linux字符设备驱动程序相关的数据结构及操作

以下数据结构以内核2.4.0为例:

file结构(定义在<linux/fs.h>中):
struct file {
     struct list_head   f_list;
     struct dentry      *f_dentry;
     struct vfsmount         *f_vfsmnt;
     struct file_operations    *f_op;
     atomic_t      f_count;
     unsigned int     f_flags;
     mode_t     f_mode;
     loff_t     f_pos;
     unsigned long     f_reada, f_ramax, f_raend, f_ralen, f_rawin;
     struct fown_struct     f_owner;
     unsigned int     f_uid, f_gid;
     int       f_error;

     unsigned long     f_version;

     /* needed for tty driver, and maybe others */
     void       *private_data;
};

file_operations结构(定义在<linux/fs.h>中）:
struct file_operations {
     struct module *owner;
     loff_t (*llseek) (struct file *, loff_t, int);
     ssize_t (*read) (struct file *, char *, size_t, loff_t *);
     ssize_t (*write) (struct file *, const char *, size_t, loff_t *);
     int (*readdir) (struct file *, void *, filldir_t);
     unsigned int (*poll) (struct file *, struct poll_table_struct *);
     int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);
     int (*mmap) (struct file *, struct vm_area_struct *);
     int (*open) (struct inode *, struct file *);
     int (*flush) (struct file *);
     int (*release) (struct inode *, struct file *);
     int (*fsync) (struct file *, struct dentry *, int datasync);
     int (*fasync) (int, struct file *, int);
     int (*lock) (struct file *, int, struct file_lock *);
     ssize_t (*readv) (struct file *, const struct iovec *, unsigned long, loff_t *);
     ssize_t (*writev) (struct file *, const struct iovec *, unsigned long, loff_t *);
};
     在2.4.0内核的file和file_operations的结构与O'Reilly的《Linux设备驱动程序》所讲的版本有些不一样：
     比如在O'Reilly的书中所讲file结构有一个struct inode成员，而在2.4.0版本中却没有，但是它有个struct dentry成员，而在struct dentry包含了struct inode。
    再如file_operations，read, write函数原型同样是四个参数，但2.4.0中，与O'Reilly的书中所讲的版本相比少了inode结构指针的参数，但是多了一个loff_t的文件偏移指针，因此在实际的编写驱动程序时要注意一下内核的版本问题。