TX_DESC_INFO
TX_DESC_INFO(txring, fill).dma = nfrags;
TX_DESC_INFO(txring, fill).skb = skb;
TX_DESC_INFO(txring, fill+i).dma = map[i];
prefetch(&TX_DESC_INFO(txring, start+1).skb);
skb = TX_DESC_INFO(txring, i+1).skb;
nr_frags = TX_DESC_INFO(txring, i).dma;
dmas[descr_count][j] = TX_DESC_INFO(txring, i+1+j).dma;