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

From: Tudor.Ambarus
Date: Fri Jun 04 2021 - 09:08:01 EST


On 6/4/21 1:02 PM, Michael Walle wrote:
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>
> 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:

Reviewed-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>

> + /*
> + * If any of the affected OTP regions are locked the entire range is
> + * considered locked.
> + */
> + for (region = spi_nor_otp_offset_to_region(nor, ofs);
> + region <= spi_nor_otp_offset_to_region(nor, ofs + len - 1);
> + region++) {
> + locked = ops->is_locked(nor, region);
> + /* take the branch it is locked or in case of an error */
> + if (locked)
> + return locked;
> + }
> +
> + return 0;
> +}
> +
> static int spi_nor_mtd_otp_read_write(struct mtd_info *mtd, loff_t ofs,
> size_t total_len, size_t *retlen,
> const u8 *buf, bool is_write)
> @@ -271,6 +297,16 @@ static int spi_nor_mtd_otp_read_write(struct mtd_info *mtd, loff_t ofs,
> /* don't access beyond the end */
> total_len = min_t(size_t, total_len, spi_nor_otp_size(nor) - ofs);
>
> + if (is_write) {
> + ret = spi_nor_mtd_otp_range_is_locked(nor, ofs, total_len);
> + if (ret < 0) {
> + goto out;
> + } else if (ret) {
> + ret = -EROFS;
> + goto out;
> + }
> + }
> +
> *retlen = 0;
> while (total_len) {
> /*
> --
> 2.20.1
>