linux-kernel - Re: are device names part of sysfs ABI? (was Re: devicename part of LEDs under ethernet MAC / PHY)

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Message-ID: <YVq7oTTv5URYKVJb@kroah.com>
Date:   Mon, 4 Oct 2021 10:30:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Pavel Machek <pavel@....cz>
Cc:     Marek Behún <kabel@...nel.org>,
        Andrew Lunn <andrew@...n.ch>,
        "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
        netdev@...r.kernel.org,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: are device names part of sysfs ABI? (was Re: devicename part of
 LEDs under ethernet MAC / PHY)

On Mon, Oct 04, 2021 at 09:38:41AM +0200, Pavel Machek wrote:
> Hi!
> 
> > > > > Are device names (as returned by dev_name() function) also part of
> > > > > sysfs ABI? Should these names be stable across reboots / kernel
> > > > > upgrades?  
> > > > 
> > > > Stable in what exact way?
> > > 
> > > Example:
> > > - Board has an ethernet PHYs that is described in DT, and therefore
> > >   has stable sysfs path (derived from DT path), something like
> > >     /sys/devices/.../mdio_bus/f1072004.mdio-mii/f1072004.mdio-mii:01
> > 
> > None of the numbers there are "stable", right?
> 
> At least f1072004 part is stable (and probably whole path). DT has
> advantages here, and we should provide stable paths when we can.

The kernel should enumerate the devices as best that it can, but it
never has the requirement of always enumerating them in the same way
each time as many busses are not deterministic.