AW: [PATCH 3/9] net: mdio: realtek-rtl9300: Add ports to info structure

["Markus Stockhausen" <markus.stockhausen@gmx.de>]

Hi Andrew,

> Von: Andrew Lunn <andrew@lunn.ch> 
> Gesendet: Dienstag, 19. Mai 2026 20:00
> An: Daniel Golle <daniel@makrotopia.org>
> Betreff: Re: [PATCH 3/9] net: mdio: realtek-rtl9300: Add ports to info
structure
>
> On Tue, May 19, 2026 at 06:27:55PM +0100, Daniel Golle wrote:
> > On Tue, May 19, 2026 at 06:57:41PM +0200, Markus Stockhausen wrote:
> > > Each Realtek SOC series has different number of MDIO ports.
> > 
> > I don't think the term "MDIO ports" describes it well.
> > 
> > I'd say "switch ports", also because RTL9300_NUM_PORTS includes ports
> > used for SFP+ cages which aren't going to be (directly) associated
> > with any MDIO-connected PHY at all.
>
> Hi Markus
>
> It would be good to take a step back and explain the concepts here in
> the commit message. An MDIO bus as 32 addresses, as defined by
> 802.3. Why do we need the concept of a port when we have addresses?
>
> Once you explain the concept, we can maybe suggest a better name. Or
> throw the whole concept out because it is not needed.

I'm just trying to give the properties in the info structure the right 
name that resembles its function. The driver already builds upon
the "port" naming.

Where does this come from?

- The hardware has 1-4 SMI busses
- Each bus serves up to 32 addresses
- A switch has X physical ports
- The mdio controller can only be fed with "physical port"

To make this work:

- port->bus/address hardware mapping registers are set up. [1]
- Driver exposes bus/address to kernel as usual
- During access driver converts bus/address to port [2]
- Driver issues command towards hardware via port
- Hardware maps that back to bus/address

So basically the driver needs an "port-like-index" for all
its operations. Looking at the initial PR history [2] I assume
this design was already hard enough to implement.

Markus

[1]
https://elixir.bootlin.com/linux/v6.18.1/source/drivers/net/mdio/mdio-realte
k-rtl9300.c#L319 
[2]
https://elixir.bootlin.com/linux/v6.18.1/source/drivers/net/mdio/mdio-realte
k-rtl9300.c#L66
[3] https://marc.info/?l=linux-netdev&w=2&r=3&s=add+rtl9300+mdio+driver&q=b