linux-kernel - Re: [PATCH v2 1/2] pinctrl: add pinctrl_provide

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Date:	Wed, 25 Apr 2012 09:22:11 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Dong Aisheng <aisheng.dong@...escale.com>
CC:	Linus Walleij <linus.walleij@...aro.org>,
	Dong Aisheng-B29396 <B29396@...escale.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linus.walleij@...ricsson.com" <linus.walleij@...ricsson.com>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>
Subject: Re: [PATCH v2 1/2] pinctrl: add pinctrl_provide_dummies interface
 for platforms to use

On 04/25/2012 05:49 AM, Dong Aisheng wrote:
> On Wed, Apr 25, 2012 at 07:19:43PM +0800, Linus Walleij wrote:
>> On Wed, Apr 25, 2012 at 11:49 AM, Dong Aisheng
>> <aisheng.dong@...escale.com> wrote:
>>> On Wed, Apr 25, 2012 at 03:00:23AM +0800, Stephen Warren wrote:
>>
>>>> The only thing that should be calling pinctrl_request_gpio() is a GPIO
>>>> driver. It should only be calling it for the GPIOs it manages. I'd
>>>> expect that if a platform's pinctrl driver was not yet written to
>>>> support the GPIO functionality, then the GPIO driver would not be
>>>> calling this function.
>>>>
>>> Hmm, pinctrl gpio is in the same situation as pinctrl state that gpio
>>> driver may be shared between several platforms, with pinctrl support
>>> or not.
>>
>> I think it's mostly safe to assume that either:
>>
> I just saw your reply after i sent out the revised patch...
> 
>> - pinctrl calls from GPIO drivers gets stubbed out totally due to
>>   CONFIG_PINCTRL not being selected
>>
> Yes, we already have that in include/linux/pinctrl/consumer.h
> 
>> or:
>>
>> - You need to pass a token through platform data to the
>>   GPIO driver telling it whether it needs to request pins for
>>   it's GPIOs or not. Just a bool should work fine?
>>
> Yes, this is an alternative way.
> I'm using a similar way, but pass the data to pinctrl core
> rather than gpio driver. Then it is be handled together with
> dummy state in platform code.
> 
> Do you think if the current way i used is ok?
> Or i need to change to your proposed way?

I think Linus was suggesting a flag in platform data for each GPIO
driver rather than a global flag for the entire pinctrl subsystem.

That way, if one of the pinctrl drivers did fully support all the GPIO
functionality and the other didn't, you'd be able to have just one of
the GPIO drivers not call into pinctrl (or ignore certain errors) yet
the other GPIO driver could still fully interact with pinctrl as desired.
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