Glass Scales G320

Can you use linear glass scale encoders with a Gecko 320, or our you limited to the rotary
type?

Also, can you create a closed-loop servo system by connecting the encoders to the parallel
port on the computer, instead of the gecko driver? It seems to me that better
compensation would be possible with this route. If so, are there advantages/disadvantages
to either method?

Thanks from a newbie!

-Christopher