[ghostpepper]

Just to be pedantic, firmware and drivers are not the same thing.

I'm not familiar with Stadia but when I saw 'Dump of controller BT firmware' I assumed that this is the code that runs on the actual bluetooth controller chip inside the controller. Presumably this handles at least the lower layers of comms between the controller and the host PC.

Maybe there's another application processor in the controller that handles higher-level communications or maybe the BT chip has a small general-purpose CPU core inside it, but regardless I don't see why this firmware would need to be modified to make the controller work on a windows PC.

Drivers, on the other hand, would run on the host PC side and would likely need to be rewritten for each platform that you want the controller to work with (although hopefully at least some of the lower-level bluetooth layers are already handled in windows/linux/etc. and the actual code required might not be too extensive)

[kvathupo]

Definitely not pedantry: I admittedly conflated the two!