linux-kernel - Re: [PATCH V4] Docs/sound: Update codec-to-codec documentation

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Message-ID: <Z1LTUDDJZyg1+OOz@opensource.cirrus.com>
Date: Fri, 6 Dec 2024 10:34:56 +0000
From: Charles Keepax <ckeepax@...nsource.cirrus.com>
To: anish kumar <yesanishhere@...il.com>
CC: <lgirdwood@...il.com>, <broonie@...nel.org>, <perex@...ex.cz>,
        <tiwai@...e.com>, <corbet@....net>, <linux-kernel@...r.kernel.org>,
        <linux-sound@...r.kernel.org>, <linux-doc@...r.kernel.org>
Subject: Re: [PATCH V4] Docs/sound: Update codec-to-codec documentation

On Thu, Oct 31, 2024 at 02:14:11PM -0700, anish kumar wrote:
> Updated documentation to provide more details
> for codec-to-codec connection especially around
> the scenarios and DAPM core details for C2C
> creation.
> 
> Signed-off-by: anish kumar <yesanishhere@...il.com>
> ---
> +Boot-up logs will display message similar to:
> +
> +.. code-block:: text
> +
> +   ASoC: registered pcm #0 codec2codec(Playback Codec)
> +
> +To trigger this DAI link, a control interface is established by the

Probably better to describe this as a widget rather than a
control interface. This widget may have a control to switch the
params but really the key point is the widget here.

> +DAPM core during internal DAI creation. This interface links to
> +the ``snd_soc_dai_link_event`` function, which is invoked when a
> +path connects in the DAPM core. A mixer must be created to trigger
> +the connection, prompting the DAPM core to evaluate path

I am not 100% sure what we are going for here with "A mixer must
be created", I think we are saying that the DAPM graph must route
into the C2C link to power it up. I would be inclined to drop
this and just mention the callbacks that get called.

> +connections and call the ``snd_soc_dai_link_event`` callback with
> +SND_SOC_DAPM_*_PMU and SND_SOC_DAPM_*_PMD events.
> +
> +It is important to note that not all operations defined in
> +``snd_soc_dai_ops`` are invoked as C2C connections offer
> +limited control over DAI configuration. The operations typically
> +executed in C2C setups include startup, ``hw_params``, ``hw_free``,
> +digital mute, and shutdown from the ``snd_soc_dai_ops`` struct.
> +

But I think those are my only remaining comments.

Thanks,
Charles