mtd: introduce mtd_has_oob helper

We are working in the direction of making sure that MTD clients to not
use 'mtd->func' pointers directly. In some places we want to know if
OOB operations are supported by an MTD device. Introduce 'mtd_has_oob()'
helper for these purposes.
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtdchar.c

@@ -1004,7 +1004,7 @@ static int mtdchar_ioctl(struct file *file, u_int cmd, u_long arg)
 			break;
 
 		case MTD_FILE_MODE_RAW:
-			if (!mtd->read_oob || !mtd->write_oob)
+			if (!mtd_has_oob(mtd))
 				return -EOPNOTSUPP;
 			mfi->mode = arg;
 

drivers/mtd/sm_ftl.c

@@ -645,8 +645,8 @@ int sm_get_media_info(struct sm_ftl *ftl, struct mtd_info *mtd)
 	if (!ftl->smallpagenand && mtd->oobsize < SM_OOB_SIZE)
 		return -ENODEV;
 
-	/* We use these functions for IO */
-	if (!mtd->read_oob || !mtd->write_oob)
+	/* We use OOB */
+	if (!mtd_has_oob(mtd))
 		return -ENODEV;
 
 	/* Find geometry information */

include/linux/mtd/mtd.h

@@ -454,6 +454,11 @@ static inline uint32_t mtd_mod_by_ws(uint64_t sz, struct mtd_info *mtd)
 	return do_div(sz, mtd->writesize);
 }
 
+static inline int mtd_has_oob(const struct mtd_info *mtd)
+{
+	return mtd->read_oob && mtd->write_oob;
+}
+
 	/* Kernel-side ioctl definitions */
 
 struct mtd_partition;