Okay, @zapposh , so I started messing with it today. Good news is that the controller works with Godot out of the box. I only tested the modern controller, but it appears to mostly work (with a few issues), First I'll explain how I tested it. I'm running Ubuntu, and I installed the app "jstest-gtk". This showed me that the controller was connected and the OS was receiving input. Next I made a Godot project and had a single script with this code.
func _input(event):
print(event.as_text())
This will print out any input events from the system that Godot can see. I saw that events were coming in from the controller, as well as their button/axis numbers.
Then I created a bunch of input maps for the various buttons and axis. One thing that was confusing was that the Atari controller was listed as Device 1, whereas the Xbox controller (and other ones I've tried) are always Device 0. I don't know if that is something with my system, or the fact that I have other controllers connected, but you have to watch out for this. You can also set the input map to All Devices, or possibly switch Device numbers dynamically, but for this test I just used Device 1. You can download the project here.
However, I found some problems. The face buttons (A, B, X, Y), both analog sticks, d-pad, and bumpers work perfectly. The triggers are weird. Instead of giving a value from 0 to 1, they are treated as 2 axis, one going from 0 to 1 and and the other 0 to -1 (and meeting halfway in the middle). I wrote some code to check for this and convert it into 0 - 1, but it's not perfect, and there is a big dead-zone in the middle. In addition, the back and options buttons are both registering as the A button. There is not much to do to fix this in Godot, as if you don't have a unique button number you can't know which was pressed. However, the event text does list "Back" so you can register back events (A still gets pressed) so that is okay. I could not get the options button to work at all (it just says A). However, depending on your game, maybe you can work with this.
One other thing. You can switch the controller into Xbox mode by holding both the Back and Options buttons for about 20 seconds. Once it is in Xbox mode, everything works perfect, all buttons, same as a real Xbox controller.
Also, I can't believe how good this controller is. It is at least 10 times better than the Microsoft Xbox controller. I played a bit of Cyberpunk 2077 with the Atari VCS gamepad and it was almost as good as playing with the mouse. The analog sticks are so smooth and responsive. You can also turn the camera just a little bit, really good controls. I'm so glad I decided to buy these, I will be playing with Atari from now on. Thanks.
