说明：  no intro
(To the free Linux operating system represented by one of the many advantages is that they are internal is open to everyone to see. Operating system, was once a hidden and mysterious places, it s code only a limited number of programmers, and now is ready to let anyone have the necessary skills to examine, understand and modify. Linux has helped make the operating system of democratization. Linux kernel to retain a large number of complex code, but those who want to become a kernel hacker people need a entry point so that they can enter the code, you will not be an overwhelming complexity of the code. Typically, the device driver to provide such opportunities.)