linux-kernel - Re: [RFC PATCH v8 1/4] media: Media Device Allocator API

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Message-ID: <73c22137-9c7a-75c8-8cd1-3736c63c2d40@kernel.org>
Date:   Thu, 6 Dec 2018 08:33:14 -0700
From:   shuah <shuah@...nel.org>
To:     Pavel Machek <pavel@....cz>
Cc:     mchehab@...nel.org, perex@...ex.cz, tiwai@...e.com,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        alsa-devel@...a-project.org, shuah <shuah@...nel.org>
Subject: Re: [RFC PATCH v8 1/4] media: Media Device Allocator API

On 11/19/18 1:59 AM, Pavel Machek wrote:
> On Thu 2018-11-01 18:31:30, shuah@...nel.org wrote:
>> From: Shuah Khan <shuah@...nel.org>
>>
>> Media Device Allocator API to allows multiple drivers share a media device.
>> 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.
> 
> Sounds like a ... bad idea?
> 
> That's what new "media control" framework is for, no?
> 
> Why do you need this?
> 								Pavel
> 

Media control framework doesn't address this problem of ownership of the 
media device when non-media drivers have to own the pipeline. In this 
case, snd-usb owns the audio pipeline when an audio application is using 
the device. Without this work, media drivers won't be able to tell if 
snd-usb is using the tuner and owns the media pipeline.

I am going to clarify this in the commit log.

thanks,
-- Shuah