Getting the IRQ number (Was: Basic driver devel questions ?)

[Scott Wood]

On Wed, 1 Dec 2010 17:35:58 +0100
Guillaume Dargaud <dargaud at lpsc.in2p3.fr> wrote:

> OK, here goes then: how do I get the IRQ number so that I can install an 
> interrupt handler on it ?
> 
> In my dts file I have:
> 		xps_acqui_data_0: xps-acqui-data at c9800000 {
> 			compatible = "xlnx,xps-acqui-data-3.00.a";
> 			interrupt-parent = <&xps_intc_0>;
> 			interrupts = < 0 2 >;
> 			reg = < 0xc9800000 0x10000 >;
> 			xlnx,family = "virtex4";
> 			xlnx,include-dphase-timer = <0x1>;
> 			xlnx,mplb-awidth = <0x20>;
> 			xlnx,mplb-clk-period-ps = <0x2710>;
> 			xlnx,mplb-dwidth = <0x40>;
> 			xlnx,mplb-native-dwidth = <0x40>;
> 			xlnx,mplb-p2p = <0x0>;
> 			xlnx,mplb-smallest-slave = <0x20>;
> 		} ;
> 
> In my minimal driver init, I have:
>   first = MKDEV (my_major, my_minor);
>   register_chrdev_region(first, count, NAME);
>   cdev_init(my_cdev, &fops);
>   cdev_add (my_cdev, first, count);
> So far so good.
> 
> Now how do I connect the dots between the hardware definitions from the dts and 
> my driver ?

How was your driver probed?  If you can get a pointer to the device
node, use irq_of_parse_and_map() to get a virtual irq that you can pass
to request_irq().

> But first I'm not sure where to find the IRQ in there, and also I'm not sure if 
> reading the filesystem from a module is allowed.

There's no need; there are much easier ways to access the device tree
from within the kernel.

> How do I know if this interrupt is shared or not (is it important ?)

Can your driver tolerate it being shared?  If so, request it as shared.

-Scott