I would count this as premature optimization, and really, I'd be surprised if any overhead within the Bluetooth driver is going to beat the overhead of interacting with the driver over RPC.
Yeah, the RPC overhead probably would shadow this.
Why, though? Frankly, given the other option is making bluetoothapis.dll do as little as possible, that would centralize all the logic in one place, and effectively avoid even needing to design a separate API.
Hm, fair. The latest revision should simplify this to use `bthledefs.h` types instead for the IOCTL.