I have a debian 9 hp elitebook 840 G2 laptop with a docking station. When powering up or resuming in the docking station, the kernel does not detect that the LID is closed and the internal display becomes active. This used to work with debian 8 (kernel 3.16). The workaround is to open the LID and then close it and in this case the kernel detect that the LID has been closed.
This has actually already been reported in bug 195455. Therefore I am closing. *** This bug has been marked as a duplicate of bug 195455 ***