Dynadock / DisplayLink under Linux

I got one of those Toshiba Dynadock Docking Stations at work, and am quite impressed how easy it was to set it up. The only hard part is the DisplayLink graphics card, more to that later.
I just plugged it into my USB port (thats how this Docking Station works, everything goes through USB), and voila, my openSUSE 11 automatically discovered the network and connected to it. Mouse and Keyboard worked as well, but I guess its just a USB hub, so why wouldn’t it work. The network card gets identified as this:

ASIX AX88772 USB 2.0 Ethernet

The soundcard gets detected, as a USB Sound Device, didn’t give me more information, and I don’t use it, but it seems to work with ALSA.

DisplayLink

First off, I don’t use the Monitor on the docking station in production, but I got it to work (somewhat at least ;-)). My windows using colleagues aren’t too excited about this, due to the display lagging. When you open something full screen or maximised, you see a lag, probably due to the USB limitations / compression going on. So its not ideal to use that docking station monitor as the primary monitor. However, they still use it this way, so its not too bad.
My docking station has a DVI and a VGA output, I couldn’t get the DVI port to work, only the VGA worked. I’m not sure why, seemed like some EDID issues with xorg. Even though that docking station has these two ports, they can only be used to clone each other, but you won’t be able to use them as separate displays (I tried that in Vista).

I downloaded the linux drivers from the freedesktop project. I installed those two packages in my openSUSE 11, and could install the module (displaylink) without problems. The attached screen turns bright green afterwards, which shows that the driver is actually working. Nice color choice. 😉

Then I modified my xorg config file, and added these lines:

Section "Device"
 Identifier      "DisplayLinkDevice"
 driver          "displaylink"
 Option  "fbdev" "/dev/fb1"
EndSection

Section "Monitor"
 Identifier      "DisplayLinkMonitor"
EndSection

Section "Screen"
 Identifier      "DisplayLinkScreen"
 Device          "DisplayLinkDevice"
 Monitor         "DisplayLinkMonitor"
 SubSection "Display"
 Depth   24
 Modes   "1280x1024"
 EndSubSection
EndSection

I also modified the ServerLayout section and modified / added these three lines:

Option        "RandR" "false"
 Screen 0      "Screen[0]" 0 0
 Screen 1      "DisplayLinkScreen" RIghtOf "Screen[0]"

Screen[0] is the screen I had in there before.
And that was all, I restarted the X server, and the additional monitor works, in X. However, KDE 4.x doesn’t (yet?) support multiple devices (graphics cards), and therefor you can’t use it within the same session. I wasn’t able to get Gnome to do that either, even though I read somewhere (huh), that it should be possible. Well, you could run a second instance of KDE/Gnome/whatever on that screen, but I didn’t go there. As I change jobs soon, there’s not much point in getting this setup all running, just to abandon everything afterwards. 😉

Conclusion

Even though this docking station works mostly under Linux, I wouldn’t recommend it. You’d rather buy yourself a real business notebook, that comes with docking station support. Even under Windows the docking station isn’t the best, due to the USB limitations. That might change with USB 3.0 around, but for now, the bus speed is just a tad too slow for graphics. There’s also a wireless version of this docking station out there, I wonder if thats even worse?

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