Oh boy, where do we start,,, or rather where do we finish !!! Linux is forever morphing and evolving into such spectacular applications that the “learning” really never stops as long as the appreciation and interest lives. However, in a nut-shell, since you asked, I guess we can summarise the foundation topics as follows. You can study lots about building custom kernels, and the intricacies of module entry and exit code. Lessons deal with working with module parameters, and communicating with modules via the ioctl mechanism. There is also the art of debugging using the /proc file system and sequence files, and the mechanics of system calls. You can also study the modules and the kernel symbol table and memory allocation primitives in kernel space. Learn the rules about device registration and just about anything and everything to do with the vast world which is Kernel programming. And that’s just the basics before you get into the likes of device drivers. Sounds like a lot but it’s one of the most revolutionary freeware type lessons in the World, so enjoy it.