linux-kernel - Re: [PATCH][GPIO] Add IRQ edge setter to gpiolib

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Date:	Thu, 11 Oct 2012 18:26:44 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Drasko DRASKOVIC <drasko.draskovic@...il.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Grant Likely <grant.likely@...retlab.ca>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH][GPIO] Add IRQ edge setter to gpiolib

On Tue, Oct 9, 2012 at 4:22 PM, Drasko DRASKOVIC
<drasko.draskovic@...il.com> wrote:
> [Me]
>> So can you explain exactly why userspace want to configure
>> GPIO pins in interrupt mode, when there is no way whatsoever
>> for userspace to handle these IRQs?
>
> Maybe I understand something wrong, but explicit configuration of GPIO
> interrupt trigger type visible in sysfs is possible __only__ from the
> userspace today, and that is exactly limitation I am addressing.

So this is the real problem is it not?

So if we consider this:

static irqreturn_t my_callback(int irq, void *dev_id)
{
        return IRQ_HANDLED;
}

int my_gpio, my_irq, ret;

my_gpio = 17; /* For some reason I like this pin */
ret = gpio_request(my_gpio);
ret = gpio_direction_input(my_gpio);
my_irq = gpio_to_irq(my_gpio);
ret = request_any_context_irq(my_irq,
    my_callback,
    IRQF_TRIGGER_FALLING,
    "my gpio thing");

(some error handling removed, based on drivers/mmc/host/mmci.c)

What is wrong with this picture? Do you mean that the problem is
that the trigger type I just set up for the IRQ connected to the pin
is not reflected in GPIO sysfs?

Yours,
Linus Walleij
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