ALSA: usb-audio: skip UAC2 EFFECT_UNIT

Current code mishandles the case where the device is a UAC2
and the bDescriptorSubtype is a UAC2 Effect Unit (0x07).
It tries to parse it as a Processing Unit (which is similar to two
other UAC1 units with overlapping subtypes), but since the structure
is different (See: 4.7.2.10, 4.7.2.11 in UAC2 standard), the parsing
is done incorrectly and prevents the device from initializing.
For now, just ignore the unit.

Signed-off-by: Eldad Zack <eldad@fogrefinery.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 12 insertions, 1 deletions

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index b0fc6ae037a2..4eacbe2e2d64 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -723,8 +723,19 @@ static int check_input_term(struct mixer_build *state, int id, struct usb_audio_
                         return 0;
                 }
                 case UAC1_PROCESSING_UNIT:
-                case UAC1_EXTENSION_UNIT: {
+                case UAC1_EXTENSION_UNIT:
+                /* UAC2_PROCESSING_UNIT_V2 */
+                /* UAC2_EFFECT_UNIT */ {
                         struct uac_processing_unit_descriptor *d = p1;
+
+                        if (state->mixer->protocol == UAC_VERSION_2 &&
+                                hdr[2] == UAC2_EFFECT_UNIT) {
+                                /* UAC2/UAC1 unit IDs overlap here in an
+                                 * uncompatible way. Ignore this unit for now.
+                                 */
+                                return 0;
+                        }
+
                         if (d->bNrInPins) {
                                 id = d->baSourceID[0];
                                 break; /* continue to parse */