linux设备驱动初学(二)

1. #include <linux/init.h>
2. #include <linux/kernel.h>
3. #include <linux/module.h>
4. #include <linux/types.h>
5. #include <linux/fs.h>
6. #include <linux/mm.h>
7. #include <linux/errno.h>
8. #include <asm/segment.h>
9. #include <linux/module.h>
10. #include <linux/sched.h>
11. #include <linux/cdev.h>
12. MODULE_LICENSE("Dual BSD/GPL");
13. unsigned int test_major=0;
14. static char *book_name = "dissecting Linux Device Drviver";
15. static int num = 4000;
16. static int global_major = 0;
18. struct cc_dev_t
19. {
20.   struct cdev cdev;
21. } cc_dev;
23. static int cc_read(struct inode *inode,struct file *file,char *buf,int count)
24. {
25.     printk(KERN_INFO "*******cc_read********\n");
26.     return 0;
27. }
29. static int cc_write(struct inode *inode,struct file *file,const char *buf,int count)
30. {
31.   printk(KERN_INFO "*******cc_write*******\n");
32.   return 0;
33. }
35. static int cc_open(struct inode *inode,struct file *file)
36. {
37.   printk(KERN_INFO "********cc_open*******\n");
38.   return 0;
39. }
41. static void cc_release(struct inode *inode,struct file *file)
42. {
43.   printk(KERN_INFO "*******cc_release*****\n");
44. }
46. struct file_operations cc_fops={
47.  .owner = THIS_MODULE,
48.  .read = cc_read,
49.  .write = cc_write,
50.  .open = cc_open,
51.  .release = cc_release,
52. };
54. static int __init cc_init(void)
55. {
56.   int result,err;
57.   dev_t devno = MKDEV(0,0);
58.   result = alloc_chrdev_region(&devno,0,1,"cc");
59.   global_major = MAJOR(devno);
60.   if(result < 0)
61.   {
62.     return result;
63.   }
64.   cdev_init(&cc_dev.cdev,&cc_fops);
65.   err = cdev_add(&cc_dev.cdev,devno,1);
66.   if(err)
67.     printk(KERN_NOTICE "Error");
68.   return 0;
69. }
71. void cc_exit(void)
72. {
73.   cdev_del(&cc_dev.cdev);
74.   unregister_chrdev_region(MKDEV(global_major,0),1);
75. }
77. module_init(cc_init);
78. module_exit(cc_exit);
79. module_param(num,int,S_IRUGO);
80. module_param(book_name,charp,S_IRUGO);
82. MODULE_AUTHOR("xyl");
83. MODULE_DESCRIPTION("A simple Hello world Moudle");
84. MODULE_ALIAS("a simplest moudle");

写完驱动部分 make一下 在/proc/devices下面就会有对应的主设备号了

makefile文件

1.     PWD = $(shell pwd)
2.     CC=gcc
3.     KERNEL_SRC = /usr/src/linux-source-2.6.38/
4.     obj-m := cc.o
5.     module-objs := cc.o
6. all:   
7.     $(MAKE) -C $(KERNEL_SRC)  M=$(PWD) modules
8. clean:
9.     rm *.ko
10.     rm *.o

之后在/dev下面创建设备节点  cat /proc/devices获得主设备号  mknod /dev/cc c major minor

在/dev下面就会有对应的设备节点了  如果想要删除的话直接rm掉

下面是test.c

1. #include<stdio.h>
2. #include<fcntl.h>
3. int main()
4. {
5.   int myfile;
6.   char buffer[100];
7.   int retval;
8.   myfile = open("/dev/cc",O_RDWR);
9.   if(myfile < 0)
10.     printf("Open filed /n");
11.   write(myfile,"hello_world",sizeof("hello_world"));
12.   retval = read(myfile,buffer,100);
13.   buffer[retval] = 1;
14.   printf("redponse:%s/n",buffer);
15.   close(myfile);
16. }

其中close对应驱动中的release.上面的 write read 内容就随便写啦，因为我驱动中并没有实现。

编译一下执行，看内核输出信息dmesg 如下

[ 5096.422497] ********cc_open*******
[ 5096.422512] *******cc_write*******
[ 5096.422519] *******cc_read********
[ 5096.422572] *******cc_release*****
这样就说明调用成功了