Well +Marcelo Luis Bermudez L.
. Unfortunately that doesn't have anything to do with your video driver. If you were having low frame rates when you ran $glxgears or $glxspheres, that would be different.
What your problem is that Ubuntu doesn't know that your FN keys are. But your lucky day is today I guess. As a recent owner of a nice 17" Chronos 7 laptop I found this ppa that you can add. I take no responsibility for you laptop breaking if it does, I will take credit if it does fix it tho ;)
$ sudo add-apt-repository ppa:voria/ppa
$ sudo apt-get update && sudo apt-get upgrade
Then from here add what ever packages make sense, remember that you can always remove them if they screw something up. Even if you cant boot you can get into grub (by holding shift) and get into a recovery terminal. or at your login manager (aka lightdm) press ALT+CTRL+F1 ,or F2.
$sudo apt-get install backlight
$sudo apt-get install samsung-tools
$sudo apt-get install easy-slow-down-manager
$sudo apt-get remove "package name here"
to remove package plus dependencies:
$sudo apt-get purge "package name here"
Hope this helps. Most of my function keys worked out of the box since Voria sends his code up stream to Canonical The only ones that needed fixed were the fan speed function (now fixed) and my keyboard back-light function (still WIP). If I don't have a simple fix for it soon I'll have to hack it into the system, which is why you go open source to begin with, you can fix everything yourself, if you know how that is.