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 <linux/module.h>#include <linux/kernel.h>#include <linux/init.h>#include <linux/fs.h>#include <linux/type

2、s.h>#include <linux/uaccess.h>#include <linux/cdev.h>/（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 _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(.); MODU

3、LE_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:make -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

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 <linux/module.h>#include <linux/init.h>#include <linux/fs.h>#include &

5、lt;linux/types.h>#include <linux/uaccess.h>#include <linux/kernel.h>#include <linux/cdev.h>#include <linux/device.h>#include <asm/io.h>static int first_drv_open(struct inode *in, struct file *fp)printk("first driver open called!n");return 0;static int first

6、_drv_release(struct inode *in, struct file *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 writ

7、e called!data is %dn",data);return sizeof(int);static ssize_t first_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_fop

8、s = .owner = THIS_MODULE,.open = first_drv_open,.release =first_drv_release,.write = first_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_drv"static int _init first_drv_init(void)dev_t dev;alloc_chrdev_region(&a

9、mp;dev, 0, 1, FIRST_DRV_NAME);major = MAJOR(dev);first_drv_cdev = cdev_alloc();cdev_init(first_drv_cdev,&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;d

10、ev = MKDEV(major,0);cdev_del(first_drv_cdev);unregister_chrdev_region(dev, 1);printk("first driver module remove!n");module_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<stdio.h>#include<sys/types.h>#include<sys/stat.h>#include<unistd.h>#include<fcntl.h>#define FILE_NAME "/dev/abc"int main(void)int fd;fd=open(FILE_