ue_watchdog
struct usb_callout ue_watchdog;
usb_callout_init_mtx(&ue->ue_watchdog, ue->ue_mtx, 0);
usb_callout_drain(&ue->ue_watchdog);
usb_callout_reset(&ue->ue_watchdog, hz, ue_watchdog, ue);
usb_callout_stop(&ue->ue_watchdog);
usb_callout_reset(&ue->ue_watchdog, hz, ue_watchdog, ue);
static void ue_watchdog(void *);