The USB subsystem currently invokes /sbin/hotplug when USB devices
are added or removed from system. The invocation is done by the kernel
-hub daemon thread [khubd], or else as part of root hub initialization
+hub workqueue [hub_wq], or else as part of root hub initialization
(done by init, modprobe, kapmd, etc). Its single command line parameter
is the string "usb", and it passes these environment variables: