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

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Message-ID: <87il9xoddo.wl-tiwai@suse.de>
Date:   Wed, 02 Aug 2023 14:08:35 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Shengjiu Wang <shengjiu.wang@...il.com>
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, 02 Aug 2023 14:02:29 +0200,
Shengjiu Wang wrote:
> 
> 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.

Can you explain a bit more details of your demand?
At least, a "big picture" showing how your hardware is implemented and
what is exactly necessary would be helpful for understanding the
problem.


thanks,

Takashi