1 files changed, 21 insertions, 8 deletions

diff --git a/sound/usb/stream.c b/sound/usb/stream.c
index c4339f97226b..d737d0e6e558 100644
--- a/sound/usb/stream.c
+++ b/sound/usb/stream.c
@@ -281,8 +281,6 @@ static struct snd_pcm_chmap_elem *convert_chmap(int channels, unsigned int bits,
 	const unsigned int *maps;
 	int c;
 
-	if (!bits)
-		return NULL;
 	if (channels > ARRAY_SIZE(chmap->map))
 		return NULL;
 
@@ -293,9 +291,19 @@ static struct snd_pcm_chmap_elem *convert_chmap(int channels, unsigned int bits,
 	maps = protocol == UAC_VERSION_2 ? uac2_maps : uac1_maps;
 	chmap->channels = channels;
 	c = 0;
-	for (; bits && *maps; maps++, bits >>= 1) {
-		if (bits & 1)
-			chmap->map[c++] = *maps;
+
+	if (bits) {
+		for (; bits && *maps; maps++, bits >>= 1)
+			if (bits & 1)
+				chmap->map[c++] = *maps;
+	} else {
+		/* If we're missing wChannelConfig, then guess something
+		    to make sure the channel map is not skipped entirely */
+		if (channels == 1)
+			chmap->map[c++] = SNDRV_CHMAP_MONO;
+		else
+			for (; c < channels && *maps; maps++)
+				chmap->map[c++] = *maps;
 	}
 
 	for (; c < channels; c++)
@@ -579,6 +587,7 @@ int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no)
 
 			num_channels = as->bNrChannels;
 			format = le32_to_cpu(as->bmFormats);
+			chconfig = le32_to_cpu(as->bmChannelConfig);
 
 			/* lookup the terminal associated to this interface
 			 * to extract the clock */
@@ -586,7 +595,8 @@ int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no)
 									    as->bTerminalLink);
 			if (input_term) {
 				clock = input_term->bCSourceID;
-				chconfig = le32_to_cpu(input_term->bmChannelConfig);
+				if (!chconfig && (num_channels == input_term->bNrChannels))
+					chconfig = le32_to_cpu(input_term->bmChannelConfig);
 				break;
 			}
 
@@ -652,7 +662,6 @@ int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no)
 					* (fp->maxpacksize & 0x7ff);
 		fp->attributes = parse_uac_endpoint_attributes(chip, alts, protocol, iface_no);
 		fp->clock = clock;
-		fp->chmap = convert_chmap(num_channels, chconfig, protocol);
 
 		/* some quirks for attributes here */
 
@@ -688,12 +697,16 @@ int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no)
 		/* ok, let's parse further... */
 		if (snd_usb_parse_audio_format(chip, fp, format, fmt, stream) < 0) {
 			kfree(fp->rate_table);
-			kfree(fp->chmap);
 			kfree(fp);
 			fp = NULL;
 			continue;
 		}
 
+		/* Create chmap */
+		if (fp->channels != num_channels)
+			chconfig = 0;
+		fp->chmap = convert_chmap(fp->channels, chconfig, protocol);
+
 		snd_printdd(KERN_INFO "%d:%u:%d: add audio endpoint %#x\n", dev->devnum, iface_no, altno, fp->endpoint);
 		err = snd_usb_add_audio_stream(chip, stream, fp);
 		if (err < 0) {