linux-kernel - Re: [PATCH 4/6] ASoC: fsl_asrc: Add memory to memory driver

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Message-ID: <f234b307-9ee6-489d-af8f-46cdc966a6cb@sirena.org.uk>
Date:   Fri, 30 Jun 2023 12:22:31 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Shengjiu Wang <shengjiu.wang@...il.com>
Cc:     Shengjiu Wang <shengjiu.wang@....com>, tfiga@...omium.org,
        m.szyprowski@...sung.com, mchehab@...nel.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xiubo.Lee@...il.com, festevam@...il.com, nicoleotsuka@...il.com,
        lgirdwood@...il.com, perex@...ex.cz, tiwai@...e.com,
        alsa-devel@...a-project.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 4/6] ASoC: fsl_asrc: Add memory to memory driver

On Fri, Jun 30, 2023 at 11:37:29AM +0800, Shengjiu Wang wrote:
> On Thu, Jun 29, 2023 at 7:39 PM Mark Brown <broonie@...nel.org> wrote:
> > On Thu, Jun 29, 2023 at 09:37:51AM +0800, Shengjiu Wang wrote:

> > > Implement the ASRC memory to memory function using
> > > the v4l2 framework, user can use this function with
> > > v4l2 ioctl interface.

> > This feels like the bit where we interface v4l to ASoC should be a
> > separate library, there shouldn't be anything device specific about
> > getting an audio stream into a block of memory.  I'm thinking something
> > like the way we handle dmaengine here.

> > I've not dug into the code yet though.

> Users may want to get the ASRC output in the user space, then
> do mixing with other streams before sending to ALSA.

> As there is no such API in ASoC,  the best interface I found is
> the V4L2, but I need to do a little modification of the V4L2 API,

> extend it for audio usage.

> Could you please suggest more about the "separate library"?
> Should I place this "sound/soc/fsl/fsl_asrc_m2m.c" in another folder?

The concept of connecting an audio stream from v4l directly to something
in ASoC isn't specific to this driver or even to the i.MX platform, the
code that deals with that part of things should be split out so that it
works the same for any other drivers that do this.

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