Well, i accept it. I tried everything available on Google and nothing seems to work for me to control my Lenovo laptop's screen's brightness.
So i wrote a little script to get my work done.
if [ $# -ne 1 ]
echo "Usage: bright 50"
n=$(echo "ibase=10;obase=16;$x" | bc)
sudo setpci -s 00:02.0 F4.B="$n"
#End of setbright.sh
Then modfied my .bashrc as:
bright 50 #Set Brightness to 50%
Now use on command line as:
Am happy as of now with this!!