Re: request_irq return errno 38

On Wed, 2009-02-11 at 14:13 +0530, Vijay Nikam wrote:

Hello All,

I have mpc8313erdb evaluation board and currently I am writing GPIO
driver. Actually it is just simple test driver.

I did the irq_request in the driver init function, as request_irq
returns zero (0) if successful, otherwise -1 on error and errno
indicates the error. But when I load or insert the module using insmod
request_irq return with Return Value -38. I checked in errno.h file in
asm-generic and 38 means ENOSYS - Function not implemented.
Following is irq_request code:
----------------------
ret = request_irq(74, interrupt_handler, SA_INTERRUPT | SA_SHIRQ ,
"gpio", &mydev);
if(ret)
    printk(KERN_INFO "Error in request_irq, value return = %d \n", ret);
----------------------
NOTE: 74 is the Interrupt ID Number for GPIO Interrupt. this
information is from Processor User Manual.

Following is the handler:
---------------------
static int interrupt_handler(int irqn, void *dev_id)
{
    printk(KERN_INFO "Enter in interrupt handler\n");
    return IRQ_HANDLED;
}
--------------------

Usually request_irq return EBUSY, EINVAL but in my case it returns
ENOSYS (errno 38). I tried to look information for this errno in
interrupt context but could not able to find anything useful or
understable. Could anyone please let me know why this specific errno
38 generated in request_irq ? ? ? and what are the possiblities for
resolving this error ? ?  ?

You don't mention what kernel version you're using. But you might be
hitting the check in __setup_irq():

        if (desc->chip == &no_irq_chip)
                return -ENOSYS;


That would make sense because you're trying to map a raw irq number,
which doesn't work. You first need to call irq_create_mapping(), like:

int virq;
virq = irq_create_mapping(NULL, 74);
rc = request_irq(virq, ...);


cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person