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");