Add comments explaining a couple "mystery" bits.

diff --git a/src/mesa/drivers/dri/savage/savage_3d_reg.h b/src/mesa/drivers/dri/savage/savage_3d_reg.h
index b7d1c3960a39c5e9f3c64ff6b1dd35bf2e65f924..bc81d732967862f01cc1fd326b49c6bc623bab31 100644 (file)
--- a/src/mesa/drivers/dri/savage/savage_3d_reg.h
+++ b/src/mesa/drivers/dri/savage/savage_3d_reg.h
@@ -290,6 +290,14 @@ typedef union
     struct
     {
         unsigned dstAlphaMode        :  3;
+
+       /**
+        * This bit enables \c GL_FUNC_SUBTRACT.  Like most DirectX oriented
+        * hardware, there's no way to do \c GL_FUNC_REVERSE_SUBTRACT.
+        * 
+        * \todo
+        * Add support for \c GL_FUNC_SUBTRACT!
+        */
         unsigned dstMinusSrc         :  1;
         unsigned srcAlphaMode        :  3;
         unsigned binaryFinalAlpha    :  1;
@@ -327,7 +335,11 @@ typedef union
         unsigned texBlendCtrl      : 3;
         unsigned flushPdDestWrites : 1;
         unsigned flushPdZbufWrites : 1;
-       /* havn't found an equivalent for Savage4. Utah-driver sets it to 0. */
+
+       /**
+        * Disable perspective correct interpolation for vertex color, vertex
+        * fog, and vertex alpha.  For OpenGL, this should \b always be zero.
+        */
         unsigned interpMode        : 1;
     }ni;
     u_int32_t ui;