DisplayLink devices on Linux still only have experimental support. While some people have had success in using them, it is generally not an easy process and not guaranteed to work. The steps on this page describe the generally most successful methods of using external monitors with DisplayLink.
Install thepackage, which provides framebuffer video for X.org.
Hardware-level support is provided by the kernel module
udlfb, which should be loadable by default in Arch.
A rewrite of the
udlfb module is underway. It is being replaced by
udl and integrated into the kernel's drm infrastructure. The new drivers are part of the stock Arch kernel and found in
These new drivers may be added with
modprobe udl if you would like to try them out. The old drivers generally have a better success rate, but this is likely to change sometime soon.
These instructions assume that you already have an up and running X server and are simply adding a monitor to your existing setup.
Load the framebuffer device
Before your system will recognize your DisplayLink device, the
udlfb kernel module must be loaded. To do this, run
# modprobe udlfb
If your DisplayLink device is connected, it should show some visual indication of this. Although a green screen is the standard indicator of this, other variations have been spotted and are perfectly normal. Most importantly, the output of
dmesg should show something like the following, indicating a new DisplayLink device was found:
usb 2-1.2: new high-speed USB device number 5 using ehci-pci udlfb: DisplayLink Lenovo LT1421 wide - serial #6V9BBRM1 udlfb: vid_17e9&pid_03e0&rev_0108 driver's dlfb_data struct at ffff880231e54800 udlfb: console enable=1 udlfb: fb_defio enable=1 udlfb: shadow enable=1 udlfb: vendor descriptor length:17 data:17 5f 01 0015 05 00 01 03 00 04 udlfb: DL chip limited to 1500000 pixel modes udlfb: allocated 4 65024 byte urbs udlfb: 1366x768 @ 60 Hz valid mode udlfb: Reallocating framebuffer. Addresses will change! udlfb: 1366x768 @ 60 Hz valid mode udlfb: set_par mode 1366x768 udlfb: DisplayLink USB device /dev/fb1 attached. 1366x768 resolution. Using 4104K framebuffer memory
/dev should contain a new
fb device, likely
/dev/fb1 if you already had a framebuffer for your primary display.
To automatically load
udlfb at boot, create the file
/etc/modules-load.d/ with the following contents:
For more information on loading kernel modules, see Kernel modules#Loading.
Configuring X Server
There are two primary ways people use DisplayLink devices with X on desktop Linux computers:
- Xinerama with a single X server
- Two separate X servers, linked together in some way
While Xinerama is probably the more desirable setup, it is also less likely to work. Both methods are described below.
You must update or create an xorg.conf with a properly configured
ServerLayout to use a DisplayLink monitor, as Xorg will prefer internal monitors by default. The DisplayLink device is normally only usable if it is set as
screen0 and the internal display as
Add this to the bottom of your
################ DisplayLink ################### Section "Device" Identifier "DisplayLinkDevice" Driver "fbdev" BusID "USB" # needed to use multiple DisplayLink devices Option "fbdev" "/dev/fb0" # change to whatever device you want to use # Option "rotate" "CCW" # uncomment for rotation EndSection Section "Monitor" Identifier "DisplayLinkMonitor" EndSection Section "Screen" Identifier "DisplayLinkScreen" Device "DisplayLinkDevice" Monitor "DisplayLinkMonitor" DefaultDepth 16 EndSection
Then edit your server layout to look something like this
Screen 0 "DisplayLinkScreen" Screen 1 "Internal" RightOf "DisplayLinkScreen" Option "Xinerama" "on"
Change Internal to your main display, then restart X.
Dual X setup
This section is a work in progress. For now, please refer to the steps covered in the Gentoo Wiki for details on this setup.
X crashes or keeps blank
If X crashes, or nothing is shown at load, try to start X only using the external display by updating
xorg.conf as follows:
Screen 0 "DisplayLinkScreen" #Screen 1 "Internal" RightOf "DisplayLinkScreen" #Option "Xinerama" "on"
There are reported instances in which Xinerama requires all its
Screen color depths to be the same. In both
Screen sections, try changing the
DefaultDepth to 16.
Section "Screen" ... DefaultDepth 16 ... EndSection
DefaultDepth 24. However, USB 2.0 has less bandwidth than a standard monitor, so a performance update may be seen from setting it to 16 bit mode.
Cannot start in framebuffer mode. Please specify busIDs for all framebuffer devices
With two monitors configured in Xinerama mode,
/var/log/Xorg.0.log will sometimes display the following error:
Fatal server error: Cannot run in framebuffer mode. Please specify busIDs for all framebuffer devices
As indicated by this Gentoo Forums thread, KMS might be incompatible with fbdev. They also suggested the possible fix of running
startx -- -retro which will allow X to run even when, to X itself, it doesn't appear to be working.