rpi4-osdev/part11-breakout-smp

Writing a "bare metal" operating system for Raspberry Pi 4 (Part 11)

Putting it all together

Frankly, I'm unlikely to write much documentation for this part. I'm also only providing a Clang Makefile for now. If you're using gcc, have a go at putting your own Makefile together, referencing the previous parts.

This part simply builds on the work we've done so far, and delivers a new Breakout codebase with:

• Gameplay running in the foreground on the main CPU core 0
• Graphics updated in the background on CPU core 1
• Looped 8-bit music playing in the background on CPU core 2
• Bluetooth communications managed in the background on CPU core 3

I've taken the opportunity to organise the code a little better and so you'll see some changes to the Makefile, and a new directory structure in place. Tidy codebase = tidy mind!

Important takeaway

As you read through this code, you'll maybe notice that a very different style has emerged. Multi-processing adds a dimension of complexity when coding and requires a total mindset shift.

There's a lot more signalling/semaphores, so the cores can be sure they're doing the right thing at the right time.

You're no longer "dry-running" a single, sequential thread. You're having to spot the potential for bugs/unexpected behaviour from the interplay of four concurrent threads!

Good luck as you explore the code!

Progress video

Click on the picture below to watch a quick video of the game in action.

PS: Sorry for the bad audio quality - the game itself sounds great in real life, I promise!