linux-kernel - Re: Keyboard interrupt

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Message-id: <47BE49DD.6070404@shaw.ca>
Date:	Thu, 21 Feb 2008 22:04:45 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	Pioz <pioz84@...il.com>
Cc:	linux-kernel@...r.kernel.org
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.
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