Nothing stops ethtool from providing a combined operation on the command
line, but that doesn't mean we necessarily have to have a single kernel
interface doing both thing.

Sounds good. We can have a combined operation on the command line and can still have different data structure, command and kernel interface for each of the sub operations.

I really still think that adding just a new key operation is the way to go.

Ben and David,
I don't mind going back to the original approach of adding a new hash key operation. Please let me know what you guys think, combined operation or a new operation.