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

[Andrew Lunn <andrew@lunn.ch>]

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.

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.

     Andrew