UCOM_ATTACHED
sc->sc_state = UCOM_ATTACHED;
KASSERTMSG(sc->sc_state == UCOM_ATTACHED || sc->sc_state == UCOM_OPEN,
sc->sc_state = UCOM_ATTACHED;
sc->sc_state = UCOM_ATTACHED;
KASSERTMSG(state == UCOM_OPEN || state == UCOM_ATTACHED,
bool firstopen = (state == UCOM_ATTACHED);