S3C6410实时时钟RTC 秒字符设备

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/*《linux 设备驱动开发详解》

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);

/*应用程序*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/stat.h>
main()
{
int fd;
int counter = 0;
int old_counter = 0;
/*打开/dev/second设备文件*/
fd = open("/dev/second", O_RDONLY);
if (fd != - 1) {
while (1) {
read(fd,&counter, sizeof(unsigned int));/* 读目前经历的秒数 */
if(counter!=old_counter) { 
printf("seconds after open /dev/second :%d\n",counter);
old_counter = counter;
} 
}   
} else {
printf("Device open failure\n");
}
}