S3C6410實時時鐘RTC 秒字符設備

/*《Linux 設備驅動開發詳解》 http://www.linuxidc.com/Linux/2011-07/38211.htm

驅動程序

*/

1. #include <linux/module.h>  
2. #include <linux/types.h>  
3. #include <linux/fs.h>  
4. #include <linux/errno.h>  
5. #include <linux/mm.h>  
6. #include <linux/sched.h>  
7. #include <linux/init.h>  
8. #include <linux/cdev.h>  
9. #include <asm/io.h>  
10. #include <asm/system.h>  
11. #include <asm/uaccess.h>  
12.   
13. #define SECOND_MAJOR 248    /*預設的second的主設備號*/                        
14.                                                                               
15. static int second_major = SECOND_MAJOR;                                       
16.                                                                               
17. /*second設備結構體*/                                                          
18. struct second_dev {                                                           
19.   struct cdev cdev; /*cdev結構體*/                                            
20.   atomic_t counter;/* 一共經歷了多少秒？*/                                    
21.   struct timer_list s_timer; /*設備要使用的定時器*/                           
22. };                                                                            
23.                                                                               
24. struct second_dev *second_devp; /*設備結構體指針*/                            
25.                                                                               
26. /*定時器處理函數*/                                                            
27. static void second_timer_handle(unsigned long arg)                            
28. {                                                                             
29.   mod_timer(&second_devp->s_timer,jiffies + HZ);                              
30.   atomic_inc(&second_devp->counter);                                          
31.                                                                               
32.   printk(KERN_NOTICE "current jiffies is %ld\n", jiffies);                    
33. }                                                                             
34.                                                                               
35. /*文件打開函數*/                                                              
36. int second_open(struct inode *inode, struct file *filp)                       
37. {                                                                             
38.   /*初始化定時器*/                                                            
39.   init_timer(&second_devp->s_timer);                                          
40.   second_devp->s_timer.function = &second_timer_handle;                       
41.   second_devp->s_timer.expires = jiffies + HZ;                                
42.                                                                               
43.   add_timer(&second_devp->s_timer); /*添加（注冊）定時器*/                    
44.                                                                               
45.   atomic_set(&second_devp->counter,0); //計數清0                              
46.                                                                               
47.   return 0;                                                                   
48. }                                                                             
49. /*文件釋放函數*/                                                              
50. int second_release(struct inode *inode, struct file *filp)                    
51. {                                                                             
52.   del_timer(&second_devp->s_timer);                                           
53.                                                                               
54.   return 0;                                                                   
55. }                                                                             
56.                                                                               
57. /*讀函數*/                                                                    
58. static ssize_t second_read(struct file *filp, char __user *buf, size_t count,  
59.   loff_t *ppos)                                                               
60. {                                                                             
61.   int counter;                                                                
62.                                                                               
63.   counter = atomic_read(&second_devp->counter);                               
64.   if(put_user(counter, (int*)buf))                                            
65.    return - EFAULT;                                                          
66.   else                                                                        
67.    return sizeof(unsigned int);                                              
68. }                                                                             
69.                                                                               
70. /*文件操作結構體*/                                                            
71. static const struct file_operations second_fops = {                           
72.   .owner = THIS_MODULE,                                                       
73.   .open = second_open,                                                        
74.   .release = second_release,                                                  
75.   .read = second_read,                                                        
76. };                                                                            
77.                                                                               
78. /*初始化並注冊cdev*/                                                          
79. static void second_setup_cdev(struct second_dev *dev, int index)              
80. {                                                                             
81.   int err, devno = MKDEV(second_major, index);                                
82.                                                                               
83.   cdev_init(&dev->cdev, &second_fops);                                        
84.   dev->cdev.owner = THIS_MODULE;                                              
85.   err = cdev_add(&dev->cdev, devno, 1);                                       
86.   if (err)                                                                    
87.     printk(KERN_NOTICE "Error %d adding LED%d", err, index);                  
88. }                                                                             
89.                                                                               
90. /*設備驅動模塊加載函數*/                                                      
91. int second_init(void)                                                         
92. {                                                                             
93.   int ret;                                                                    
94.   dev_t devno = MKDEV(second_major, 0);                                       
95.                                                                               
96.   /* 申請設備號*/                                                             
97.   if (second_major)                                                           
98.     ret = register_chrdev_region(devno, 1, "second");                         
99.   else { /* 動態申請設備號 */                                                 
100.     ret = alloc_chrdev_region(&devno, 0, 1, "second");                        
101.     second_major = MAJOR(devno);                                              
102.   }                                                                           
103.   if (ret < 0)                                                                
104.     return ret;                                                               
105.   /* 動態申請設備結構體的內存*/                                               
106.   second_devp = kmalloc(sizeof(struct second_dev), GFP_KERNEL);               
107.   if (!second_devp) {   /*申請失敗*/                                          
108.     ret =  - ENOMEM;                                                          
109.     goto fail_malloc;                                                         
110.   }                                                                           
111.   
112.   memset(second_devp, 0, sizeof(struct second_dev));                          
113.   
114.   second_setup_cdev(second_devp, 0);                                          
115.   
116.   return 0;                                                                   
117.   
118. fail_malloc:  
119.   unregister_chrdev_region(devno, 1);  
120.   return ret;                            
121. }                                                                             
122.   
123. /*模塊卸載函數*/                                                              
124. void second_exit(void)                                                        
125. {                                                                             
126.   cdev_del(&second_devp->cdev);   /*注銷cdev*/                                
127.   kfree(second_devp);     /*釋放設備結構體內存*/                              
128.   unregister_chrdev_region(MKDEV(second_major, 0), 1); /*釋放設備號*/         
129. }                                                                             
130.                                                                               
131. MODULE_AUTHOR("Barry Song <21cnbao@gmail.com>");                              
132. MODULE_LICENSE("Dual BSD/GPL");                                               
133.                                                                               
134. module_param(second_major, int, S_IRUGO);                                     
135.                                                                               
136. module_init(second_init);                                                     
137. module_exit(second_exit);       

/*應用程序*/

1. #include <stdio.h>  
2. #include <stdlib.h>  
3. #include <unistd.h>  
4. #include <fcntl.h>  
5. #include <signal.h>  
6. #include <sys/stat.h>  
7.   
8. main()  
9. {  
10.   int fd;  
11.   int counter = 0;  
12.   int old_counter = 0;  
13.    
14.   /*打開/dev/second設備文件*/  
15.   fd = open("/dev/second", O_RDONLY);  
16.   if (fd != - 1) {  
17.     while (1) {  
18.       read(fd,&counter, sizeof(unsigned int));/* 讀目前經歷的秒數 */  
19.       if(counter!=old_counter) {   
20.        printf("seconds after open /dev/second :%d\n",counter);  
21.        old_counter = counter;  
22.       }   
23.     }     
24.   } else {  
25.     printf("Device open failure\n");  
26.   }  
27. }