ALSA: usb-audio: work around Anroid accessory firmware bug

ALSA: usb-audio: work around Anroid accessory firmware bug

[Clemens Ladisch]

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>
---
 sound/usb/card.c |   22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 563854a..5a5153c 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -148,14 +148,32 @@ 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) {

Re: ALSA: usb-audio: work around Anroid accessory firmware bug

[Takashi Iwai]

At Sat, 15 Jun 2013 11:21:09 +0200,
Clemens Ladisch wrote:
> 
> 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>

Thanks, applied (with a typo correction of the subject line :)


Takashi

> ---
>  sound/usb/card.c |   22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/usb/card.c b/sound/usb/card.c
> index 563854a..5a5153c 100644
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -148,14 +148,32 @@ 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) {
>