DisplayLink: Comprehensive Guide to Installation, Troubleshooting, and Optimization on Linux

At revWhiteShadow, we are dedicated to providing in-depth technical solutions and insights. This comprehensive guide addresses common challenges encountered when setting up DisplayLink devices on Linux, specifically focusing on troubleshooting broken package links and ensuring seamless functionality. This guide, tailored for users of all levels, delves into the intricacies of DisplayLink, offering step-by-step solutions and best practices for a superior user experience.

DisplayLink technology allows connecting additional monitors to a computer via USB. This is achieved by using a software driver that compresses the video signal and sends it over the USB connection to the DisplayLink device, which then decompresses the signal and outputs it to the connected monitor. This technology offers flexibility in expanding screen real estate, particularly for laptops or systems with limited video outputs.

The core components needed for DisplayLink to operate correctly on a Linux system are the evdi driver and the displaylink driver itself. These packages work in tandem to enable the DisplayLink device to interface with the operating system and render the display output.

Importance of evdi (Enhanced Video Driver Interface)

evdi (Enhanced Video Driver Interface) acts as a bridge between the DisplayLink driver and the Linux kernel. It provides the necessary kernel modules to manage virtual displays and handle frame buffer operations. It is crucial for enabling the system to recognize and utilize the DisplayLink device as a valid output source. Without a functional evdi installation, the displaylink driver will be unable to create the virtual displays needed for the connected monitors.

The displaylink driver is the primary software component that communicates directly with the DisplayLink device. It handles the compression and decompression of video data, manages the USB connection, and controls the display output settings such as resolution and refresh rate. This driver is essential for converting the video signal from the computer into a format that the DisplayLink device can understand and display on the connected monitor.

One of the most common issues users face is encountering broken package links during the installation of evdi and displaylink. This typically occurs when the package repository is outdated or the package has been renamed or removed. Here’s a detailed process to resolve this issue:

Updating the Package Repositories

The first step is to ensure that your system’s package repositories are up-to-date. This ensures that you are accessing the latest package information and that any renamed or relocated packages can be found. Execute the following command in your terminal:

sudo apt update  # For Debian/Ubuntu based systems
sudo pacman -Sy  # For Arch Linux based systems
sudo yum update  # For Fedora/CentOS based systems

This command refreshes the package lists, retrieving the most recent information about available packages and their locations.

Identifying the Correct Package Names

If the package link is still broken after updating the repositories, it is possible that the package name has changed. To identify the correct package names, use the package manager’s search function:

apt search evdi  # For Debian/Ubuntu based systems
pacman -Ss evdi  # For Arch Linux based systems
yum search evdi  # For Fedora/CentOS based systems

apt search displaylink  # For Debian/Ubuntu based systems
pacman -Ss displaylink  # For Arch Linux based systems
yum search displaylink  # For Fedora/CentOS based systems

These commands will list all packages that match the search term, allowing you to identify the correct and current package names.

Using evdi-dkms as an Alternative

In many cases, evdi may be replaced or superseded by evdi-dkms. dkms (Dynamic Kernel Module Support) allows the kernel module to be automatically rebuilt when the kernel is updated, ensuring compatibility and preventing the need for manual recompilation. If evdi is unavailable or causing issues, try installing evdi-dkms instead:

sudo apt install evdi-dkms  # For Debian/Ubuntu based systems
sudo pacman -S evdi-dkms  # For Arch Linux based systems
sudo yum install evdi-dkms  # For Fedora/CentOS based systems

After installing evdi-dkms, reboot your system to ensure that the kernel module is loaded correctly.

Once the evdi or evdi-dkms package is successfully installed, proceed with installing the displaylink driver:

sudo apt install displaylink  # For Debian/Ubuntu based systems
sudo pacman -S displaylink  # For Arch Linux based systems
sudo yum install displaylink  # For Fedora/CentOS based systems

If you encounter any dependency issues during the installation, resolve them by installing the missing packages manually.

Addressing Potential Conflicts

Sometimes, conflicts between different versions of libraries or other installed packages can cause installation failures. Resolve these conflicts by carefully reviewing the error messages and identifying the conflicting packages. You may need to uninstall or downgrade certain packages to ensure compatibility.

Even after successfully installing both evdi-dkms and displaylink, the DisplayLink connected displays might not appear. This often happens because Xorg, the X Window System, needs to be explicitly configured to use the DisplayLink driver.

Understanding Xorg Configuration

Xorg uses configuration files to define the display settings, input devices, and other parameters. These configuration files are typically located in the /etc/X11/ directory. To enable DisplayLink, we need to create or modify an Xorg configuration file to instruct Xorg to use the modesetting driver with the video interface provided by the displaylink driver.

Identifying the DRI Device

The first step is to identify the Direct Rendering Infrastructure (DRI) device associated with the DisplayLink device. DRI is a subsystem of Xorg that allows applications to directly access the video hardware for accelerated rendering. To list all DRI devices by their path, use the following command:

ls /dev/dri/

The output will list all available DRI devices, such as card0, card1, card2, etc. The DisplayLink device will typically appear as a separate DRI card. In most cases, it is labeled similar to card2.

Creating the Xorg Configuration File

Create a new Xorg configuration file, such as /etc/X11/xorg.conf.d/20-displaylink.conf, with the following content:

Section "Device"
    Identifier  "DisplayLink"
    Driver      "modesetting"
    Option      "DRI"   "3" # May need adjusting
    Option "AccelMethod" "none"
EndSection

In this configuration:

  • Identifier: A unique identifier for the device.
  • Driver: Specifies the modesetting driver, which is compatible with the displaylink driver.
  • Option "DRI": Specifies the DRI version. Try to check which version you have and use that DRI version.
  • Option "AccelMethod" "none": Disables acceleration. This can sometimes resolve issues with display output.

Restarting the X Server

After creating the Xorg configuration file, restart the X server to apply the changes. This can be done by logging out and logging back in, or by using the following command:

sudo systemctl restart display-manager  # For systemd based systems (e.g., Ubuntu, Fedora)
sudo service lightdm restart       # For systems using LightDM
sudo service gdm restart           # For systems using GDM
sudo service sddm restart          # For systems using SDDM

After restarting the X server, check if the DisplayLink connected displays are now working correctly. Use the display settings utility provided by your desktop environment (e.g., GNOME Settings, KDE System Settings) to configure the display arrangement, resolution, and orientation.

Even with the correct drivers and configuration, you may still encounter issues with DisplayLink. Here are some common problems and their solutions:

Display Not Detected

If the DisplayLink connected display is not detected, try the following:

  • Check the USB Connection: Ensure that the USB cable is securely connected to both the computer and the DisplayLink device.
  • Test with a Different USB Port: Try using a different USB port on your computer, preferably a USB 3.0 port for better performance.
  • Verify Power Supply: If the DisplayLink device requires an external power supply, make sure it is properly connected and powered on.
  • Check Driver Installation: Verify that the evdi-dkms and displaylink drivers are correctly installed and loaded.
  • Examine Xorg Log Files: Check the Xorg log files (typically located in /var/log/Xorg.0.log) for any error messages related to DisplayLink.

Flickering or Glitching Display

Flickering or glitching displays can be caused by various factors, including:

  • USB Bandwidth Limitations: DisplayLink relies on USB bandwidth, and excessive USB traffic can cause performance issues. Try disconnecting other USB devices to free up bandwidth.
  • Driver Issues: Ensure that you are using the latest version of the displaylink driver. Older versions may have bugs that cause display issues.
  • Xorg Configuration: Review your Xorg configuration file to ensure that the settings are correct. Experiment with different settings, such as disabling hardware acceleration or adjusting the refresh rate.
  • Cable Issues: A faulty or low-quality display cable can cause signal degradation and display issues. Try using a different cable to rule out this possibility.

Performance Issues

DisplayLink performance can be affected by CPU usage, USB bandwidth, and driver optimization. To improve performance:

  • Reduce CPU Usage: Close unnecessary applications to reduce CPU load.
  • Optimize USB Bandwidth: Use a USB 3.0 port and disconnect other USB devices to maximize bandwidth.
  • Update Drivers: Ensure that you are using the latest version of the displaylink driver, as newer versions may include performance optimizations.
  • Adjust Display Settings: Reduce the resolution and refresh rate of the DisplayLink connected display to lower the amount of data being transmitted over USB.
  • Disable Compositing: Sometimes compositing managers can cause performance issues. Try disabling the desktop environment’s compositor.

Advanced Configuration and Optimization

For advanced users, there are several additional configuration options that can further improve DisplayLink functionality and performance.

Using xrandr for Dynamic Configuration

xrandr is a command-line utility for configuring X server outputs. It allows you to dynamically adjust display settings, such as resolution, orientation, and arrangement, without needing to edit the Xorg configuration file.

To list all available outputs, use the following command:

xrandr

The output will show all connected displays, including the DisplayLink connected display. You can then use xrandr to configure the display settings. For example, to set the resolution of the DisplayLink display to 1920x1080, use the following command:

xrandr --output DisplayLink-0 --mode 1920x1080

Replace DisplayLink-0 with the actual name of the DisplayLink output as reported by xrandr.

Creating Custom Scripts

You can create custom scripts to automate the configuration of DisplayLink displays. For example, you can create a script that automatically configures the display settings when the DisplayLink device is connected.

Adjusting Kernel Parameters

In some cases, adjusting kernel parameters can improve DisplayLink performance. For example, you can increase the amount of memory allocated to the kernel for handling USB traffic.

Conclusion

Setting up DisplayLink on Linux requires careful attention to detail and a thorough understanding of the underlying system components. By following this comprehensive guide, you can effectively troubleshoot broken package links, configure Xorg for DisplayLink, and optimize performance for a seamless user experience. At revWhiteShadow, we strive to provide the most accurate and up-to-date technical solutions, empowering our users to overcome challenges and achieve their goals. We hope this guide has been helpful in resolving your DisplayLink issues and enhancing your Linux experience. We will continuously update this guide as new information becomes available.