On Wed,  7 May 2025 15:53:19 +0200
Maxime Chevallier [off-list ref] 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@bootlin.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.

...

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