Re: [PATCH net-next v10 07/15] net: phy: Introduce generic SFP handling for PHY drivers

[Maxime Chevallier]

Hello Russell,

I'm re-replying here even though a more recent version was sent, as I 
realise I forgot to fully address that.

On 27/07/2025 11:56, Russell King (Oracle) wrote:
> On Tue, Jul 22, 2025 at 02:16:12PM +0200, Maxime Chevallier wrote:
> > +static int phy_sfp_module_insert(void *upstream, const struct sfp_eeprom_id *id)
> > +{
> > +	struct phy_device *phydev = upstream;
> > +	struct phy_port *port = phy_get_sfp_port(phydev);
> > +
> > +	__ETHTOOL_DECLARE_LINK_MODE_MASK(sfp_support);
> > +	DECLARE_PHY_INTERFACE_MASK(interfaces);
> > +	phy_interface_t iface;
> > +
> > +	linkmode_zero(sfp_support);
> > +
> > +	if (!port)
> > +		return -EINVAL;
> > +
> > +	sfp_parse_support(phydev->sfp_bus, id, sfp_support, interfaces);
> > +
> > +	if (phydev->n_ports == 1)
> > +		phydev->port = sfp_parse_port(phydev->sfp_bus, id, sfp_support);
> > +
> > +	linkmode_and(sfp_support, port->supported, sfp_support);
> > +
> > +	if (linkmode_empty(sfp_support)) {
> > +		dev_err(&phydev->mdio.dev, "incompatible SFP module inserted\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	iface = sfp_select_interface(phydev->sfp_bus, sfp_support);
>
> I've been moving phylink away from using sfp_select_interface() because
> it requires two stages of translation - one from the module capabilties
> to linkmodes, and then linkmodes to interfaces.
>
> sfp_parse_support() now provides the interfaces that the optical module
> supports, and the possible interfaces that a copper module _might_
> support (but we don't know for certain about that until we discover a
> PHY.)
>
> The only place in phylink where this function continues to be used is
> when there's an optical module which supports multiple different
> speeds, and we need to select it based on the advertising mask provided
> by userspace. Everywhere else shouldn't use this function, but should
> instead use the interfaces returned from sfp_parse_support().

In any case, we'll eventually have to select one of the interfaces if 
there are multiple matches from the sfp_parse_support. phylink maintains 
a sorted list of interfaces used as a preference, I think we should use 
the same list for phy-driver SFP. I'm thinking about moving 
phylink_choose_sfp_interface() in the sfp code, would you be OK with that ?

Maxime