AGE_RR_RING_CNT
AGE_DESC_INC(rr_cons, AGE_RR_RING_CNT);
((AGE_RR_RING_CNT << DESC_RRD_CNT_SHIFT) &
rrd_hi = (AGE_RR_RING_CNT * 7) / 8;
rrd_lo = AGE_RR_RING_CNT / 16;
(sizeof(struct rx_rdesc) * AGE_RR_RING_CNT)