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author | Christian Riesch | 2014-03-06 12:42:37 +0100 |
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committer | Brian Norris | 2014-03-11 06:42:31 +0100 |
commit | 9a78bc83b4c31f67202b7b0a77fa25da732f44a3 (patch) | |
tree | 386d354b6cba9a22eca92c07ab10206c476c955a /drivers/mtd/devices | |
parent | mtd: block2mtd: check device size (diff) | |
download | kernel-qcow2-linux-9a78bc83b4c31f67202b7b0a77fa25da732f44a3.tar.gz kernel-qcow2-linux-9a78bc83b4c31f67202b7b0a77fa25da732f44a3.tar.xz kernel-qcow2-linux-9a78bc83b4c31f67202b7b0a77fa25da732f44a3.zip |
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>
Diffstat (limited to 'drivers/mtd/devices')
-rw-r--r-- | drivers/mtd/devices/mtd_dataflash.c | 16 |
1 files changed, 10 insertions, 6 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 |