netdev - Re: [PATCH] net-sysfs: allow changing sysfs carrier when interface is down

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Message-ID: <2765ed7299a05d6740ce7040b6ebe724b5979620.camel@infinera.com>
Date:   Thu, 2 Jun 2022 18:01:08 +0000
From:   Joakim Tjernlund <Joakim.Tjernlund@...inera.com>
To:     "kuba@...nel.org" <kuba@...nel.org>
CC:     "stephen@...workplumber.org" <stephen@...workplumber.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] net-sysfs: allow changing sysfs carrier when interface is
 down

On Thu, 2022-06-02 at 10:52 -0700, Jakub Kicinski wrote:
> On Thu, 2 Jun 2022 17:15:13 +0000 Joakim Tjernlund wrote:
> > > What is "our HW", what kernel driver does it use and why can't the
> > > kernel driver take care of making sure the device is not accessed
> > > when it'd crash the system?  
> > 
> > It is a custom asic with some homegrown controller. The full config path is too complex for kernel too
> > know and depends on user input.
> 
> We have a long standing tradition of not caring about user space
> drivers in netdev land. I see no reason to merge this patch upstream.

This is not a user space driver. View it as a eth controller with a dum PHY
which cannot convey link status. The kernel driver then needs help with managing carrier.
  
> 
> > > > Maybe so but it seems to me that this limitation was put in place without much thought.  
> > > 
> > > Don't make unnecessary disparaging statements about someone else's work.
> > > Whoever that person was.  
> > 
> > That was not meant the way you read it, sorry for being unclear.
> > The commit from 2012 simply says:
> > net: allow to change carrier via sysfs
> >     
> >     Make carrier writable
> 
> Yeah, IIUC the interface was created for software devices.

software devices? like dummy device? I guess that is the first user of
this feature but not restricted to that.

 Jocke