snd_pcm_open
err = snd_pcm_open(file, pcm, SNDRV_PCM_STREAM_PLAYBACK);
err = snd_pcm_open(file, pcm, SNDRV_PCM_STREAM_CAPTURE);
static int snd_pcm_open(struct file *file, struct snd_pcm *pcm, int stream);
err = snd_pcm_open(&handle, name, data->stream, 0);
err = snd_pcm_open(handle, pcm_name, stream, 0);