Re: [PATCH 0/2] Add USB Ethernet controller (LAN7500) node in VAR-SOM-OM44 devicetree

Nicolai Buchwitz
2026-04-03T22:21:31Z

On 4.4.2026 00:15, Jakub Kicinski wrote:
> On Fri, 03 Apr 2026 22:33:26 +0200 Nicolai Buchwitz wrote:
>> On 3.4.2026 22:18, Jakub Kicinski wrote:
>> > On Fri, 03 Apr 2026 21:02:22 +0200 Thomas Richard wrote:
>> >> The goal of this series is to add the USB Ethernet controller node in
>> >> the
>> >> VAR-SOM-OM44 devicetree in order to allow the bootloader to patch the
>> >> devicetree and pass a MAC address to the smsc75xx driver. This was
>> >> also a
>> >> good opportunity to create the schema file for LAN75XX devices.
>> >
>> > But there's no driver for it yet, right?
>> > IDK what the best practices are here, just unusual to see a schema
>> > without a driver, is all.
>>
>> The smsc75xx driver has been in the tree since 2010 (d0cad871703b) and
>> already reads local-mac-address/mac-address from devicetree via
>> platform_get_ethdev_address() in smsc75xx_init_mac_address(), so the
>> binding should be covered on the driver side.
>
> Curious. So USB core can tie the right USB device to the DT / OF
> information automatically? I was thrown by the fact that there
> are no matches on the compatibles anywhere in the kernel.

Yes, USB core matches DT nodes by port topology (reg property), not by
compatible (usb_of_get_device_node() in drivers/usb/core/of.c if you
want to have a deeper look).

The existing microchip,lan95xx.yaml binding works the same way.
For example Raspberry Pi models before the Pi 4 use exactly this
pattern to pass the MAC address via firmware -> devicetree to the
smsc95xx driver.