Linux驱动开发file_operations结构体

Posted 2022-04-21 XXX_UUU_XXX

file_operations结构体是Linux内核驱动操作函数集合，在内核文件include/linux/fs.h中。根据具体驱动需求实现哪些函数。

字符设备驱动开发中常用的函数

owner

• 拥有该结构体的模块的指针，一般设置为THIS_MODULE

llseek

• 修改文件当前的读写位置

read

• 读取设备文件

write

• 向设备文件写入数据

poll

• 查询设备是否可以进行非阻塞的读写

unlocked_ioctl

• 提供对设备的控制功能，与应用程序中的ioctl函数对应

compat_ioctl

• 与unlocked_ioctl功能一样，不同的是64位系统中的32位的应用程序会调用compat_ioctl，32位系统中的32位的应用程序会调用unlocked_ioctl

mmap

• 将设备的内存映射到用户空间，一般帧缓冲设备会用mmap函数，如LCD驱动的显存，将LCD显存映射到用户空间后，应用程序就可以直接操作显存，不需要在用户空间和内核空间来回复制。

open

• 打开设备文件

release

• 释放设备文件

fasync

• 刷新待处理的数据，将缓冲区的数据刷新到磁盘中

aio_fsync

• 与fasync功能类似，aio_fsync是异步刷新待处理的数据

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 *);
	unsigned int (*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 *);
	int (*mremap)(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 *, loff_t, loff_t, 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 **, 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
;