I have a thinkpad X270 that I use on a docking station "Lenovo thinkpad pro dock". Jack output is working correctly on the laptop port, but I get nothing out when I connect headphones to the dock port. This seems to be related to a known bug, mentioned in this question: ThinkPad T440p docking station: no sound on external speakers
But it also says that the bug should have been fixed in newer kernels, and this bug dates back from 2014... I am running the LTS Ubuntu 16.04.
Anyway, the workaround described in the solution to the above question did not solve my problem (adding the codecs in /lib/firmware/ and then adding a line in /etc/modprobe.d/hda-intel.conf).
Does someone has any clue about the status of this bug for Ubuntu 16.04 and a Thinkpad X270?