How to make back-light Brightness Fn keys work on LXDE.

Back-light Brightness is set on my Laptop by Fn+F11 (down) and Fn+F12 (up) keys. These keys worked on Ubuntu Unity Desktop but not on LXDE Desktop.

I tried xbacklight command but it did not work. Then after googling I discovered that xbacklight does not work on radeon driver.

Then I tried how it works on Ubuntu Unity Desktop and found that following command was executed by USER=root

/usr/lib/unity-settings-daemon/usd-backlight-helper --set-brightness 24

Since the command to be executed required root privileges I created two bash shell files on my desktop:File ~/home/Desktop/Brightness1

#! /bin/bash
# script to set the initial brightness on login
[ "$UID" -eq 0 ] || exec gksu bash "$0" "$@"
/usr/lib/unity-settings-daemon/usd-backlight-helper --set-brightness 12

File ~/home/Desktop/Brightness2

#! /bin/bash
# script to set the initial brightness on login
[ "$UID" -eq 0 ] || exec gksu bash "$0" "$@"
/usr/lib/unity-settings-daemon/usd-backlight-helper --set-brightness 24

I made the files executable and tested them. The script asked for sudo password and set the required brightness.

Then I inserted following Keycodes in ~/.config/openbox/rc.xml

<!-- Keybindings for LCD Backlight -->    <keybind key="XF86MonBrightnessDown">        # decrease screen brightness      <action name="Execute"><command>/home/user/Desktop/Brightness1</command></action>    </keybind>    <keybind key="XF86MonBrightnessUp">        # increase screen brightness      <action name="Execute"><command>/home/user/Desktop/Brightness2</command></action>    </keybind>

and it works by pressing Fn+F11 and Fn+F12 i.e. it asks for sudo password and sets the required brightness.