ALSA: usb-audio: work around Android accessory firmware bug (342cda29) · Commits · 戴 / test

When the Android firmware enables the audio interfaces in accessory mode, it always declares in the control interface's baInterfaceNr array that interfaces 0 and 1 belong to the audio function. However, the accessory interface itself, if also enabled, already is at index 0 and shifts the actual audio interface numbers to 1 and 2, which prevents the PCM streaming interface from being seen by the host driver. To get the PCM interface interface to work, detect when the descriptors point to the (for this driver useless) accessory interface, and redirect to the correct one. Reported-by:

Jeremy Rosen <jeremy.rosen@openwide.fr> Tested-by:

Jeremy Rosen <jeremy.rosen@openwide.fr> Cc: <stable@vger.kernel.org> Signed-off-by:

Clemens Ladisch <clemens@ladisch.de> Signed-off-by:

Takashi Iwai <tiwai@suse.de>

sound/usb/card.c

+20 −2

Original line number	Diff line number	Diff line
		@@ -147,14 +147,32 @@ static int snd_usb_create_stream(struct snd_usb_audio *chip, int ctrlif, int int
		return -EINVAL;
		}

		alts = &iface->altsetting[0];
		altsd = get_iface_desc(alts);

		/*
		* Android with both accessory and audio interfaces enabled gets the
		* interface numbers wrong.
		*/
		if ((chip->usb_id == USB_ID(0x18d1, 0x2d04) \|\|
		chip->usb_id == USB_ID(0x18d1, 0x2d05)) &&
		interface == 0 &&
		altsd->bInterfaceClass == USB_CLASS_VENDOR_SPEC &&
		altsd->bInterfaceSubClass == USB_SUBCLASS_VENDOR_SPEC) {
		interface = 2;
		iface = usb_ifnum_to_if(dev, interface);
		if (!iface)
		return -EINVAL;
		alts = &iface->altsetting[0];
		altsd = get_iface_desc(alts);
		}

		if (usb_interface_claimed(iface)) {
		snd_printdd(KERN_INFO "%d:%d:%d: skipping, already claimed\n",
		dev->devnum, ctrlif, interface);
		return -EINVAL;
		}

		alts = &iface->altsetting[0];
		altsd = get_iface_desc(alts);
		if ((altsd->bInterfaceClass == USB_CLASS_AUDIO \|\|
		altsd->bInterfaceClass == USB_CLASS_VENDOR_SPEC) &&
		altsd->bInterfaceSubClass == USB_SUBCLASS_MIDISTREAMING) {

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