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Date:   Mon, 3 Jul 2023 13:53:51 +0100
From:   Mark Brown <broonie@kernel.org>
To:     Takashi Iwai <tiwai@suse.de>
Cc:     Shengjiu Wang <shengjiu.wang@gmail.com>,
        Sakari Ailus <sakari.ailus@iki.fi>,
        Shengjiu Wang <shengjiu.wang@nxp.com>, tfiga@chromium.org,
        m.szyprowski@samsung.com, mchehab@kernel.org,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        Xiubo.Lee@gmail.com, festevam@gmail.com, nicoleotsuka@gmail.com,
        lgirdwood@gmail.com, perex@perex.cz, tiwai@suse.com,
        alsa-devel@alsa-project.org, linuxppc-dev@lists.ozlabs.org,
        hverkuil@xs4all.nl, Jacopo Mondi <jacopo@jmondi.org>
Subject: Re: [PATCH 1/6] media: v4l2: Add audio capture and output support
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On Mon, Jul 03, 2023 at 02:07:10PM +0200, Takashi Iwai wrote:
> Shengjiu Wang wrote:

> > There is no such memory to memory interface defined in ALSA.=A0 Seems
> > ALSA is not designed for M2M cases.

> There is no restriction to implement memory-to-memory capture in ALSA
> framework.  It'd be a matter of the setup of PCM capture source, and
> you can create a corresponding kcontrol element to switch the mode or
> assign a dedicated PCM substream, for example.  It's just that there
> was little demand for that.

Yeah, it's not a terrible idea.  We might use it more if we ever get
better support for DSP audio, routing between the DSP and external
devices if driven from the CPU would be a memory to memory thing.

> I'm not much against adding the audio capture feature to V4L2,
> though, if it really makes sense.  But creating a crafted /dev/audio*
> doesn't look like a great idea to me, at least.

I've still not looked at the code at all.

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