Re: [PATCH v2 1/2] pinctrl: add pinctrl_provide_dummies interface for platforms to use

From: Dong Aisheng <aisheng.dong@freescale.com>
To: Stephen Warren <swarren@wwwdotorg.org>
Cc: Dong Aisheng-B29396 <B29396@freescale.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linus.walleij@stericsson.com" <linus.walleij@stericsson.com>,
	"s.hauer@pengutronix.de" <s.hauer@pengutronix.de>
Subject: Re: [PATCH v2 1/2] pinctrl: add pinctrl_provide_dummies interface for platforms to use
Date: Thu, 26 Apr 2012 15:48:54 +0800	[thread overview]
Message-ID: <20120426074853.GA26070@shlinux2.ap.freescale.net> (raw)
In-Reply-To: <4F9816A3.5090907@wwwdotorg.org>

On Wed, Apr 25, 2012 at 11:22:11PM +0800, Stephen Warren wrote:
> 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@freescale.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.
> 
Yes, it's true.
I will drop the dummy gpio support in pinctrl subsystem and let gpio
driver to decide whether it wants to use pinctrl gpio mux function.

Regards
Dong Aisheng