UFTDI_BULK_DT_RD
usbd_xfer_set_stall(sc->sc_xfer[UFTDI_BULK_DT_RD]);
usbd_transfer_start(sc->sc_xfer[UFTDI_BULK_DT_RD]);
usbd_transfer_stop(sc->sc_xfer[UFTDI_BULK_DT_RD]);
[UFTDI_BULK_DT_RD] = {