lance_tx_head
struct lance_tx_head tx_head[TX_RING_SIZE];
struct lance_tx_head *head;
struct lance_tx_head tx_ring[TX_RING_SIZE];
struct lance_tx_head tx_head[TX_RING_SIZE];
struct lance_tx_head *head;
struct lance_tx_head *head = &(MEM->tx_head[old_tx]);