LDD：linux device driver ,在操作系统作用下，应用程序必须要通过设备驱动程序操作设备
驱动程序：应用程序和设备之间必须通过驱动程序
应用程序 ——> write(ioctl)驱动程序——>(write)设备
应用程序 <——read(ioctl)驱动程序——>(read)设备
LDD程序结构：
LDD程序加载方式：
LDD程序测试：
文件操作结构体在/lib/modules/5.5.2-1-MANJARO/build/include/linux/fs.h中的定义为：
1 struct file_operations { 2 struct module *owner; 3 loff_t (*llseek) (struct file *, loff_t, int); 4 ssize_t (*read) (struct file *, char __user *, size_t, loff_t *); 5 ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *); 6 ssize_t (*read_iter) (struct kiocb *, struct iov_iter *); 7 ssize_t (*write_iter) (struct kiocb *, struct iov_iter *); 8 int (*iopoll)(struct kiocb *kiocb, bool spin); 9 int (*iterate) (struct file *, struct dir_context *); 10 int (*iterate_shared) (struct file *, struct dir_context *); 11 __poll_t (*poll) (struct file *, struct poll_table_struct *); 12 long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); 13 long (*compat_ioctl) (struct file *, unsigned int, unsigned long); 14 int (*mmap) (struct file *, struct vm_area_struct *); 15 unsigned long mmap_supported_flags; 16 int (*open) (struct inode *, struct file *); 17 int (*flush) (struct file *, fl_owner_t id); 18 int (*release) (struct inode *, struct file *); 19 int (*fsync) (struct file *, loff_t, loff_t, int datasync); 20 int (*fasync) (int, struct file *, int); 21 int (*lock) (struct file *, int, struct file_lock *); 22 ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int); 23 unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long); 24 int (*check_flags)(int); 25 int (*setfl)(struct file *, unsigned long); 26 int (*flock) (struct file *, int, struct file_lock *); 27 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int); 28 ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int); 29 int (*setlease)(struct file *, long, struct file_lock **, void **); 30 long (*fallocate)(struct file *file, int mode, loff_t offset, 31 loff_t len); 32 void (*show_fdinfo)(struct seq_file *m, struct file *f); 33 #ifndef CONFIG_MMU 34 unsigned (*mmap_capabilities)(struct file *); 35 #endif 36 ssize_t (*copy_file_range)(struct file *, loff_t, struct file *, 37 loff_t, size_t, unsigned int); 38 loff_t (*remap_file_range)(struct file *file_in, loff_t pos_in, 39 struct file *file_out, loff_t pos_out, 40 loff_t len, unsigned int remap_flags); 41 int (*fadvise)(struct file *, loff_t, loff_t, int); 42 } __randomize_layout;