Re: [PATCH] Input: gpio-keys: Support for one-directional interrupts

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Cory Maccarrone <darkstar6262@gmail.com>
Cc: Ferenc Wagner <wferi@niif.hu>,
	linux-input@vger.kernel.org, linux-omap@vger.kernel.org
Subject: Re: [PATCH] Input: gpio-keys: Support for one-directional interrupts
Date: Wed, 9 Dec 2009 09:58:31 -0800	[thread overview]
Message-ID: <20091209175831.GD4456@core.coreip.homeip.net> (raw)
In-Reply-To: <6cb013310912090815u396fd84chfab3c7bf4d5f4bc9@mail.gmail.com>

On Wed, Dec 09, 2009 at 08:15:26AM -0800, Cory Maccarrone wrote:
> On Wed, Dec 9, 2009 at 3:32 AM, Ferenc Wagner <wferi@niif.hu> wrote:
> > Cory Maccarrone <darkstar6262@gmail.com> writes:
> >
> > Interesting.  Btw. I'd like to convert gpio-keys from edge-triggered to
> > level-triggered interrupts.  Would that work for your hardware?
> 
> I'm fairly certain it wouldn't.  Each of the interrupts on my hardware
> has a corresponding bit in a control register that determines if it's
> rising or falling-edge triggered -- thus the need for my patch.  To
> capture both directions, it's necessary to modify the control register
> when a falling edge is detected, so that the corresponding rising edge
> can be collected afterward.

This kind of ugliness should be hidden in irqchip driver. See
mfd/asic3.c for an example.

> May I ask why you're thinking of
> converting to level-triggering?
> 
> Perhaps it would be better to provide an option in the platform_device
> structure to set edge- or level-triggering, similar to the change I'm
> proposing for interrupts that can only signal one way at a time.
> 

Yes, we need a way fro platform code to specify desired interrupt flags
but I don't believe we should be reconfiguring them on the fly.

-- 
Dmitry
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