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

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Message-ID: <20250804155115.4a301cdc@fedora.home>
Date: Mon, 4 Aug 2025 15:51:15 +0200
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: davem@...emloft.net, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 thomas.petazzoni@...tlin.com, Andrew Lunn <andrew@...n.ch>, Jakub Kicinski
 <kuba@...nel.org>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <pabeni@...hat.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>, Heiner Kallweit
 <hkallweit1@...il.com>, Vladimir Oltean <vladimir.oltean@....com>,
 Köry Maincent <kory.maincent@...tlin.com>, Marek
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 <nicveronese@...il.com>, Simon Horman <horms@...nel.org>,
 mwojtas@...omium.org, Antoine Tenart <atenart@...nel.org>,
 devicetree@...r.kernel.org, Conor Dooley <conor+dt@...nel.org>, Krzysztof
 Kozlowski <krzk+dt@...nel.org>, Rob Herring <robh@...nel.org>, Romain
 Gantois <romain.gantois@...tlin.com>, Daniel Golle <daniel@...rotopia.org>,
 Dimitri Fedrau <dimitri.fedrau@...bherr.com>
Subject: Re: [PATCH net-next v10 07/15] net: phy: Introduce generic SFP
 handling for PHY drivers

On Sun, 27 Jul 2025 10:56:52 +0100
"Russell King (Oracle)" <linux@...linux.org.uk> 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().

Thanks for the input, it'll make things even simpler so I'm all in for
that. I'll rework this for the next iteration, thanks a lot for taking
a look at this !

Maxime

>