UKBD_INTR_DT
usbd_xfer_set_interval(sc->sc_xfer[UKBD_INTR_DT], rate);
usbd_transfer_start(sc->sc_xfer[UKBD_INTR_DT]);
usbd_transfer_stop(sc->sc_xfer[UKBD_INTR_DT]);
usbd_transfer_start(sc->sc_xfer[UKBD_INTR_DT]);
[UKBD_INTR_DT] = {