一、结构体
1. cdev 结构体
struct cdev {
struct kobject kobj; /* 内嵌的 kobject 对象 */
struct module *owner; /*所属模块*/
struct file_operations *ops; /*文件操作结构体*/
struct list_head list;
dev_t dev; /*设备号*/
unsigned int count;
8 };
2. file_operations 结构体
struct file_operations {
struct module *owner;
/* 拥有该结构的模块的指针,一般为 THIS_MODULES */
loff_t(*llseek)(struct file *, loff_t, int);
/* 用来修改文件当前的读写位置 */
ssize_t(*read)(struct file *, char _ _user *, size_t, loff_t*);
/* 从设备中同步读取数据 */
ssize_t(*write)(struct file *, const char _ _user *, size_t, loff_t*);
/* 向设备发送数据*/
ssize_t(*aio_read)(struct kiocb *, char _ _user *, size_t, loff_t);
/* 初始化一个异步的读取操作*/
ssize_t(*aio_write)(struct kiocb *, const char _ _user *, size_t, loff_t);
/* 初始化一个异步的写入操作*/
int(*readdir)(struct file *, void *, filldir_t);
/* 仅用于读取目录,对于设备文件,该字段为 NULL */
unsigned int(*poll)(struct file *, struct poll_table_struct*);
/* 轮询函数,判断目前是否可以进行非阻塞的读取或写入*/
int(*ioctl)(struct inode *, struct file *, unsigned int, unsigned long);
/* 执行设备 I/O 控制命令*/
long(*unlocked_ioctl)(struct file *, unsigned int, unsigned long);
/* 不使用 BLK 的文件系统,将使用此种函数指针代替 ioctl */
long(*compat_ioctl)(struct file *, unsigned int, unsigned long);
/* 在 64 位系统上,32 位的 ioctl 调用,将使用此函数指针代替*/
int(*mmap)(struct file *, struct vm_area_struct*);
/* 用于请求将设备内存映射到进程地址空间*/
int(*open)(struct inode *, struct file*);
/* 打开 */
int(*flush)(struct file*);
int(*release)(struct inode *, struct file*);
/* 关闭*/
int (*fsync) (struct file *, struct dentry *, int datasync);
/* 刷新待处理的数据*/
int(*aio_fsync)(struct kiocb *, int datasync);
/* 异步 fsync */
int(*fasync)(int, struct file *, int);
/* 通知设备 FASYNC 标志发生变化*/
int(*lock)(struct file *, int, struct file_lock*);
ssize_t(*sendpage)(struct file *, struct page *, int, size_t, loff_t *, int);
/* 通常为 NULL */
unsigned long(*get_unmapped_area)(struct file *,unsigned long, unsigned long, unsigned long, unsigned long);
/* 在当前进程地址空间找到一个未映射的内存段 */
int(*check_flags)(int);
/* 允许模块检查传递给 fcntl(F_SETEL...)调用的标志 */
int(*dir_notify)(struct file *filp, unsigned long arg);
/* 对文件系统有效,驱动程序不必实现*/
int(*flock)(struct file *, int, struct file_lock*);
ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
/* 由 VFS 调用,将管道数据粘接到文件 */
ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
/* 由 VFS 调用,将文件数据粘接到管道 */
int (*setlease)(struct file *, long, struct file_lock **);
};