sound: usb-audio: add workaround for Blue Microphones devices
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@ladisch.de>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index c7b9023..44b9cdc 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -2661,7 +2661,7 @@
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;
@@ -2734,6 +2734,18 @@
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)