Can't understand /proc/interrupts output for GICv3 case

[Chan Kim]

Hi Greg KH,
I see, I understand what the proper method should be for this.
I'll take it as an almost official answer from the linux people :)
Thank you.
Chan Kim

> -----Original Message-----
> From: 'Greg KH' <greg at kroah.com>
> Sent: Tuesday, April 12, 2022 1:50 PM
> To: Chan Kim <ckim at etri.re.kr>
> Cc: 'qemu-discuss' <qemu-discuss at nongnu.org>;
> kernelnewbies at kernelnewbies.org
> Subject: Re: Can't understand /proc/interrupts output for GICv3 case
> 
> On Tue, Apr 12, 2022 at 11:18:03AM +0900, Chan Kim wrote:
> > > You can replace all of the above code by just using the miscdevice
> > > interface instead.  Please use that, it ensures that you do
> > > everything properly and simplifies it all.
> 
> Again, use the misc device api please.
> 
> > > > 	vaddr = ioremap(AXPU_BASE, 0x80000);
> > >
> > > Wait, where are you picking those random values from?
> >
> > Yes, it now looks weird to me. I have passed the register address
> > information in the device tree and the kernel already knows my
> > device's address range. Then, how should I get this virtual io address
> > in this driver? I need it to access some registers. How can I ask the
> system bus?
> 
> Use a platform driver and bind your driver to that device based on that
> api.
> 
> > And my driver is a kernel module because I want to use it in
> > ubuntu-20.04 on a virtual machine, I want it to be a kernel module
> > that I can insmod or rmmod.(actually my job is to provide this virtual
> machine to some folks).
> > And I cannot build the ubuntu image even if I change it to a platform
> > device driver and add it in the kernel tree.
> 
> This all does not matter, just write a proper platform driver and all will
> be fine.
> 
> > > > 	ret = request_irq(6, axpu_irq_handler, IRQF_SHARED,
"axpu_irq",
> > > > &axpu_cdev);
> > >
> > > Same for that, just picking 6 will not work, sorry.
> > >
> >
> > Yes, that was my original question. How can I get my irq number (I
> > know it's hwirq 47) and I peeked into kernel that irq 6 was assigned for
> the irq_desc.
> > So I changed my driver to request irq 6 for my device and I found at
> > least it works for now, all the register access and interrupts. I know
> > this is not the solution and I'm curious how I should get the irq
> > number of io virtual address in this situation.
> 
> Again, the platform driver interface will provide you with the needed
> information.  We have thousands of working examples in the kernel tree.
> 
> >
> > > Perhaps take a look at the book, Linux Device Drivers, 3rd edition.
> > > It's free online and should help you out a lot.
> > >
> > > > 	printk("request_irq returned %d\n", ret); // -EINVAL
> > > > 	printk(KERN_INFO "Device driver inserted ..done
properly..\n");
> > > > 	return 0;
> > > >
> > > > r_device :
> > > > 	class_destroy(dev_class);
> > > >
> > > > r_class :
> > > > 	unregister_chrdev_region(dev,1);
> > > > 	return -1;
> > >
> > > One final comment, don't make up error values like this, use real
> > > ERROR codes.
> > >
> > > thanks,
> > >
> > > greg k-h
> >
> > Yes, I've read the book sometimes (not the whole part) but if I read
> > it now, I'll be able to more understand it. It's a bit outdated
> > though. Why don't you update your book? :)
> 
> Because the publisher does not want to publish a new version.
> 
> thanks,
> 
> greg k-h