linux-kernel - Re: [PATCH v2] gpio: interrupt consistency check for OF GPIO IRQs

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Date:	Mon, 02 Sep 2013 11:43:26 +0200
From:	Lars Poeschel <poeschel@...onage.de>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Lars Poeschel <larsi@....tu-dresden.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>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	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 v2] gpio: interrupt consistency check for OF GPIO IRQs

Am Freitag, 30. August 2013, 14:08:41 schrieb Stephen Warren:
> On 08/29/2013 01:00 PM, Linus Walleij wrote:
> > On Fri, Aug 23, 2013 at 9:52 PM, Stephen Warren <swarren@...dotorg.org> 
wrote:
> >> On 08/23/2013 12:45 PM, Linus Walleij wrote:
> >>> This is a perfectly OK thing to do as long as it is done like
> >>> this:
> >>> 
> >>> request_gpio(gpio);
> >>> gpio_direction_input(gpio);
> >>> request_irq(gpio_to_irq(gpio));
> >> 
> >> But I'm not aware that there's a rule saying it's illegal to:
> >> 
> >> request_irq(gpio_to_irq(gpio));
> >> request_gpio(gpio);
> >> gpio_direction_input(gpio);
> > 
> > No but I think there should be one ... maybe I'm an oddball
> > but it seems natural to request a GPIO before tying
> > IRQs to fire off it.
> 
> What if there is no GPIO?

If there is no GPIO there is no gpio-controller and there is no problem.

> There are plenty of chips with dedicated IRQ input pins that can't be
> read as GPIOs, or treated as GPIOs in any way.
> 
> If a driver only needs IRQ input functionality, it should just request
> an IRQ and be done with it. There should be no need at all for the
> driver to know that the IRQ might be routed into a GPIO controller, and
> hence that the driver may (or may not) need to additionally request the
> GPIO before requesting the IRQ.

Yes, you're right, but reality is different. Legacy drivers / board-files do:

request_gpio(gpio);
gpio_direction_input(gpio);
request_irq(gpio_to_irq(gpio));
 
> In other words, request_irq() must do everything necessary for the input
> signal to operate as an IRQ input, irrespective of whether it might be
> possible to use that input signal as a GPIO.

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