【原创】Linux应用程序完整调用自己写的字符设备驱动过程

Linux应用程序完整调用自己写的字符设备驱动过程

 

 

一、先写驱动程序hello.c

实现字符驱动的打开、关闭、读、写的函数框架，加载和卸载程序入口调用

 

通过dmesg来查看内核printk的打印

使用makefile来编写驱动，生成ko文件

 

lsmod查看驱动

insmod 加载驱动

rmmod卸载驱动

cat /proc/devices,查看主设备号使用情况,

在dev目录下创建hello设备节点

mknod /dev/hello c 200 0

 

//驱动hello.c代码

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

static struct file_operations chardev_fops;
#define CAHRDEV_MAJOR 200
#define CHARDEV_NAME "hello kernel!"
char writebuf[100];
char readbuf[100];

static struct file_operations chardev_fops;

static int chardev_open(struct inode *inode, struct file *file)
{
printk("chrdev_open! ");
return 0;
}

static int chardev_close(struct inode *inode, struct file *filp)
{
printk("chrdev_release! ");
return 0;
}

static ssize_t chardev_read(struct file *filp, __user char *buf,size_t
count,loff_t *ppos)
{
int ret = 0;
snprintf(readbuf,sizeof(readbuf),CHARDEV_NAME);
ret = copy_to_user(buf,readbuf,count);
if(ret == 0)
{
printk("chardev_read. ");
}
return 0;
}

static ssize_t chardev_write(struct file *filp, const char __user *buf,size_t
count,loff_t *ppos)
{
int ret = 0;
ret = copy_from_user(writebuf,buf,count);
if(ret == 0)
{
printk("chrdev_write is : %s ",&writebuf);
}

return 0;
}

static int hello_init(void)
{
int retvalue = 0;
/* 注册字符设备驱动 */
//cat /proc/devices,查看主设备号使用情况,
retvalue = register_chrdev(CAHRDEV_MAJOR, CHARDEV_NAME, &chardev_fops);
if(retvalue < 0)
{
/* 字符设备注册失败,自行处理 */
printk("hello_init fail. ");

}
else
{
printk("hello world enter modules!!! ");
}

return 0;
}

static void hello_exit(void)
{
/* 注销字符设备驱动 */
unregister_chrdev(CAHRDEV_MAJOR, CHARDEV_NAME);
printk("hello world exit modules! ");
}

static struct file_operations chardev_fops={
.owner = THIS_MODULE,
.open = chardev_open,
.read = chardev_read,
.write = chardev_write,
.release= chardev_close,
};

module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("panda");

 

二、再写应用程序helloAPP.c

应用层调用打开、读、写、关闭字符底层驱动函数

查看创建的节点

ls /dev/hello -l

应用程序调用设备驱动节点

./helloAPP /dev/hello

 

//应用代码helloAPP.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

//argc:应用程序参数个数
//argv[]:具体参数内容，是字符串形式
int main(int argc,char *argv[])
{
int fd = 0;
int ret = 0;
char *filename;
char readbuf[100];
char writebuf[100] = "hello APP!!!";

filename = argv[1];

fd = open(filename,O_RDWR);
if(fd <0)
{
printf("can't open %s fail! ",filename);
return -1;
}
else{
printf("open OK! ");
}

ret = read(fd,readbuf,50);
if(ret <0)
{
printf("can't read %s fail! ",filename);
}
else{
printf("read data is: %s ",readbuf);
}

ret = write(fd,writebuf,50);
if(ret <0)
{
printf("can't write %s fail! ",filename);
}
else{
printf("write OK! ");
}

ret = close(fd);
if(ret <0)
{
printf("can't close %s fail! ",filename);
}else
{
printf("close OK! ");
}

printf("hello world! ");

return 0;

}

 

三、最终打印内容

应用层调用打印：

 驱动层调用打印，输入dmesg打印printk内容

注意：

主设备号高12位，次设备号低20位，所以请注意Linux系统中主设备号范围为 0~4095，

 

man 1 命令查询

man 2 系统调用查询

man 3 库查询

man 2 open