一.驅動框架

初始化：insmod 加載

1.確定主設備號：

分為靜態和動態分配，其中LED_GPIO_SIZE 表示支持的次設備號數目，一般默認為1. 相關實現代碼如下：

1. int result;
2. dev_t dev;
4. /*分配主設備號*/
5. if (scull_major) /*靜態分配一個主設備號*/
6. {
7. dev = MKDEV(scull_major,0);
8. result = register_chrdev_region(dev,LED_GPIO_SIZE,DEVICE_NAME);
9. }
10. else /*動態分配一個主設備號*/
11. {
12. result = alloc_chrdev_region(&dev,0,LED_GPIO_SIZE,DEVICE_NAME);
13. scull_major = MAJOR(dev);
14. }
15. if(result <0)
16. {
17. printk("LED:can not get major:%d\n",scull_major);
18. return result;
19. }

2.構造 file_operations 結構：結構成員對應相應的處理函數：

1. static struct file_operations mini2440_leds_fops = {
2. .owner = THIS_MODULE, /* 這是一個宏，推向編譯模塊時自動創建的__this_module變量 */
3. .open = mini2440_leds_open,
4. .write = mini2440_leds_write,
5. };

3.將相關操作告訴內核：

內核用cdev結構來表示字符設備，cev_init()將文件操作和cdev關聯。cdev_add（）將之前生成的主次設備號和cdev連接在一起，

1. led_class = class_create(THIS_MODULE,DEVICE_NAME);
2. cdev_init(&led_gpio_cdev, &mini2440_leds_fops);
3. result = cdev_add(&led_gpio_cdev, dev, 1);
4. if(result <0)
5. {
6. printk("LED:cdev_add error\n");
7. return result;
8. }
10. device_create(led_class, NULL, MKDEV(scull_major, 0), NULL, "led0");

卸載驅動 rmmod 卸載 代碼實現如下：

1. dev_t dev_id = MKDEV(scull_major, 0);
3. /*卸載主設備號*/
4. unregister_chrdev_region(dev_id, LED_GPIO_SIZE);
6. device_destroy(led_class,MKDEV(scull_major, 0));
7. cdev_del(&led_gpio_cdev);
9. class_destroy(led_class);

最後附上一個較為完整的驅動框架，其中創建了主設備號和次設備號，驅動代碼如下：

1. #include <linux/module.h>
2. #include <linux/kernel.h>
3. #include <linux/fs.h>
4. #include <linux/init.h>
5. #include <linux/delay.h>
6. #include <asm/uaccess.h>
7. #include <asm/irq.h>
8. #include <mach/io.h>
9. #include <mach/regs-gpio.h>
10. #include <mach/hardware.h>
11. #include <linux/device.h>
13. #include <linux/cdev.h>
16. #define DEVICE_NAME "led_1"
17. #define LED_GPIO_SIZE 4
19. static int scull_major = 0;
21. static struct class *led_class;
22. static struct cdev led_gpio_cdev[LED_GPIO_SIZE];
24. static int mini2440_leds_open(struct inode *inode, struct file *file)
25. {
27. int minor = MINOR(inode->i_rdev); //MINOR(inode->i_cdev);
28. printk("/dev/led%d has opened\n",minor);
29. return 0;
30. }
33. static ssize_t mini2440_leds_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
34. {
35. char val;
36. int minor = MINOR(filp->f_dentry->d_inode->i_rdev);
37. copy_from_user(&val, buf, 1);
39. printk("/dev/led%d write the val = %d\n",minor,val);
40. return 0;
41. }
43. static struct file_operations mini2440_leds_fops = {
44. .owner = THIS_MODULE, /* 這是一個宏，推向編譯模塊時自動創建的__this_module變量 */
45. .open = mini2440_leds_open,
46. .write = mini2440_leds_write,
47. };
49. /*
50. * 執行insmod命令時就會調用這個函數
51. */
53. static int mini2440_leds_init(void)
54. {
56. int result,i;
57. dev_t dev;
59. /*分配主設備號*/
60. if (scull_major) /*靜態分配一個主設備號*/
61. {
62. dev = MKDEV(scull_major,0);
63. result = register_chrdev_region(dev,LED_GPIO_SIZE,DEVICE_NAME);
64. }
65. else /*動態分配一個主設備號*/
66. {
67. result = alloc_chrdev_region(&dev,0,LED_GPIO_SIZE,DEVICE_NAME);
68. scull_major = MAJOR(dev);
69. }
70. if(result <0)
71. {
72. printk("LED:can not get major:%d\n",scull_major);
73. return result;
74. }
76. led_class = class_create(THIS_MODULE,DEVICE_NAME);
77. if (IS_ERR(led_class)) {
78. return PTR_ERR(led_class);
79. }
81. for (i=0; i<LED_GPIO_SIZE;i++)
82. {
83. cdev_init(&led_gpio_cdev[i], &mini2440_leds_fops);
84. result = cdev_add(&led_gpio_cdev[i], (dev+i), 1);
85. if(result <0)
86. {
87. printk("LED:cdev_add error\n");
88. return result;
89. }
90. device_create(led_class, NULL, MKDEV(scull_major, i), NULL, "led%d",i);
91. }
93. return 0;
94. }
96. /*
97. * 執行rmmod命令時就會調用這個函數
98. */
99. static void mini2440_leds_exit(void)
100. {
101. int i;
102. dev_t dev_id = MKDEV(scull_major, 0);
104. /*卸載主設備號*/
105. unregister_chrdev_region(dev_id, LED_GPIO_SIZE);
107. for(i=0;i<LED_GPIO_SIZE;i++)
108. {
109. device_destroy(led_class,MKDEV(scull_major, i));
110. cdev_del(&led_gpio_cdev[i]);
111. }
112. class_destroy(led_class);
114. }
117. /* 這兩行指定驅動程序的初始化函數和卸載函數 */
118. module_init(mini2440_leds_init);
119. module_exit(mini2440_leds_exit);
121. /* 描述驅動程序的一些信息，不是必須的 */
123. MODULE_LICENSE("GPL");

linux 測試代碼：

1. #include <sys/types.h>
2. #include <sys/stat.h>
3. #include <fcntl.h>
4. #include <stdio.h>
7. /*
8. * ledtest <dev> <on|off>
9. */
11. void print_usage(char *file)
12. {
13. printf("Usage:\n");
14. printf("%s <dev> <on|off>\n",file);
15. printf("eg. \n");
16. printf("%s /dev/led0 a\n", file);
17. printf("%s /dev/led1 b\n", file);
18. printf("%s /dev/led2 c\n", file);
19. printf("%s /dev/led3 d\n", file);
20. }
22. int main(int argc, char **argv)
23. {
24. int fd;
25. char* filename;
26. char val;
28. if (argc != 3)
29. {
30. print_usage(argv[0]);
31. return 0;
32. }
34. filename = argv[1];
36. fd = open(filename, O_RDWR);
37. if (fd < 0)
38. {
39. printf("error, can‘t open %s\n", filename);
40. return 0;
41. }
43. if (!strcmp("a", argv[2]))
44. {
45. val = 10;
46. write(fd, &val, 1);
47. }
48. else if (!strcmp("b", argv[2]))
49. {
50. val = 11;
51. write(fd, &val, 1);
52. }
53. else if (!strcmp("c", argv[2]))
54. {
55. val = 12;
56. write(fd, &val, 1);
57. }
58. else if (!strcmp("d", argv[2]))
59. {
61. val = 13;
62. write(fd, &val, 1);
63. }
67. return 0;
68. }

linux驅動摸索 --驅動框架初始化（結合韋東山視頻教程）