CP_RING_BYTES
mem = dma_alloc_coherent(d, CP_RING_BYTES, &cp->ring_dma, GFP_KERNEL);
dma_free_coherent(d, CP_RING_BYTES, cp->rx_ring, cp->ring_dma);
dma_free_coherent(&cp->pdev->dev, CP_RING_BYTES, cp->rx_ring,