diff --git a/include/rtdef.h b/include/rtdef.h
index f2f1266de..37082f8a7 100644
--- a/include/rtdef.h
+++ b/include/rtdef.h
@@ -647,6 +647,13 @@ struct rt_device
 	void* private;
 };
 
+struct rt_device_blk_geometry
+{
+	rt_uint32_t sector_count;		/* count of sectors */
+	rt_uint32_t bytes_per_sector;	/* number of bytes per sector */
+	rt_uint32_t block_size;			/* size to erase one block */
+};
+
 /*@}*/
 #endif