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

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Message-ID: <ef6fd852-0e9a-41fb-a4f9-8cc95c78f9bd@redhat.com>
Date: Thu, 9 Oct 2025 10:02:42 +0200
From: Paolo Abeni <pabeni@...hat.com>
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>,
 Oleksij Rempel <o.rempel@...gutronix.de>
Cc: netdev@...r.kernel.org, linux-usb@...r.kernel.org,
 linux-kernel@...r.kernel.org, khalid@...nel.org,
 linux-kernel-mentees@...ts.linuxfoundation.org, skhan@...uxfoundation.org,
 david.hunter.linux@...il.com, stable@...r.kernel.org
Subject: Re: [PATCH] net: usb: lan78xx: Fix lost EEPROM write timeout
 error(-ETIMEDOUT) in lan78xx_write_raw_eeprom

Hello,

On 10/9/25 7:41 AM, Bhanu Seshu Kumar Valluri wrote:
> 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@...gutronix.de>
>> Fixes: 8b1b2ca83b20 ("net: usb: lan78xx: Improve error handling in EEPROM and OTP operations")
>> cc: stable@...r.kernel.org
>> Signed-off-by: Bhanu Seshu Kumar Valluri <bhanuseshukumar@...il.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?

This is not a review, and given the current amount of queued patches a
real one will not follow soon, but please do not send a new version just
for this.

Thanks,

Paolo