ALSA: usb-audio: uac1: Invalidate ctl on interrupt

When an interrupt occurs, the value of at least one of the belonging
controls should have changed. To make sure they get re-read from device
on the next read, invalidate the cache. This was correctly implemented
for uac2 already, but missing for uac1.

Signed-off-by: Julian Scheel <julian@jusst.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/mixer.c

@@ -2330,9 +2330,14 @@ void snd_usb_mixer_notify_id(struct usb_mixer_interface *mixer, int unitid)
 {
 	struct usb_mixer_elem_list *list;
 
-	for (list = mixer->id_elems[unitid]; list; list = list->next_id_elem)
+	for (list = mixer->id_elems[unitid]; list; list = list->next_id_elem) {
+		struct usb_mixer_elem_info *info =
+			(struct usb_mixer_elem_info *)list;
+		/* invalidate cache, so the value is read from the device */
+		info->cached = 0;
 		snd_ctl_notify(mixer->chip->card, SNDRV_CTL_EVENT_MASK_VALUE,
 			       &list->kctl->id);
+	}
 }
 
 static void snd_usb_mixer_dump_cval(struct snd_info_buffer *buffer,