* USB hubs. That makes it stay the same until systems are physically
* reconfigured, by re-cabling a tree of USB devices or by moving USB host
* controllers. Adding and removing devices, including virtual root hubs
* USB hubs. That makes it stay the same until systems are physically
* reconfigured, by re-cabling a tree of USB devices or by moving USB host
* controllers. Adding and removing devices, including virtual root hubs