型別的封裝（核心裡的繼承）

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <asm/uaccess.h>

#define MYMA  1234
#define MYMI  7788
#define COUNT 1

//為了方便重用和維護，把驅動所用到的資料封裝成一個型別
typedef struct {
    dev_t devid;
    struct
 
 cdev mycdev;
    u8 *data; //驅動資料緩衝區
    int dlen; //驅動資料緩衝區長度
}mydev_t;

ssize_t myread(struct file *fl, char __user *buf, size_t len, loff_t *off)
{
    struct cdev *cdev = fl->f_path.dentry->d_inode->i_cdev; //這裡可能得到mydev_t物件的mycdev成員地址
    mydev_t *dev = container_of(cdev, mydev_t, mycdev); //通過mycdev成員的地址得到mydev_t物件的首地址
 

    int len_copy, ret;

    if ((fl->f_pos + len) > strlen(dev->data)) 
            len_copy = strlen(dev->data) - fl->f_pos;
    else
            len_copy = len; 

    ret = copy_to_user(buf, dev->data+fl->f_pos, len_copy);

    *off += len_copy - ret; 

    return len_copy - ret;
}

struct
 
 file_operations fops = {
    .owner = THIS_MODULE,
    .read = myread,
};

mydev_t *dev;

static int __init test_init(void)
{
    int ret, i;

    dev = kzalloc(sizeof(*dev), GFP_KERNEL);

    dev->devid = MKDEV(MYMA, MYMI);

    ret = register_chrdev_region(dev->devid, COUNT, "mydev");
    if (ret < 0)
        goto err0;

    cdev_init(&(dev->mycdev), &fops);
    dev->mycdev.owner = THIS_MODULE;

    ret = cdev_add(&(dev->mycdev), dev->devid, COUNT);
    if (ret < 0)
        goto err1;

    dev->dlen = 26;
    dev->data = kzalloc(dev->dlen, GFP_KERNEL); 
    for (i = 0; i < 26; i++)
         dev->data[i] = 'A' + i;

    return 0;

err1:
    unregister_chrdev_region(dev->devid, COUNT);
err0:
    return ret;
}

static void __exit test_exit(void)
{
    unregister_chrdev_region(dev->devid, COUNT);
    cdev_del(&(dev->mycdev));

    kfree(dev->data);
    kfree(dev);
}

module_init(test_init);
module_exit(test_exit);

MODULE_LICENSE("GPL");