From 1234097efbc87c436ce0fe710b7869804f87a493 Mon Sep 17 00:00:00 2001
From: Hans Petter Selasky <hselasky@FreeBSD.org>
Date: Wed, 24 Oct 2012 08:00:01 +0000
Subject: [PATCH] Fix USB audio specification compliance by filtering which
 descriptors can appear on which interface. This fixes detection of some USB
 audio adapters. Also increase the channel limit for FULL speed devices to 4
 channels.

Tested by:	gavin
MFC after:	1 week
---
 sys/dev/sound/usb/uaudio.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/sys/dev/sound/usb/uaudio.c b/sys/dev/sound/usb/uaudio.c
index a5b2b3c2768..986be439d8c 100644
--- a/sys/dev/sound/usb/uaudio.c
+++ b/sys/dev/sound/usb/uaudio.c
@@ -1054,13 +1054,20 @@ uaudio_chan_fill_info_sub(struct uaudio_softc *sc, struct usb_device *udev,
 			sed.v1 = NULL;
 		}
 
-		if ((acdp == NULL) &&
-		    (desc->bDescriptorType == UDESC_CS_INTERFACE) &&
-		    (desc->bDescriptorSubtype == AS_GENERAL) &&
-		    (desc->bDescriptorSubtype == UDESCSUB_AC_HEADER) &&
-		    (desc->bLength >= sizeof(*acdp))) {
-			acdp = (void *)desc;
-			audio_rev = UGETW(acdp->bcdADC);
+		if (audio_if == 0) {
+			if ((acdp == NULL) &&
+			    (desc->bDescriptorType == UDESC_CS_INTERFACE) &&
+			    (desc->bDescriptorSubtype == UDESCSUB_AC_HEADER) &&
+			    (desc->bLength >= sizeof(*acdp))) {
+				acdp = (void *)desc;
+				audio_rev = UGETW(acdp->bcdADC);
+			}
+
+			/*
+			 * Don't collect any USB audio descriptors if
+			 * this is not an USB audio stream interface.
+			 */
+			continue;
 		}
 
 		if ((acdp != NULL) &&
@@ -1132,9 +1139,8 @@ uaudio_chan_fill_info_sub(struct uaudio_softc *sc, struct usb_device *udev,
 					sed.v1 = (void *)desc;
 			}
 		}
-		if (audio_if == 0 || asid.v1 == NULL ||
-		    asf1d.v1 == NULL || ed1 == NULL ||
-		    sed.v1 == NULL) {
+		if (asid.v1 == NULL || asf1d.v1 == NULL ||
+		    ed1 == NULL || sed.v1 == NULL) {
 			/* need more descriptors */
 			continue;
 		}
@@ -1349,7 +1355,7 @@ uaudio_chan_fill_info(struct uaudio_softc *sc, struct usb_device *udev)
 			 * disable surround setups on FULL-speed USB
 			 * by default
 			 */
-			channels = 2;
+			channels = 4;
 			break;
 		default:
 			channels = 16;