USB

CONFIG_USB_UHCI

Plus, of course, the drivers for any USB hardware you might have. I usually compile drivers for all possible and impossible USB device as a module; that way, it doesn't waste any space in my laptop's memory, nor do I have to recompile should I ever choose to buy or borrow some USB device.

When I first loaded the driver for the USB root hub, I noticed that there were three USB root hubs in my laptop. As it turned out, that's because the built-in wireless LAN has a USB interface, too. Counting them, we get:

1. The two USB slots at the back,
2. The built-in wireless LAN,
3. The port replicator

Which makes up for three USB root hubs. Getting the built-in wireless to work is a joke by itself; read on.