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

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Message-ID: <20250513155325.2f423087@kmaincent-XPS-13-7390>
Date: Tue, 13 May 2025 15:53:25 +0200
From: Kory Maincent <kory.maincent@...tlin.com>
To: Maxime Chevallier <maxime.chevallier@...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
 <kuba@...nel.org>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <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>,
 Florian Fainelli <f.fainelli@...il.com>, Heiner Kallweit
 <hkallweit1@...il.com>, Vladimir Oltean <vladimir.oltean@....com>, Marek
 Behún <kabel@...nel.org>, Oleksij Rempel
 <o.rempel@...gutronix.de>, Nicolò Veronese
 <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 v6 03/14] net: phy: Introduce PHY ports
 representation

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.

...

> @@ -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?

> +/**
> + * 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?

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com