diff --git a/gbm.h b/gbm.h
index 9992db3..91b021a 100644
--- a/gbm.h
+++ b/gbm.h
@@ -84,6 +84,13 @@
 /* color index */
 #define GBM_FORMAT_C8		__gbm_fourcc_code('C', '8', ' ', ' ') /* [7:0] C */
 
+/* 8 bpp Red */
+#define GBM_FORMAT_R8		__gbm_fourcc_code('R', '8', ' ', ' ') /* [7:0] R */
+
+/* 16 bpp RG */
+#define GBM_FORMAT_RG88		__gbm_fourcc_code('R', 'G', '8', '8') /* [15:0] R:G 8:8 little endian */
+#define GBM_FORMAT_GR88		__gbm_fourcc_code('G', 'R', '8', '8') /* [15:0] G:R 8:8 little endian */
+
 /* 8 bpp RGB */
 #define GBM_FORMAT_RGB332	__gbm_fourcc_code('R', 'G', 'B', '8') /* [7:0] R:G:B 3:3:2 */
 #define GBM_FORMAT_BGR233	__gbm_fourcc_code('B', 'G', 'R', '8') /* [7:0] B:G:R 2:3:3 */