Conflicts when enabling LAN966X_SWITCH_APPL and using "compatible = "microchip,lan9691-switch";"

[AlbrechtL]

We integrated your Microchip kernel into our custom Linux distribution.

During development we realized that there is a mismatch when using compatible = "microchip,lan9691-switch"; in the device tree and enabling the kernel features LAN966X_SWITCH_APPL=y and LAN966X_SWITCH=y. If course this is wrong but there is no kernel error message or compile error. Instead the Linux IP stacks tries something with a Microchip specific EtherType which results in a behavior which some difficult to understand and debug .

In the best case this should not be possible.

[steen-hegelund-mchp]

@AlbrechtL Thanks for the report.

The LAN966X_SWITCH_APPL and LAN966X_SWITCH settings are not meant to be used together, so I will add a check for that in the next release.

On the other hand nothing in the kernel build system provides a dependency/check across device trees and kernel configuration - so there you are free to do whatever you please and nothing will catch that.

BR
Steen