linux-kernel - Re: [PATCH V5] Docs/sound: Update codec-to-codec documentation

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Message-ID: <Z1ggwXLAu+/Y817c@opensource.cirrus.com>
Date: Tue, 10 Dec 2024 11:06:41 +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-doc@...r.kernel.org>, <linux-sound@...r.kernel.org>
Subject: Re: [PATCH V5] Docs/sound: Update codec-to-codec documentation

On Sat, Dec 07, 2024 at 11:34:41AM -0800, anish kumar wrote:
> +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
> +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
> +connections and call the ``snd_soc_dai_link_event`` callback with
> +SND_SOC_DAPM_*_PMU and SND_SOC_DAPM_*_PMD events.
> +

I am still not really following this, what are we trying to
convey in this paragraph?

What do we mean by a "control interface" here, is that referring
to the kcontrol that is created to select the rate in the case
of multiple rates? Or is it simply refering to the fact we call
snd_soc_dapm_new_control_unlocked? But really that function is
adding widgets, as I noted in my last email.

Also what do we mean by a "A mixer must be created", I am not
aware of any requirement for a mixer? The DAI link needs to be on
a valid DAPM path, but I don't see any requirements other than
that.

Thanks,
Charles