linux-kernel - Re: [PATCH net-next 12/13] net: phy: phylink: Use phy_caps

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Message-ID: <20250224150440.7fe5458d@kmaincent-XPS-13-7390>
Date: Mon, 24 Feb 2025 15:04:40 +0100
From: Kory Maincent <kory.maincent@...tlin.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Maxime Chevallier <maxime.chevallier@...tlin.com>, davem@...emloft.net,
 Andrew Lunn <andrew@...n.ch>, Jakub Kicinski <kuba@...nel.org>, Eric
 Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Heiner
 Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com,
 linux-arm-kernel@...ts.infradead.org, Christophe Leroy
 <christophe.leroy@...roup.eu>, Herve Codina <herve.codina@...tlin.com>,
 Florian Fainelli <f.fainelli@...il.com>, Vladimir Oltean
 <vladimir.oltean@....com>, Oleksij Rempel <o.rempel@...gutronix.de>, Simon
 Horman <horms@...nel.org>, Romain Gantois <romain.gantois@...tlin.com>
Subject: Re: [PATCH net-next 12/13] net: phy: phylink: Use phy_caps_lookup
 for fixed-link configuration

On Mon, 24 Feb 2025 13:53:28 +0000
"Russell King (Oracle)" <linux@...linux.org.uk> wrote:

> On Mon, Feb 24, 2025 at 02:44:31PM +0100, Kory Maincent wrote:
> > On Sat, 22 Feb 2025 15:27:24 +0100
> > Maxime Chevallier <maxime.chevallier@...tlin.com> wrote:
> >   
> > > When phylink creates a fixed-link configuration, it finds a matching
> > > linkmode to set as the advertised, lp_advertising and supported modes
> > > based on the speed and duplex of the fixed link.
> > > 
> > > Use the newly introduced phy_caps_lookup to get these modes instead of
> > > phy_lookup_settings(). This has the side effect that the matched
> > > settings and configured linkmodes may now contain several linkmodes (the
> > > intersection of supported linkmodes from the phylink settings and the
> > > linkmodes that match speed/duplex) instead of the one from
> > > phy_lookup_settings().  
> > 
> > ...
> >   
> > >  
> > >  	linkmode_set_bit(ETHTOOL_LINK_MODE_Pause_BIT, mask);
> > >  	linkmode_set_bit(ETHTOOL_LINK_MODE_Asym_Pause_BIT, mask);
> > > @@ -588,9 +591,9 @@ static int phylink_parse_fixedlink(struct phylink *pl,
> > >  
> > >  	phylink_set(pl->supported, MII);
> > >  
> > > -	if (s) {
> > > -		__set_bit(s->bit, pl->supported);
> > > -		__set_bit(s->bit, pl->link_config.lp_advertising);
> > > +	if (c) {
> > > +		linkmode_or(pl->supported, pl->supported, match);
> > > +		linkmode_or(pl->link_config.lp_advertising,
> > > pl->supported, match);  
> > 
> > You are doing the OR twice. You should use linkmode_copy() instead.  
> 
> No, we don't want to copy pl->supported to
> pl->link_config.lp_advertising. We just want to set the linkmode bit
> that corresponds to the speed/duplex in each mask.
> 
> That will result in e.g. the pause mode bits will be overwritten despite
> being appropriately set in the advertising mask in the code above this.

Ok, so the right thing should be this:
linkmode_or(pl->link_config.lp_advertising, pl->link_config.lp_advertising,
	    match)

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com