/*======================================================================    A "seond" device driver as an example of kernel timer        The initial developer of the original code is Baohua Song    <author@linuxdriver.cn>. All Rights Reserved.======================================================================*/#include <linux/module.h>#include <linux/types.h>#include <linux/fs.h>#include <linux/errno.h>#include <linux/mm.h>#include <linux/sched.h>#include <linux/init.h>#include <linux/cdev.h>#include <asm/io.h>#include <asm/system.h>#include <asm/uaccess.h>#include <linux/timer.h> /*包括timer.h頭文件*/#include <asm/atomic.h> #define SECOND_MAJOR 252    /*預設的second的主設備號*/static int second_major = SECOND_MAJOR;/*second設備結構體*/struct second_dev{  struct cdev cdev; /*cdev結構體*/  atomic_t counter;/* 一共經歷了多少秒？*/  struct timer_list s_timer; /*設備要使用的定時器*/};struct second_dev *second_devp; /*設備結構體指針*//*定時器處理函數*/static void second_timer_handle(unsigned long arg){  mod_timer(&second_devp->s_timer,jiffies + HZ);  atomic_inc(&second_devp->counter);    printk(KERN_NOTICE "current jiffies is %ld\n", jiffies);}/*文件打開函數*/int second_open(struct inode *inode, struct file *filp){  /*初始化定時器*/  init_timer(&second_devp->s_timer);  second_devp->s_timer.function = &second_timer_handle;  second_devp->s_timer.expires = jiffies + HZ;    add_timer(&second_devp->s_timer); /*添加（注冊）定時器*/    atomic_set(&second_devp->counter,0); //計數清0  return 0;}/*文件釋放函數*/int second_release(struct inode *inode, struct file *filp){  del_timer(&second_devp->s_timer);    return 0;}/*讀函數*/static ssize_t second_read(struct file *filp, char __user *buf, size_t count,  loff_t *ppos){    int counter;    counter = atomic_read(&second_devp->counter);  if(put_user(counter, (int*)buf))  	return - EFAULT;  else  	return sizeof(unsigned int);  }/*文件操作結構體*/static const struct file_operations second_fops ={  .owner = THIS_MODULE,   .open = second_open,   .release = second_release,  .read = second_read,};/*初始化并注冊cdev*/static void second_setup_cdev(struct second_dev *dev, int index){  int err, devno = MKDEV(second_major, index);  cdev_init(&dev->cdev, &second_fops);  dev->cdev.owner = THIS_MODULE;  dev->cdev.ops = &second_fops;  err = cdev_add(&dev->cdev, devno, 1);  if (err)    printk(KERN_NOTICE "Error %d adding LED%d", err, index);}/*設備驅動模塊加載函數*/int second_init(void){  int ret;  dev_t devno = MKDEV(second_major, 0);  /* 申請設備號*/  if (second_major)    ret = register_chrdev_region(devno, 1, "second");  else  /* 動態申請設備號 */  {    ret = alloc_chrdev_region(&devno, 0, 1, "second");    second_major = MAJOR(devno);  }  if (ret < 0)    return ret;  /* 動態申請設備結構體的內存*/  second_devp = kmalloc(sizeof(struct second_dev), GFP_KERNEL);  if (!second_devp)    /*申請失敗*/  {    ret =  - ENOMEM;    goto fail_malloc;  }  memset(second_devp, 0, sizeof(struct second_dev));  second_setup_cdev(second_devp, 0);  return 0;  fail_malloc: unregister_chrdev_region(devno, 1);}/*模塊卸載函數*/void second_exit(void){  cdev_del(&second_devp->cdev);   /*注銷cdev*/  kfree(second_devp);     /*釋放設備結構體內存*/  unregister_chrdev_region(MKDEV(second_major, 0), 1); /*釋放設備號*/}MODULE_AUTHOR("Song Baohua");MODULE_LICENSE("Dual BSD/GPL");module_param(second_major, int, S_IRUGO);module_init(second_init);module_exit(second_exit);