[alsa-devel] [PATCH 2/3] ALSA: usb - For class 2 devices, use channel map from altsettings

[David Henningsson]

The channel config from the streaming descriptor is probably a
better indicator of the channel map than the input terminal.
Use the input terminal's channel map as fallback only.

Signed-off-by: David Henningsson <david.henningsson at canonical.com>
---
 sound/usb/stream.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/usb/stream.c b/sound/usb/stream.c
index b43b6ee..badd1d6d 100644
--- a/sound/usb/stream.c
+++ b/sound/usb/stream.c
@@ -587,6 +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 */
@@ -594,7 +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;
 			}
 
-- 
1.7.9.5