Re: [PATCH net-next v2 0/3] net: mdio: support dynamic OF device changes

[James Hilliard]

On Mon, Aug 3, 2026 at 8:06 PM Andrew Lunn <andrew@xxxxxxx> wrote:
>
> On Mon, Aug 03, 2026 at 05:48:09PM -0600, James Hilliard wrote:
> > MDIO buses enumerate firmware children only when the bus is registered. A
> > later devicetree overlay or status transition is ignored, unlike on I2C and
> > SPI buses. Supporting live reconfiguration also means that population and
> > removal can race address scanning, PHY attachment and bus teardown.
> >
> > Patch 1 factors fixed-address child registration and legacy PHY scanning
> > into helpers shared by initial and dynamic population.
> >
> > Patch 2 serializes MDIO device-map changes, reserves addresses while
> > registration is in progress, and coordinates scans, attachment, removal
> > and bus teardown. Dynamically removed devices remain pinned until bus
> > teardown, preserving the borrowed-pointer convention of
> > mdiobus_get_phy().
> >
> > Patch 3 adds the OF reconfiguration notifier. It supports fixed-address
> > PHYs and generic MDIO devices, scanned PHY addresses, and Ethernet PHY
> > packages. It also preflights overlay removal and rejects removal of
> > attached or in-flight PHYs before their firmware nodes can disappear.
>
> This is a lot of complexity which i think should be avoided by just
> getting the bootloader to put the correct nodes in DT.

This should all be generic OF_DYNAMIC support for MDIO, so the
changes shouldn't really be tied to a specific PHY driver in any case.

> If this was a hat on top of a SBC, with an EEPROM indicating what the
> hat was, then maybe DT overlays would make sense. But from what you
> have said, this is a fixed PCB design, nothing hot/cold plugable.

Some H616/H618 boards have the ethernet port on an expansion board:
http://www.orangepi.org/html/hardWare/computerAndMicrocontrollers/details/2W-expansion-board.html

>
>      Andrew
>