驱动学习3--添加copy_from_user&copy_to_user

驱动代码

#include <linux/module.h>       // module_init  module_exit
#include <linux/init.h>         // __init   __exit
#include <linux/fs.h>           //register_chrdev   file_operations
#include <asm/uaccess.h>        //copy_from_user    copy_to_user

#define DEMO_NAME   "demo_char"
static int my_major;

static int demo_chrdev_open(struct inode *inode, struct file *file)
{
printk(KERN_INFO "demo_chrdev_open\n");/*open的调试代码*/
return 0;
}

static int demo_chrdev_release(struct inode *inode, struct file *file)
{
printk(KERN_INFO "demo_chrdev_release\n");/*close的调试代码*/
return 0;
}

static ssize_t demo_chrdev_write(struct file *file, const char __user *ubuf, size_t count, loff_t *ppos)
{
int ret = -1;
char kbuf[100] = {0};
ret = copy_from_user(kbuf,ubuf,count);/*返回值为0成功*/
if(ret)
{
printk(KERN_ERR "copy_from_user fail\n");
return -EINVAL;
}
printk(KERN_INFO "copy_from_user %s\r\n",kbuf);
return 0;
}
static ssize_t demo_chrdev_read(struct file *file, char __user *ubuf, size_t count, loff_t *ppos)
{
int ret = -1;
char kbuf[100] = "demo_chrdev_read.";

ret = copy_to_user(ubuf,kbuf,count);/*返回值为0成功*/
if(ret)
{
printk(KERN_ERR "copy_to_user fail\n");
return -EINVAL;
}
return 0;
}

static const struct file_operations demo_fops = {
.owner
4000
= THIS_MODULE,/*惯例，直接写即可*/
.open       = demo_chrdev_open,/*把open的api与此函数联系起来*/
.release    = demo_chrdev_release,/*把close的api于此函数联系起来*/
.write      = demo_chrdev_write,/*把write的api于此函数联系起来*/
.read       = demo_chrdev_read,/*把read的api于此函数联系起来*/
};

static int __init chrdev_init(void) /*模块安装*/
{
my_major = register_chrdev(0,DEMO_NAME,&demo_fops);/*注册设备,0表示自动分配设备号*/
if(my_major<0){
printk(KERN_ERR "chrdev_init error.\n");
return -EINVAL;
}
printk(KERN_INFO "chrdev_init success.\n");
return 0;
}

static void __exit chrdev_exit(void)/*模块卸载*/
{
unregister_chrdev(my_major,DEMO_NAME);/*注销设备*/
printk(KERN_INFO "chrdev_exit\n");
}

module_init(chrdev_init);
module_exit(chrdev_exit);

MODULE_LICENSE("GPL");/*描述模块的许可证*/
MODULE_AUTHOR("Xin-Ya Zhu<mhzhuxinya@outlook.com>");/*描述模块的作者*/
MODULE_DESCRIPTION("demo test");/*描述模块的介绍信息*/
MODULE_ALIAS("alias xxx");/*描述模块的别名信息*/
/**************运行结果*****************
[root@zhuxinya text]# lsmod
Module                  Size  Used by    Not tainted
[root@zhuxinya text]# insmod demo.ko
[ 5456.922445] chrdev_init success.
[root@zhuxinya text]# lsmod
Module                  Size  Used by    Not tainted
demo                    1056  0
[root@zhuxinya text]# cat /proc/devices
Character devices:
250 demo_char
[root@zhuxinya text]# rmmod demo.ko
[ 5524.153407] chrdev_exit
*************************************/

应用代码

#include <stdio.h>

#include <sys/types.h>  //open close
#include <sys/stat.h>
#include <fcntl.h>

#define FILE    "/dev/demo_text"

int main(void)
{
int fd = -1,ret = -1;
char buf[100] = {0};

fd = open(FILE,O_RDWR);
if(fd<0)
{
printf("open error.\n");
return -1;
}

ret = write(fd,"123",3);
sleep(1);
ret = read(fd,buf,100);
printf("buf = %s\r\n",buf);
sleep(1);
close(fd);

return 0;
}

/***************************
安装好驱动后执行
mknod /dev/demo_text c 250 0

[root@zhuxinya text]# ./app
[  799.487045] demo_chrdev_open
[  799.488461] copy_from_user 123
buf = demo_chrdev_read.
[  801.491904] demo_chrdev_release
*****************************/