round_pow2
ret = min(round_pow2(v), CHN_2NDBUFMAXSIZE >> 1);
bufsz = round_pow2(snd_xbytes(1 << bufsz, CHN_LATENCY_DATA_REF,
sblkcnt = round_pow2(blkcnt);
hblkcnt = round_pow2(sndbuf_getblkcnt(bs));