【一文秒懂】Linux字符设备驱动
Jan 19, 2024
本文阅读量次【一文秒懂】Linux字符设备驱动 # 1、前言 # 众所周知，Linux内核主要包括三种驱动模型，字符设备驱动，块设备驱动以及网络设备驱动。 其中，Linux字符设备驱动，可以说是Linux驱动开发中最常见的一种驱动模型。 我们该系列文章，主要为了帮助大家快速入门Linux驱动开发，该篇主要来了解一些字符设备驱动的框架和机制。 系列文章基于Kernel 4.19 2、关键数据结构 # 2.1 cdev # struct cdev { struct kobject kobj; struct module *owner; const struct file_operations *ops; struct list_head list; dev_t dev; unsigned int count; } __randomize_layout; 结构体名称：cdev 文件位置：include/linux/cdev.h 主要作用：cdev可以理解为char device，用来抽象一个字符设备。 核心成员及含义： kobj：表示一个内核对象。 owner：指向该模块的指针 ops：指向文件操作的指针，包括open、read、write等操作接口 list：用于将该设备加入到内核模块链表中 dev：设备号，由主设备号和次设备号构成 count：表示有多少个同类型设备，也间接表示设备号的范围 __randomize_layout：一个编译器指令，用于随机化结构体的布局，以增加安全性。 2.2 file_operations # 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 (*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 ssize_t (*copy_file_range)(struct file *, loff_t, struct file *, loff_t, size_t, unsigned int); int (*clone_file_range)(struct file *, loff_t, struct file *, loff_t, u64); int (*dedupe_file_range)(struct file *, loff_t, struct file *, loff_t, u64); int (*fadvise)(struct file *, loff_t, loff_t, int); } __randomize_layout; 结构体名称：file_operations ...