I have successfully connected my Dell XPS 8700 desktop to the U3415W’s DP (display port) and my Dell Latitude ES430 laptop to the U3415W’s mDP (mini display port). I can change the input source between the two computers. I have configured the monitor’s USB hub and it works.
However, when I try to select the source for the PBP(Sub) (the sub screen source for PBP or PIP), I can only select HDMI or MHL. DP and mDP are greyed out.