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-   -   Dual external monitors on Lenovo T420s (http://www.linuxquestions.org/questions/slackware-14/dual-external-monitors-on-lenovo-t420s-4175451929/)

kfritz 02-27-2013 11:09 AM

Dual external monitors on Lenovo T420s
 
I have 2 external monitors connected to a docking-station for the above mentioned laptop. Both monitors are identical Dell 1280x1024, one is connected to the DVI connector, the other to the VGA connector (and routed through a KVM switch).

I've mastered enough xrandr-fu to get the first monitor and the laptop display to work together with either being primary. Here's the `xrandr` output:
Code:

# xrandr
Screen 0: minimum 320 x 200, current 2880 x 1024, maximum 8192 x 8192
LVDS1 connected 1600x900+1280+0 (normal left inverted right x axis y axis) 310mm x 174mm
  1600x900      60.0*+
  1024x768      60.0 
  800x600        60.3    56.2 
  640x480        59.9 
VGA1 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
DP1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
HDMI3 connected 1280x1024+0+0 (normal left inverted right x axis y axis) 376mm x 301mm
  1280x1024      60.0*+  75.0 
  1152x864      75.0 
  1024x768      75.1    60.0 
  800x600        75.0    60.3 
  640x480        75.0    60.0 
  720x400        70.1 
DP2 disconnected (normal left inverted right x axis y axis)
DP3 disconnected (normal left inverted right x axis y axis)

What I want is the laptop screen (LVDS1) to be off, and the 2 external monitors active. I can't figure out which output to use, or how to turn it on. Hate to say this, but this works fine in Windows 7.

Any hints?

Thanks.

Habitual 02-27-2013 02:21 PM

Code:

xrandr --output LVDS1 --off
as an 'example'

kfritz 02-27-2013 02:49 PM

Yes, that is half of the solution -- turning off the laptop screen. What eludes me is getting the second external monitor activated. That is: "xrandr --output [VGA1|HDMI1|DP1|HDMI2|DP2|DP3] --right-of HDMI3" does nothing for me.

chess 02-27-2013 02:54 PM

Try adding either --auto or --mode (and the mode) to the external outputs. Here is what I do on my X200s and external monitor:

xrandr --output LVDS --off --output HDMI-2 --auto

kfritz 02-27-2013 06:54 PM

xrandr --output LVDS1 --off --output HDMI3 --auto

This turns off my laptop screen, and activates the first external monitor. I can't get the second external monitor to do anything. I can add a third "--output" clause with any of the other recognized, but "disconnected", displays to no effect.

I think the problem is that X is not seeing the second external display.

kfritz 02-27-2013 07:08 PM

KVM switch is the problem?
 
I unplugged the second monitor from the KVM switch, and jacked it directly into the VGA on the docking station, and it now does exactly what I want.

xrandr --output HDMI3 --auto --output VGA1 --auto --right-of HDMI3

If I swap it back through the KVM, the second display is black, but I can move the mouse there, and can get parts of windows to drag there, but it's not usable. Weird.

EDIT: Marking this thread as solved -- I'll search for a solution to recognizing a monitor through a cheapo KVM as a separate problem.

OscarMike 03-05-2013 05:06 PM

I have this same problem with my X230 but I'm in a Lenovo Series 3 Docking station, Have you come up with any other solutions?


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