linux-kernel - Re: [PATCH] net: usb: lan78xx: Fix lost EEPROM write timeout error(-ETIMEDOUT) in lan78xx_write_raw

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Message-ID: <866d28f8-616c-4a79-9030-2ebc971e73fd@kernel.org>
Date: Mon, 6 Oct 2025 13:00:59 -0600
From: Khalid Aziz <khalid@...nel.org>
To: Bhanu Seshu Kumar Valluri <bhanuseshukumar@...il.com>,
 Thangaraj Samynathan <Thangaraj.S@...rochip.com>,
 Rengarajan Sundararajan <Rengarajan.S@...rochip.com>,
 UNGLinuxDriver@...rochip.com, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Oleksij Rempel <o.rempel@...gutronix.de>
Cc: linux-kernel-mentees@...ts.linuxfoundation.org,
 skhan@...uxfoundation.org, david.hunter.linux@...il.com,
 netdev@...r.kernel.org, linux-usb@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: usb: lan78xx: Fix lost EEPROM write timeout
 error(-ETIMEDOUT) in lan78xx_write_raw_eeprom

On 10/3/25 10:07 PM, 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@...gutronix.de>
> Fixes: 8b1b2ca83b20 ("net: usb: lan78xx: Improve error handling in EEPROM and OTP operations")
> Signed-off-by: Bhanu Seshu Kumar Valluri <bhanuseshukumar@...il.com>
> ---
>   Note:
>   The patch is compiled and tested.
>   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/
> 
>   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,

You were able to test the change to read eeprom code by forcing a 
timeout while doing probe on EVB-LAN7800LC. Were you able to test this 
code change the same way just to make sure callers of the write function 
handle the new ETIMEDOUT return value correctly?

Thanks,
Khalid