ocelot_fdma_idx_next
idx = ocelot_fdma_idx_next(idx, OCELOT_FDMA_RX_RING_SIZE);
idx = ocelot_fdma_idx_next(idx, OCELOT_FDMA_RX_RING_SIZE);
rx_ring->next_to_alloc = ocelot_fdma_idx_next(rx_ring->next_to_alloc,
idx = ocelot_fdma_idx_next(idx, OCELOT_FDMA_RX_RING_SIZE);
tx_ring->next_to_clean = ocelot_fdma_idx_next(ntc,
next_idx = ocelot_fdma_idx_next(tx_ring->next_to_use,
idx = ocelot_fdma_idx_next(idx, OCELOT_FDMA_RX_RING_SIZE);
idx = ocelot_fdma_idx_next(idx, OCELOT_FDMA_TX_RING_SIZE);