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

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Date:	Thu, 25 Jun 2009 23:09:49 +0800
From:	Alek Du <alek.du@...el.com>
To:	Jani Nikula <ext-jani.1.nikula@...ia.com>
CC:	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 Thu, 25 Jun 2009 23:05:55 +0800
Jani Nikula <ext-jani.1.nikula@...ia.com> wrote:

> On Thu, 2009-06-25 at 16:52 +0200, Jani Nikula wrote:
> > On Thu, 2009-06-25 at 16:08 +0200, ext Alek Du wrote:
> > > If you schedule the timer when you decide it "stabilized", the final gpio_get_value()
> > > could still return 0 in the timer handler, if the key released at that time. So your previous
> > > "stabilized" state is useless.
> > 
> > True, gpio_keys_report_event should also compare the value to the
> > previous state and bail out if it's unchanged. Something along the lines
> > of:
> > 
> > @@ -46,6 +46,10 @@ static void gpio_keys_report_event(struct work_struct *work)
> >  	unsigned int type = button->type ?: EV_KEY;
> >  	int state = (gpio_get_value(button->gpio) ? 1 : 0) ^ button->active_low;
> >  
> > +	if (state == bdata->state)
> > +		return;
> > +	bdata->state = state; 
> 
> Actually scrap that, the input layer already ignores events with no
> state changes, right?
> 
Yes, correct. I just want to reply your previous mail, but seems you find that. :-)
> > Debouncing should also completely ignore a single spike shorter than
> > debounce_interval. Admittedly gpio-keys was flawed, but please consider
> > a change like above which should fix that.
> 
> Same here, gpio-keys did ignore spikes shorter than debounce_interval.
> 
Yes, sending first state 0 to input layer does nothing wrong. 
> 
> BR,
> Jani.
> 
> 
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