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

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Date:	Fri, 23 Aug 2013 13:49:53 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Tomasz Figa <tomasz.figa@...il.com>,
	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>,
	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

On 08/23/2013 12:38 PM, Linus Walleij wrote:
> On Thu, Aug 22, 2013 at 10:53 PM, Stephen Warren <swarren@...dotorg.org> wrote:
>> On 08/21/2013 05:27 PM, Linus Walleij wrote:
>>> On Thu, Aug 22, 2013 at 1:10 AM, Stephen Warren <swarren@...dotorg.org> wrote:
>>>>> On Wednesday 21 of August 2013 15:38:54 Lars Poeschel wrote:
>>>
>>>>>> To solve this dilemma, perform an interrupt consistency check
>>>>>> when adding a GPIO chip: if the chip is both gpio-controller and
>>>>>> interrupt-controller, walk all children of the device tree,
>>>>
>>>> It seems a little odd to solve this only for DT. What about the non-DT case?
>>>
>>> DT is the hardware configuration system that lets you request
>>> the same resource in two ways, i.e. it allows one and the same
>>> node to be both gpio-controller and interrupt-controller, and
>>> start handing out the same line as both GPIO and IRQ
>>> independently.
>>
>> Huh? What stops systems using board files and platform data from having
>> this issue?
> 
> It can't be stopped but I consider it a bug if they do, as the proper
> way to handle such GPIO lines is the sequence:
> 
> request_gpio(gpio);
> request_irq(gpio_to_irq(gpio));

Back in the old days of ARM board files, there were many boards that
didn't do this. I guess that doesn't make it any less of a bug, but it
certainly implies to me that solving this in a way that caters to that
bug being present will be a lot more useful.

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