Device Drivers:
	Generally a kernel module
	Often makes an entry in /dev
		Some things in /dev aren't hardware devices
		Some hardware devices don't make an entry in /dev

Devices themselves:
	Connected with a bus
		Internal busses:  PCI Express, SATA, relics
		External busses:  USB, Firewire, Parallel Port, etc.
		There is a lot of mixing possible!
			Internal USB devices
			External sata
	Busses generally have a method of polling
		Some devices respond to that
		Older model:  Driver checks to see if device is present
		Most primitive:  Driver assumes device is present
			Can still be appropriate if you're sure
	Character devices vs. block devices (ioctl for special cases):
		mouse
		keyboard
		hard drive
		printer
		video cards are more complicated:
			block exposed to X11
			/dev/nvidia character device, proprietary
	mknod and making a device node:
		Not exactly like /proc!
		Making a file in /dev
		So it's a regular directory!
		Nodes are special files in a regular directory

Parallel Port Devices:
	Hardware Setup:
		parallel port pinout
		+5, or kind of sorta close, for high
		Low current
		Don't short it out!  Expansion cards, docking station, etc.
		Parallel cables (not all that common anymore!)
		PowerSwitch Tail II
		Lamp, extension cord
	Polling for devices
	Hopefully the driver makes sense to me still
		Works in FreeBSD
		Wrote it a couple years ago
	
Making stuff happen with the computer:
	Serial port is more powerful, but has less pins
	decoder, demultiplexer, etc.
	USB:  Not very many outputs to work with!
		You're expected to communicate with a chip
		That's when it gets complicated!
		https://numato.com/product/8-channel-usb-gpio-module-with-analog-inputs
	Raspberry pi and GPIO pins
	Sainsmart relays