What I also noticed: All other hotkeys generate two events of the same kind in xev while the brightness buttons generate four of them. Example output for one button pressed each:
keycode 160 = (keysym 0x1008ff2d, XF86ScreenSaver), state = 0x10
keycode 160 = (keysym 0x1008ff2d, XF86ScreenSaver), state = 0x10
keycode 122 = (keysym 0x1008ff11, XF86AudioLowerVolume), state = 0x10
keycode 122 = (keysym 0x1008ff11, XF86AudioLowerVolume), state = 0x10
keycode 123 = (keysym 0x1008ff13, XF86AudioRaiseVolume), state = 0x10
keycode 123 = (keysym 0x1008ff13, XF86AudioRaiseVolume), state = 0x10
keycode 232 = (keysym 0x1008ff03, XF86MonBrightnessDown), state = 0x10
keycode 232 = (keysym 0x1008ff03, XF86MonBrightnessDown), state = 0x10
keycode 232 = (keysym 0x1008ff03, XF86MonBrightnessDown), state = 0x10
keycode 232 = (keysym 0x1008ff03, XF86MonBrightnessDown), state = 0x10
keycode 233 = (keysym 0x1008ff02, XF86MonBrightnessUp), state = 0x10
keycode 233 = (keysym 0x1008ff02, XF86MonBrightnessUp), state = 0x10
keycode 233 = (keysym 0x1008ff02, XF86MonBrightnessUp), state = 0x10
keycode 233 = (keysym 0x1008ff02, XF86MonBrightnessUp), state = 0x10
What I also noticed: All other hotkeys generate two events of the same kind in xev while the brightness buttons generate four of them. Example output for one button pressed each:
keycode 160 = (keysym 0x1008ff2d, XF86ScreenSaver), state = 0x10 olume), state = 0x10 olume), state = 0x10 olume), state = 0x10 olume), state = 0x10 ssDown) , state = 0x10 ssDown) , state = 0x10 ssDown) , state = 0x10 ssDown) , state = 0x10 ssUp), state = 0x10 ssUp), state = 0x10 ssUp), state = 0x10 ssUp), state = 0x10
keycode 160 = (keysym 0x1008ff2d, XF86ScreenSaver), state = 0x10
keycode 122 = (keysym 0x1008ff11, XF86AudioLowerV
keycode 122 = (keysym 0x1008ff11, XF86AudioLowerV
keycode 123 = (keysym 0x1008ff13, XF86AudioRaiseV
keycode 123 = (keysym 0x1008ff13, XF86AudioRaiseV
keycode 232 = (keysym 0x1008ff03, XF86MonBrightne
keycode 232 = (keysym 0x1008ff03, XF86MonBrightne
keycode 232 = (keysym 0x1008ff03, XF86MonBrightne
keycode 232 = (keysym 0x1008ff03, XF86MonBrightne
keycode 233 = (keysym 0x1008ff02, XF86MonBrightne
keycode 233 = (keysym 0x1008ff02, XF86MonBrightne
keycode 233 = (keysym 0x1008ff02, XF86MonBrightne
keycode 233 = (keysym 0x1008ff02, XF86MonBrightne