How to register an interrupt under linux?

How to register an interrupt under linux?

[wael showair]

Dear all,
First here is the setup i've:
1. The board is SPTWIMAX-CC1E board 
2. The processor is MPC8555 i found it in the powerpc family NOT ppc family.
Also the board contains DSP core.
3. Linux Kernel 2.6.19-rc5 running on the MPC8555 processor side.

I aim to let the DSP processor interrupts the MPC8555 processor so i think
the first step is to register an interrupt handler for an interrupt number.
i found this in the linux API request_irq. so 

i make a simple module & write in it
request_irq(4,my_handler,SA_INTERRUPT,"DSP",NULL); but unfortunately it
returns -ENOSYS. i have tracked the error & i found this is because the
irq_chip structure was not set.

so i added the API of set_irq_chip as follows:

irqChip.enable = NULL;
irqChip.disable = NULL;
irqChip.startup = NULL;
irqChip.shutdown = NULL;

so that all of these functions will be set to the default APIs
(default_enable,default_disable,default_startup & default_shutdown)

then i passed this struct to the set_irq_chip as follows:

set_irq_chip(4,&irqChip);

& at last i call request_irq.
 ***********************************************************
My code:

irqChip.enable = NULL;
irqChip.disable = NULL;
irqChip.startup = NULL;
irqChip.shutdown = NULL;

set_irq_chip(4,&irqChip);

request_irq(4,my_handler,SA_INTERRUPT,"DSP",NULL);
********************************************************

 but unfortunately when i tried to insert my module i got a segmentation
fault. i have tracked it & i found this is because of the unmask function of
my interrupt irq_chip was not set.
so do i have to implement it & if so, should i write a code that enables my
irq_number for the MPC8555 processor or what?

At last i want you to tell me if this is the right way to register my
interrupt_handler for a certain interrupt_number under linux? this is my
aim.
thanks in advance for your help
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Re: How to register an interrupt under linux?

[Scott Wood]

wael showair wrote:
> Dear all,
> First here is the setup i've:
> 1. The board is SPTWIMAX-CC1E board 
> 2. The processor is MPC8555 i found it in the powerpc family NOT ppc family.
> Also the board contains DSP core.
> 3. Linux Kernel 2.6.19-rc5 running on the MPC8555 processor side.

That's rather old...

> I aim to let the DSP processor interrupts the MPC8555 processor so i think
> the first step is to register an interrupt handler for an interrupt number.
> i found this in the linux API request_irq. so 
> 
> i make a simple module & write in it
> request_irq(4,my_handler,SA_INTERRUPT,"DSP",NULL); but unfortunately it
> returns -ENOSYS.

If we had a FAQ, this would be entry #1.  request_irq() takes virtual 
IRQ numbers, not hardware numbers of some specific PIC.  You need to 
create a mapping, typically via the device tree.  Google should be able 
to provide more details.

> i have tracked the error & i found this is because the
> irq_chip structure was not set.
> 
> so i added the API of set_irq_chip as follows:
> 
> irqChip.enable = NULL;
> irqChip.disable = NULL;
> irqChip.startup = NULL;
> irqChip.shutdown = NULL;

That's kind of like commenting out every line with an error until the 
code builds. :-P

>  but unfortunately when i tried to insert my module i got a segmentation
> fault.

That tends to happen if you tell the kernel to call a NULL pointer.

  i have tracked it & i found this is because of the unmask function of
> my interrupt irq_chip was not set.
> so do i have to implement it

No, it's already implemented in the MPIC driver.

-Scott