Steam Controller

The Steam Controller is a game controller developed by Valve, which features two trackpads (in place of thumbsticks) with haptic feedback, and sixteen buttons. The Steam controller is designed not only for games supporting traditional controllers, but also for games that support keyboard and mouse.

Kernel
The Steam Controller is fully supported by Linux without the need for a specific device driver, however it does require USB and user level driver support.

Permissions
If Steam was installed manually and systemd is not installed, create the following udev rules file :

The above udev rule will only grant access to the Steam Controller for users in the group:

If Steam was installed manually and systemd is installed, the upstream udev rules file should be used:

Next, reload the udev rules files and trigger a device event for the new rule:

If Steam was installed from an overlay, the upstream udev rules file should already be installed.

Once the udev rules files are reloaded, the user using the Steam Controller will need log out/in for the correct ownership and permissions to be set.