Although I am on Mint Nadia, my research should be helpfull:
First of all you should know that if the grub tweak did not work and if in ubuntu you have no keycode on pressing Fn+F5 or Fn+F6 those keys will be suported from 3.7 kernel version (as I read somewhere). My case is this: those combinations just don't exist under ubuntu or mint (tried both), instead all other Fn combinations work properly or at least they generate a code for the combination (in easystroke, when adding new action, selecting key, then pressing desired Fn combination you get for example XF86WebCam). My notebook is Asus K55VD with I7 processor and nvidia 610m.
I've managed to do a workaround with
The main ideea for the workaround to work is to actually have other
Fn combinations, not working by default in your distro and void key combinations like Ctrl + Key, Alt + Key (once you press
Ctrl, for example no other key has effect).
Xdotool is used to emulate a virtual key -
xdotool key XF86MonBrightnessUp for increasing brightness emulates XF86MonBrightnessUp and
xdotool key XF86MonBrightnessDown for lowering brightness(emulates XF86MonBrightnessDown, and if you use
Ctrl + <KEY> command,
Ctrl won't let XF86MonBrightnessDown/Up to work.
There is a workaround for this too (the use of "Release" key modifier in
xbindkeys and creating scripts for both commands including some delay) but it will give you hard time with your brightness: you will have to try the combination a few times before succeeding once, and I mean emulating one movement of the brightness slider (on Asus there are 10 before reaching bottom).
So how I did it:
1. install xbindkeys
2. install xdotool
2. "xbindkeys" in terminal to start it
3. "xbindkeys --defaults > $HOME/.xbindkeysrc" in terminal to generate the file where your keybinds will be.
4. open ".xbindkeysrc" from /home/user directory. There you will see some default examples. Either delete them or comment them with #.
5. for Asus add lines like this:
xdotool key XF86MonBrightnessUp
xdotool key XF86MonBrightnessDown
XF86Launch1 is Fn+c and XF86WebCam is Fn+v and they are close to each other, therefor proper.
Save, then end or kill xbindkeys (from System Monitor for ex) , then start xbindkeys (from terminal for ex).
They work for me, but not continuesly - every XF86WebCam results in one level brightness up, then holding Fn I have to press again on V and so on. You will not have this luxury if you use a standard combination (assuming they work). You will have to release both keys, then press them again, not getting quick result.
I tried using Fn + Arrow Up and Fn + Arrow Down. The first didn't work, the second worked, so i could only change brightness down (or up).
for other notebooks: kind of the same thing but you have to test you own keys,
There is a way without xdotool:
install xbindkeys, install xbacklight, generate .xbindkeysrc, and edit it with this:
xbacklight -dec 10
Control + F5
xbacklight -inc 10
Control + F6
This time you can use modifiers combinations (there is no virtual key generated), but brightness doesn't change that smoothly, and if you keep pressing the combination, in System Monitor you will see multiple xbacklight instances. It's continuous, but it often seems, (if you are not patient) that brightness flickers (from bright to brighter, then from bright to less brighter even though you want only one thing) until you release the keys. It also doesn't show the brightness applet (with the slider), like in the other case.
OK. That's all. Have fun!