I don't see what it has to do with "registers" at all.
It is also not clear exactly what you mean by "the switch controller".
No Layer 2 switch is required to provide that kind of communications. When the switch -does- provide it, *something* in the switch has to have been built or configured to provide the service. Whether that "something" is the "switch controller" or is the Quantum Pixies From Mars is irrelevant: the device either can do it or it cannot. (And if the device wasn't -designed- to allow it but accidently allows it anyhow, then that wouldn't be the first time.)