Re: [PATCH net-next v4 09/13] net: phylink: Use phy_caps_lookup for fixed-link configuration

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

On Thu, 6 Mar 2025 09:56:32 +0100
Paolo Abeni <pabeni@redhat.com> wrote:

> On 3/3/25 10:03 AM, Maxime Chevallier wrote:
> > @@ -879,8 +880,10 @@ static int phylink_parse_fixedlink(struct phylink *pl,
> >  	linkmode_copy(pl->link_config.advertising, pl->supported);
> >  	phylink_validate(pl, pl->supported, &pl->link_config);
> >  
> > -	s = phy_lookup_setting(pl->link_config.speed, pl->link_config.duplex,
> > -			       pl->supported, true);
> > +	c = phy_caps_lookup(pl->link_config.speed, pl->link_config.duplex,
> > +			    pl->supported, true);
> > +	if (c)
> > +		linkmode_and(match, pl->supported, c->linkmodes);  
> 
> How about using only the first bit from `c->linkmodes`, to avoid
> behavior changes?

If what we want is to keep the exact same behaviour, then we need to
go one step further and make sure we keep the same one as before, and
it's not guaranteed that the first bit in c->linkmodes is this one.

We could however have a default supported mask for fixed-link in phylink
that contains all the linkmodes we allow for fixed links, then filter
with the lookup, something like :


-       linkmode_fill(pl->supported);
+       /* (in a dedicated helper) Linkmodes reported for fixed links below
+        * 10G */
+       linkmode_zero(pl->supported);
+
+       linkmode_set_bit(ETHTOOL_LINK_MODE_10baseT_Half_BIT, pl->supported);
+       linkmode_set_bit(ETHTOOL_LINK_MODE_10baseT_Full_BIT, pl->supported);
+       linkmode_set_bit(ETHTOOL_LINK_MODE_100baseT_Half_BIT, pl->supported);
+       linkmode_set_bit(ETHTOOL_LINK_MODE_100baseT_Full_BIT, pl->supported);
+       linkmode_set_bit(ETHTOOL_LINK_MODE_1000baseT_Half_BIT, pl->supported);
+       linkmode_set_bit(ETHTOOL_LINK_MODE_1000baseT_Full_BIT, pl->supported);
+       linkmode_set_bit(ETHTOOL_LINK_MODE_2500baseT_Full_BIT, pl->supported);
+       linkmode_set_bit(ETHTOOL_LINK_MODE_5000baseT_Full_BIT, pl->supported);
+       linkmode_set_bit(ETHTOOL_LINK_MODE_10000baseT_Full_BIT, pl->supported);
+
        linkmode_copy(pl->link_config.advertising, pl->supported);
        phylink_validate(pl, pl->supported, &pl->link_config);
 
-       s = phy_lookup_setting(pl->link_config.speed, pl->link_config.duplex,
-                              pl->supported, true);
+       c = phy_caps_lookup(pl->link_config.speed, pl->link_config.duplex,
+                           pl->supported, true);
+       if (c)
+               linkmode_and(match, pl->supported, c->linkmodes);

That way we should have a consistent behaviour with what we currently
have, and to me it's more explicit what will the  fixed-link linkmodes
be.

I'd like to make sure Russell is OK with that though :)

Thanks you for the review Paolo !

Maxime