linux-kernel - Re: [PATCH]input: Change timer function to workqueue for gpio

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Message-ID: <20090626002345.07928230@dxy.sh.intel.com>
Date:	Fri, 26 Jun 2009 00:23:45 +0800
From:	Alek Du <alek.du@...el.com>
To:	"ext-phil.2.carmody@...ia.com" <ext-phil.2.carmody@...ia.com>
CC:	"Nikula Jani.1 (EXT-Nixu/Helsinki)" <ext-jani.1.nikula@...ia.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Trilok Soni <soni.trilok@...il.com>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"Dmitry Torokhov" <dmitry.torokhov@...il.com>,
	"ben-linux@...ff.org" <ben-linux@...ff.org>
Subject: Re: [PATCH]input: Change timer function to workqueue for gpio_keys
 driver

On Fri, 26 Jun 2009 00:09:14 +0800
Phil Carmody <ext-phil.2.carmody@...ia.com> wrote:

> If you stopped calling the delay after the first transition "debouncing
> time" and simply called it a "delay" you might more easily see that it
> does *no* debouncing at all. Imagine putting noise on the line
> constantly - the original code's timer would never expire. Your timer
> will expire after a delay, and while the line is still toggling
> frantically - you've not debounced.

I don't know if it is really meaningful if you want to handle such pool signal... 
Ok, if you want to handle this ultimate case, will this patch work?

        BUG_ON(irq != gpio_to_irq(button->gpio));

+       cancel_delayed_work_sync(&bdata->work);
        delay = button->debounce_interval ?
                        msecs_to_jiffies(button->debounce_interval) : 0;
        schedule_delayed_work(&bdata->work, delay);

Alek
> Please investigate the meaning and implications of "debouncing" before
> claiming your code does it.
> 
> Phil
> 
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