Linux 驱动开发简单实例

Xiuye_XY于 2021-08-03 19:17:07 发布343 收藏 3

分类专栏： 笔记 C/C++ Linux

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驱动源码

1. #include <linux/init.h>

2. #include <linux/module.h>

3. #include <linux/kernel.h>

4. #include <linux/fs.h>

5. #include <linux/delay.h>

7. #define major_version 200

8. #define driver1_name "driver1"

10. static char read_buf[100] = "Hello driver1";

11. static char write_buf[100];

13. static int driver1_open(struct inode *inode,struct file *file){

14. printk("driver1 open\r\n");

15. return 0;

16. }

18. static int driver1_close(struct inode *inode,struct file *file){

19. printk("driver1 close\r\n");

20. return 0;

21. }

25. static ssize_t driver1_read(struct file *file, char __user * buf, size_t count, loff_t *ppos){

26. printk("driver1 read\r\n");

27. copy_to_user(buf,read_buf,count);

28. return 0;

29. }

31. static ssize_t driver1_write(struct file *file, const char __user * buf, size_t count, loff_t *ppos){

33. int ret = 0;

35. printk("driver1 write\r\n");

37. ret = copy_from_user(write_buf,buf,count);

38. if(!ret){

39. printk("receive data: %s \r\n",write_buf);

40. }

42. return 0;

43. }

46. static struct file_operations ops={

47. .owner = THIS_MODULE,

48. .open = driver1_open,

49. .release = driver1_close,

50. .read = driver1_read,

51. .write = driver1_write

53. };

57. static int __init driver1_init(void)

58. {

60. int ret ;

62. printk("%s,%d\r\n", __func__, __LINE__);

65. ret= register_chrdev(major_version,driver1_name, &ops);

70. return ret;

71. }

73. static void __exit driver1_exit(void)

74. {

75. printk("%s,%d\r\n", __func__, __LINE__);

76. unregister_chrdev(major_version, driver1_name);

77. }

79. module_init(driver1_init);

80. module_exit(driver1_exit);

82. MODULE_LICENSE("GPL");

Makefile文件：（像obj-m ，-C， M= 等好像是规定的，不要随便改写）

2. #内核的源码路径, ?= 条件赋值, uname -r 得到内核的版本号

3. KERNELDIR = /lib/modules/$(shell uname -r)/build

6. # 生成模块

7. obj-m := driver1.o

9. # := 立即赋值, 得到当前的绝对路径

10. PWD := $(shell pwd)

13. # -C 切换工作路径, make -c

14. modules:

15. $(MAKE) -C $(KERNELDIR) M=$(PWD) modules

17. clean:

18. rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions Module* modules* *.mod

20. .PHONY: modules clean

应用程序调用驱动文件:

1. #include<iostream>

2. #include<unistd.h>

3. #include <sys/types.h>

4. #include <sys/stat.h>

5. #include <fcntl.h>

7. using namespace std;

9. int main(int argc,char*argv[]){

11. int ret = 0;

12. int fd = 0;

13. char *filename;

14. char read_buf[100],write_buf[100]="hello,driver1";

16. if(argc < 2){

17. cout << "cmd one param!" << endl;

18. return -5;

19. }

21. filename = argv[1];

23. fd = open(filename,O_RDWR);

24. if(fd < 0){

25. cout << "Cannot open file,"<<filename<< endl;

26. return -1;

27. }

29. ret = read(fd,read_buf,100);

30. if(ret < 0){

31. cout << "read file "<<filename << " failed."<<endl;

32. return -2;

33. }

34. cout<< "read buf:" << read_buf << endl;

36. ret = write(fd,write_buf,100);

38. if(ret <0){

39. cout << "write file "<< filename << " failed." <<endl;

40. return -3;

41. }

43. ret = close(fd);

45. if(ret <0){

46. cout << "close file "<< filename << " failed." <<endl;

47. return -3;

48. }

50. cout << "app end" << endl;

52. return 0;

53. }

编译驱动

1. make -C /lib/modules/5.8.0-63-generic/build M=/home/xiuye/Documents/cpp/driver1 modules

2. make[1]: Entering directory '/usr/src/linux-headers-5.8.0-63-generic'

3. CC [M] /home/xiuye/Documents/cpp/driver1/driver1.o

4. MODPOST /home/xiuye/Documents/cpp/driver1/Module.symvers

5. CC [M] /home/xiuye/Documents/cpp/driver1/driver1.mod.o

6. LD [M] /home/xiuye/Documents/cpp/driver1/driver1.ko

7. make[1]: Leaving directory '/usr/src/linux-headers-5.8.0-63-generic'

加载驱动

insmod driver1.ko 或者 modprobe driver1.ko

创建设备文件(如果/dev下没有驱动名的文件)

mknod /dev/driver1 c 200 0

1. root@ubuntu:cpp/driver1# ls /dev/driver1

2. /dev/driver1

3. root@ubuntu:cpp/driver1# cat /proc/devices | grep driver1

4. 200 driver1

应用程序调用驱动（只能在root下调用，否则失败，不知道原因）：

1. root@ubuntu:cpp/driver1# ./a.out /dev/driver1

2. read buf:Hello driver1

3. app end

查看驱动打印消息：

1. root@ubuntu:cpp/driver1# dmesg

2. [ 5062.671752] driver1_exit,76

3. [ 5078.688136] driver1_init,63

4. [ 5303.464000] driver1 open

5. [ 5303.464002] driver1 read

6. [ 5303.464030] driver1 write

7. [ 5303.464030] receive data: hello,driver1

8. [ 5303.464031] driver1 close

删除驱动：

1. root@ubuntu:cpp/driver1# rmmod driver1

2. root@ubuntu:cpp/driver1# dmesg

3. [ 5438.032293] driver1_exit,76

删除设备文件，直接用 rm 命令。

echo $? 显示当前程序返回值。