For unknown (anyway, for my side) reason, the NVIDIA driver is not well configured after installation on the Samsung R580. In fact, brightness control does not work, with Fn+Keys or using the brightness applet, telling back to you that « Brightness status can not be read in Bios side ».
So, in only one line, the issue can be solved: just edit the /etc/X11/xorg.conf file and add the following line (the bold one) into the Device section:
Section « Device »
Identifier « Default Device »
Driver « nvidia »
Option « NoLogo » « True »
Option « RegistryDwords » « EnableBrightnessControl=1 »
EndSection
And that’s it ! Brightness control with Fn+keys is working great.
thanks to this forum entry (end of page) : http://ubuntuforums.org/archive/index.php/t-1357776.html
Have fun !
McGivrer 
Thx!
Thank you 🙂
My pleasure 😉
you know how you said ..post this line in device section… where is this device section?
hey, man, just read the sample code 🙂 starting with :Section "Device"…EndSectionin the file /etc/X11/xorg.conf