Re: [PATCH net-next v13 08/11] net: mdio: realtek-rtl9300: Check for C45 support during setup

On Fri, Aug 07, 2026 at 07:10:55PM +0200, Markus Stockhausen wrote:
> The to-be-merged RTL83xx devices have only 1G ports. Thus the MDIO
> bus always runs with C22 mode. For now it makes no sense to add
> those devices with C45 helpers that are not used at all. Add a
> consistency check in the mapping helper so that it aborts setup
> if devicetree defines a C45 PHY for a device that has no such
> read/write functions.

I know the concept of an MDIO bus is completely messed up with this
hardware, but C22 transactions and C45 transactions are a bus
concept.

ethernet-phy-ieee802.3-c45 is not about MDIO transactions, but C22 and
C45 address spaces. The PHY has its registers in the C22 address
space, or the C45 address space. A PHY with ethernet-phy-ieee802.3-c45
can use C22 bus transactions, C45 over C22, to access the C45 address
space.

So what you are testing is conceptually wrong. It might in practice
work because of the way the hardware is broken, but that does not make
it correct.

A PHY with ethernet-phy-ieee802.3-c45 should fail to enumerate, and
that should be obvious. So i don't think you need this.

	Andrew