Maybe I had misunderstood your meaning.

You are meaning I have assign 0 to my device major number?

The major variable is reassigned by the kernel in blkplay_init function.

http://stackoverflow.com/questions/13518404/add-disk-hangs-on-insmod

This post solve the problem.

Now, I can compile it, insmod it. But it’s give me a permission error when I open the device.

On Mar 21, 2016, at 10:55 AM, Valdis.Kletnieks@vt.edu wrote:

On Mon, 21 Mar 2016 09:53:47 +0800, 张云 said:
The code is just for learning block driver

THe kernel doesn't know that. You call a routine with the wrong
parameters, it will not work properly.