linux-kernel - Re: [alsa-devel] [PATCH v9 4/4] sound/usb: Use Media Controller API to share media resources

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Date:   Wed, 19 Dec 2018 14:51:33 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     shuah@...nel.org
Cc:     mchehab@...nel.org, perex@...ex.cz, tiwai@...e.com,
        hverkuil@...all.nl, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: [alsa-devel] [PATCH v9 4/4] sound/usb: Use Media Controller API to share media resources

On Tue, 18 Dec 2018 18:59:39 +0100,
shuah@...nel.org wrote:
> 
> From: Shuah Khan <shuah@...nel.org>
> 
> 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 <shuah@...nel.org>

Feel free to take my ack regarding the sound stuff:
  Reviewed-by: Takashi Iwai <tiwai@...e.de>


Thanks!

Takashi