Re: [PATCH 1/6] media: v4l2: Add audio capture and output support

From: Mark Brown
Date: Mon Jul 03 2023 - 08:54:06 EST


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.  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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