sndbuf_xbytes
unsigned int sndbuf_xbytes(unsigned int v, struct snd_dbuf *from, struct snd_dbuf *to);
sndbuf_xbytes(sndbuf_getsize(pb), pb, bs) : 0;
sndbuf_xbytes(sndbuf_getblksz(pb), pb, bs) * 2 : 0;
hblksz = round_blksz(sndbuf_xbytes(sblksz, bs, b),
sndbuf_xbytes(sndbuf_getblksz(b), b, bs),
limit = sndbuf_xbytes(sndbuf_getblksz(b), b, bs) * 2;
imax(0, sndbuf_xbytes(sndbuf_getsize(bs), bs, b) -
i = sndbuf_xbytes(sndbuf_getready(bs), bs, pb);
sndbuf_xbytes(sndbuf_getsize(bs), bs, b));
minflush = threshold + sndbuf_xbytes(sndbuf_getready(b), b, bs);
minflush += sndbuf_xbytes(sndbuf_getsize(b), b, bs);
count = sndbuf_xbytes(minflush + resid, bs, b) / blksz;