usbser_state
static struct usbser_state *usbser_list;
usbser_insert(struct usbser_state *usp)
struct usbser_state *tmp;
usbser_remove(struct usbser_state *usp)
struct usbser_state *tmp, *prev = NULL;
_NOTE(LOCK_ORDER(usbser_state::us_mutex usbser_port::port_mutex))
typedef struct usbser_state usbser_state_t;
struct usbser_state *us_next; /* linked list */
_NOTE(MUTEX_PROTECTS_DATA(usbser_state::us_mutex, usbser_state::us_dev_state))