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authorChristian Riesch <christian.riesch@omicron.at>2014-03-06 15:42:37 +0400
committerBrian Norris <computersforpeace@gmail.com>2014-03-11 09:42:31 +0400
commit9a78bc83b4c31f67202b7b0a77fa25da732f44a3 (patch)
tree386d354b6cba9a22eca92c07ab10206c476c955a
parentea6d833a3fddcd1d60414d48f34c7f4fbe88608f (diff)
downloadlinux-9a78bc83b4c31f67202b7b0a77fa25da732f44a3.tar.xz
mtd: Fix the behavior of OTP write if there is not enough room for data
If a write to one time programmable memory (OTP) hits the end of this memory area, no more data can be written. The count variable in mtdchar_write() in drivers/mtd/mtdchar.c is not decreased anymore. We are trapped in the loop forever, mtdchar_write() will never return in this case. The desired behavior of a write in such a case is described in [1]: - Try to write as much data as possible, truncate the write to fit into the available memory and return the number of bytes that actually have been written. - If no data could be written at all, return -ENOSPC. This patch fixes the behavior of OTP write if there is not enough space for all data: 1) mtd_write_user_prot_reg() in drivers/mtd/mtdcore.c is modified to return -ENOSPC if no data could be written at all. 2) mtdchar_write() is modified to handle -ENOSPC correctly. Exit if a write returned -ENOSPC and yield the correct return value, either then number of bytes that could be written, or -ENOSPC, if no data could be written at all. Furthermore the patch harmonizes the behavior of the OTP memory write in drivers/mtd/devices/mtd_dataflash.c with the other implementations and the requirements from [1]. Instead of returning -EINVAL if the data does not fit into the OTP memory, we try to write as much data as possible/truncate the write. [1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/write.html Signed-off-by: Christian Riesch <christian.riesch@omicron.at> Signed-off-by: Brian Norris <computersforpeace@gmail.com>
-rw-r--r--drivers/mtd/devices/mtd_dataflash.c16
-rw-r--r--drivers/mtd/mtdchar.c9
-rw-r--r--drivers/mtd/mtdcore.c12
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);