reduced swizzle comment

diff --git a/src/mesa/tnl/t_vb_arbprogram.h b/src/mesa/tnl/t_vb_arbprogram.h
index 92ae46113f18a8fa500ee355a1ec034914f09bba..27f878c4e987afe61c2c3a6486c6205430e7368c 100644 (file)
--- a/src/mesa/tnl/t_vb_arbprogram.h
+++ b/src/mesa/tnl/t_vb_arbprogram.h
@@ -112,6 +112,10 @@ union instruction {
    GLuint dword;
 };
 
+
+/**
+ * Reduced swizzle is a 2-bit field; only X/Y/Z/W are allowed, not 0/1.
+ */
 #define RSW_NOOP ((0<<0) | (1<<2) | (2<<4) | (3<<6))
 #define GET_RSW(swz, idx)      (((swz) >> ((idx)*2)) & 0x3)