Re: [PATCH net-next v22 03/14] net: phy: Introduce PHY ports representation

[Andrew Lunn <andrew@lunn.ch>]

On Thu, Jan 08, 2026 at 09:00:28AM +0100, Maxime Chevallier 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 pairs of a BaseT 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 pairs 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. 100BaseTX works using only 2
> pairs on a Cat 5 cables. However, in the situation where a 10/100/1000
> capable PHY is wired to its RJ45 port through 2 pairs 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";
> 		pairs = <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.
> 
> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew