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>
13. #define SECOND_MAJOR 248 /*預設的second的主設備號*/
15. static int second_major = SECOND_MAJOR;
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. };
24. struct second_dev *second_devp; /*設備結構體指針*/
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);
32. printk(KERN_NOTICE "current jiffies is %ld\n", jiffies);
33. }
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;
43. add_timer(&second_devp->s_timer); /*添加（注冊）定時器*/
45. atomic_set(&second_devp->counter,0); //計數清0
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);
54. return 0;
55. }
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;
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. }
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. };
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);
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. }
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);
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. }
112. memset(second_devp, 0, sizeof(struct second_dev));
114. second_setup_cdev(second_devp, 0);
116. return 0;
118. fail_malloc:
119. unregister_chrdev_region(devno, 1);
120. return ret;
121. }
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. }
131. MODULE_AUTHOR("Barry Song <21cnbao@gmail.com>");
132. MODULE_LICENSE("Dual BSD/GPL");
134. module_param(second_major, int, S_IRUGO);
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>
8. main()
9. {
10. int fd;
11. int counter = 0;
12. int old_counter = 0;
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. }