I want to be able to use the DisplayPort on my laptop hooked up to a [DP to (2) DVI] adapter to drive two external displays (both using DVI).

This is the adapter I have: http://www.startech.com/AV/Splitters/DisplayPort/DisplayPort-to-Dual-DVI-Multi-Monitor-Adapter-Male-to-Female-DP-to-2x-DVI-3840x1200~SP122DP2DVI

I am currently able to use the little Startech box to passthrough only one DVI output, but when I hook up a second one it does not work (Ubuntu will not detect any additional displays).

EDIT - I am able to get the adapter to show duplicated display data on both DVI outputs now... but I want to expand desktop rather than duplicate - Amazingly, I am able to change the resolution on what the driver believes to be 1 display to a resolution of 1920x1080 x2 = 3840x1080 which does technically give me display space expanded to both monitors BUT it's weird and the system things it's one huge monitor. Maybe there's a way to logically divide one display into more display areas? My current situation looks kind of like this issue which unfortunately was never really solved unless I want to add a source change myself:


If I look at amdcccle (amd catalyst control center) and view the display info for the monitors hooked up though the displayPort, it mysteriously says that MST is not available.

Support wise - everything I have seems to indicate that support is present. ATI has Eyefinity support on the graphics chip. DisplayPort is new enough to have Multi-monitor support. StarTech claims that the adapter supports Linux (this may be an empty notion of course).

Current setup (not working):

HP Elitebook 8570w + XUbuntu 14.04 x64 LTS + DisplayPort using MST (multi streaming support) + Startech.com SP122DP2DVI (adapter with DisplayPort to 2 DVI ports)

Also using 2 ACER 1080p monitors that are DVI compatible.

Notes -

Graphics stuff on HP Elitebook is ATI/AMD Chelsea XT GL [Firepro M4000] with Eyefinity support through the DisplayPort connector. Currently running the proprietary driver from ATI (fglrx) as listed in the XUbuntu system. An open source driver is available, but I figure I'll get less success that way (xserver-xorg-video-ati).


1 Answer 1


I found a solution after digging for a while!

The ATI driver (fglrx) with the Startech adapter allowed me to set one monitor at 3840x1080 resolution (which really was 2 1920x1080 monitors passed through the adapter as one giant monitor). This worked in terms of hardware output, but my desktop was split down the middle between the two DVI outputs because XUbuntu + ATI driver still thinks it's only one monitor coming through the display port. Enter fakeXRandr!

Read more here: https://github.com/phillipberndt/fakexrandr

git clone https://github.com/phillipberndt/fakexrandr
make && sudo make install

This points xrandr to a hacked version of libXrandr.so. Now at this point, I re-ran the config in the ATI driver to pull in the giant monitor (3840x1080) and doing so re-ran xrandr with the hacked lib which finally spit out the two seperate displays recognized by X!

When it works you can do:

xrandr --verbose

Then see that xrandr has detected another logical monitor space ( mine was called DFP_ derived from DFP1 )!

UPDATE - fakexrandr now provides its own tool that lets you customize how to split displays into logical xrandr monitors. See here: https://github.com/phillipberndt/fakexrandr Under sections Installation and How To After configuring with tool fakexrandr-manage, reboot the system to reload xrandr and it will take your fakexrandr configuration into account -- xrandr will then have sub-displays labelled with numbers at the end for each split.

Notes -

  • I'm pretty sure this solution doesn't solve the MST problem, but the little passthrough box I have is basically configured to output the two DVI displays as one single DisplayPort display. This works, but is annoying and we have to use a software hack like fakeXRandr to go around it.

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