copy_to_user()和copy_from_user()的使用

#include 
#include 
#include 
#include 
#include 

MODULE_LICENSE("Dual BSD/GPL");

static int count = 10;
static char *init_mesg = "hello,world\n";
static char *exit_mesg = "goodbye\n";

static int major = 252;
static int minor = 0;
dev_t devnum;
int static hello_dev_open(struct inode *inode, struct file *file)

{
	printk("file open in hello_dev_open......finished!\n");
	return 0;
}

int static hello_dev_release(struct inode *inode, struct file *file)

{
	printk("file release in hello_dev_release......finished!\n");
	return 0;
}

ssize_t hello_dev_read(struct file *file, char __user *buf,size_t count, loff_t *offset)
{
	char alpha[27];
	int i, cnt;
	memset(alpha, 0, 27);
	for(i = 0; i < 26; i++)
		alpha[i] = 'a' + i;
	if(count > 26)
		cnt = 26;
	else
		cnt = count;
	//使用copy_to_user ()函数从driver读数据到user
	if(!copy_to_user((char *)buf, alpha, cnt))
		return cnt;
	else
		return -1;
}

ssize_t hello_dev_write(struct file *file, const char __user *buf, size_t count, loff_t *offset)
{
	char alpha[27];
	int cnt;
	memset(alpha, 0, 27);
	if(count > 26)
		cnt = 26;
	else
		cnt = count;
//使用copy_from_user()函数从user写数据到driver
	if(!copy_from_user((char *)alpha, buf, cnt))
	{  
		printk(alpha);
		printk("\n");
		return cnt;
	}  
	else
		return -1;
}

static struct cdev hello_dev;

static struct file_operations fops ={
	.owner = THIS_MODULE,
	.open  = hello_dev_open,
	.release = hello_dev_release,
	.read = hello_dev_read,
	.write = hello_dev_write,
};

static int __init hello_init(void)
{
	int i;
	int ret;

	for(i = 0; i < count; i++)
		 printk(init_mesg);
	//ret = register_chrdev_region(MKDEV(major,minor), 1, "hello_dev");
	ret = alloc_chrdev_region(&devnum, 10, 1, "hello_dev");
	if(!ret)
	{
		major = MAJOR(devnum);
		minor = MINOR(devnum);
		printk("major = %d; minor = %d\n", major, minor);
	}
	cdev_init(&hello_dev, &fops);
	ret = cdev_add(&hello_dev, devnum, 1);
	return ret;
}

void hello_exit(void)
{
	printk(exit_mesg);
	cdev_del(&hello_dev);
	unregister_chrdev_region(MKDEV(major, minor),1);
	return;
}

void hello(void)
{
	printk("good mornig1\n");
}

module_param(count, int, S_IRUGO);
module_param(init_mesg, charp, S_IRUGO);
module_param(exit_mesg, charp, S_IRUGO);

module_init(hello_init);

module_exit(hello_exit);

测试程序：

main.c:
#include 
#include 
#include 
#include 
#include 
#define DEVNAME "/dev/hello"

int main()
{
	char alpha[27];
	int fd,i; 
	memset(alpha, 0, 27);
	for(i = 0; i < 26; i++)
		alpha[i] = 'A' + i;
	fd = open(DEVNAME, O_RDWR);
	if(fd == -1)
		("file %s is opening......failure!", DEVNAME);
	else
		printf("file %s is opening......successfully!\nits fd is %d\n", DEVNAME, fd);
	getchar();
	printf("write A-Z to kernel......\n");
	write(fd, alpha, 26);
	getchar();
	printf("read datas from kernel.......\n");
	read(fd, alpha, 26);
	printf("%s\n", alpha);
	getchar();
	close(fd);
	return 0;
}

测试结果：

file /dev/hello is opening……successfully!

Its fd is 3

(输入回车)

write  A-Z  to  kernel……

(输入回车)

read  datas  from  kernel……

abcdefghijklmnopqrstuvwxyz

(输入回车)

 

 

输入dmesg命令，结果如下：

file open in hello_dev_open……finished!

ABCDEFGHIJKLMNOPQRSTUVWXYZ

file release in hello_dev_open……finished!