snd_ctl_get_preferred_subdevice
int snd_ctl_get_preferred_subdevice(struct snd_card *card, int type);
EXPORT_SYMBOL_GPL(snd_ctl_get_preferred_subdevice);
prefer_subdevice = snd_ctl_get_preferred_subdevice(card, SND_CTL_SUBDEV_PCM);
subdevice = snd_ctl_get_preferred_subdevice(card, SND_CTL_SUBDEV_RAWMIDI);