The channel mapping is defined by bChRelationship, not bChPurpose.
Fixes: 9a2fe9b801f5 ("ALSA: usb: initial USB Audio Device Class 3.0 support")
Reviewed-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
Signed-off-by: Michael Drake <michael.drake@codethink.co.uk>
Signed-off-by: Jorge Sanjuan <jorge.sanjuan@codethink.co.uk>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
                         * TODO: this conversion is not complete, update it
                         * after adding UAC3 values to asound.h
                         */
-                       switch (is->bChPurpose) {
+                       switch (is->bChRelationship) {
                        case UAC3_CH_MONO:
                                map = SNDRV_CHMAP_MONO;
                                break;