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) {