chn_setspeed
r = chn_setspeed(c, spd);
int chn_setspeed(struct pcm_channel *c, uint32_t speed);
chn_setspeed(wrch, p->play_rate);
chn_setspeed(rdch, p->rec_rate);
ret = chn_setspeed(wrch, *arg_i);
ret = chn_setspeed(rdch, *arg_i);