前言
驱动写好后，用户层使用系统函数调用操作相关驱动从而实现与系统内核的关联，本篇主要就是理解清楚驱动如何让用户编程来实现与内核的交互。
杂项设备文件操作集
cd /usr/src/linux-headers-4.18.0-15vi include/linux/fs.h
搜索到（vi则直接使用“/”）:
struct file_operations {
struct module *owner;
loff_t (*llseek) (struct file *, loff_t, int);
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
int (*iterate) (struct file *, struct dir_context *);
int (*iterate_shared) (struct file *, struct dir_context *);
__poll_t (*poll) (struct file *, struct poll_table_struct *);
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*mmap) (struct file *, struct vm_area_struct *);
unsigned long mmap_supported_flags;
int (*open) (struct inode *, struct file *);
int (*flush) (struct file *, fl_owner_t id);
int (*release) (struct inode *, struct file *);
int (*fsync) (struct file *, loff_t, loff_t, int datasync);
int (*fasync) (int, struct file *, int);
int (*lock) (struct file *, int, struct file_lock *);
ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
int (*check_flags)(int);
int (*setfl)(struct file *, unsigned long);
int (*flock) (struct file *, int, struct file_lock *);
ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
ssize_t (*copy_file_range)(struct file *, loff_t, struct file *,
loff_t, size_t, unsigned int);
int (*setlease)(struct file *, long, struct file_lock **, void **);
long (*fallocate)(struct file *file, int mode, loff_t offset,
loff_t len);
void (*show_fdinfo)(struct seq_file *m, struct file *f);#ifndef CONFIG_MMU
unsigned (*mmap_capabilities)(struct file *);#endif
int (*clone_file_range)(struct file *, loff_t, struct file *, loff_t,
u64);
ssize_t (*dedupe_file_range)(struct file *, u64, u64, struct file *,
u64);} __randomize_layout;
例如read函数，那么就是打开驱动使用系统read，打开这个设备驱动的句柄，那么就会调用read函数，其他的以此类推，还比较好理解。
Linux文件操作集的意义
概述
Linux一切都是文件，都有对应的打开、关闭和读写等相关操作，而这些操作都是使用打开文件后的句柄来表示，那么函数再根据句柄的类型，如打开的是杂项设备驱动，就会去调用杂项设备操作文件字符集里面对应的函数来执行操作了。
在编程的时候会使用open打开一个设备节点（可以是文件打开，可以打开设备），这时候返回得到设备节点句柄标识fd（失败是-1），然后使用fd去read、write等各种操作则会相当于调用这个设备驱动里面文件操作集的read、write。
下面是常用的文件操作。
open函数（实现测试）
int (*open) (struct inode *, struct file *);
read函数（实现测试）
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *)
write函数（实现测试）
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
poll/select函数（本篇没写）
__poll_t (*poll) (struct file *, struct poll_table_struct *);
ioctl函数（本篇没写）
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
close函数（实现测试）
int (*release) (struct inode *, struct file *);
驱动模板准备
首先复制之前的registerMiscDev的驱动，改个名字为：testFileOpts：
cd ~/work/drivecp -arf registerMiscDev testFileOptscd testFileOptsmake cleanmv registerMiscDev testFileOpts.c
然后修改makefile里面的（obj-m模块名称改下），模板准备好了
gedit Makefile
下面基于testFileOpts.c文件进行注册杂项设备，修改.c文件：
gedit testFileOpts.c
#include #include #include #include struct file_operations misc_fops = {
.owner = THIS_MODULE,};struct miscdevice misc_dev = {
.minor = MISC_DYNAMIC_MINOR, // 这个宏是动态分配次设备号，避免冲突
.name = "register_hongPangZi_testFileOpt", // 设备节点名称
.fops = &misc_fops, // 这个变量记住，自己起的，步骤二使用};static int registerMiscDev_init(void){
int ret;
// 在内核里面无法使用基础c库printf，需要使用内核库printk
printk("Hello, I’m hongPangZi, registerMiscDev_init\n");
ret = misc_register(&misc_dev);
if(ret
