audio_record
[AUDIO_RECORD_INDEX] = &audio_record,
usb_make_str_desc(&audio_record, sizeof(audio_record),
&audio_record, sizeof(audio_record), usb_temp_sysctl,
static struct usb_string_descriptor audio_record;
int audio_record(struct audio *aud, uint8_t *buf, size_t count);
err = audio_record(aud, st->buf, sizeof(st->buf));