字符設備驅動程序設計

1、實驗七 字符設備驅動程序設計實驗目的掌握字符設備驅動程序編寫的框架；掌握設備驅動相關的知識；實驗原理參考本周大課課件字符設備驅動程序.PPT。實驗步驟建立一個工作目錄，我們的驅動程序模塊程序保存在這個目錄下；#mkdir first_drv#cd first_drv1 自己編寫一個字符設備驅動程序,程序格式參考下面；#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）編寫硬件底層操作函數(shù)實現(xiàn)open,release,write,read./（2）創(chuàng)建一個file_operations結構. static int _init xxx_init(void) /（3）申請設備號./（4）初始化cdev結構./（5）注冊cdev結構.return 0; static void _exit XXX_exit(void) /注銷cdev結構./注銷設備號 module_init(.); module_exit(.); MODU

3、LE_LICENSE(.);注意：要求底層函數(shù)要實現(xiàn)open,release,write,read方法。2 編寫Makefile文件內容格式，參考如下：obj-m+=模塊程序文件名.oall:make -C 內核源碼路徑 M=pwd modules #這一行要以TAB鍵開頭clean:make -C 內核源碼路徑 M=pwd modules clean #這一行要以TAB鍵開頭3 編譯模塊，拷貝到根文件系統(tǒng)中編譯內核模塊，直接使用make命令就可以了；#make編譯沒有錯誤時，將模塊拷貝到跟文件系統(tǒng)中；#cp xxx.ko/opt/rootfs/lib/modules/3.5.0-yyy/4

4、啟動開發(fā)板，進入linux系統(tǒng)后，在開發(fā)板上加載和卸載模塊加載：# insmod/lib/modules/3.5.0-yyy/xxxx.ko查看系統(tǒng)分配的設備號#cat /proc/devices手動添加設備文件（設備節(jié)點）# mknod /dev/first_drv c 主設備號 次設備號5 交叉編譯應程序，打開設備文件進行讀寫操作實驗成功后，叫老師查看實驗結果，作為平時考察成績；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, ;/驅動注冊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_