lsinput clarified the situation, there's event9 which is called "Asus EeePC extra buttons". with keymap -i, I get these results when pressing the Fn-F3 through Fn-F9 buttons (not in that order).
$ sudo /lib/udev/keymap -i input/event9 Press ESC to finish scan code: 0x00 key code: mute scan code: 0x00 key code: volumedown scan code: 0x00 key code: volumeup scan code: 0x00 key code: switchvideomode scan code: 0x00 key code: brightnessup scan code: 0x00 key code: brightnessdown
lsinput clarified the situation, there's event9 which is called "Asus EeePC extra buttons". with keymap -i, I get these results when pressing the Fn-F3 through Fn-F9 buttons (not in that order).
$ sudo /lib/udev/keymap -i input/event9
Press ESC to finish
scan code: 0x00 key code: mute
scan code: 0x00 key code: volumedown
scan code: 0x00 key code: volumeup
scan code: 0x00 key code: switchvideomode
scan code: 0x00 key code: brightnessup
scan code: 0x00 key code: brightnessdown