I use Ubuntu 18.04 and upgraded to Linux kernel mainline 4.19.2 with ukuu, which purportedly supports DisplayPort alternate mode for USB-C.

alex@gta-65:~$ uname -a
Linux gta-65 4.19.2-041902-generic #201811132032 SMP Tue Nov 13 20:34:19 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Other USB-C devices work fine on this Lenovo X270. However alternate mode doesn't kick in when my generic dongle is inserted, which works fine with a colleague's Windows PC; no events are generated in kern.log & dmesg.

Is there something I need to look into further, or another display-related library I need to update to have this working?


The simplest cause is usually the easiest - the confusing bundle of cables on this hot desk, once untangled, revealed that the DisplayPort cable was not plugged in.

Now, when connected, kern.log tells me:

Nov 19 14:36:02 GTA-65 kernel: [17099.717660] [drm] Reducing the compressed framebuffer size. This may lead to less power savings than a non-reduced-size. Try to increase stolen memory size if available in BIOS.

So Linux kernel 4.19 does support alternate mode for USB-C to Display Port

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.