usb_root_hub_lost_power — called by HCD if the root hub lost Vbus power
struct usb_device for the root hub
The USB host controller driver calls this function when its root hub is resumed and Vbus power has been interrupted or the controller has been reset. The routine marks rhdev as having lost power. When the hub driver is resumed it will take notice; if CONFIG_USB_PERSIST is enabled then it will carry out power-session recovery, otherwise it will disconnect all the child devices.