[PATCH 3.2 026/140] ALSA: usb-audio: Add check return value for usb_string()

[Ben Hutchings]

3.2.100-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jaejoong Kim <climbbb.kim@xxxxxxxxx>

commit 89b89d121ffcf8d9546633b98ded9d18b8f75891 upstream.

snd_usb_copy_string_desc() returns zero if usb_string() fails.
In case of failure, we need to check the snd_usb_copy_string_desc()'s
return value and add an exception case

Signed-off-by: Jaejoong Kim <climbbb.kim@xxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1928,12 +1928,14 @@ static int parse_audio_selector_unit(str
 	if (len)
 		;
 	else if (nameid)
-		snd_usb_copy_string_desc(state, nameid, kctl->id.name, sizeof(kctl->id.name));
-	else {
+		len = snd_usb_copy_string_desc(state, nameid, kctl->id.name,
+					 sizeof(kctl->id.name));
+	else
 		len = get_term_name(state, &state->oterm,
 				    kctl->id.name, sizeof(kctl->id.name), 0);
-		if (! len)
-			strlcpy(kctl->id.name, "USB", sizeof(kctl->id.name));
+
+	if (!len) {
+		strlcpy(kctl->id.name, "USB", sizeof(kctl->id.name));
 
 		if (desc->bDescriptorSubtype == UAC2_CLOCK_SELECTOR)
 			append_ctl_name(kctl, " Clock Source");