[Libdlo] Tips for setting up displaylink with Xinerama

[Bernie Thompson]

On Mon, Jan 11, 2010 at 4:57 AM, Christoph Rissner <c.r at visotech.at> wrote:
> I had no issues building both, but to get X running I had to patch udlfb
> (for reasons yet unknown EDID queries do not work on my system).

Reading EDID can sometimes be problematic, but usually only with a VGA
connection and long cables, or older monitors ...

But I exchanged some mails with Christoph, and he said the Windows
drivers are working with the DisplayLink device and monitor (and the
problem can be repro'd with at least one other monitor), so this
should be a solvable problem.

To help track it down, this checkin adds support for re-querying and
reading back the edid via the sysfs filesystem:
http://git.plugable.com/gitphp/index.php?p=udlfb&a=commitdiff&h=437b2878cefeca304d3048f6fae47fadc6ec4b2e

pulling the latest from udlfb at git.plugable.com will get it.  Once
installed, you'll see a new file

/sys/class/graphics/fb0/edid

Reading this file re-queries EDID from the DisplayLink device and
returns the 128-byte EDID block to the application.

This block can be parsed by applications, e.g. "parse-edid < edid"
("sudo apt-get install read-edid" to get the parse-edid app on
Ubuntu), and it returns a nice pretty-printed description of the
monitor capabilities.

Christoph - Can you try reading this file and see if you're still
getting no edid?  Probably will, but this is at least another
datapoint.

Thanks,
Bernie
http://plugable.com/