Re: Thinkpad T440s with built-in display + external monitor

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 <gebser@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.