linux-kernel - Re: [PATCH V2 4/5] gpio: DT: Rephrase "gpios" of hog node to support multiple gpios

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Message-ID: <56E82CE0.4010102@wwwdotorg.org>
Date:	Tue, 15 Mar 2016 09:40:16 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Laxman Dewangan <ldewangan@...dia.com>
Cc:	linus.walleij@...aro.org, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, mpa@...gutronix.de, treding@...dia.com,
	bparrot@...com, acourbot@...dia.com, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 4/5] gpio: DT: Rephrase "gpios" of hog node to support
 multiple gpios

On 03/15/2016 12:37 AM, Laxman Dewangan wrote:
>
> On Monday 14 March 2016 10:01 PM, Stephen Warren wrote:
>> On 03/11/2016 06:43 AM, Laxman Dewangan wrote:
>>> The property "gpios" of GPIO hog node support the multiple GPIO entries.
>>> Rephrase the details of this property for this new support.
>>>
>>> Add details of new property "label" for GPIO label name.
>>
>>> diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt
>>> b/Documentation/devicetree/bindings/gpio/gpio.txt
>>
>>>   Optional properties:
>>>   - line-name:  The GPIO label name. If not present the node name is
>>> used.
>>> +- label:      The GPIO lable name. This can have multiple string for
>>> GPIO
>>> +          label names to match with the GPIOs in "gpios" properties.
>>> +          If line-name is prosent than name is taken from line-name. If
>>> +          it is not then the name will be taken from label. If both are
>>> +          not available then node name is used for GPIO label name.
>>
>> Why are there two properties for the same thing? Why not just allow
>> line-name to have multiple entries instead of introducing a new property?
>>
>
> We can use the lin-names also but per disucssion on the patch V1 of
>      gpio: of: Add support to have multiple gpios in gpio-hog
>
> Markus suggested the discussion about the discussion
> (https://lkml.org/lkml/2016/3/10/194):
>      "Device tree binding documentation for gpio-switch"
>
>
> and on that, label is used.  Also for names, "label" is going to very
> common.
>
> So I added new property "label" to support multiple names.

It makes sense to standardize on a common name for new bindings, but 
this binding has already picked a name. It'd be much simpler for anyone 
looking at the binding (and backwards-compatibility) to just stick with 
it. We have to support the old name forever no matter what. Supporting 
two different names will just be confusing.