NR_RX_DESC
static struct ring_desc rx_ring[NR_RX_DESC]
static unsigned char rxb[NR_RX_DESC * REAL_RX_BUF_SIZE]
for (i = 0; i < NR_RX_DESC; i++) {
for (i = 0; i < NR_RX_DESC; i++) {
ns->cur_rx = ++ns->cur_rx % NR_RX_DESC;