From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alek Du <alek.du@intel.com>
Subject: Re: [PATCH]input: Change timer function to workqueue for gpio_keys
 	driver
Date: Thu, 25 Jun 2009 21:06:42 +0800
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To: Jani Nikula <ext-jani.1.nikula@nokia.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Trilok Soni <soni.trilok@gmail.com>, "linux-input@vger.kernel.org" <linux-input@vger.kernel.org>, Dmitry Torokhov <dmitry.torokhov@gmail.com>, "ben-linux@fluff.org" <ben-linux@fluff.org>

On Thu, 25 Jun 2009 18:29:25 +0800
Jani Nikula <ext-jani.1.nikula@nokia.com> wrote:

> On Fri, Jun 12, 2009 at 8:40 PM, Trilok Soni<soni.trilok@gmail.com> w=
rote:
> >> =C2=A0static irqreturn_t gpio_keys_isr(int irq, void *dev_id)
> >> =C2=A0{
> >> =C2=A0 =C2=A0 =C2=A0 =C2=A0struct gpio_button_data *bdata =3D dev_=
id;
> >> @@ -62,10 +61,10 @@ static irqreturn_t gpio_keys_isr(int irq, void=
 *dev_id)
> >> =C2=A0 =C2=A0 =C2=A0 =C2=A0BUG_ON(irq !=3D gpio_to_irq(button->gpi=
o));
> >>
> >> =C2=A0 =C2=A0 =C2=A0 =C2=A0if (button->debounce_interval)
> >> - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 mod_timer(&bdat=
a->timer,
> >> - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 jiffies + msecs_to_jiffies(button->debounce_interval));
> >> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 schedule_delaye=
d_work(&bdata->work,
> >> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 msecs_to_jiffies(button->debounce_interval));
> >> =C2=A0 =C2=A0 =C2=A0 =C2=A0else
> >> - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 gpio_keys_repor=
t_event(bdata);
> >> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 schedule_work(&=
bdata->work.work);
> >>
> >> =C2=A0 =C2=A0 =C2=A0 =C2=A0return IRQ_HANDLED;
> >> =C2=A0}
>=20
> Correct me if I'm wrong, but as far as I can tell,
> schedule_delayed_work doesn't modify the timer if the work was alread=
y
> pending. The result is not the same as with the timer. This breaks th=
e
> debouncing.

No. The workqueue is per button, if the work is already pending, then l=
ast
key press is not handled yet. That keeps the debouncing. Why you want t=
he second
key press to break the first one? The second key press should be ignore=
d, that's
the meaning of debouncing right?

>=20
> It looks like a slightly modified version of this patch has already
> been committed [1], but it has the same problem.
>=20
> [1] 0b346838c5862bfe911432956a106d602535d030 Input: gpio-keys - chang=
e
> timer to workqueue

Yes, the patch is already in Linus tree.


Thanks,
Alek
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