ALSA: usb-audio: Skip broken EU on Dell dock USB-audio

[ Upstream commit 1d8d6428d1da642ddd75b0be2d1bb1123ff8e017 ]

The Dell Dock USB-audio device with 0bda:4014 is behaving notoriously
bad, and we have already applied some workaround to avoid the firmware
hiccup.  Yet we still need to skip one thing, the Extension Unit at ID
4, which doesn't react correctly to the mixer ctl access.

Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1090658
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>

diff --git a/sound/usb/mixer_maps.c b/sound/usb/mixer_maps.c
index 1f8fb0d904e059d4e6084d0c221489d598e9e4c1..f5cf23ffb35b1d957a0186367b39df642e150188 100644 (file)
--- a/sound/usb/mixer_maps.c
+++ b/sound/usb/mixer_maps.c
@@ -351,8 +351,11 @@ static struct usbmix_name_map bose_companion5_map[] = {
 /*
  * Dell usb dock with ALC4020 codec had a firmware problem where it got
  * screwed up when zero volume is passed; just skip it as a workaround
+ *
+ * Also the extension unit gives an access error, so skip it as well.
  */
 static const struct usbmix_name_map dell_alc4020_map[] = {
+       { 4, NULL },    /* extension unit */
        { 16, NULL },
        { 19, NULL },
        { 0 }