linux-kernel - Re: [RFC PATCH v2 5/5] ASoC: apple: Add macaudio machine driver

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Date:   Thu, 9 Jun 2022 14:16:04 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Martin Povišer <povik+lin@...ebit.org>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mark Kettenis <kettenis@...nbsd.org>,
        Hector Martin <marcan@...can.st>,
        Sven Peter <sven@...npeter.dev>, asahi@...ts.linux.dev
Subject: Re: [RFC PATCH v2 5/5] ASoC: apple: Add macaudio machine driver

On Mon, Jun 06, 2022 at 09:19:10PM +0200, Martin Povišer wrote:

> + *  ┌──────────┐       ┌───────────────► ┌─────┐     ┌──────────┐
> + *  │ Primary  ├───────┤                 │ Mux │ ──► │ Speakers │
> + *  └──────────┘       │    ┌──────────► └─────┘     └──────────┘
> + *                ┌─── │ ───┘             ▲
> + *  ┌──────────┐  │    │                  │
> + *  │Secondary ├──┘    │     ┌────────────┴┐
> + *  └──────────┘       ├────►│Plug-in Demux│
> + *                     │     └────────────┬┘
> + *                     │                  │
> + *                     │                  ▼
> + *                     │                 ┌─────┐     ┌──────────┐
> + *                     └───────────────► │ Mux │ ──► │Headphones│
> + *                                       └─────┘     └──────────┘

As far as I can tell this demux is entirely software based - why not
just expose the routing control to userspace and let it handle
switching (which I suspect may be more featureful than what's
implemented here)?

> +static int macaudio_jack_event(struct notifier_block *nb, unsigned long event,
> +                               void *data)
> +{
> +       struct snd_soc_jack *jack = data;
> +       struct macaudio_snd_data *ma = snd_soc_card_get_drvdata(jack->card);
> +
> +       ma->jack_plugin_state = !!event;
> +
> +       if (!ma->plugin_demux_kcontrol)
> +               return 0;
> +
> +       snd_soc_dapm_mux_update_power(&ma->card.dapm, ma->plugin_demux_kcontrol,
> +                                     ma->jack_plugin_state,
> +                                     (struct soc_enum *) &macaudio_plugin_demux_enum, NULL);
> +
> +       return 0;
> +}

This should be integrated with the core jack detection stuff in
soc-jack.c and/or the core stuff that's wrapping - that way you'll
ensure that events are generated and status readable via all the
interfaces userspace might be looking for.  The ASoC stuff also has some
DAPM integration for turning on/off outputs which might DTRT for you if
you do need it in kernel.

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