diff --git a/drivers/mmc/mmc_block.c b/drivers/mmc/mmc_block.c
index b5b4a7b..d4eee99 100644
--- a/drivers/mmc/mmc_block.c
+++ b/drivers/mmc/mmc_block.c
@@ -383,7 +383,10 @@
 	struct mmc_blk_data *md;
 	int err;
 
-	if (card->csd.cmdclass & ~0x1ff)
+	/*
+	 * Check that the card supports the command class(es) we need.
+	 */
+	if (!(card->csd.cmdclass & CCC_BLOCK_READ))
 		return -ENODEV;
 
 	if (card->csd.read_blkbits < 9) {
diff --git a/include/linux/mmc/protocol.h b/include/linux/mmc/protocol.h
index 7b904c5..8963428 100644
--- a/include/linux/mmc/protocol.h
+++ b/include/linux/mmc/protocol.h
@@ -195,6 +195,33 @@
 #define MMC_VDD_35_36	0x00800000	/* VDD voltage 3.5 ~ 3.6 */
 #define MMC_CARD_BUSY	0x80000000	/* Card Power up status bit */
 
+/*
+ * Card Command Classes (CCC)
+ */
+#define CCC_BASIC		(1<<0)	/* (0) Basic protocol functions */
+					/* (CMD0,1,2,3,4,7,9,10,12,13,15) */
+#define CCC_STREAM_READ		(1<<1)	/* (1) Stream read commands */
+					/* (CMD11) */
+#define CCC_BLOCK_READ		(1<<2)	/* (2) Block read commands */
+					/* (CMD16,17,18) */
+#define CCC_STREAM_WRITE	(1<<3)	/* (3) Stream write commands */
+					/* (CMD20) */
+#define CCC_BLOCK_WRITE		(1<<4)	/* (4) Block write commands */
+					/* (CMD16,24,25,26,27) */
+#define CCC_ERASE		(1<<5)	/* (5) Ability to erase blocks */
+					/* (CMD32,33,34,35,36,37,38,39) */
+#define CCC_WRITE_PROT		(1<<6)	/* (6) Able to write protect blocks */
+					/* (CMD28,29,30) */
+#define CCC_LOCK_CARD		(1<<7)	/* (7) Able to lock down card */
+					/* (CMD16,CMD42) */
+#define CCC_APP_SPEC		(1<<8)	/* (8) Application specific */
+					/* (CMD55,56,57,ACMD*) */
+#define CCC_IO_MODE		(1<<9)	/* (9) I/O mode */
+					/* (CMD5,39,40,52,53) */
+#define CCC_SWITCH		(1<<10)	/* (10) High speed switch */
+					/* (CMD6,34,35,36,37,50) */
+					/* (11) Reserved */
+					/* (CMD?) */
 
 /*
  * CSD field definitions