auring_get_contig_free
KASSERTMSG(auring_get_contig_free(ring) >= n,
auring_get_contig_free(ring), n);
dstcount = auring_get_contig_free(stage->dst);
count = auring_get_contig_free(&track->outbuf);
KASSERT(auring_get_contig_free(input) > 0);
bytes1 = auring_get_contig_free(usrbuf);
KASSERTMSG(auring_get_contig_free(&mixer->hwbuf) >= frame_count,
auring_get_contig_free(&mixer->hwbuf), frame_count);