Questions on DisplayLink
Thank you for your contribution to the DisplayLink wiki page! I am planning on buying a ThinkVision LT1421 as well, but I am just wondering...are you able to see the DisplayLink device in the output of xrandr? Is it possible to simply turn on and specify the relative position of DisplayLink display by using xrandr instead of Xinerama? Thanks! If you would kindly reply by writing on my discussion page or email me at [...] that would be great! Thanks in advance! --Jiehanzheng (talk) 22:43, 8 June 2013 (UTC)
I emailed a reply, which I'll copy here:
You can see my progress on DisplayLink on Arch detailed here. Unfortunately nobody replied, and a true solution was never achieved. It looks like true two-monitor DisplayLink support is still in its early days on Linux.
No, I'm not able to see the output on xrandr: I have only been able to get it working by running two separate X servers and making them talk using the ancient x2x tool (1998 or something). I'm still planning on updating the wiki page more to reflect these changes, but for now I've had little luck.
Kernel level support is good, and getting better as udl (the recent rewrite, I think driven by Red Hat) slowly replaces udlfb, but it's a process.
Supposedly there was a working driver for X back in the day, called xf86-video-displaylink, but since recent X.org updates (bug 50762) that driver won't even compile. I've been working on improving my C skills to see if I can go in and fix that driver myself, but even if I can (which is no guarantee) it'll still probably take a few months. Presumably, this driver would enable xrandr to work and everything to be nice and pretty.
Suggestion: don't buy that Lenovo monitor. I own it. Support is garbage on Linux. Unless you're a kernel hacker who also is deeply familiar with writing Xorg display drivers, I would highly suggest against it.
I don't suspect we are going to see anything in the vein of working USB display hotplugging under Linux until early-mid 2014.
The exception to this rule is if you want single-monitor support. I plan on picking up a Raspberry Pi (or similar device with wifi capabilities) and setting it up with my ThinkVision and and one of those ThinkPad USB keyboards and making my own lightweight ThinkPad. That's a cool project and it will make the display worth owning. If you want it for the purpose of running a dual-monitor xorg, though, avoid the ThinkVision at all costs.