Created attachment 142721 [details]
Video-related lines from the kernel log when booted docked with lid closed

Hello,

I am presently a happy user of a Lenovo ThinkPad T440s laptop, which among other components features Intel Haswell-ULT graphics. Obviously I run Linux on it, in 64-bit mode. The kernel contains support for the i915 drm driver and has KMS enabled.

The computer in question is normally used docked to a Lenovo Pro Dock. As a result, Linux running on it sees five available video outputs:
 - eDP1 for the built-in display,
 - DP1 and HDMI1 for the mini-DisplayPort on the laptop, and
 - DP2 and HDMI2 for the DisplayPort on the docking station.
There are also two D-Sub ports (one on the laptop and one on the dock) but these are not directly exposed to the system, as they simply mirror whatever is sent to, respectively, DP1/HDMI1 and DP2/HDMI2. There is also a DVI-D port on the dock but as it is not independent either (it shows whatever is sent to DP2 if there is no display connected to the DisplayPort and nothing otherwise), it can be ignored here. Anyway, the laptop is typically used with two DisplayPort monitors - one connected as DP1 and the other as DP2.

Now, everything works fine display-wise - i.e. all outputs show, report as connected when they should be and can be reconfigured using the command xrandr - if the system is used undocked or booted undocked and docked later, regardless of whether the lid is closed or not or whether there is anything connected to DP1/HDMI1 at boot time. If, however, the system is booted *docked* and *with the lid closed*, I get some error messages pertaining to eDP1 in the kernel log (see the attachment) and the built-in display is disabled - permanently, i.e. even removing the laptop from the docking station and disconnecting DP1/HDMI1 does not bring it back. As I have yet to find a way to tell the kernel to reactivate this output, getting the built-in display working requires either docking the computer only after boot or restarting it after undocking. Needless to say, both options can be a serious nuisance at times.

Please let me know should you require any additional information or if I can otherwise assist you in debugging the problem. Thanks in advance!