ZYD_TX_DESC_SIZE
usbd_copy_in(pc, 0, &data->desc, ZYD_TX_DESC_SIZE);
usbd_m_copy_in(pc, ZYD_TX_DESC_SIZE, m, 0,
usbd_xfer_set_frame_len(xfer, 0, ZYD_TX_DESC_SIZE + m->m_pkthdr.len);
pktlen = ZYD_TX_DESC_SIZE + 10;