linux-kernel - Re: [PATCH 2/3] ASoC: rt5677: add a platform config option for MICBIAS voltage

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Date:	Fri, 12 Dec 2014 15:48:51 -0800
From:	Ben Zhang <benzh@...gle.com>
To:	Mark Brown <broonie@...nel.org>
Cc:	alsa-devel <alsa-devel@...a-project.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Bard Liao <bardliao@...ltek.com>,
	Oder Chiou <oder_chiou@...ltek.com>,
	Anatol Pomozov <anatol@...gle.com>,
	Dylan Reid <dgreid@...omium.org>,
	Albert Chen <albertchen@...ltek.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] ASoC: rt5677: add a platform config option for
 MICBIAS voltage

On Fri, Dec 12, 2014 at 5:27 AM, Mark Brown <broonie@...nel.org> wrote:
> On Wed, Dec 10, 2014 at 08:15:26PM -0800, Ben Zhang wrote:
>
>> The MICBIAS voltage for IN1 can be set to 1.476V/2.970V/1.242V/2.475V
>
> The changelog says "platform config" but this is adding DT binding.
>
>> +- realtek,micbias1
>> +  Select 0/1/2/3 to set MICBIAS1 voltage to 1.476V/2.970V/1.242V/2.475V
>> +
>
> Why is this being specified as some magic number rather than using the
> voltage (or at least providing defines for the voltage) - this is going
> to do little to make the DT legible and...
>
>> +enum rt5677_micbias {
>> +     RT5677_MICBIAS_1_476V = 0,
>> +     RT5677_MICBIAS_2_970V = 1,
>> +     RT5677_MICBIAS_1_242V = 2,
>> +     RT5677_MICBIAS_2_475V = 3,
>> +};
>
> ...I see there are defined for platform data.

This patch adds both an entry to the platform data and a DT binding
for MICBIAS level selection. The 4 voltage options
(1.476V/2.970V/1.242V/2.475V) are the only ones supported by the codec
hardware, so it seems an enum is better than specifying the exact
voltage directly. I was following the two examples below:

Documentation/devicetree/bindings/sound/cs42l52.txt (cirrus,micbias-lvl)
Documentation/devicetree/bindings/sound/tlv320aic3x.txt (ai3x-micbias-vg)

I'm new to devicetree bindings. Is there something like an enum in DT?
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