[Libdlo] Testing a Displaylink adapter. Works with custom driver, but not with standard "fbdev" ?

[Bernie Thompson]

Hi Eric,

Thanks for asking.

On Tue, Jan 3, 2012 at 10:50 AM,  <ericf at operamail.com> wrote:
> I'm running a Linux v3.1.0 64-bit kernel.  It looks like the "udlfb"
> kernel driver this needs is included with the kernel's modules.  But
> which X11 driver do we have to use for this thing?
>
> I tried it with the "fbdev" driver that comes with the distro, setting
> it in my xorg.conf, but I just get a black screen when I "startx".

You can use the standard fbdev driver (and that's easiest, as you say,
so you don't ever need to rebuild anything).  Only with kernel 3.2+ is
this on by default.  On older kernels (back to 2.6.35), you'll just
need to turn on the fb_defio option (which means turning on page
faults to detect where drawing has happened).  Here's how to enable
fb_defio when it's not on by default:

create or edit a file like
/etc/modprobe.d/50-displaylink.conf
and add the single line
options udlfb fb_defio=1

Save and reboot.  More background is at:

http://plugable.com/2011/12/23/usb-graphics-and-linux/

Hope that helps,
Bernie