Timers in device drivers

timer.c

#include "timer.h"

#define MAX_SIZE  48

static int timer_val = 100;
module_param(timer_val, int, 0);
MODULE_PARM_DESC(timer_val, "Configurable, default timer is set to 100msec's");

static int arr[10];
static int p;
module_param_array(arr, int, &p, 0644);
MODULE_PARM_DESC(arr, "Array need to be initialized");

static char str[] = "Test String";
module_param_string(s, str, MAX_SIZE, 0644);
MODULE_PARM_DESC(str, "Default string is \"Test String\", can be changed");

static char *sp;
module_param(sp, charp, 0644);
MODULE_PARM_DESC(sp, "Char pointer, default is NULL");

struct timer_list timer;

void timer_func(unsigned long data)
{
  printk("Inside timer function \n");
}

static int __init timer_init(void)
{
  int ret;
  int i = 0;
  char *p = "Gautham Kantharaju";
  
  setup_timer(&timer, timer_func, 0);
  
  if ((ret = mod_timer(&timer, jiffies + msecs_to_jiffies(timer_val))))
     printk("Modify timer error \n");
  else
     printk("Modify timer success \n");
     
  for(i=0; i < 10; i++)
    printk("arr[%d]=%d \n", i, arr[i]);
    
  printk("String from cmdline is= %s \t %s \t %s \n", str, sp, p);  
  
  return 0;
} 

static void __exit timer_exit(void)
{
  if (!(timer_pending(&timer)))
  {
    del_timer( &timer );
    printk("Kernel timer deleted \n");
  }

  printk("Unloading timer module \n");
}

module_init(timer_init);
module_exit(timer_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Gautham Kantharaju <[email protected]>");
MODULE_DESCRIPTION("Kernel timer usage driver");

timer.h

#ifndef _TIMER_H_
#define _TIMER_H_

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/timer.h>

#endif /* _TIMER_H_ */