linux-kernel - Re: [PATCH 1/3] irq: If an IRQ is a GPIO, request and configure it

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Date:	Fri, 5 Aug 2011 06:35:11 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Stephen Warren <swarren@...dia.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Liam Girdwood <lrg@...com>,
	Chris Ball <cjb@...top.org>,
	"ccross@...roid.com" <ccross@...roid.com>,
	"olof@...om.net" <olof@...om.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH 1/3] irq: If an IRQ is a GPIO, request and configure it

On Thu, Aug 04, 2011 at 08:53:34PM -0700, Stephen Warren wrote:

> Well, things break. This is essentially the problem I was describing in
> the PATCH 0 email, just with a slightly different motivation.

There's a bunch of existing code using that idiom.

> I suppose that an alternative here would be to simply ignore any errors
> from gpio_request. This might have the benefit of removing the need for
> the other two patches I posted in the series. However, it seems a little
> dirty; one benefit of the IRQ code calling gpio_request and honoring
> errors would be to detect when some completely unrelated code had a bug
> and had called gpio_request on the GPIO before. Such detection would be
> non-existent if we don't error out on gpio_request. Perhaps some mechanism
> is needed to indicate that the driver has explicitly already called
> gpio_request for a legitimate shared purpose, and only then ignore
> errors?

But it's not a bug to use a GPIO as an IRQ source, otherwise we wouldn't
have gpio_to_irq() in the first place.  Feels like we need a backchannel
between gpiolib and the IRQ code to do this.  Or perhaps the drivers
that implement this should be taking care of setting up the GPIO mode?
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