linux-kernel - Re: [PATCH v4 13/13] ASoC: Intel: bytcr

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Message-ID: <9492d03c-2198-1298-b15c-944b2cdd7876@redhat.com>
Date:   Sat, 30 Jan 2021 19:26:32 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Charles Keepax <ckeepax@...nsource.cirrus.com>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
        Jie Yang <yang.jie@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>, patches@...nsource.cirrus.com,
        linux-kernel@...r.kernel.org,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        alsa-devel@...a-project.org
Subject: Re: [PATCH v4 13/13] ASoC: Intel: bytcr_wm5102: Add jack detect
 support

Hi,

On 1/30/21 4:40 PM, Charles Keepax wrote:
> On Sat, Jan 23, 2021 at 01:17:20PM +0100, Hans de Goede wrote:
>> Add jack detect support by creating a jack and calling
>> snd_soc_component_set_jack to register the created jack
>> with the codec.
>>
>> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
>> Signed-off-by: Hans de Goede <hdegoede@...hat.com>
>> ---
>> +static struct snd_soc_jack_pin byt_wm5102_pins[] = {
>> +	{
>> +		.pin	= "Headphone",
>> +		.mask	= SND_JACK_HEADPHONE,
>> +	},
>> +	{
>> +		.pin	= "Headset Mic",
>> +		.mask	= SND_JACK_MICROPHONE,
>> +	},
>> +};
>> +
> 
> This patch looks fine to me, but I did have one small question.
> What is the thinking behind punting this to the machine driver?
> 
> I guess you can not register it if there is no jack present
> on the board, or if you have multiple jacks name them
> meaningfully. Although I sort of feel like those applied to
> the old extcon approach that just internally registered all
> the interfaces.

To be honest I'm not 100% sure why this is done this way,
this is how *all* ASoC drivers do it (AFAICT).

I think it is done this way because of 2 reasons:

1. The pins controlled by the jack are what for lack of
a better word I call "end-point" pins. And these get
registered by the machine-driver, so to make sure that
the names match it makes sense to also declare the
snd_soc_jack_pin array in the machine-driver.
For example the "Headphone" pin is a widget registered
by the machine driver as:

        SND_SOC_DAPM_HP("Headphone", NULL),

2. Probe ordering, the jack gets attached to the card and
when the coded driver's probe function runs the card does
not exist yet. But I think that could be worked around by
doing things in the component-probe function.

Regards,

Hans