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

[Nicolai Buchwitz]

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@xxxxxxxxx>
> > ---
> > 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@xxxxxxxxxxx>
Tested-by: Nicolai Buchwitz <nb@xxxxxxxxxxx> # Raspberry Pi 3B+ 
(LAN7515)

Thanks,
Nicolai