字符设备驱动程序设计

1、实验七 字符设备驱动程序设计实验目的掌握字符设备驱动程序编写的框架；掌握设备驱动相关的知识；实验原理参考本周大课课件字符设备驱动程序.ppt。实验步骤建立一个工作目录，我们的驱动程序模块程序保存在这个目录下；#mkdir first_drv#cd first_drv1 自己编写一个字符设备驱动程序,程序格式参考下面；#include #include #include #include #include #include #include /（1）编写硬件底层操作函数实现open,release,write,read./（2）创建一个file_operations结构. static int

2、_init xxx_init(void) /（3）申请设备号./（4）初始化cdev结构./（5）注册cdev结构.return 0; static void _exit xxx_exit(void) /注销cdev结构./注销设备号 module_init(.); module_exit(.); module_license(.);注意：要求底层函数要实现open,release,write,read方法。2 编写makefile文件内容格式，参考如下：obj-m+=模块程序文件名.oall:make -c 内核源码路径 m=pwd modules #这一行要以tab键开头clean:mak

3、e -c 内核源码路径 m=pwd modules clean #这一行要以tab键开头3 编译模块，拷贝到根文件系统中编译内核模块，直接使用make命令就可以了；#make编译没有错误时，将模块拷贝到跟文件系统中；#cp xxx.ko/opt/rootfs/lib/modules/3.5.0-yyy/4 启动开发板，进入linux系统后，在开发板上加载和卸载模块加载：# insmod/lib/modules/3.5.0-yyy/xxxx.ko查看系统分配的设备号#cat /proc/devices手动添加设备文件（设备节点）# mknod /dev/first_drv c 主设备号 次设备号

4、5 交叉编译应程序，打开设备文件进行读写操作实验成功后，叫老师查看实验结果，作为平时考察成绩；first_drv：#include #include #include #include #include #include #include #include #include static int first_drv_open(struct inode *in, struct file *fp)printk(first driver open called!n);return 0;static int first_drv_release(struct inode *in, struct file

5、 *fp)printk(first driver release called!n);return 0;static int data=0;static ssize_t first_drv_write(struct file *fp, const char _user *buf, size_t len, loff_t *offset)copy_from_user(void *)&data,buf,sizeof(int);printk(first driver write called!data is %dn,data);return sizeof(int);static ssize_t fir

6、st_drv_read(struct file *fp, char _user *buf, size_t len, loff_t * offset)data=data+1;copy_to_user(buf,&data,sizeof(int);printk(first driver read called!n);return sizeof(int);static struct file_operations first_fops = .owner = this_module,.open = first_drv_open,.release =first_drv_release,.write = f

7、irst_drv_write,.read = first_drv_read, ;/驱动注册static int major = 0;static struct cdev *first_drv_cdev;#define first_drv_name first_drvstatic int _init first_drv_init(void)dev_t dev;alloc_chrdev_region(&dev, 0, 1, first_drv_name);major = major(dev);first_drv_cdev = cdev_alloc();cdev_init(first_drv_cde

8、v,&first_fops);first_drv_cdev-owner = this_module;cdev_add(first_drv_cdev, dev, 1);printk(first driver module insert!n);return 0;static void _exit first_drv_exit(void)dev_t dev;dev = mkdev(major,0);cdev_del(first_drv_cdev);unregister_chrdev_region(dev, 1);printk(first driver module remove!n);module_

9、init(first_drv_init);module_exit(first_drv_exit);module_license(gpl);makefile：obj-m += first_drv.oall:make -c /home/sice/linux-4.4.19m=pwdmodulesclean:make -c /home/sice/linux-4.4.19m=pwdmodules cleantest：#include#include#include#include#include#define file_name /dev/abcint main(void)int fd;fd=open(file_name,o_r