I am keeping the original description of the problem here, but found some more leads that hint at a wider problem, so I added that information below the original part.
I am having a problem on my Ubuntu 18.04 that external monitors are no longer recognized since a while. It seems natural to assume that this is related to some package update, but I have not been able to identify anything. I checked with different external monitors, connected them via the USB-C port (with adapter, see also below) and the HDMI port that the laptop has, rebooted etc but there was no change. I checked the external monitor with a different laptop and it connects without any problem, clearly hinting at a problem in my system. When connecting a USB-c to display port adapter, I see the following in
[55399.996567] usb 1-4: new full-speed USB device number 8 using xhci_hcd
[55400.147389] usb 1-4: New USB device found, idVendor=17ef, idProduct=7213
[55400.147395] usb 1-4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[55400.147399] usb 1-4: Product: Lenovo USB-C to DisplayPort Adapter
[55400.147402] usb 1-4: Manufacturer: Lenovo
[55400.147405] usb 1-4: SerialNumber: 0002
[55400.151950] hid-generic 0003:17EF:7213.0003: hiddev0,hidraw0: USB HID v1.11 Device [Lenovo Lenovo USB-C to DisplayPort Adapter] on usb-0000:00:14.0-4/input1
i.e. the adapter itself is recognized without problem, but there is nothing in
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-2 disconnected (normal left inverted right x axis y axis)
and also nothing hinting at an external display being seen in dmesg.
I am at a loss on where to start looking, the system is up-to-date as far as
Discover tells me, as said above, I cannot easily pin point a particular update. If anybody can provide hints on what to investigate, commands to run to check things, etc I’d be more than happy to provide further details.
More details on the system (from
- Ubuntu 18.04.5 LTS
- Display Manager: sddm
- Kernel: 4.15.0-112-generic
- HW Base: Lenovo ThinkPad X1 Carbon 6th
- CPU: Intel(R) Core(TM) i7-8650U CPU @ 1.90GHz,
- Graphics: UHD Graphics 620
Edit and expansion:
as additional note I was able to try with a port replicator connected via the USB-C port. Here the behavior is very confusing:
- power over USB-C is working fine
- on connection nothing about the port replicator shows up in
dmesg, neither mouse nor monitor connected to port replicator work
- when disconnecting the replicator there is a message in
thinkpad_acpi: undocked from hotplug port replicator, i.e. strangely enough the system recognizes that something has been unplugged that before it did not recognize upon connection.
Get this bounty!!!