Making a few charecter device in linux

Question

I'm very new to writing kernel module and In my assignment I'm supposed to write 2 sysfs_device in the folders:

/sys/class/A/B/B_attr
/sys/class/A/C/C_attr

This is my code that I think is relevant:

static int __init sysfs_example_init(void)
{
    // create char device
    major_number = register_chrdev(0, "A", &fops);
    if (major_number < 0)
        return -1;

    // create sysfs class
    sysfs_class = class_create(THIS_MODULE, "A");
    if (IS_ERR(sysfs_class))
    {
        unregister_chrdev(major_number, "A");
        return -1;
    }
    
    // create sysfs device
    sysfs_device = device_create(sysfs_class, NULL, MKDEV(major_number, 0), NULL, "B"); 
    if (IS_ERR(sysfs_device))
    {
        class_destroy(sysfs_class);
        unregister_chrdev(major_number, "A");
        return -1;
    }
    
    // create sysfs file attributes  
    if (device_create_file(sysfs_device, (const struct device_attribute *)&dev_attr_B.attr))
    {
        device_destroy(sysfs_class, MKDEV(major_number, 0));
        class_destroy(sysfs_class);
        unregister_chrdev(major_number, "A");
        return -1;
    }
    // create sysfs device
    sysfs_device_rules = device_create(sysfs_class, NULL, MKDEV(major_number, 0), NULL, "C");   
    if (IS_ERR(sysfs_device_rules))
    {
        class_destroy(sysfs_class);
        unregister_chrdev(major_number, "A");
        return -1;
    }
    if (device_create_file(sysfs_device_rules, (const struct device_attribute *)&dev_attr_C.attr))
    {
        device_destroy(sysfs_class, MKDEV(major_number, 0));
        class_destroy(sysfs_class);
        unregister_chrdev(major_number, "A");
        return -1;
    }
    
    return 0;
}

But then when I try to insmod program.c I get the error:

insmod: ERROR: could not insert module example.ko: Operation not permitted