mychar.c

字符驱动程序

#include <asm/segment.h>
#include <asm/uaccess.h>
#include <linux/config.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/version.h>
#define __NO_VERSION__  //版本信息
unsigned int regist=0;  //注册标志
unsigned int count=0;  //用户数目

static ssize_t chopen(struct file *file, const char *buf, size_t length, loff_t *f_pos)
{
	count++;  //增加用户数目
	printk("The character device 'mychar' has been open!\n");
	return 0;
}

static ssize_t chread(struct file *file,const char *buf,size_t length,loff_t *f_pos)
{
	int i,j;
	if(!count) return 0;
	printk("Reading...\n");
	for(i=length,j=0; i>0; i--){
		__put_user(++j,buf);  //向用户传送数据
		buf++;
	}
	printk("Finish!\n");
	return 1;
}

static ssize_t chwrite(struct file *file, const char *buf, size_t length, loff_t *f_pos)
{
	char c;
	int i;
	if(!count) return 0;
	printk("Writing...\n");
	for(i=0; i<length; i++){
		__get_user(c, buf);  //从用户接收数据
		printk("%c ",c);
		buf++;
	}
	printk("\nFinish!\n");
	return 1;
}

static ssize_t chrelease(struct file *file, const char *buf, size_t length, loff_t *f_pos)
{
	count--;  //减少用户数目
	printk("The character device 'mychar' has been closed!\n");
	return 0;
}

struct file_operations mychar_fops={
	open:	chopen,  //打开字符设备
	read:	chread,  //读取字符设备
	write:	chwrite,  //写入字符设备
	release:	chrelease  //关闭字符设备
	};  //字符设备结构

int init_module(void)
{
	int num;
	num=register_chrdev(0, "mychar", &mychar_fops);  //注册设备
	if(num<0){
		printk(KERN_INFO "Regist failed!\n");  //注册失败
		return num;
	}
	if(!regist) regist=num; //修改注册标志
	return 0;
}

void cleanup_module(void)
{
	unregister_chrdev(regist,"mychar");  //卸载设备
}

MODULE_LICENSE("GPL");
MODULE_AUTHOR("BECKHAM");  //版权信息