RX_RETURN_RING_ENTRIES
info->rx_return_ctrl.max_len = RX_RETURN_RING_ENTRIES;
RX_RETURN_RING_ENTRIES * sizeof(struct rx_desc));
idx = (idx + 1) % RX_RETURN_RING_ENTRIES;
RX_RETURN_RING_ENTRIES));
RX_RETURN_RING_ENTRIES));