Linux 設備驅動框架代碼（open, release, write close）

Linux 設備驅動框架代碼：

#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");