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

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Message-ID: <CABCoZhAqhUxJSrELx1if1QYQK0wt_wrHMVcPwVbkRoqmHA2==A@mail.gmail.com>
Date: Fri, 3 Jan 2025 10:10:25 -0800
From: anish kumar <yesanishhere@...il.com>
To: Charles Keepax <ckeepax@...nsource.cirrus.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 Thu, Dec 12, 2024 at 1:35 PM anish kumar <yesanishhere@...il.com> wrote:
>
> On Tue, Dec 10, 2024 at 3:06 AM Charles Keepax
> <ckeepax@...nsource.cirrus.com> wrote:
> >
> > 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.
>
> I mean snd_soc_dapm_new_control_unlocked gets called to
> create the widget which gets triggered as part of DAPM path
> enablement.
>
> >
> > 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.
>
> In my case, I was implementing a mixer widget that users could
> trigger to enable the entire DAPM path. However, I believe it's
> sufficient to simply state that there should be a mechanism to
> trigger the codec-to-codec widget, enabling the full DAPM path.
> >
> > Thanks,
> > Charles
Could you please confirm if this explanation is clear? If so,
I will proceed with submitting another revision of the patch.