sound: usb-audio: add workaround for Blue Microphones devices (8886f33f) · Commits · 戴 / test

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>

sound/usb/usbaudio.c

+13 −1

Original line number	Diff line number	Diff line
		@@ -2661,7 +2661,7 @@ static int parse_audio_endpoints(struct snd_usb_audio *chip, int iface_no)
		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 @@ static int parse_audio_endpoints(struct snd_usb_audio *chip, int iface_no)
		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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