实现一个简单的linux字符设备驱动

实现一个简单的linux字符设备驱动

步骤1：编写驱动程序

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1. #include

2. #include

3. #include

4. #include

5. #include

6. #include

7. #include

8. #include

9. #define DEVICE_NAME "cdev_zhangwei"

10. int number_of_devices = 1;

11. struct cdev mydev;

12. dev_t dev = 0;

13. char data[128] = "/0"; // the data of my device

14. struct class *myclass;

15. static int mydev_open(struct inode *inode, struct file *file)

16. {

17. pr_info("mydev driver open!/n");

18. return 0;

19. }

20. static int mydev_release(struct inode *inode, struct file *file)

21. {

22. pr_info("mydev driver released!/n");

23. return 0;

24. }

25. ssize_t mydev_write(struct file *file, const char __user *buf, size_t count, loff_

t *f_pos)

26. {

27. ssize_t ret = 0;

28. pr_info("mydev_write!/n");

29. pr_info("writing %d bytes/n", count);

30. if (count > 127)

31. return -ENOMEM;

32. if (count < 0)

33. return -EINVAL;

34. if (copy_from_user(data, buf, count)) {

35. ret = -EFAULT;

36. }

37. else {

38. data[127] = ''/0'';

39. pr_info("kernel received: %s/n", data);

40. ret = count;

41. }

42. return ret;

43. }

44. static ssize_t mydev_read(struct file* filp, char* buf, size_t len,loff_t* off)

45. {

46. if( copy_to_user(buf,data,len) )

47. {

48. return -EFAULT;

49. }

50.

51. return len;

52. }

53. struct file_operations mydev_fops = {

54. .owner = THIS_MODULE,

55. .open = mydev_open,

56. .read = mydev_read,

57. .write = mydev_write,

58. .release = mydev_release

59.

60. };

61. static int __init mydev_init(void)

62. {

63. int result, error;

64. result = register_chrdev(0, DEVICE_NAME, &mydev_fops);

65. pr_info("udev_cdev: get major number: %d/n", result);

66. dev = MKDEV(result, 0);

67. myclass = class_create(THIS_MODULE, "mydev_class");

68. device_create(myclass, NULL, dev, NULL, DEVICE_NAME);

69. return 0;

70. }

71. static void __exit mydev_exit(void)

72. {

73. cdev_del(&mydev);

74. unregister_chrdev_region(dev, number_of_devices);

75. device_destroy(myclass, dev);

76. class_destroy(myclass);

77. pr_info("Goodbye cdev!/n");

78. }

79. module_init(mydev_init);

80. module_exit(mydev_exit);

81. MODULE_LICENSE("GPL");

82. MODULE_DESCRIPTION("Simple cdev udev driver test");

Makefile:

obj-m := mydrive.o

KDIR := /lib/modules/$(shell uname -r)/build

PWD := $(shell pwd)

default:

$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules

clean:

$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) clean

rm -rf Module.markers modules.order Module.symvers

insmod mydrive.ko

lsmod查看

步骤3：创建设备节点：mknod /dev/mydriver c 主设备号次设备号

次设备号这里填0，主设备号可以利用cat /proc/devices 查看

ls –l /dev/mydriver

用df看看/dev/mydriver的使用情况了

步骤4：编写用户程序（测试咱们的驱动是否可行），如以下代码，这个嘛，简单的用gcc 命令编译就好了

1. #include

2. #include

3. #include

4. #include

5. #include

6. i nt main (void)

7. {

8. int fd,len;

9. pid_t pid;

10. char buff[] = "This is from userspace zhangwei fight it!";

11. char buff_read[100] ;

12. fd = open ("/dev/cdev_zhangwei", O_RDWR);

13. if (fd < 0) {

14. perror("open failed");

15. exit(0);

16. }

17. pid = fork();

18. if(pid>0)

19. {

20. len = write (fd, buff, sizeof(buff));

21. printf ("son Write returns %d/n",len );

22. }

23. else // parent

24. {

25. //waitpid(pid);

26. printf ("read returns %d/n", read(fd,buff_read,len) );

27. printf("buff_read = %s/n",buff_read);

28. }

29. close (fd);

30. return 0;

31. }