linux-kernel - Re: [PATCHv2] Input: omap4-keypad: Add pinctrl support

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Date:	Wed, 24 Oct 2012 19:18:53 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	balbi@...com
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Benoit Cousson <b-cousson@...com>,
	Sourav Poddar <sourav.poddar@...com>, tony@...mide.com,
	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org,
	linux-arm-kernel@...ts.infradead.org, linux-input@...r.kernel.org
Subject: Re: [PATCHv2] Input: omap4-keypad: Add pinctrl support

On Wed, Oct 24, 2012 at 6:57 PM, Felipe Balbi <balbi@...com> wrote:
> On Wed, Oct 24, 2012 at 09:18:01AM -0700, Dmitry Torokhov wrote:
>> OK, so with drivers/base/, have you considered doing default pinctrl
>> selection in bus's probe() methods? Yo would select the default
>> configuration before starting probing the device and maybe select idle
>> when probe fails or device is unbound? That would still keep the link
>> between device object and pinctrl and there less busses than device
>> drivers out there.
>
> it starts to become confusing after a while. I mean, there's a reason
> why all drivers explictly call pm_runtim_enable(), right ?
>
> From a first thought, one could think of just yanking that into bus'
> probe() as you may suggest, but sometimes the device is already enabled,
> so we need extra tricks:
>
> pm_runtime_set_active();
> pm_runtime_enable();
> pm_runtime_get();
>
> the same could happen with pinctrl eventually. What if a device needs to
> do something else (an errata fix as an example) before requesting
> pinctrl's default state ?

I can confirm this. Just the ordering between enabling/disabling
resources like clock/pins/powerdomain screw things up for us
and even if we can surely centralize parts of this code as such
into the drivers/base or pm_* namespace we would still need
explicit calls from the driver.

I'm thinking that maybe the best helpers are actually static
inline functions in the <linux/pinctrl/consumer.h> header
rather than moving anything into drivers/base/* if the
code duplication is the real problem.

Yours,
Linus Walleij
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