MID_TX_DESCRSTART
(unsigned) eni_in(MID_TX_DESCRSTART(tx->index)));
eni_in(MID_TX_DESCRSTART(tx->index))) {
tx->tx_pos = eni_in(MID_TX_DESCRSTART(tx->index)) &
eni_in(MID_TX_DESCRSTART(eni_vcc->tx->index)))