2008-02-21 16:04:45

by Pioz

Subject: Keyboard interrupt - request_irq()

Hi all,
I have a problem.
I want handle the keyboard interrupt and for this purpose I have write
this module (I have kernel 2.6.23):


#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/interrupt.h>

[...]

irqreturn_t
irq_myhandler (int irqn, void *dev)
{
printk (KERN_INFO "Key pressed...\n");
return IRQ_HANDLED;
}

int
init_module ()
{
int res;
printk (KERN_INFO "Hello World!\n");
free_irq (1, NULL);
res = request_irq (1, irq_myhandler, IRQF_SHARED, "bao", dev_id);
printk (KERN_INFO "res: %d\n", res);
return 0;
}

void
cleanup_module ()
{
free_irq (1, NULL);
printk (KERN_INFO "Goodbye World!\n");
}


The return value of request_irq() function is -EBUSY. Why? Is the
default handler? How can I do to change handler with my function?
Thanks...

2008-02-22 04:05:05

by Robert Hancock

Subject: Re: Keyboard interrupt - request_irq()

Pioz wrote:
> Hi all,
> I have a problem.
> I want handle the keyboard interrupt and for this purpose I have write
> this module (I have kernel 2.6.23):
>
>
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/interrupt.h>
>
> [...]
>
> irqreturn_t
> irq_myhandler (int irqn, void *dev)
> {
> printk (KERN_INFO "Key pressed...\n");
> return IRQ_HANDLED;
> }
>
> int
> init_module ()
> {
> int res;
> printk (KERN_INFO "Hello World!\n");
> free_irq (1, NULL);
> res = request_irq (1, irq_myhandler, IRQF_SHARED, "bao", dev_id);
> printk (KERN_INFO "res: %d\n", res);
> return 0;
> }
>
> void
> cleanup_module ()
> {
> free_irq (1, NULL);
> printk (KERN_INFO "Goodbye World!\n");
> }
>
>
> The return value of request_irq() function is -EBUSY. Why? Is the
> default handler? How can I do to change handler with my function?
> Thanks...

Normally one doesn't register multiple interrupt handlers for the same
device. For a PCI level-triggered interrupt one can do it (for the case
where multiple devices share the IRQ), but the PC keyboard interrupt is
edge-triggered and isn't sharable.

2008-02-22 09:28:54

by Jiri Kosina

Subject: Re: Keyboard interrupt - request_irq()

On Thu, 21 Feb 2008, Pioz wrote:

> I have a problem.
> I want handle the keyboard interrupt and for this purpose I have write
> this module (I have kernel 2.6.23):
[ ... ]
> res = request_irq (1, irq_myhandler, IRQF_SHARED, "bao", dev_id);
[ ... ]
> The return value of request_irq() function is -EBUSY. Why? Is the
> default handler? How can I do to change handler with my function?
> Thanks...

The check in setup_irq() very probably triggers for you:

/*
* Can't share interrupts unless both agree to and are
* the same type (level, edge, polarity). So both flag
* fields must have IRQF_SHARED set and the bits which
* set the trigger type must match.
*/
if (!((old->flags & new->flags) & IRQF_SHARED) ||
((old->flags ^ new->flags) & IRQF_TRIGGER_MASK)) {
old_name = old->name;
goto mismatch;
}

--
Jiri Kosina
SUSE Labs