__rdsv3_ib_ring_used
ASSERT(!__rdsv3_ib_ring_used(ring));
return (__rdsv3_ib_ring_used(ring) == 0);
avail = ring->w_nr - __rdsv3_ib_ring_used(ring);
return (__rdsv3_ib_ring_used(ring) <= (ring->w_nr >> 2));