chn_setblocksize
int chn_setblocksize(struct pcm_channel *c, int blkcnt, int blksz);
chn_setblocksize(wrch, 2, *arg_i);
chn_setblocksize(rdch, 2, *arg_i);
ret = chn_setblocksize(rdch, maxfrags, fragsz);
ret = chn_setblocksize(wrch, maxfrags, fragsz);
chn_setblocksize(wrch, 2, p->play_size);
chn_setblocksize(rdch, 2, p->rec_size);