ALSA: usb-audio - Check the dB-range validity in the later read, too

When the initial check of dB-range failed due to the read error, try to
check again at the later read, too.  When an invalid dB range is found,
remove TLV flags and notify the mixer info change.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/mixer.c

@@ -881,8 +881,17 @@ static int mixer_ctl_feature_info(struct snd_kcontrol *kcontrol, struct snd_ctl_
 		uinfo->value.integer.min = 0;
 		uinfo->value.integer.max = 1;
 	} else {
-		if (! cval->initialized)
-			get_min_max(cval,  0);
+		if (!cval->initialized) {
+			get_min_max(cval, 0);
+			if (cval->initialized && cval->dBmin >= cval->dBmax) {
+				kcontrol->vd[0].access &= 
+					~(SNDRV_CTL_ELEM_ACCESS_TLV_READ |
+					  SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK);
+				snd_ctl_notify(cval->mixer->chip->card,
+					       SNDRV_CTL_EVENT_MASK_INFO,
+					       &kcontrol->id);
+			}
+		}
 		uinfo->value.integer.min = 0;
 		uinfo->value.integer.max =
 			(cval->max - cval->min + cval->res - 1) / cval->res;