ALSA: usb-audio: fix missing input volume controls in MAYA44 USB(+)

commit ea114fc2 upstream.

The driver worked around an error in the MAYA44 USB(+)'s mixer unit
descriptor by aborting before parsing the missing field.  However,
aborting parsing too early prevented parsing of the other units
connected to this unit, so the capture mixer controls would be missing.

Fix this by moving the check for this descriptor error after the parsing
of the unit's input pins.
Reported-by: nightmixes <nightmixes@gmail.com>
Tested-by: nightmixes <nightmixes@gmail.com>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[bwh: Backported to 3.2:
 - Adjust context
 - Logging statement was different]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

sound/usb/mixer.c

@@ -1425,11 +1425,6 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid, void *r
 		snd_printk(KERN_ERR "invalid MIXER UNIT descriptor %d\n", unitid);
 		return -EINVAL;
 	}
-	/* no bmControls field (e.g. Maya44) -> ignore */
-	if (desc->bLength <= 10 + input_pins) {
-		snd_printdd(KERN_INFO "MU %d has no bmControls field\n", unitid);
-		return 0;
-	}
 
 	num_ins = 0;
 	ich = 0;
@@ -1437,6 +1432,9 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid, void *r
 		err = parse_audio_unit(state, desc->baSourceID[pin]);
 		if (err < 0)
 			return err;
+		/* no bmControls field (e.g. Maya44) -> ignore */
+		if (desc->bLength <= 10 + input_pins)
+			continue;
 		err = check_input_term(state, desc->baSourceID[pin], &iterm);
 		if (err < 0)
 			return err;