In a switch case, they all translate to programming a MDB entry for
a given switch port, right?

No, in fact it is the exact opposite.

A normal switchdev MDB says send traffic for a group OUT this port.

A host switchdev MDB says send traffic coming IN from a port to the
CPU.

This is why i think there should be two different switchdev calls, but
Vivien wants one call, and to look carefully at the parameters to
determine which of the two above to do.

	  Andrew