_DXT1_SRGBA            , compressed, 4, 4, x64 ,     ,     ,     , xyzw, srgb
-PIPE_FORMAT_DXT3_SRGBA            , compressed, 4, 4, x128,     ,     ,     , xyzw, srgb
-PIPE_FORMAT_DXT5_SRGBA            , compressed, 4, 4, x128,     ,     ,     , xyzw, srgb
+# - http://en.wikipedia.org/wiki/S3_Texture_Compression
+# - http://www.opengl.org/registry/specs/EXT/texture_compression_s3tc.txt
+# - http://www.opengl.org/registry/specs/ARB/texture_compression_rgtc.txt
+# - http://msdn.microsoft.com/en-us/library/bb694531.aspx
+PIPE_FORMAT_DXT1_RGB              , s3tc, 4, 4, x64 ,     ,     ,     , xyz1, rgb
+PIPE_FORMAT_DXT1_RGBA             , s3tc, 4, 4, x64 ,     ,     ,     , xyzw, rgb
+PIPE_FORMAT_DXT3_RGBA             , s3tc, 4, 4, x128,     ,     ,     , xyzw, rgb
+PIPE_FORMAT_DXT5_RGBA             , s3tc, 4, 4, x128,     ,     ,     , xyzw, rgb
+PIPE_FORMAT_DXT1_SRGB             , s3tc, 4, 4, x64 ,     ,     ,     , xyz1, srgb
+PIPE_FORMAT_DXT1_SRGBA            , s3tc, 4, 4, x64 ,     ,     ,     , xyzw, srgb
+PIPE_FORMAT_DXT3_SRGBA            , s3tc, 4, 4, x128,     ,     ,     , xyzw, srgb
+PIPE_FORMAT_DXT5_SRGBA            , s3tc, 4, 4, x128,     ,     ,     , xyzw, srgb
 
 # Straightforward D3D10-like formats (also used for 
 # vertex buffer element description)

src/gallium/auxiliary/util/u_format.h

@@ -56,15 +56,23 @@ enum util_format_layout {
     *
     * This is for formats like YV12 where there is less than one sample per
     * pixel.
-    *
-    * XXX: This could actually b
     */
    UTIL_FORMAT_LAYOUT_SUBSAMPLED = 3,
 
    /**
-    * An unspecified compression algorithm.
+    * S3 Texture Compression formats.
+    */
+   UTIL_FORMAT_LAYOUT_S3TC = 4,
+
+   /**
+    * Red-Green Texture Compression formats.
+    */
+   UTIL_FORMAT_LAYOUT_RGTC = 5,
+
+   /**
+    * Everything else that doesn't fit in any of the above layouts.
     */
-   UTIL_FORMAT_LAYOUT_COMPRESSED = 4
+   UTIL_FORMAT_LAYOUT_OTHER = 6
 };
 
 
@@ -210,7 +218,7 @@ util_format_name(enum pipe_format format)
 }
 
 static INLINE boolean 
-util_format_is_compressed(enum pipe_format format)
+util_format_is_s3tc(enum pipe_format format)
 {
    const struct util_format_description *desc = util_format_description(format);
 
@@ -219,7 +227,7 @@ util_format_is_compressed(enum pipe_format format)
       return FALSE;
    }
 
-   return desc->layout == UTIL_FORMAT_LAYOUT_COMPRESSED ? TRUE : FALSE;
+   return desc->layout == UTIL_FORMAT_LAYOUT_S3TC ? TRUE : FALSE;
 }
 
 static INLINE boolean