Management C Project Files with Emacs?

[Daniel]

Hi,

If I want to compile a large project like Linux Kernel, I don't know
how I can use emacs.

1. For example, if I modified <linux>/drivers/usb/core/hcd.c with
emacs, then How I can compile linux kernel by M-x compile command?
When I do the command, it is saying that there is no makefile. So, I
use "M-x compile RET make -f /usr/src/linux/makefile", but it
complains that there is no definition of u32 etc. How do I do that?

2. Whenever opening a file, it seems that emacs change current
directory. So, I cannot simply type "M-x compile RET make". Is there
anyway to have emacs to stick on specific directory?