1. struct cdev {
struct kobject kobj;
struct module *owner;
const struct file_operations *ops;
struct list_head list;
dev_t dev;
unsigned int count;
};//描述字元裝置
2. void cdev_init(struct cdev *cdev, const struct file_operations *fops){
memset(cdev, 0, sizeof *cdev);
INIT_LIST_HEAD(&cdev->list);
cdev->kobj.ktype = &ktype_cdev_default;
kobject_init(&cdev->kobj);
cdev->ops = fops;
}//用于初始化cdev的成員，并建立cdev和file_operations之間的連結
3. struct cdev *cdev_alloc(void){
struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
if (p) {
p->kobj.ktype = &ktype_cdev_dynamic;
INIT_LIST_HEAD(&p->list);
kobject_init(&p->kobj);
}
return p;
}//用于動态申請一個cdev記憶體
4．int cdev_add(struct cdev *p, dev_t dev, unsigned count){
p->dev = dev;
p->count = count;
return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
}//添加（注冊）一個cdev
5. void cdev_del(struct cdev *p){
cdev_unmap(p->dev, p->count);
kobject_put(&p->kobj);
}//删除（登出）一個cdev
6. MAJOR(dev_t dev)//得到主裝置号
7.MINOR(dev_t dev)//得到次裝置号
8. MKDEV(int major,int minor)//生成dev_t
9. int register_chrdev_region(dev_t from, unsigned count, const char *name){
struct char_device_struct *cd;
dev_t to = from + count;
dev_t n, next;
for (n = from; n < to; n = next) {
next = MKDEV(MAJOR(n)+1, 0);
if (next > to)
next = to;
cd = __register_chrdev_region(MAJOR(n), MINOR(n),
next - n, name);
if (IS_ERR(cd))
goto fail;
}
return 0;
fail:
to = n;
for (n = from; n < to; n = next) {
next = MKDEV(MAJOR(n)+1, 0);
kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
}
return PTR_ERR(cd);
}//向系統申請裝置号，已知起始裝置的裝置号
10．int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
const char *name){
struct char_device_struct *cd;
cd = __register_chrdev_region(0, baseminor, count, name);
if (IS_ERR(cd))
return PTR_ERR(cd);
*dev = MKDEV(cd->major, cd->baseminor);
return 0;
}//向系統申請裝置号，裝置号未知，向系統申請未被暫用的裝置号
11．void unregister_chrdev_region(dev_t from, unsigned count){
dev_t to = from + count;
dev_t n, next;
for (n = from; n < to; n = next) {
next = MKDEV(MAJOR(n)+1, 0);
if (next > to)
next = to;
kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
}
}//釋放申請的裝置号
12. 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 (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long, 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);
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 (*open) (struct inode *, struct file *);
int (*flush) (struct file *, fl_owner_t id);
int (*release) (struct inode *, struct file *);
int (*fsync) (struct file *, struct dentry *, 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 (*sendfile) (struct file *, loff_t *, size_t, read_actor_t, void *);
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 (*dir_notify)(struct file *filp, unsigned long arg);
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);
};//結構體中的成員函數是字元裝置驅動程式設計的主體内容
由于字元裝置的上層沒有磁盤檔案系統，是以字元裝置的file_operations成員函數就直接由裝置驅動提供了，file_operations正是字元裝置驅動的核心。
字元裝置驅動子產品加載
想要實作一個驅動子產品的加載至少應該實作以下幾個步驟：
1. 對裝置進行初始化
2. 擷取裝置号
3. 添加（注冊）裝置
字元裝置驅動子產品解除安裝
驅動子產品的解除安裝至少應該實作以下幾個步驟：
1. 釋放占用的裝置号
2. 删除（登出）裝置
![linux-svn解除安裝與安裝[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)