5 files changed, 15 insertions, 10 deletions
diff --git a/src/mesa/drivers/dri/r300/r300_cmdbuf.c b/src/mesa/drivers/dri/r300/r300_cmdbuf.c
index 203c108012..f781c53328 100644
--- a/src/mesa/drivers/dri/r300/r300_cmdbuf.c
+++ b/src/mesa/drivers/dri/r300/r300_cmdbuf.c
@@ -319,8 +319,8 @@ void r300InitCmdBuf(r300ContextPtr r300)
 	r300->hw.unk21DC.cmd[0] = cmdpacket0(0x21DC, 1);
 
 	if (has_tcl) {
-		ALLOC_STATE(unk221C, always, 2, 0);
-		r300->hw.unk221C.cmd[0] = cmdpacket0(R300_VAP_UNKNOWN_221C, 1);
+		ALLOC_STATE(vap_clip_cntl, always, 2, 0);
+		r300->hw.vap_clip_cntl.cmd[0] = cmdpacket0(R300_VAP_CLIP_CNTL, 1);
 		ALLOC_STATE(vap_clip, always, 5, 0);
 		r300->hw.vap_clip.cmd[0] = cmdpacket0(R300_VAP_CLIP_X_0, 4);
 		ALLOC_STATE(unk2288, always, 2, 0);
diff --git a/src/mesa/drivers/dri/r300/r300_context.h b/src/mesa/drivers/dri/r300/r300_context.h
index f853d08057..795cd4d98d 100644
--- a/src/mesa/drivers/dri/r300/r300_context.h
+++ b/src/mesa/drivers/dri/r300/r300_context.h
@@ -458,7 +458,7 @@ struct r300_hw_state {
 	struct r300_state_atom vir[2];	/* vap input route (2150/21E0) */
 	struct r300_state_atom vic;	/* vap input control (2180) */
 	struct r300_state_atom unk21DC;	/* (21DC) */
-	struct r300_state_atom unk221C;	/* (221C) */
+	struct r300_state_atom vap_clip_cntl;
 	struct r300_state_atom vap_clip;
 	struct r300_state_atom unk2288;	/* (2288) */
 	struct r300_state_atom pvs;	/* pvs_cntl (22D0) */
diff --git a/src/mesa/drivers/dri/r300/r300_ioctl.c b/src/mesa/drivers/dri/r300/r300_ioctl.c
index ceb2e2d432..d4914c9cb6 100644
--- a/src/mesa/drivers/dri/r300/r300_ioctl.c
+++ b/src/mesa/drivers/dri/r300/r300_ioctl.c
@@ -261,8 +261,8 @@ static void r300EmitClearState(GLcontext * ctx)
 	e32(0x0);
 
 	if (has_tcl) {
-	    R300_STATECHANGE(r300, unk221C);
-	    reg_start(R300_VAP_UNKNOWN_221C, 0);
+	    R300_STATECHANGE(r300, vap_clip_cntl);
+	    reg_start(R300_VAP_CLIP_CNTL, 0);
 	    e32(R300_221C_CLEAR);
         }
 
diff --git a/src/mesa/drivers/dri/r300/r300_reg.h b/src/mesa/drivers/dri/r300/r300_reg.h
index 2e998bc5fe..6ca4257cbd 100644
--- a/src/mesa/drivers/dri/r300/r300_reg.h
+++ b/src/mesa/drivers/dri/r300/r300_reg.h
@@ -326,8 +326,13 @@ USE OR OTHER DEALINGS IN THE SOFTWARE.
 /* I do not know the purpose of this register. However, I do know that
  * it is set to 221C_CLEAR for clear operations and to 221C_NORMAL
  * for normal rendering.
+ *
+ * 2007-11-05: This register is the user clip plane control register, but there
+ * also seems to be a rendering mode control; the NORMAL/CLEAR defines.
+ *
+ * See bug #9871. http://bugs.freedesktop.org/attachment.cgi?id=10672&action=view
  */
-#define R300_VAP_UNKNOWN_221C               0x221C
+#define R300_VAP_CLIP_CNTL                       0x221C
 #       define R300_221C_NORMAL                  0x00000000
 #       define R300_221C_CLEAR                   0x0001C000
 #define R300_VAP_UCP_ENABLE_0 (1 << 0)
diff --git a/src/mesa/drivers/dri/r300/r300_state.c b/src/mesa/drivers/dri/r300/r300_state.c
index cd8bcdb47d..9491f98b47 100644
--- a/src/mesa/drivers/dri/r300/r300_state.c
+++ b/src/mesa/drivers/dri/r300/r300_state.c
@@ -1717,13 +1717,13 @@ static void r300Enable(GLcontext * ctx, GLenum cap, GLboolean state)
 			return;
 
 		p = cap-GL_CLIP_PLANE0;
-		R300_STATECHANGE( r300, unk221C );
+		R300_STATECHANGE( r300, vap_clip_cntl );
 		if (state) {
-			r300->hw.unk221C.cmd[1] |= (R300_VAP_UCP_ENABLE_0<<p);
+			r300->hw.vap_clip_cntl.cmd[1] |= (R300_VAP_UCP_ENABLE_0<<p);
 			r300ClipPlane( ctx, cap, NULL );
 		}
 		else {
-			r300->hw.unk221C.cmd[1] &= ~(R300_VAP_UCP_ENABLE_0<<p);
+			r300->hw.vap_clip_cntl.cmd[1] &= ~(R300_VAP_UCP_ENABLE_0<<p);
 		}
 		break;
 	case GL_DEPTH_TEST:
@@ -1842,7 +1842,7 @@ static void r300ResetHwState(r300ContextPtr r300)
 
 	/* XXX: Other families? */
 	if (has_tcl) {
-		r300->hw.unk221C.cmd[1] = R300_221C_NORMAL;
+		r300->hw.vap_clip_cntl.cmd[1] = R300_221C_NORMAL;
 
 		r300->hw.vap_clip.cmd[1] = r300PackFloat32(1.0); /* X */
 		r300->hw.vap_clip.cmd[2] = r300PackFloat32(1.0); /* X */