Thanks! I tried for a bit to do the sensor fusion myself, but all the resources were like PhD papers with complex math. Finally found the Fusion library, and it was very simple to integrate. MIT license C code, just a few files. Really great to work with, only took a few hours to get hooked up. The HID code was just the same plugin I used for the Space Navigator (HIDAPI) with some small edits to the report parsing. So that was easy too.
The touch pad is recognized by default as a mouse cursor. It also has 2 finger scrolling and clicking with the trigger. So you can essentially control your computer without doing anything special. My idea was to make an alternative control scheme for the Godot editor, so you can place and rotate objects with the Dual Shock gamepad. Orientation is no problem, I was thinking of mapping the position to the rotation (with a hotkey) so you can place objects as well. This would be like the Space Mouse plugin, but more advanced.