boom_rx_desc
vp->rx_ring = dma_alloc_coherent(gendev, sizeof(struct boom_rx_desc) * RX_RING_SIZE
vp->tx_ring_dma = vp->rx_ring_dma + sizeof(struct boom_rx_desc) * RX_RING_SIZE;
sizeof(struct boom_rx_desc) * RX_RING_SIZE +
vp->rx_ring[i].next = cpu_to_le32(vp->rx_ring_dma + sizeof(struct boom_rx_desc) * (i+1));
sizeof(struct boom_rx_desc) * RX_RING_SIZE +
struct boom_rx_desc* rx_ring;