question in request_threaded_irq

[Javier Martinez Canillas]

On Sat, Aug 13, 2011 at 9:25 PM, radhika bhaskaran <radhibhas at gmail.com> wrote:
> Hi,
> I have a question with respect to request_threaded_irq.
> Assume that one driver has registered and ISR on some particular irq number.
> Can i use the same irq number and register and isr in another driver.
> Because that is my requirement.
> when i try to do that is an error message with an error no as -19.
>  err = request_threaded_irq(pdata->irq , NULL, testing_fucntion,
>                             IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING,
> "testing_function", dev);
> Can some one please help me whether it is possible.
> Regards,
> RB

You have to use the IRQF_SHARED flag that specifies the IRQ will be
shared for two devices:

err = request_threaded_irq(pdata->irq , NULL, testing_fucntion, IRQF_SHARED |
                                      IRQF_TRIGGER_FALLING |
IRQF_TRIGGER_RISING,
                                      "testing_function", dev);

Have in mind that the kernel invokes every handler registered for that
IRQ every time an interrupt occurs on that line. So you have to check
in each ISR if the hardware raised the interrupt.

Hope it helps,

-- 
Javier Martínez Canillas
(+34) 682 39 81 69
Barcelona, Spain