struct file_operations {
struct module *owner; //模块所有者指针,一般初始化为THIS_MODULES
loff_t (*llseek) (struct file *, loff_t, int); //用来修改文件当前的读写位置,返回新的位置loff_t 为一个"长偏移"
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *); //同步读取函数,读取成功返回读取的字节数,设置为NULL,调用时返回-EINVAL
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);//同步写入函数
ssize_t (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t);//异步读取操作,为NULL时全部通过read处理
ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long, loff_t);//异步写入函数
int (*readdir) (struct file *, void *, filldir_t); //仅用于读取目录,对设备文件,该字段为NULL
unsigned int (*poll) (struct file *, struct poll_table_struct *); //判断目前是否可以对设备进行读写操作,字段为空时,设备会被认为既可读也可写
int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);//向设备发送I/O控制命令的函数,不设置入口点返回-ENOTTY
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 *);
int (*open) (struct inode *, struct file *);
int (*flush) (struct file *, fl_owner_t id);
int (*release) (struct inode *, struct file *);
int (*fsync) (struct file *, struct dentry *, int datasync);
int (*aio_fsync) (struct kiocb *, 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 (*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);
int (*setlease)(struct file *, long, struct file_lock **);
};
