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>
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@ -2661,7 +2661,7 @@ static int parse_audio_endpoints(struct snd_usb_audio *chip, int iface_no)
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struct usb_interface_descriptor *altsd;
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int i, altno, err, stream;
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int format;
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struct audioformat *fp;
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struct audioformat *fp = NULL;
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unsigned char *fmt, *csep;
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int num;
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@ -2734,6 +2734,18 @@ static int parse_audio_endpoints(struct snd_usb_audio *chip, int iface_no)
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continue;
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}
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/*
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* Blue Microphones workaround: The last altsetting is identical
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* with the previous one, except for a larger packet size, but
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* is actually a mislabeled two-channel setting; ignore it.
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*/
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if (fmt[4] == 1 && fmt[5] == 2 && altno == 2 && num == 3 &&
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fp && fp->altsetting == 1 && fp->channels == 1 &&
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fp->format == SNDRV_PCM_FORMAT_S16_LE &&
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le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize) ==
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fp->maxpacksize * 2)
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continue;
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csep = snd_usb_find_desc(alts->endpoint[0].extra, alts->endpoint[0].extralen, NULL, USB_DT_CS_ENDPOINT);
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/* Creamware Noah has this descriptor after the 2nd endpoint */
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if (!csep && altsd->bNumEndpoints >= 2)
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