How kernel derive irq number for particular irq line

[priyaranjan]

Hi Abhinav,

On Mon, Jun 25, 2018 at 12:17 AM, Abhinav Misra
<abhitheextremeeng at gmail.com> wrote:
> Hi Guys,
>
> I want to know how the irq number is derived in linux kernel.
> In kernel we are using below function for registering ISR.
>

For platform drivers, usually this information comes from the device tree entry.
which you get originally from the System On chip HW interface documents or
from specification sheets.

> int request_threaded_irq(unsigned int irq, irq_handler_t handler,
> irq_handler_t thread_fn, unsigned long irqflags, const char *devname, void
> *dev_id)
>
> 1st arg is irq number. Now suppose for an i2c device, want to configure an
> interrupt then we can enable interrupt by configuring the particular
> register
> but from where we will get the irq number details.

In kernel drivers, DT entries of that driver are read
by some APIs and then used by request_irq

>
> Do we as a programmer need to map it ?
>
> Please provide your views.
>
> BR,Abhinav
>
>
>
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