Re: [PATCH] leds: triggers: netdev: add a check, whether device is up

[Klaus Kudielka]

On Sat, 2023-11-04 at 15:29 +0100, Andrew Lunn wrote:
> On Sat, Nov 04, 2023 at 01:58:40PM +0100, Klaus Kudielka wrote:
> > Some net devices do not report NO-CARRIER, if they haven't been brought
> > up.
> 
> Hi Klaus
> 
> We should probably fix the driver. What device is it?
> 
> > In that case, the netdev trigger results in a wrong link state being
> > displayed. Fix this, by adding a check, whether the device is up.
> 
> Is it wrong? Maybe the carrier really is up, even if the interface is
> admin down. Broadcast packets are being received by the
> hardware. Maybe there is a BMC sharing the link and it is active?

My particular example is Turris Omnia, eth2 (WAN), connected to SFP.
SFP module is inserted, but no fiber connected, so definitely no carrier. 

*Without* the patch:

After booting, the device is down, but netdev trigger reports "link" active.
This looks wrong to me.

I can then "ip link set eth2 up", and the "link" goes away - as I
would have expected it to be from the beginning.

> It is not a clear cut wrong to me. And its a way to find broken
> drivers. We might want to discuss this some more.

Maybe an initialization issue.
Just a guess, I'm really not an expert here:

phylink_start() is the first one that does netif_carrier_off() and thus
sets the NOCARRIER bit, but that only happens when bringing the device up.

Before that, I would not know who cares about setting the NOCARRIER bit.


Anyway, it's only a cosmetic issue, but it has been bugging me for too
long :)


Best regards, Klaus