IX_TX_RESERVED
maxsegs = txr->tx_avail - IX_TX_RESERVED;
if (txr->tx_avail > IX_MAX_SCATTER + IX_TX_RESERVED) {
if (nsegs >= txr->tx_ndesc - IX_MAX_SCATTER - IX_TX_RESERVED) {
if (txr->tx_avail <= IX_MAX_SCATTER + IX_TX_RESERVED) {