Thank you all! The problem was effectively the one Eugen said. For some reason the brightness of the built-in display changes to 0, which looks the same as effectively disabling the display. So I guess every time this happens I will need to turn the brightness up again.
I don't know what causes this, but at least I know how to workaround this problem now. Thanks Eugen! Regards, André. On Wed, Apr 8, 2015 at 12:34 PM, ken <geb...@mousecar.com> wrote: > On 04/08/2015 04:03 AM, André Pinto wrote: > >> Hi, >> >> I'm having problems with having both the built-in display of my Thinkpad >> T440s and an external monitor working. If I boot the system without the >> external monitor connected, the built-in display works, but as soon as I >> connect the external monitor the external monitor starts working and the >> built-in display goes blank. If I boot with the external monitor >> connected, the initial boot screens (bios, grub...) show up on the >> built-in display but as soon as I get to the GDM login screen it goes >> blank and only the external monitor works. >> >> In any of these cases, even if I disconnect the external monitor after >> the built-in display stops working, it doesn't start working again (i.e. >> it is not "re-enabled"). >> >> Both of the displays are properly enabled in the Displays configuration >> screen (I've tried with both primary-secondary and secondary-primary >> configurations, the problem is the same). >> >> Do you have any ideas about how can I solve this problem? Is it a known >> issue with the T440s? >> >> This is the debian version that I'm using: >> 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt7-1 (2015-03-01) x86_64 GNU/Linux >> >> Thanks in advance, >> André. >> > > I've never had a thinkpad, but in the dual-monitor systems I've had and > others I've resolved similar problems for it was necessary to hit Fn-F9 to > switch monitors; that is, hit that once to switch monitors, hit it again to > engage both monitors, hit it again to go back to the first monitor. > > Of course the keyboard is programmable, so there may be nothing > particularly magical about the F9 key, but that's just the one which has > always worked for me. > > You might also want to check out the gnome display settings. There might > even be a GIU thing to fix this. >
