TX_NEXT
for (i = sc->tx.next; sc->tx.queued > 0; i = TX_NEXT(i)) {
for (; sc->tx.queued > 0; i = TX_NEXT(i)) {
for (i = sc->tx.next; sc->tx.queued > 0; i = TX_NEXT(i)) {
cur = TX_NEXT(cur);
htole32(sc->tx.desc_ring_paddr + DESC_OFF(TX_NEXT(i)));
cur = TX_NEXT(cur, q->nentries);
index = TX_NEXT(index, q->nentries);
i = TX_NEXT(i, q->nentries), total--) {
sc->tx.head = TX_NEXT(sc->tx.head);
sc->tx.tail = TX_NEXT(sc->tx.tail);