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

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Message-ID: <Z7x52C5dE3eXWomq@shell.armlinux.org.uk>
Date: Mon, 24 Feb 2025 13:53:28 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Kory Maincent <kory.maincent@...tlin.com>
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, 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.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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