ALSA: core: Allow card id change to the same string

When user want to change the card id to the same string
on the card via /sys/class/sound/cardX/id, do not
report error. Instead return with success without
doing anything.
Signed-off-by: NPeter Ujfalusi <peter.ujfalusi@nokia.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/core/init.c

@@ -607,11 +607,16 @@ card_id_store_attr(struct device *dev, struct device_attribute *attr,
 		return -EEXIST;
 	}
 	for (idx = 0; idx < snd_ecards_limit; idx++) {
-		if (snd_cards[idx] && !strcmp(snd_cards[idx]->id, buf1))
-			goto __exist;
+		if (snd_cards[idx] && !strcmp(snd_cards[idx]->id, buf1)) {
+			if (card == snd_cards[idx])
+				goto __ok;
+			else
+				goto __exist;
+		}
 	}
 	strcpy(card->id, buf1);
 	snd_info_card_id_change(card);
+__ok:
 	mutex_unlock(&snd_card_mutex);
 
 	return count;