usbd_transfer_drain
usbd_transfer_drain(sc->sc_xfer[sc->sc_last_xfer_index]);
usbd_transfer_drain(xfer);
void usbd_transfer_drain(struct usb_xfer *xfer);
usbd_transfer_drain(sc->sc_xfer[i]);
usbd_transfer_drain(sc->sc_xfer[i]);
usbd_transfer_drain(sc->sc_xfer[RUM_BULK_WR]);
usbd_transfer_drain(sc->sc_xfer[RUM_BULK_RD]);
usbd_transfer_drain(sc->sc_xfer[i]);
usbd_transfer_drain(sc->sc_xfer[x]);
usbd_transfer_drain(sc->sc_xfer[i]);