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    Subject[PATCH 053/105] ALSA: usb-audio: work around Android accessory firmware bug
    Date
    3.8.13.4 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Clemens Ladisch <clemens@ladisch.de>

    commit 342cda29343a6272c630f94ed56810a76740251b upstream.

    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>
    Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    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 a9d5779..3e4565f 100644
    --- a/sound/usb/card.c
    +++ b/sound/usb/card.c
    @@ -144,14 +144,32 @@ 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) {
    --
    1.8.1.2


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