驱动程序
*/
#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> #define SECOND_MAJOR 248 /*预设的second的主设备号*/ static int second_major = SECOND_MAJOR; /*second设备结构体*/ struct second_dev { struct cdev cdev; /*cdev结构体*/ atomic_t counter;/* 一共经历了多少秒？*/ struct timer_list s_timer; /*设备要使用的定时器*/ }; struct second_dev *second_devp; /*设备结构体指针*/ /*定时器处理函数*/ 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); } /*文件打开函数*/ int second_open(struct inode *inode, struct file *filp) { /*初始化定时器*/ 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（注册）定时器*/ atomic_set(&second_devp->counter,0); //计数清0 return 0; } /*文件释放函数*/ int second_release(struct inode *inode, struct file *filp) { del_timer(&second_devp->s_timer); return 0; } /*读函数*/ 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); } /*文件操作结构体*/ static const struct file_operations second_fops = { .owner = THIS_MODULE, .open = second_open, .release = second_release, .read = second_read, }; /*初始化并注册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; err = cdev_add(&dev->cdev, devno, 1); if (err) printk(KERN_NOTICE "Error %d adding LED%d", err, index); } /*设备驱动模块加载函数*/ int second_init(void) { int ret; dev_t devno = MKDEV(second_major, 0); /* 申请设备号*/ if (second_major) ret = register_chrdev_region(devno, 1, "second"); else { /* 动态申请设备号 */ ret = alloc_chrdev_region(&devno, 0, 1, "second"); second_major = MAJOR(devno); } if (ret < 0) return ret; /* 动态申请设备结构体的内存*/ second_devp = kmalloc(sizeof(struct second_dev), GFP_KERNEL); if (!second_devp) { /*申请失败*/ 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); return ret; } /*模块卸载函数*/ void second_exit(void) { cdev_del(&second_devp->cdev); /*注销cdev*/ kfree(second_devp); /*释放设备结构体内存*/ unregister_chrdev_region(MKDEV(second_major, 0), 1); /*释放设备号*/ } MODULE_AUTHOR("Barry Song <21cnbao@gmail.com>"); MODULE_LICENSE("Dual BSD/GPL"); module_param(second_major, int, S_IRUGO); module_init(second_init); module_exit(second_exit);