linux-kernel - Re: [PATCH v3] gpio: interrupt consistency check for OF GPIO IRQs

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Date:	Tue, 3 Sep 2013 14:43:57 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Stephen Warren <swarren@...dotorg.org>,
	Alexandre Courbot <acourbot@...dia.com>
Cc:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Lars Poeschel <larsi@....tu-dresden.de>,
	Lars Poeschel <poeschel@...onage.de>,
	Grant Likely <grant.likely@...aro.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ian.campbell@...rix.com>,
	Kumar Gala <galak@...eaurora.org>,
	Pawel Moll <pawel.moll@....com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Enric Balletbo i Serra <eballetbo@...il.com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Kevin Hilman <khilman@...aro.org>,
	Balaji T K <balajitk@...com>,
	Tony Lindgren <tony@...mide.com>,
	Jon Hunter <jgchunter@...il.com>
Subject: Re: [PATCH v3] gpio: interrupt consistency check for OF GPIO IRQs

On Fri, Aug 30, 2013 at 9:55 PM, Stephen Warren <swarren@...dotorg.org> wrote:
> On 08/29/2013 06:24 PM, Javier Martinez Canillas wrote:
> ...
>> We have been trying to solve this issue for a few months by now and Linus'
>> approach seems to be the most sensible solution to me.
>>
>> Drivers that request an IRQ and assume that platform code will request and setup
>> the GPIO have been broken since the boards using these drivers were migrated to
>> DT (e.g: smsc911x on OMAP2+ boards).
>
> That's only true if the driver for the GPIO controller is buggy.
> Whatever request_irq() maps down to in the GPIO/IRQ controller driver
> simply needs to set up the pin as an interrupt input, then it doesn't
> matter which order the driver does things.

As mentioned it can't do that, because doing that creates a
restriction on which order the driver does things...

But you mentioned that you wanted an API that would account
for the case where the *same driver* requested the same resource
(a GPIO line) to be used for both IRQ and GPIO, through two
different calls.

I would be happy to see how we could do that, preferably in a
generic way.

Since the gpio_request() does not contain the signature of the
calling driver I don't see how we could do this without refactoring
the whole world.

In that case it would probably be easiest to
*first* proceed to complete Alexandre's suggested refactorings for
GPIO descriptors, which tie down GPIOs to be requested like
clocks and regulators and thus tied to a device, so we can from
there proceed to implement such a conditional request,
as we will then have the required information in the GPIO
subsystem.

Yours,
Linus Walleij
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