request_irq not working.. what else should I do?

Chan Kim ckim at
Tue Apr 5 01:01:19 EDT 2022

I found request_irq(32+176, axpu_irq_handler, IRQF_SHARED, "axpu_irq",
&axpu_cdev); returned -22. (EINVALID).
And this is the sanity-check code of request_thread_irq function where
-EINVAL is returned.
Because I'm running my app/driver on ubuntu-20.04 (kernel 5.4.0-77) on a
virtual machine, I cannot debug the kernel code right now.
I suspect one of the "if (!desc)" case or "if
(!irq_settings_can_request(desc))" will be returning it -EINVAL.
Do I have to do something before I call request_irq? Can I use request_irq
in kernel module driver? (I think so).

     * Sanity-check: shared interrupts must pass in a real dev-ID,
     * otherwise we'll have trouble later trying to figure out
     * which interrupt is which (messes up the interrupt freeing
     * logic etc).
     * Also IRQF_COND_SUSPEND only makes sense for shared interrupts and
     * it cannot be set along with IRQF_NO_SUSPEND.
    if (((irqflags & IRQF_SHARED) && !dev_id) ||
        (!(irqflags & IRQF_SHARED) && (irqflags & IRQF_COND_SUSPEND)) ||
        ((irqflags & IRQF_NO_SUSPEND) && (irqflags & IRQF_COND_SUSPEND)))
        return -EINVAL;

    desc = irq_to_desc(irq);
    if (!desc)
        return -EINVAL;
    if (!irq_settings_can_request(desc) ||
        return -EINVAL;
    if (!handler) {
        if (!thread_fn)
            return -EINVAL;
        handler = irq_default_primary_handler;

Thanks for reading.
Chan Kim

> -----Original Message-----
> From: Chan Kim <ckim at>
> Sent: Monday, April 4, 2022 11:16 PM
> To: kernelnewbies at
> Subject: request_irq not working.. what else should I do?
> Hello,
> When I register interrupt handler in arm64 machine, I use request_irq( )
> function defined below.
> (on ubuntu 20.04 on qemu arm64 virtual machine)
> static inline int __must_check
> request_irq(unsigned int irq, irq_handler_t handler, unsigned long flags,
>         const char *name, void *dev)
> {
>     return request_threaded_irq(irq, handler, NULL, flags, name, dev); }
> I found even though I registered the handler for arm64 SPI (shared
> peripheral interrupt) 176, it is not generating interrupt in the qemu
> virtual machine. The OS should set the priority and enable it in the
> interrupt controller but it doesn't work. That's what OS is for, isn't it?
> But when I follow the qemu code, in the distributor stage, it says there
> is no pending interrupt.
> How can I set the interrupt priority using request_irq function above?
> Thank you!
> Chan Kim

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