linux 设备驱动框架代码（open, release, write close）

最新推荐文章于 2024-10-11 17:09:56 发布

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本文介绍了一个简单的Linux字符设备驱动程序实现，并提供了一个用于测试该驱动的应用程序示例。驱动程序包括基本的文件操作，如打开、关闭、读取和写入。

驱动代码：

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/device.h>

#include <linux/uaccess.h>
#include <linux/string.h>

struct message_to_app_dev
{
	struct cdev* pcdev;
	dev_t devno;

	struct class *message_class;
};

static int message_open(struct inode *node, struct file *filp)
{
	printk("message_open()++\n");
	printk("message_open()--\n");

	return 0;
}

static int message_release(struct inode *node, struct file *filp)
{
	printk("message_release()++\n");
	printk("message_release()--\n");

	return 0;
}

static ssize_t message_write(struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
{
	char temp_buffer [20];
	int print_size = 0;
	
	printk("message_wirte()++\n");
	if(len > 20)
		print_size = 20;
	else
		print_size = len;
	printk("print_size = %d; len = %d\n", print_size, len);
	if(copy_from_user(temp_buffer, buf, print_size))
		return -EFAULT;
	
	printk("writing data:%s", temp_buffer);
	
	printk("message_wirte()--\n");

	return print_size;
}
static ssize_t message_read(struct file *fd, char __user *buf, size_t len, loff_t *ptr)
{
      char *temp_buffer = "Hello message_read !\n";
      int print_size = 0;
	  
	printk("message_read()++\n");
	
	if(len > strnlen(temp_buffer,20))
		print_size = strnlen(temp_buffer,20);
	else
		print_size = len;
	printk("print_size = %d; len = %d\n", print_size, len);
	if(copy_to_user(buf, temp_buffer, print_size))
		return -EFAULT;
	printk("%s", temp_buffer);
	printk("message_read()--\n");

	return print_size;
}
struct file_operations meassage_operatons =
{
	.owner = THIS_MODULE,
	.open = message_open,
	.release = message_release,
	.write = message_write,
	.read = message_read,
};

struct message_to_app_dev message_dev;
static int __init message_to_app_init(void)
{
	struct message_to_app_dev * dev;

	printk("message_to_app_init(void)++\n");

	dev = &message_dev;

	alloc_chrdev_region(&dev->devno, 0, 1, "message_to_app");
	dev->pcdev = cdev_alloc();
	cdev_init(dev->pcdev, &meassage_operatons);
	cdev_add(dev->pcdev, dev->devno, 1);

	dev->message_class = class_create(THIS_MODULE, "message_class");
	if(IS_ERR(dev->message_class)) {
	     printk("Err: failed in creating class./n");
	     return -1; 
	 }
	device_create(dev->message_class, NULL, dev->devno, NULL, "message");
	printk("message_to_app_init(void)--\n");	
	return 0;
}
static void __exit message_to_app_exit(void)
{
	struct message_to_app_dev *dev = &message_dev;

	printk("message_to_app_exit(void)++\n");
	device_destroy(dev->message_class, dev->devno);
	class_destroy(dev->message_class); 
	cdev_del(dev->pcdev);
	unregister_chrdev_region(dev->devno, 1);
	 
	printk("message_to_app_exit(void)--\n");
}
module_init(message_to_app_init);
module_exit(message_to_app_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Driver Monkey");
MODULE_DESCRIPTION("Test message to App");

测试程序：

#include<stdio.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<sys/select.h>
#include<unistd.h>
#include<signal.h>
#include<string.h>

unsigned int flag;

void sig_handler(intsig)
{
  printf("<app>%s\n",__FUNCTION__);
  flag=1;
}
int main(void)
{
	char r_buf[20];
	char *w_buf = "hello write!\n";
	int r_count = 0;
	int fd;
	int f_flags;
	flag=0;
	fd=open("/dev/message",O_RDWR);
	if(fd<0)
	{
		perror("open");
		return-1;
	}

	r_count=read(fd, r_buf, 20);
	printf("r_count = %d\n", r_count);
	printf("app read:\n%s", r_buf);
	
	write(fd, w_buf, strlen(w_buf));

	close(fd);

	return 0;
}