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SubjectRe: [alsa-devel] [PATCH v9 4/4] sound/usb: Use Media Controller API to share media resources
On 12/19/18 6:51 AM, Takashi Iwai wrote:
> On Tue, 18 Dec 2018 18:59:39 +0100,
> wrote:
>> From: Shuah Khan <>
>> Media Device Allocator API to allows multiple drivers share a media device.
>> This API solves a very common use-case for media devices where one physical
>> device (an USB stick) provides both audio and video. When such media device
>> exposes a standard USB Audio class, a proprietary Video class, two or more
>> independent drivers will share a single physical USB bridge. In such cases,
>> it is necessary to coordinate access to the shared resource.
>> Using this API, drivers can allocate a media device with the shared struct
>> device as the key. Once the media device is allocated by a driver, other
>> drivers can get a reference to it. The media device is released when all
>> the references are released.
>> Change the ALSA driver to use the Media Controller API to share media
>> resources with DVB, and V4L2 drivers on a AU0828 media device.
>> The Media Controller specific initialization is done after sound card is
>> registered. ALSA creates Media interface and entity function graph nodes
>> for Control, Mixer, PCM Playback, and PCM Capture devices.
>> snd_usb_hw_params() will call Media Controller enable source handler
>> interface to request the media resource. If resource request is granted,
>> it will release it from snd_usb_hw_free(). If resource is busy, -EBUSY is
>> returned.
>> Media specific cleanup is done in usb_audio_disconnect().
>> Signed-off-by: Shuah Khan <>
> Feel free to take my ack regarding the sound stuff:
> Reviewed-by: Takashi Iwai <>
> Thanks!
> Takashi

Hi Mauro,

Any update on this patch series?

-- Shuah

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