igc_next_desc
next_desc = igc_next_desc(last_desc, 1, igc->igc_tx_ndesc);
desc = igc_next_desc(desc, 1, igc->igc_tx_ndesc)) {
igc_next_desc(ring->itr_ring_tail, 1, igc->igc_tx_ndesc)) {
ring->itr_ring_tail = igc_next_desc(ring->itr_ring_tail, 1,
cur_head = igc_next_desc(cur_head, 1, igc->igc_rx_ndesc);