Finding the interrupt vector of a given IRQ

[anish kumar]

On Fri, 2012-10-19 at 10:34 +0530, Arun KS wrote:
> Hi Anish,
> 
> On Mon, May 28, 2012 at 9:16 AM, anish singh
> <anish198519851985 at gmail.com> wrote:
>         On Mon, May 28, 2012 at 2:57 AM, richard -rw- weinberger
>         <richard.weinberger at gmail.com> wrote:
>         > On Sun, May 27, 2012 at 2:02 AM, Mark Farnell
>         <mark.farnell at gmail.com> wrote:
>         >> In the kernel, how can I find out the interrupt vector
>         number of a
>         >> given IRQ (for example, IRQ7)?
>         >>
>         >> Within the kernel module, I would like to manually set the
>         IRQ using
>         >> the assembly code:
>         >>
>         >> asm("int $<irq vector>");
>         >>
>         >> and let the IRQ handler installed by a different module
>         catch that interrupt.
>         >>
>         >> Is this possible?
>         >
>         > No really because not all IRQ have an interrupt line to the
>         CPU.
>         > Linux can multiplex and emulate them. Think of GPIO drivers
>         with
>         > interrupt support.
>         
>         Can you please describe this in detail?It would really help a
>         lot of
>         people like me.Does multiplex mean that all numbers starting
>         from
>         0,1,2,3,...... TOTAL-interrupt will have interrupt lines
>         associated with it
>         eventhough all interrupt numbers are not linear?
> 
> GPIOs are grouped as banks. Let’s say 32 gpios are in a bank.
> There will be only single interrupt line to interrupt controller for a
> bank.
> 
> 
> Consider that you have configured gpio1 and gpio16 as interrupts.
> Even if interrupt happens on gpio 1 or gpio 16, the same interrupt
> line will be triggered to 
>   
> Interrupt controller.
> 
> 
> Now the gpio driver has to figure out reading the Interrupt status 
> 
> Register of GPIO to find which interrupt (gpio1 or gpio16) has really
> fired.
And this is done by this way:
Suppose we have a chip(mfd-multi-funcion-driver) driver which is
connected to processor using a gpio - this gpio line acts as interrupt
line from the processor

++++++++++++              ++++++++++
+ Processor+              + Chip   +---->USB  interrupt handler
+          +gpio--------->+ MFD    +---->dock interrupt handler
++++++++++++              +        +---->UART interrupt handler
			  ++++++++++---->Factory cable interrupt handler

So the code will be as follows:

handler_function()
{	
	/* find out which interrupt is triggered */
	/* it can be usb,dock,uart or factory cable */
	ret_irq = read_mfd_register();
	/*
        * ok we found out the interrupt line, get a corresponding
	* software linux irq number by calling
        * irq_domain_add_linear 
        * irq_create_mapping 
        * you would have made this calls in the probe probably
	*/ 
 	handle_nested_irq(ret_irq); 
}

handle_nested_irq inturn will call all the irq_handlers in the system
for your UART,usb and dock driver.

mfd_driver()
{	
	request_irq(gpio_to_irq(gpio), handler_function);
}

Hope I have not missed anything.
> 
> So in this case a single interrupt line is multiplex for 32 gpio
> interrupts.
> 
> 
> HTH.
> 
> Thanks,
> Arun
>  
>         > Anyway, why to you think you need to trigger the raw IRQ
>         manually?
>         > This sounds really odd...
>         >
>         >
>         > --
>         > Thanks,
>         > //richard
>         >
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