linux-kernel - Re: [RFC PATCH v2 0/7] Add audio support in v4l2 framework

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Message-ID: <CAA+D8ANmBKMp_L2GS=Lp-saMQKja6L4E6No3yP-e=a5YQBD_jQ@mail.gmail.com>
Date:   Wed, 2 Aug 2023 20:02:29 +0800
From:   Shengjiu Wang <shengjiu.wang@...il.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Hans Verkuil <hverkuil@...all.nl>,
        Shengjiu Wang <shengjiu.wang@....com>, sakari.ailus@....fi,
        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, broonie@...nel.org, perex@...ex.cz,
        tiwai@...e.com, alsa-devel@...a-project.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [RFC PATCH v2 0/7] Add audio support in v4l2 framework

On Wed, Aug 2, 2023 at 7:22 PM Takashi Iwai <tiwai@...e.de> wrote:
>
> On Wed, 02 Aug 2023 09:32:37 +0200,
> Hans Verkuil wrote:
> >
> > Hi all,
> >
> > On 25/07/2023 08:12, Shengjiu Wang wrote:
> > > Audio signal processing has the requirement for memory to
> > > memory similar as Video.
> > >
> > > This patch is to add this support in v4l2 framework, defined
> > > new buffer type V4L2_BUF_TYPE_AUDIO_CAPTURE and
> > > V4L2_BUF_TYPE_AUDIO_OUTPUT, defined new format v4l2_audio_format
> > > for audio case usage.
> > >
> > > The created audio device is named "/dev/audioX".
> > >
> > > And add memory to memory support for two kinds of i.MX ASRC
> > > module
> >
> > Before I spend time on this: are the audio maintainers OK with doing
> > this in V4L2?
> >
> > I do want to have a clear statement on this as it is not something I
> > can decide.
>
> Well, I personally don't mind to have some audio capability in v4l2
> layer.  But, the only uncertain thing for now is whether this is a
> must-have or not.
>

Thanks,  I am also not sure about this.  I am also confused that why
there is no m2m implementation for audio in the kernel.  Audio also
has similar decoder encoder post-processing as video.

>
> IIRC, the implementation in the sound driver side was never done just
> because there was no similar implementation?  If so, and if the
> extension to the v4l2 core layer is needed, shouldn't it be more
> considered for the possible other route?
>

Actually I'd like someone could point me to the other route. I'd like to
try.

The reason why I select to extend v4l2 for such audio usage is that v4l2
looks best for this audio m2m implementation.  v4l2 is designed for m2m
usage.  if we need implement another 'route',  I don't think it can do better
that v4l2.

I appreciate that someone can share his ideas or doable solutions.
And please don't ignore my request, ignore my patch.

Best regards
Wang shengjiu