Re: [PATCH net] net: usb: lan78xx: reject invalid EEPROM write requests

[Nicolai Buchwitz <nb@tipi-net.de>]

On 9.10.2026 03:27, Andrew Lunn wrote:
> On Fri, Oct 09, 2026 at 02:57:02AM +0200, Stefano Munari wrote:
>> The runtime PM handling removed the -EINVAL return for invalid
>> EEPROM/OTP write requests. These requests now return zero from a
>> successful usb_autopm_get_interface() call, even though no data is
>> written.
>> 
>> Set ret to -EINVAL for invalid requests while preserving the runtime
>> PM reference release.
>> 
>> Fixes: 8a7ffeb795f8 ("lan78xx: Fix for eeprom read/write when device 
>> auto suspend")
>> Signed-off-by: Stefano Munari <stefanomunari.sm@gmail.com>
>> ---
>> Tested on a Raspberry Pi 3 Model B+ with the onboard Ethernet
>> controller, using raspberrypi/linux commit bba53a117a4a on the
>> rpi-6.6.y branch as the baseline.
>> 
>>   ethtool -E eth0 magic 0 offset 0 length 1 value 0
>> 
>> The command succeeds without the patch and reports "Invalid argument"
>> with the patch applied.
>> ---
>>  drivers/net/usb/lan78xx.c | 2 ++
>>  1 file changed, 2 insertions(+)
>> 
>> diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
>> index 5655941f1478..7ac263454d45 100644
>> --- a/drivers/net/usb/lan78xx.c
>> +++ b/drivers/net/usb/lan78xx.c
>> @@ -1719,6 +1719,8 @@ static int lan78xx_ethtool_set_eeprom(struct 
>> net_device *netdev,
>>  		 (ee->len == 512) &&
>>  		 (data[0] == OTP_INDICATOR_1))
>>  		ret = lan78xx_write_raw_otp(dev, ee->offset, ee->len, data);
>> +	else
>> +		ret = -EINVAL;
> 
> It might be the nested if's without {} which caused the broken patch?
> 
> Maybe add some brackets to make it clearer?
> 
>       Andrew

8a7ffeb795f8 dropped the final return -EINVAL when it converted the
returns to ret = ..., braces wouldn't have caught that. Fine with
adding them for a v2 though.

In either case:

Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>
Tested-by: Nicolai Buchwitz <nb@tipi-net.de> # Raspberry Pi 3B+ 
(LAN7515)

Thanks,
Nicolai