[MMC] Use command class to determine read-only status

If a card doesn't support the "write block" command class then
any attempts to open the device should reflect this by denying
write access.
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/mmc/mmc_block.c

@@ -85,6 +85,12 @@ static void mmc_blk_put(struct mmc_blk_data *md)
 	up(&open_lock);
 }
 
+static inline int mmc_blk_readonly(struct mmc_card *card)
+{
+	return mmc_card_readonly(card) ||
+	       !(card->csd.cmdclass & CCC_BLOCK_WRITE);
+}
+
 static int mmc_blk_open(struct inode *inode, struct file *filp)
 {
 	struct mmc_blk_data *md;
@@ -97,7 +103,7 @@ static int mmc_blk_open(struct inode *inode, struct file *filp)
 		ret = 0;
 
 		if ((filp->f_mode & FMODE_WRITE) &&
-			mmc_card_readonly(md->queue.card))
+			mmc_blk_readonly(md->queue.card))
 			ret = -EROFS;
 	}
 
@@ -410,7 +416,7 @@ static int mmc_blk_probe(struct mmc_card *card)
 	printk(KERN_INFO "%s: %s %s %dKiB %s\n",
 		md->disk->disk_name, mmc_card_id(card), mmc_card_name(card),
 		(card->csd.capacity << card->csd.read_blkbits) / 1024,
-		mmc_card_readonly(card)?"(ro)":"");
+		mmc_blk_readonly(card)?"(ro)":"");
 
 	mmc_set_drvdata(card, md);
 	add_disk(md->disk);