How to change value of module_param parameter in the device driver? - linux-device-driver

Question

I wrote a simple program for taking a value through command line into my driver. I used module_param() for this and gave permission argument, i.e third arg of module_param(), as S_IWUSR.
This I guess would allow user to modify the value of that parameter once driver is loaded in the kernel. I tried to modify the value of that parameter by:
echo 1 > /sys/module/ghost/parameters/num
But this shows me Permission denied error every time I try to do this, even when I execute the command with sudo. I also tried changing permission in module_param() to 0770 but still was not able to change the parameter value. Is there a way to change the value of parameter passed while inserting the driver ? Why does the above command shows permission denied, even if I run as sudo ?
After the answer of #Ian Abott I am to change the value of the parameter. Now I tried to define a callback function to notify me any changes in the value of that parameter while my driver is loaded. Here is the code
#include"headers.h"
#include"declarations.h"
static int my_set(const char *val, const struct kernel_param *kp)
{
int n = 0, ret;
ret = kstrtoint(val,10,&n); // Kernel function to convert string to integer
if (ret !=0 || n > 10) {
return -EINVAL;
}
printk(KERN_ALERT "my-set function running\n");
return param_set_int(val,kp);
}
static const struct kernel_param_ops param_ops = {
.set = my_set,
.get = param_get_int,
};
module_param(num,int,0600);
static char *name = "hello";
module_param(name,charp,0770);
static int __init init_func(void)
{
int i;
module_param_cb(callBack, &param_ops, &num, 0770);
printk(KERN_INFO "Value of num is %d\n",num);
for( i=0; i<num; i++)
{
printk(KERN_INFO "%s\n", name);
}
return 0;
}
static void __exit exit_func(void)
{
printk(KERN_INFO "Value of num is %d\n",num);
printk(KERN_ALERT "Module removed successfully\n");
}
module_init(init_func);
module_exit(exit_func);
But it doesn't seem to work because my_set function never runs, even if I change the value. My doubt is
1) Is this correct way to implement callback function for the parameter?
2) What is significance of first argument to the function module_param_cb?