Re: [PATCH] net: usb: lan78xx: Fix lost EEPROM write timeout error(-ETIMEDOUT) in lan78xx_write_raw_eeprom

Bhanu Seshu Kumar Valluri
2025-10-09T05:41:14Z

On 09/10/25 11:00, Bhanu Seshu Kumar Valluri wrote:
> The function lan78xx_write_raw_eeprom failed to properly propagate EEPROM
> write timeout errors (-ETIMEDOUT). In the timeout fallthrough path, it first
> attempted to restore the pin configuration for LED outputs and then
> returned only the status of that restore operation, discarding the
> original timeout error saved in ret.
>
> As a result, callers could mistakenly treat EEPROM write operation as
> successful even though the EEPROM write had actually timed out with no
> or partial data write.
>
> To fix this, handle errors in restoring the LED pin configuration separately.
> If the restore succeeds, return any prior EEPROM write timeout error saved
> in ret to the caller.
>
> Suggested-by: Oleksij Rempel <o.rempel@pengutronix.de>
> Fixes: 8b1b2ca83b20 ("net: usb: lan78xx: Improve error handling in EEPROM and OTP operations")
> cc: stable@vger.kernel.org
> Signed-off-by: Bhanu Seshu Kumar Valluri <bhanuseshukumar@gmail.com>
> ---
> Note:
> The patch is compiled and tested using EVB-LAN7800LC.
> The patch was suggested by Oleksij Rempel while reviewing a fix to a bug
> found by syzbot earlier.
> The review mail chain where this fix was suggested is given below.
> https://lore.kernel.org/all/aNzojoXK-m1Tn6Lc@pengutronix.de/
>
> ChangeLog:
> v1->v2:
> Added cc:stable tag as asked during v1 review.
> V1 Link : https://lore.kernel.org/all/20251004040722.82882-1-bhanuseshukumar@gmail.com/
>
> drivers/net/usb/lan78xx.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
> index d75502ebbc0d..5ccbe6ae2ebe 100644
> --- a/drivers/net/usb/lan78xx.c
> +++ b/drivers/net/usb/lan78xx.c
> @@ -1174,10 +1174,13 @@ static int lan78xx_write_raw_eeprom(struct lan78xx_net *dev, u32 offset,
> }
>
> write_raw_eeprom_done:
> - if (dev->chipid == ID_REV_CHIP_ID_7800_)
> - return lan78xx_write_reg(dev, HW_CFG, saved);
> -
> - return 0;
> + if (dev->chipid == ID_REV_CHIP_ID_7800_) {
> + int rc = lan78xx_write_reg(dev, HW_CFG, saved);
> + /* If USB fails, there is nothing to do */
> + if (rc < 0)
> + return rc;
> + }
> + return ret;
> }
>
> static int lan78xx_read_raw_otp(struct lan78xx_net *dev, u32 offset,

Hi,

The subject prefix must be [PATCH v2] instead. I overlooked it. Should I resend it?

Regards,
Bhanu Seshu Kumar Valluri