aq_next
pidx=aq_next(pidx, ring->rx_size - 1);
i = aq_next(i, ring->rx_size - 1);
cidx = aq_next(cidx, ring->rx_size - 1);
pidx = aq_next(pidx, ring->tx_size - 1);
pidx = aq_next(pidx, ring->tx_size - 1);