RX_SGE_CNT
#define MAX_RX_SGE_CNT (RX_SGE_CNT - NEXT_PAGE_SGE_DESC_CNT)
#define RX_SGE_MASK (RX_SGE_CNT - 1)
#define NUM_RX_SGE (RX_SGE_CNT * NUM_RX_SGE_PAGES)
sge = &fp->rx_sge_ring[RX_SGE_CNT * i - 2];
int idx = RX_SGE_CNT * i - 1;