Major device number?

Thanks you, hippo. I have found this file, but I am a little confused, I don't know how to find useful information in it, how can I find the major number I can used?

And I have another question about register device driver:

I am studying two examples of led driver, they use different register methods,

one just uses the register_chrdev() function, but another uses devfs_register_chrdev(), devfs_mk_dir(), devfs_register() to finish register.

Can you tell me the difference betweem them?

thank you very much.