linux-kernel - Re: About GPIO interrupt function with sysfs

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Date:	Thu, 3 Mar 2011 11:56:32 -0700
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Tomoya MORINAGA <tomoya-linux@....okisemi.com>
Cc:	linux-kernel@...r.kernel.org,
	"'Ewe, Kok Howg'" <kok.howg.ewe@...el.com>,
	"'Lai, Mee Sim'" <mee.sim.lai@...el.com>,
	'Toshiharu Okada' <toshiharu-linux@....okisemi.com>
Subject: Re: About GPIO interrupt function with sysfs

On Wed, Mar 02, 2011 at 03:38:13PM +0900, Tomoya MORINAGA wrote:
> Hi Grant,
> 
> On Friday, February 18, 2011 9:43 AM, Grant Likely wrote:
> > > Can our GPIO driver (pch_gpio) have interrupt function?
> > 
> > yes.
> Need your help.
> 
> I try to add interrupt function to GPIO driver of Intel EG20T PCH(pch_gpio.c).
> 
> However, executing "echo xxx > export", there is not "edge" file in /sys/class/gpio/gpioxxx/.
> 
> Seeing source code in gpio_export@...olib.c, like below
> 
> int gpio_export(unsigned gpio, bool direction_may_change)
> {
> snip...
> 
> 	if (!status && gpio_to_irq(gpio) >= 0
> 			&& (direction_may_change
> 				|| !test_bit(FLAG_IS_OUT,
> 					&desc->flags))) {
> 		status = device_create_file(dev,
> 				&dev_attr_edge);
> 		printk("%s:device_create_file!!! status=0x%x\n", __func__, status);
> 	}
> 
> snip...
> }

Hmmm, I haven't looked at that code yet.  I didn't realize that the
irq data was exported to userspace (ignore my last email).

> 
> The above "device_create_file(dev, &dev_attr_edge);" is not executed.
> 
> Seeing gpio_to_irq@...h/x86/include/asm/gpio.h, like below.
> 
> static inline int gpio_to_irq(unsigned int gpio)
> {
> 	return -ENOSYS;
> }
> 
> Thus,  device_create_file for "edge" is never executed.
> 
> Could you tell me how to create "edge" file ?

I don't know.  I'll need to dig into that code before I can answer.  I
suggest digging into it yourself to figure out the answer as I cannot
promise that I'll get to it anytime soon.

g.
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