A Mini Monitor for a Pi

This post outlines how I used a small 2 inch display as a monitor for my pi. Where it can display tty terminals and X desktops and applications as if it was a normal screen connected over hdmi. My overall goal is to have a sort of handheld “console” that I can connect a keyboard to and use as a normal computer. This post implements the display functionality needed to fulfill part of the goal. I lay out the steps needed for interacting with the display over spi and the issues I encountered trying to use it like a monitor. The end result is a system service that runs on startup, consuming 2.5 mb of ram and ~2% of the CPU. It also respects the X display power management system (dpms) to save on battery life by going to sleep and turning the backlight off.