#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>#include <asm/atomic.h>#define SECOND_MAJOR 0static int second_major = SECOND_MAJOR;struct second_dev{struct cdev cdev;atomic_t counter;struct timer_list s_timer;};struct second_dev *second_devp;static void second_timer_handle(unsigned long arg){mod_timer(&second_devp->s_timer, jiffies + HZ);atomic_inc(&second_devp->counter);PRintk(KERN_ERR "current jiffies is %ld/n",jiffies);}int second_open(struct inode *inode, struct file *filp){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);atomic_set(&second_devp->counter, 0);return 0; }int second_release(struct inode *inode, struct file *filp){del_timer(&second_devp->s_timer);return 0;}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);}}static const struct file_Operations second_fops ={.owner = THIS_MODULE,.open = second_open,.release = second_release,.read = second_read,};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 add second%d", err, index);}}int second_init(void){int ret;dev_t devno = MKDEV(second_major, 0);if (second_major){ret = register_chrdev_region(devno, 1, "second");}else{ret = alloc_chrdev_region(&devno, 0, 1, "second");second_major = MAJOR(devno);}if (ret < 0){return ret;}second_devp = kmalloc(sizeof(struct second_dev), GFP_KERNEL);if (!second_devp){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);}void second_exit(void){cdev_del(&second_devp->cdev);kfree(second_devp);unregister_chrdev_region(MKDEV(second_major, 0), 1);}MODULE_AUTHOR("Song Baohua");MODULE_LICENSE("Dual BSD/GPL");module_param(second_major, int, S_IRUGO);module_init(second_init);module_exit(second_exit);附上用戶端的測試程序：#include <stdio.h>#include <unistd.h>#include <fcntl.h>int main(void){int fd, i;int data;fd = open("/dev/second",O_RDONLY);if (fd < 0){printf("open /dev/second error/n");}for(i = 0; i < 20; i++){read(fd, &data, sizeof(data));printf("read /dev/second is %d/n",data);sleep(1);}close(fd);}