mesa: add format-helper for rgtc

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Acked-by: Eric Engestrom <eric@igalia.com>
Tested-by: Eric Engestrom <eric@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18248>

src/mesa/main/formats.c

@@ -655,6 +655,16 @@ _mesa_is_format_s3tc(mesa_format format)
 }
 
 
+/**
+ * Return TRUE if format is an RGTC compressed format.
+ */
+bool
+_mesa_is_format_rgtc(mesa_format format)
+{
+   return _mesa_get_format_layout(format) == MESA_FORMAT_LAYOUT_RGTC;
+}
+
+
 /**
  * Return TRUE if format is an BPTC compressed format.
  */

src/mesa/main/formats.h

@@ -698,6 +698,9 @@ _mesa_is_format_astc_2d(mesa_format format);
 bool
 _mesa_is_format_s3tc(mesa_format format);
 
+bool
+_mesa_is_format_rgtc(mesa_format format);
+
 bool
 _mesa_is_format_bptc(mesa_format format);