EP_RING_INDEX
ring_frame = (struct esmem_frame *)&(epbh->ring[EP_RING_INDEX
ring_frame = (struct esmem_frame *)&(epbh->ring[EP_RING_INDEX
((_num) = EP_RING_INDEX((_num) + 1, (_max)))
(0 == EP_RING_INDEX(((_tail) - (_head)), (_max)))
(1 == EP_RING_INDEX(((_tail) - (_head)), (_max)))