3 files changed, 30 insertions, 7 deletions

diff --git a/drivers/mtd/devices/mtd_dataflash.c b/drivers/mtd/devices/mtd_dataflash.c
index a6fdbe83bad6..dd22ce2cc9ad 100644
--- a/drivers/mtd/devices/mtd_dataflash.c
+++ b/drivers/mtd/devices/mtd_dataflash.c
@@ -542,14 +542,18 @@ static int dataflash_write_user_otp(struct mtd_info *mtd,
         struct dataflash        *priv = mtd->priv;
         int                     status;
 
-        if (len > 64)
-                return -EINVAL;
+        if (from >= 64) {
+                /*
+                 * Attempting to write beyond the end of OTP memory,
+                 * no data can be written.
+                 */
+                *retlen = 0;
+                return 0;
+        }
 
-        /* Strictly speaking, we *could* truncate the write ... but
-         * let's not do that for the only write that's ever possible.
-         */
+        /* Truncate the write to fit into OTP memory. */
         if ((from + len) > 64)
-                return -EINVAL;
+                len = 64 - from;
 
         /* OUT: OP_WRITE_SECURITY, 3 zeroes, 64 data-or-zero bytes
          * IN:  ignore all
diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index 250798cf76aa..7d4e7b9da3a1 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -324,6 +324,15 @@ static ssize_t mtdchar_write(struct file *file, const char __user *buf, size_t c
                 default:
                         ret = mtd_write(mtd, *ppos, len, &retlen, kbuf);
                 }
+
+                /*
+                 * Return -ENOSPC only if no data could be written at all.
+                 * Otherwise just return the number of bytes that actually
+                 * have been written.
+                 */
+                if ((ret == -ENOSPC) && (total_retlen))
+                        break;
+
                 if (!ret) {
                         *ppos += retlen;
                         total_retlen += retlen;
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 0a7d77e65335..d201feeb3ca6 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -932,12 +932,22 @@ EXPORT_SYMBOL_GPL(mtd_read_user_prot_reg);
 int mtd_write_user_prot_reg(struct mtd_info *mtd, loff_t to, size_t len,
                             size_t *retlen, u_char *buf)
 {
+        int ret;
+
         *retlen = 0;
         if (!mtd->_write_user_prot_reg)
                 return -EOPNOTSUPP;
         if (!len)
                 return 0;
-        return mtd->_write_user_prot_reg(mtd, to, len, retlen, buf);
+        ret = mtd->_write_user_prot_reg(mtd, to, len, retlen, buf);
+        if (ret)
+                return ret;
+
+        /*
+         * If no data could be written at all, we are out of memory and
+         * must return -ENOSPC.
+         */
+        return (*retlen) ? 0 : -ENOSPC;
 }
 EXPORT_SYMBOL_GPL(mtd_write_user_prot_reg);