mtd: do not use mtd->get_*_prot_info directly

Instead, call 'mtd_get_*_prot_info()' and check for '-EOPNOTSUPP'. While
on it, fix the return code from '-EOPNOTSUPP' to '-EINVAL' for the case
when the mode parameter is invalid.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtdchar.c

@@ -919,17 +919,15 @@ static int mtdchar_ioctl(struct file *file, u_int cmd, u_long arg)
 		struct otp_info *buf = kmalloc(4096, GFP_KERNEL);
 		if (!buf)
 			return -ENOMEM;
-		ret = -EOPNOTSUPP;
 		switch (mfi->mode) {
 		case MTD_FILE_MODE_OTP_FACTORY:
-			if (mtd->get_fact_prot_info)
-				ret = mtd_get_fact_prot_info(mtd, buf, 4096);
+			ret = mtd_get_fact_prot_info(mtd, buf, 4096);
 			break;
 		case MTD_FILE_MODE_OTP_USER:
-			if (mtd->get_user_prot_info)
-				ret = mtd_get_user_prot_info(mtd, buf, 4096);
+			ret = mtd_get_user_prot_info(mtd, buf, 4096);
 			break;
 		default:
+			ret = -EINVAL;
 			break;
 		}
 		if (ret >= 0) {

include/linux/mtd/mtd.h

@@ -342,6 +342,8 @@ static inline int mtd_write_oob(struct mtd_info *mtd, loff_t to,
 static inline int mtd_get_fact_prot_info(struct mtd_info *mtd,
 					 struct otp_info *buf, size_t len)
 {
+	if (!mtd->get_fact_prot_info)
+		return -EOPNOTSUPP;
 	return mtd->get_fact_prot_info(mtd, buf, len);
 }
 
@@ -357,6 +359,8 @@ static inline int mtd_get_user_prot_info(struct mtd_info *mtd,
 					 struct otp_info *buf,
 					 size_t len)
 {
+	if (!mtd->get_user_prot_info)
+		return -EOPNOTSUPP;
 	return mtd->get_user_prot_info(mtd, buf, len);
 }