Your system information

• Steam client version (build number or date): Current stable and beta as of 10/01/17
• Distribution (e.g. Ubuntu): Xubuntu 16.04.2
• Opted into Steam client beta?: Issue appears on both
• Have you checked for system updates?: Yes

Please describe your issue in as much detail as possible:

Okay so it looks like you guys have become committed to trying to clean up the weird gamepad situation on Linux in your own way. I think this is a good thing. But since your guys interests are entirely self-contained, it will only ever work inside Steam. I have my own fix already implemented that worked both inside and outside of Steam, and somehow these two efforts have become at odds.

I installed a program called MoltenGamepad to cause all my devices to turn into 360 gamepads. It creates virtual devices via uinput, reads real devices, and translates the events according to its configuration. In order to prevent duplicate events from being sent, when installed in system mode, udev sets the real controllers to mode 0600 and changes ownership to a system user called gamepad. That is to say, the /dev/input devices, both event* and js*. Both unreadable.

So, what is the actual problem occurring? Let's take a game that has come onboard with your efforts, SpeedRunners. What do I expect to happen when I run this game? Well, if I'm playing with my friends, I take out however many of my DualShock 4s I need, turn them on, they connect to my computer. Real devices are created, udev makes them unreadable. MG connects them to virtual devices. Those virtual devices should be all that Steam and the game care about. However, somehow the real device gets read from. My one dualshock 4 is controlling two players, because both the virtual and real devices are being read!

I have no idea what's going on here, I thought this was a bug from SpeedRunners. I reported it and they mentioned Steam Controller support. After some poking around I had the idea to just turn off MoltenGamepad. When I do this, nothing should be able to read from my controller at all. Indeed, if I run Antimicro, it can't see squat. If I run one of my emulators, it can't see squat. But if I run a Steam game... all bets are off. It can see my DualShock 4 somehow!! I don't have any gamepad support turned on at all via the controller settings. And even so, the event and js devices are unreadable! It shouldn't be seeing them!

What sort of wizardry are you guys doing? Are you reading from some sort of alternative interface? And how do I get out of it?

Steps for reproducing this issue:

1. Install MoltenGamepad as a system service, rendering real devices unreadable.
2. Connect a non Xbox-360 controller, like a DualShock 3 or 4.
3. Run games outside of Steam that used to be really bad with non-360 controllers. Observe that they work great!
4. Play SpeedRunners inside of Steam. Observe that one controller is controlling two players.
5. Shut down the MoltenGamepad service.
6. Play SpeedRunners inside of Steam. Observe that the unreadable device is being read somehow.