Re: [PATCH v5 3/5] mtd: spi-nor: otp: return -EROFS if region is read-only

From: Michael Walle
Date: Mon Jun 07 2021 - 02:09:07 EST


Am 2021-06-07 07:46, schrieb Vignesh Raghavendra:
On 6/4/21 6:45 PM, Michael Walle wrote:
Am 2021-06-04 15:07, schrieb Tudor.Ambarus@xxxxxxxxxxxxx:
On 6/4/21 1:02 PM, Michael Walle wrote:
EXTERNAL EMAIL: Do not click links or open attachments unless you
know the content is safe

SPI NOR flashes will just ignore program commands if the OTP region is
locked. Thus, a user might not notice that the intended write didn't end
up in the flash. Return -EROFS to the user in this case. From what I can
tell, chips/cfi_cmdset_0001.c also return this error code.

One could optimize spi_nor_mtd_otp_range_is_locked() to read the status
register only once and not for every OTP region, but for that we would
need some more invasive changes. Given that this is
one-time-programmable memory and the normal access mode is reading, we
just live with the small overhead.

Fixes: 069089acf88b ("mtd: spi-nor: add OTP support")
Signed-off-by: Michael Walle <michael@xxxxxxxx>
Reviewed-by: Pratyush Yadav <p.yadav@xxxxxx>
---
 drivers/mtd/spi-nor/otp.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/drivers/mtd/spi-nor/otp.c b/drivers/mtd/spi-nor/otp.c
index 3898ed67ba1c..063f8fb68649 100644
--- a/drivers/mtd/spi-nor/otp.c
+++ b/drivers/mtd/spi-nor/otp.c
@@ -249,6 +249,32 @@ static int spi_nor_mtd_otp_info(struct mtd_info
*mtd, size_t len,
        return ret;
 }

+static int spi_nor_mtd_otp_range_is_locked(struct spi_nor *nor,
loff_t ofs,
+                                          size_t len)
+{
+       const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
+       unsigned int region;
+       int locked;
+
+       if (!len)
+               return 0;
+

You won't need this if you put patch 4/5 before this one. With this:

This patch will get backported to the stable kernels. Patch 4 on the
other hand does not.


I don't see why 4/5 cannot be marked for backport too as it makes 3/5
much cleaner?

What kind of problem does 4/5 fix? I can't see how that patch would
apply to any rule in Documentation/process/stable-kernel-rules.rst.

But sure, adding the same Fixes: tag, I can swap those two.

-michael