Re: [RFC PATCH 1/2] Input: add msi-wmi driver to support hotkeys in MSI Windtop AE1900-WT

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Anisse Astier <anisse@astier.eu>
Cc: linux-input@vger.kernel.org, linux-acpi@vger.kernel.org,
	Len Brown <lenb@kernel.org>,
	Carlos Corbacho <carlos@strangeworlds.co.uk>
Subject: Re: [RFC PATCH 1/2] Input: add msi-wmi driver to support hotkeys in MSI Windtop AE1900-WT
Date: Thu, 3 Dec 2009 01:34:48 -0800	[thread overview]
Message-ID: <20091203093447.GA22196@core.coreip.homeip.net> (raw)
In-Reply-To: <20091203100812.73491fb1@destiny.ordissimo>

On Thu, Dec 03, 2009 at 10:08:12AM +0100, Anisse Astier wrote:
> On Wed, 2 Dec 2009 19:11:28 -0800, Dmitry Torokhov
> <dmitry.torokhov@gmail.com> wrote :
> 
> > Hi Anisse,
> > 
> > On Wed, Dec 02, 2009 at 07:26:03PM +0100, Anisse Astier wrote:
> > > +
> > > +	if (jiffies_to_msecs(get_jiffies_64() -
> > > msi_wmi_time_last_press)
> > > +			> pression_timeout) {
> > 
> > Why don't you use time_after() instead of manual computation?
> > 
> > Also, what is the point of this? If you are trying to debounce the
> > buttons this will not quite work. To do debouncing properly you need
> > to store the value you just read and fire up a timer. When timer
> > fires - that's the stable value.
> 
> Indeed, the point is to debounce the keys. I guess I’ll just use the 
> debounce mecanism in use in the gpio_keys driver.
> But why use a timer instead of a delayed workqueue? Do we need the precison
> of a timer for a simple debounce?

Unlike timer workqueue will not be rescheduled if it is already pending.
mod_timer() will chnage the firing time.

-- 
Dmitry
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