[arch-general] Brightness keys no longer working

The screen brightness increase and decrease keys on my laptop seem to be no longer working. They were definitely working a week or so ago, so I'm thinking some recent upgrade is responsible. It's not that the keypress is registering and the app just doesn't brighten the screen. But rather, that the keypress doesn't seem to be registering at all (i.e., when I try pressing it while using the "xev" X events tester app). About a week ago, xev used to show a keypress event for something like "XF86BrightnessUp" or some such; now it shows nothing. Anyone have any idea what the culprit might be? Thanks, DR