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

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Message-ID: <359ed6810906250329x70cf380cy278f23e3ebc6a829@mail.gmail.com>
Date:	Thu, 25 Jun 2009 13:29:25 +0300
From:	Jani Nikula <ext-jani.1.nikula@...ia.com>
To:	LKML <linux-kernel@...r.kernel.org>, Alek Du <alek.du@...el.com>
Cc:	Trilok Soni <soni.trilok@...il.com>, linux-input@...r.kernel.org,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	ben-linux@...ff.org
Subject: Re: [PATCH]input: Change timer function to workqueue for gpio_keys 
	driver

On Fri, Jun 12, 2009 at 8:40 PM, Trilok Soni<soni.trilok@...il.com> wrote:
>>  static irqreturn_t gpio_keys_isr(int irq, void *dev_id)
>>  {
>>        struct gpio_button_data *bdata = dev_id;
>> @@ -62,10 +61,10 @@ static irqreturn_t gpio_keys_isr(int irq, void *dev_id)
>>        BUG_ON(irq != gpio_to_irq(button->gpio));
>>
>>        if (button->debounce_interval)
>> -               mod_timer(&bdata->timer,
>> -                       jiffies + msecs_to_jiffies(button->debounce_interval));
>> +               schedule_delayed_work(&bdata->work,
>> +                       msecs_to_jiffies(button->debounce_interval));
>>        else
>> -               gpio_keys_report_event(bdata);
>> +               schedule_work(&bdata->work.work);
>>
>>        return IRQ_HANDLED;
>>  }

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 already
pending. The result is not the same as with the timer. This breaks the
debouncing.

It looks like a slightly modified version of this patch has already
been committed [1], but it has the same problem.

[1] 0b346838c5862bfe911432956a106d602535d030 Input: gpio-keys - change
timer to workqueue


BR,
Jani.
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