[patch 04/71] sound: usb-audio: add workaround for Blue Microphones devices

[Greg KH]

2.6.30-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Clemens Ladisch <clemens@xxxxxxxxxx>

commit 8886f33f25083a47d5fa24ad7b57bb708c5c5403 upstream.

Blue Microphones USB devices have an alternate setting that sends two
channels of data to the computer.  Unfortunately, the descriptors of
that altsetting have a wrong channel setting, which means that any
recorded data from such a device has twice the sample rate from what
would be expected.

This patch adds a workaround to ignore that altsetting.  Since these
devices have only one actual channel, no data is lost.

Signed-off-by: Clemens Ladisch <clemens@xxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 sound/usb/usbaudio.c |   14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -2649,7 +2649,7 @@ static int parse_audio_endpoints(struct 
 	struct usb_interface_descriptor *altsd;
 	int i, altno, err, stream;
 	int format;
-	struct audioformat *fp;
+	struct audioformat *fp = NULL;
 	unsigned char *fmt, *csep;
 	int num;
 
@@ -2722,6 +2722,18 @@ static int parse_audio_endpoints(struct 
 			continue;
 		}
 
+		/*
+		 * Blue Microphones workaround: The last altsetting is identical
+		 * with the previous one, except for a larger packet size, but
+		 * is actually a mislabeled two-channel setting; ignore it.
+		 */
+		if (fmt[4] == 1 && fmt[5] == 2 && altno == 2 && num == 3 &&
+		    fp && fp->altsetting == 1 && fp->channels == 1 &&
+		    fp->format == SNDRV_PCM_FORMAT_S16_LE &&
+		    le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize) ==
+							fp->maxpacksize * 2)
+			continue;
+
 		csep = snd_usb_find_desc(alts->endpoint[0].extra, alts->endpoint[0].extralen, NULL, USB_DT_CS_ENDPOINT);
 		/* Creamware Noah has this descriptor after the 2nd endpoint */
 		if (!csep && altsd->bNumEndpoints >= 2)


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