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

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Message-ID: <20181209080944.GA7561@amd>
Date:   Sun, 9 Dec 2018 09:09:44 +0100
From:   Pavel Machek <pavel@....cz>
To:     shuah <shuah@...nel.org>
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
Subject: Re: [RFC PATCH v8 1/4] media: Media Device Allocator API

On Thu 2018-12-06 08:33:14, shuah wrote:
> 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?
> 
> 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.

I guess I'll need the explanation, yes.

How can usb soundcard use the tuner? I thought we'd always have
userspace component active and moving data between tuner and usb sound
card?

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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