xf86-input-joystick breaks Steam Controller bumper buttons
Submitted by Andreas Reis
Assigned to Xorg Project Team
If xf86-input-joystick is installed, using either bumper button on a Steam Controller won't just issue the (default) left/right mouse click, but also permanently execute some other mouse action until the controller is physically disconnected.
Removing xf86-input-joystick makes the controller work as intended again (it uses xpad), at least within Steam (& its games).
See eg. here for 2+ reports: https://github.com/ValveSoftware/steam-for-linux/issues/4237
I've verified it myself with git versions of the X server, xf86-input-joystick and the kernel.