DisplayLink and MacOS Catalina 10.15

- Posted in: Tech Talk
DisplayLink and MacOS Catalina 10.15

With the release of MacOS Catalina, there have been reports that DisplayLink drivers may have some issues with this new OS after the update completes.

  • Video functionality has not been enabled
  • One such issue is the user only being able to see a black screen on one or both monitors that are connected to a DisplayLink-based UDS (Universal Docking Station).
  • Catalina also requires the user to permit “Screen Recording” for a DisplayLink-based UDS to work properly.

Our DocKtor has detailed steps below that will resolve both issues.

Video functionality has not been enabled 

Since macOS High Sierra 10.13, the operating system applies a stricter security policy to software that requires kernel extensions (KEXTS). The DisplayLink driver installation includes a system extension (DisplayLinkDriver.kext) that is affected by this policy.

As a result, the user now must explicitly enable this system extension in the Security & Privacy system preference after installation and before the DisplayLink software can run.

How to check if the displaylink kext is blocked

You can check if the DisplayLink Kext is blocked by opening the System Report (Apple menu -> About) and select Extensions on the left pane and look for DisplayLinkDriver.kext. Check the "Loaded" column. See the screenshot below, which shows the Kext blocked.

Screen shot of software updates

If this is set to "No" then the kext is blocked and needs to be enabled following the steps below.

Enabling the Dispaylink Kext

Please note: It's only possible to enable the system extension in the 30 minutes following the installation. A new installation can be run to reset this timer.

At the end of the installation, the operating system should display a "System Extension Blocked after installation" warning and ask the user to enable the DisplayLink extension

Figure1

Screen shot of software updates

Important: This warning is not always shown. Even if it is not shown, for new installations the user must enable the kernel extension to use the DisplayLink product.

The Setting is available by choosing System Preferences from the Apple menu and then clicking on the Security & Privacy panel. 

Figure 2

Screen shot of the Apple menu

Follow Figure 3-5 to enable the Displaylink Software to run on the system. Please note that the interface presented may be different if multiple software requires user authorization.

Figure 3

screen shot of software updates

Figure 4

Screen shot of software updates

Figure 5

Screen shot of software updates

Occasionally popup from Figure 1 may not be displayed and after the installation and reboot, the DisplayLink additional monitors might not be functional. To resolve this, it is required to manually allow the DisplayLink driver to be loaded on the system following Figure 2 – Figure 4 and reboot the system at the end. 

Important notes:

  • On some systems, the security clearance may not take automatically effect and the DisplayLink Software will still not be functional after rebooting. In this case, simply run the installer process again to ensure all the software is correctly started. This issue has been raised by DisplayLink to Apple with bug ID 33133825.
  • Once the user approval has been granted, the following installations of the DisplayLink software will not require further approval. This also means that systems upgraded to High Sierra while the DisplayLink software was installed won't require authentication.
  • The Apple tech note linked below contains instructions about how to install third-party kexts in a managed corporate environment.
  • The detailed description of this macOS change is documented at https://developer.apple.com/library/content/technotes/tn2459

Black screen on one or both monitors are working after the upgrade

This issue might occur after upgrading from macOS Mojave to macOS Catalina.

The user will see black screens or a single screen functioning, even though two of them are plugged in and both are visible in macOS Display Preferences.

In order to fix this problem, please perform the following steps:

*Please note that this will take an average of 7-15 minutes to go through depending on the speed of your Mac and how familiar you are with Mac functions.

Uninstall DisplayLink Software 

To uninstall the DisplayLink software:

1. Open Macintosh HD

A. If you are unable to find “Macintosh HD”, click Finder in the top left next to the Apple icon

B.Click Preferences 

C. On the General tab click Show Hard Disks, to show the Hard Disk on your Desktop screen

D. Open Macintosh HD->Applications-> DisplayLink

E. Run the DisplayLink uninstall utility

Go to the MacOS Recovery Mode

* macOS Recovery is part of the built-in recovery system of your Mac. You can start up from macOS Recovery and use its utilities to recover from certain software issues or take other actions on your Mac.

How to enter MacOS Recovery Mode

1. Turn on your Mac and immediately press and hold Command (⌘)-R.

2. Release the keys when you an Apple logo, spinning globe, or other startup screen.

3. You might be prompted to enter the login password of an administrator of this Mac, or your Apple ID password, or a firmware password. Enter the requested password to continue.

4. Startup is complete when you see the utilities window:

Software screenshot

5. Run the "Disk Utility" application from the window with applications selection by clicking on it

6. You should then see this Window

software update screenshot

7. If you have FileVault enabled, or if for any reason the first internal drive is not mounted please mount it.

A. The first internal drive in our case is (on the left top) Internal: "Macintosh HD".

B. If there is an active button with the name "Mount" - please click on it, and if needed, enter your password.

C. If there is an active button with name "Unmount" - no action needed.

D. Please write the name of your drive somewhere on the paper or note - it will be needed in the next steps. In this case, it is: "Macintosh HD".

8. Close the application "Disk Utility" by clicking on the red button in the top left corner of the Disk Utility windows - just as normal as you're closing the application.

9. Run "Terminal" Application from the Top Menu Bar.

A. Navigate to the top menu bar 

B. Select "Utilities" 

C. Then run "Terminal" by clicking on it

Screen shot of software updates

10. You should then see the Terminal application window

Screenshot of Software update

11. Now, it's time to execute the single command which helps to rebuild the system cache, which is a cause of the issue

The command is: 

kextcache -i "/Volumes/<VolumeName>"

Where <VolumeName" is your disk name. It is the same name we've checked in Disk Utility step 4

So, in this case, the final command is: kextcache -i "/Volumes/Macintosh HD"

Write it in the terminal application and press <Return> key on the keyboard

Screen shot of software updates.

12. After a few seconds, you should see similar output

 Screen shot of software updates

It is OK when you see the last line with KernelCache ID.

13. Select "Reboot" from the top left menu - the menu with "Apple" icon. 

14. Install DisplayLink Software again.

Screen Recording permission

MacOS Catalina 10.15 requires the user to permit "Screen Recording" in order for DisplayLink devices to work properly. To approve the permission, follow these steps:

1. Download and install our latest 5.2.1 Beta driver.

2. Reboot your system.

Screen shot of software updates

3. Reboot your system.

4. Go to Security & Privacy.

5. Go to Privacy 

Screen shot of software updates

6. Click on the Lock to make changes.  

7. Authenticate the changes by using your login details.

8. Check the box next to DisplayLinkUserAgent.

9. Click on the Lock again to save changes.

Screen shot of software

10. Click "Quit now"

11. A reboot may be necessary with an older version of the DisplayLink driver.