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

['Greg KH' <greg@kroah.com>]

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

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