Currently, we attempt to open() everything in the /dev/input folder every 3 seconds looking for joystick (if we don't have udev, like with Flatpaks). This is problematic because opening an input device can result in I/O which may block the main thread for a short while, causing dropped frames. The delay (or lack thereof) depends on whether other processes on the system already have a fd open and what each input device driver actually does on open.

The attached patch implements a simple stat() mtime check to avoid opening devices if /dev/input hasn't changed since last time we checked. I could have gone with something more fancy like inotify, but it didn't seem worth the complexity for the (hopefully rare) non-udev codepath.