linux-kernel - Re: [PATCH net-next v6 03/14] net: phy: Introduce PHY ports representation

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Message-ID: <20250627190250.63a1848a@fedora>
Date: Fri, 27 Jun 2025 19:02:50 +0200
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: Kory Maincent <kory.maincent@...tlin.com>
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
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 <pabeni@...hat.com>, Russell King <linux@...linux.org.uk>,
 linux-arm-kernel@...ts.infradead.org, Christophe Leroy
 <christophe.leroy@...roup.eu>, Herve Codina <herve.codina@...tlin.com>,
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 Dimitri Fedrau <dimitri.fedrau@...bherr.com>
Subject: Re: [PATCH net-next v6 03/14] net: phy: Introduce PHY ports
 representation

Hi Kory,

On Tue, 13 May 2025 15:53:25 +0200
Kory Maincent <kory.maincent@...tlin.com> wrote:

> On Wed,  7 May 2025 15:53:19 +0200
> Maxime Chevallier <maxime.chevallier@...tlin.com> wrote:
> 
> > Ethernet provides a wide variety of layer 1 protocols and standards for
> > data transmission. The front-facing ports of an interface have their own
> > complexity and configurability.
> > 
> > Introduce a representation of these front-facing ports. The current code
> > is minimalistic and only support ports controlled by PHY devices, but
> > the plan is to extend that to SFP as well as raw Ethernet MACs that
> > don't use PHY devices.
> > 
> > This minimal port representation allows describing the media and number
> > of lanes of a port. From that information, we can derive the linkmodes
> > usable on the port, which can be used to limit the capabilities of an
> > interface.
> > 
> > For now, the port lanes and medium is derived from devicetree, defined
> > by the PHY driver, or populated with default values (as we assume that
> > all PHYs expose at least one port).
> > 
> > The typical example is 100M ethernet. 100BaseT can work using only 2
> > lanes on a Cat 5 cables. However, in the situation where a 10/100/1000
> > capable PHY is wired to its RJ45 port through 2 lanes only, we have no
> > way of detecting that. The "max-speed" DT property can be used, but a
> > more accurate representation can be used :
> > 
> > mdi {
> > 	connector-0 {
> > 		media = "BaseT";
> > 		lanes = <2>;
> > 	};
> > };
> > 
> > From that information, we can derive the max speed reachable on the
> > port.
> > 
> > Another benefit of having that is to avoid vendor-specific DT properties
> > (micrel,fiber-mode or ti,fiber-mode).
> > 
> > This basic representation is meant to be expanded, by the introduction
> > of port ops, userspace listing of ports, and support for multi-port
> > devices.
> > 
> > Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>  
> 
> ...
> 
> > +	for_each_available_child_of_node_scoped(mdi, port_node) {
> > +		port = phy_of_parse_port(port_node);
> > +		if (IS_ERR(port)) {
> > +			err = PTR_ERR(port);
> > +			goto out_err;
> > +		}
> > +
> > +		port->parent_type = PHY_PORT_PHY;
> > +		port->phy = phydev;
> > +		err = phy_add_port(phydev, port);
> > +		if (err)
> > +			goto out_err;  
> 
> I think of_node_put(port_node) is missing here.

I don't think so, this is the _scoped variant so it takes care of
that for us.

> 
> ...
> 
> > @@ -1968,6 +1997,7 @@ void phy_trigger_machine(struct phy_device *phydev);
> >  void phy_mac_interrupt(struct phy_device *phydev);
> >  void phy_start_machine(struct phy_device *phydev);
> >  void phy_stop_machine(struct phy_device *phydev);
> > +  
> 
> New empty line here?

Oops, this will be removed

> > +/**
> > + * struct phy_port - A representation of a network device physical interface
> > + *
> > + * @head: Used by the port's parent to list ports
> > + * @parent_type: The type of device this port is directly connected to
> > + * @phy: If the parent is PHY_PORT_PHYDEV, the PHY controlling that port
> > + * @ops: Callback ops implemented by the port controller
> > + * @lanes: The number of lanes (diff pairs) this port has, 0 if not
> > applicable
> > + * @mediums: Bitmask of the physical mediums this port provides access to
> > + * @supported: The link modes this port can expose, if this port is MDI (not
> > MII)
> > + * @interfaces: The MII interfaces this port supports, if this port is MII
> > + * @active: Indicates if the port is currently part of the active link.
> > + * @is_serdes: Indicates if this port is Serialised MII (Media Independent
> > + *	       Interface), or an MDI (Media Dependent Interface).
> > + */
> > +struct phy_port {
> > +	struct list_head head;
> > +	enum phy_port_parent parent_type;
> > +	union {
> > +		struct phy_device *phy;
> > +	};  
> 
> The union is useless here?

For now yes :( But this will change when adding support for
non-phy-driver ports.

Maxime

> 
> Regards,