一、分配cdev
cdev表示字符设备，使用cdev_alloc函数，cdev_alloc函数原型如下；
/** * cdev_alloc() - allocate a cdev structure * * Allocates and returns a cdev structure, or NULL on failure. */ struct cdev *cdev_alloc(void)
得到cdev指针
二、初始化cdev
使用cdev_init函数，cdev_init的原型如下：
/** * cdev_init() - initialize a cdev structure * @cdev: the structure to initialize * @fops: the file_operations for this device * * Initializes @cdev, remembering @fops, making it ready to add to the * system with cdev_add(). */ void cdev_init(struct cdev *cdev, const struct file_operations *fops)
将字符设备和设备的操作集合绑定在一起。
三、注册cdev
注册cdev用cdev_add函数，原型如下：
/** * cdev_add() - add a char device to the system * @p: the cdev structure for the device * @dev: the first device number for which this device is responsible * @count: the number of consecutive minor numbers corresponding to this * device * * cdev_add() adds the device represented by @p to the system, making it * live immediately. A negative error code is returned on failure. */ int cdev_add(struct cdev *p, dev_t dev, unsigned count)
四、注销cdev
用cdev_del函数