On Mon, Apr 11, 2022 at 6:16 PM Chan Kim <ckim@xxxxxxxxxx> wrote:
> > > What bus type is your driver written for?
> > >
> > That sounds very logical. In my case I added it to system bus.
>
> What exactly do you mean by "system bus"?
>
I meant 'sysbus' in qemu code that I showed in the qemu code.
And I think it's the CPU bus.
>
> Where is your kernel code?
>
This is the init function of my char driver. I thought if the struct cdev
contains struct device, maybe I could use the struct device's of_node to
call of_irq_get but it doesn't.
And I remember I've seen the cdev in usually contained in the driver data of
platform driver(?). Can I implement platform driver in kernel module form?
Below is the char driver init code. Currently it's request_irq(6, ... ) but
I want to know out the number 6 using program. If you have any advice,
please tell me.
static int __init chr_driver_init(void)
{
int ret;
/* Allocating Major number */
if ((alloc_chrdev_region(&dev, 0, 1, "axpu_Dev")) < 0) {
printk(KERN_INFO"Cannot allocate the major number..\n");
return -1;
}
printk(KERN_INFO"Major = %d Minor = %d..\n",MAJOR(dev),MINOR(dev));
/* creating cdev structure */
cdev_init(&axpu_cdev, &fops);
axpu_cdev.owner = THIS_MODULE;
/* Adding character device to the system */
if ((cdev_add(&axpu_cdev,dev,1)) < 0) {
printk(KERN_INFO "Cannot add the device to the
system...\n");
goto r_class;
}
I guess you got address 0x80000 randomly also may have this code from stackoverflow but it wont work for you.
as written stackoverflow, device_create must be a character device and an address under /sys/dev/char before getting NULL.
So did you create a char device with use mknod command?
Actually register_chrdev will do this for you but you can do it with mknod if you wish.
/* creating struct class */
if ((dev_class = class_create(THIS_MODULE, "axpu_class")) == NULL) {
printk(KERN_INFO "cannot create the struct class...\n");
goto r_class;
}
/* for interrupt test !! */
/* for vanilla work-around.. already made by mkdev */
if ((device_create(dev_class, NULL, dev, NULL, "axpu_device")) ==
NULL) {
printk(KERN_INFO "cannot create the device ..\n");
goto r_device;
}
else { printk(KERN_INFO "axpu_device created..\n"); }
/**/
vaddr = ioremap(AXPU_BASE, 0x80000); \
Please first read Documentation/devices.txt because kernel can do dynamic allocation I think.
if(!vaddr)
{
printk(KERN_INFO"Failed to map the address.\n");
release_mem_region(AXPU_BASE,AXPU_SIZE);
return 1;
}
printk("----- AXPU_BASE mapped at vaddr = %px\n", vaddr);
ret = request_irq(6, axpu_irq_handler, IRQF_SHARED, "axpu_irq",
&axpu_cdev);
printk("request_irq returned %d\n", ret); // -EINVAL
printk(KERN_INFO "Device driver inserted ..done properly..\n");
return 0;
You dont need to call manual, because it is defined in cdev.h.
in example for example device_destroy already destroys class.
r_device :
class_destroy(dev_class);
r_class :
unregister_chrdev_region(dev,1);
return -1;
}
* Understanding the Linux Kernel
* Linux Device Drivers
* Linux Kernel Development
Thank you.
Chan Kim
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