Re: [PATCH net-next v14 01/16] dt-bindings: net: Introduce the ethernet-connector description

[Andrew Lunn <andrew@lunn.ch>]

On Thu, Oct 30, 2025 at 01:13:14PM +0100, Maxime Chevallier wrote:
> Hi,
> 
> > @@ -313,5 +324,12 @@ examples:
> >                      default-state = "keep";
> >                  };
> >              };
> > +            /* Fast Ethernet port, with only 2 pairs wired */
> > +            mdi {
> > +                connector-0 {
> > +                    lanes = <2>;
> > +                    media = "BaseT";
> > +                };
> > +            };
> >          };
> >      };
> 
> As Andrew suggest clearly differentiating "lanes" and "pairs", do we
> want this difference to also affect the binding ?
> 
> I still think "lanes" makes some level of sense here, but at least
> the doc will need updating.

How do you define MDI?

For copper, one possibility is an RJ-45 plug/socket, and you have
twisted pairs, 2 or 4 of them.

Some people are old enough to remember 10Base2, using a coaxial cable
and BNC connectors. Would you consider that a pair? A lane?

How about an SFF, a soldered down module. Its MDI interface is likely
to be 2 fibre strands. But consider so called bidi modules, which use
one fibre, and two different wavelengths of light.

Or an SFP, where you have no idea what the MDI is until you plug it in
and read the EEPROM.

Do we need to be able to describe all the different MDI? Do we maybe
need to look at the media property to decide it is an RJ-45 connector
so there should be a pairs property? Or the media is -KS, so there
should be a lanes property for the number of PCS lanes on the PCB?

This needs further discussion, what are you actually trying to
represent here?

	Andrew