[Libdlo] Ubuntu with DisplayLink

[Bernie Thompson]

Hi Don,

A couple expectation-setting things:

* Configuring USB displays on Linux isn't easy for novice users yet.
It's only recommended for fairly advanced users.
* It's only plug-and-play for the kernel driver part, and there it
varies by kernel version unless you recompile the module.
* Configuring X Windows (which is what people usually want/expect) to
run on top of the kernel framebuffer driver then is the hard part,
especially to extend the desktop across a mix of PCIe and USB
graphics.  It can be done in some cases, but the instructions and
tricks vary a lot across distributions and versions of Linux.

Libdlo is just a reference library, so you can ignore it if you're not
programming.  The key thing is that kernel driver (called udlfb).

That is present in Ubuntu 9.10, and for most DisplayLink-based
hardware should show a solid green screen automatically when you plug
in any DL device, which means the kernel driver has loaded.  If you
don't see the green screen, there's three current known reasons for
that:

* There are enhancements in the udlfb in kernels 2.6.34 that let it
successfully set the default mode on more monitor types. The version
in Ubuntu 9.10 is older, but advanced users can compile and update
udlfb as a module.
* You have DisplayLink hardware that requires a USB configuration
switch to work. If on Windows your DisplayLink hardware has a flash
disk with drivers on it, then this is probably the problem.  There is
a udev rule to work around this.
* If your monitor's capability exceeds that of the DisplayLink device
- in that case, you'll get a blank screen or an "out of spec" message
from your monitor. This is a solvable problem in
software/configuration, or workaround is to get a higher-spec DL
device or a lower-spec monitor.

Once you get the green screen, then you're on to the fun of xorg.conf
twiddling.  Here's a post from a user on your distro (Ubuntu 9.10) on
how he got that part going. You can see, though, from the comments
that others are still struggling:

http://blogg.noonday.se/2010/01/28/linux-usb-video-adapter/

Best wishes,
Bernie
http://plugable.com/

On Mon, Mar 8, 2010 at 7:36 AM, don <donnnie at gmail.com> wrote:
> Hello!
>
> I found your forum online, and hope that you'll be able to help. I'm a
> life-long Windows user who just recently took the plunge and switched
> to Ubuntu 9.1 ....and I LOVE IT!!!!   All is fine except that I have
> been unable to get my Atlona HDPIX to work correctly with Displaylink
> drivers for Linux/Ubuntu 9.1.
>
> I installed libdlo-0.1.2 and it does seem to recognize the unit and
> begins to do a self test. My extended display correctly passes the
> first 2 tests but then gets stuck on the screenful of DisplayLink
> logos. At that point the system locks, and I need to literally unplug
> everything and reboot. My only thought is that during testing the
> drivers are attempting to use a screen resolution that my 26" LCD
> doesn't care for.
>
> I know I need to make changes to the settings in my XORG.CONF file but
> not sure what to do. I'm using a 2.7 mhz system with 8GB of RAM. What
> would you recommend I do?
>
> Feel free to forward me an email if you have any thoughts or ideas on
> this. I need to reiterate -I AM A NEWBIE..LIKE 3-DAYS NEWBIE!  So
> please spoonfeed me the info if you have the time
>
> Most appreciative,
>
>  Don DiMuccio
>  Cranston, RI
>  401-944-5514
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