Kernel 201 – Let’s write a kernel with keyboard and screen support (2014)

For beginners, you might want to check out the previous article (Kernel 101) first [0].

[0] http://arjunsreedharan.org/post/82710718100/kernel-101-lets-...

Ah, so tempting - putting the device drivers in the kernel. After all, how else would you start up?

The QNX solution to this is that drivers are always user processes, but you can put additional programs in the boot image which start at boot. That's how the first drivers get started. This is valuable for embedded systems, which may not have a keyboard, screen, or disk drive, but may have other ways to get info to someplace useful.

It's quite handy that the 30 year old keyboard controller subsystem is still present. If it wasn't and you had to enumerate USB first that would be a whole lot more work.

Why give the keyboard and screen access to the kernel? Do you want to get kernel exploits? Because that's how you get kernel exploits.