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[Justin Standring <me@xxxxxxxxxxxxxxxxxxx>]

I'd like to confirm that Jace's solution (#127) worked for me using a
Lenovo T440s on an Ultra Dock with two displays connected on VGA and
HDMI. I upgraded to 14.10, updated to the 3.17.4 kernel, and rebooted.
Now both external monitors are recognised.

Thanks!

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https://bugs.launchpad.net/bugs/1104230

Title:
  DisplayPort 1.2 MST support is missing in the Intel driver

Status in X.org xf86-video-intel:
  Unknown
Status in xserver-xorg-video-intel package in Ubuntu:
  Confirmed

Bug description:
  SRU Justification:

  Impact: Many users expect the possibility to use the DP1.2 MST feature which
  enables them to use a number of different display setups: daisy-chaining
  DP1.2 displays, some 4K displays appearing as 2 separate displays, 3D displays.
  This however is not supported in Ubuntu stable kernel.

  Fix: A series of 18 cherry-picks from v3.17 kernel backported to v3.16 by
  the original author of the feature: David Airlie.

  Regression Potential: These patches were merged upstream in v3.17 without any
  reported regressions.

  Original description:

  I have two recent DisplayPort monitors, both supporting the 1.2
  version of the standard and one containing an MST hub (DELL 2913WM).

  I have an Intel Haswell based NUC connected over mini-displayport to
  the display containing the hub, then the second display is plugged in
  that one over DisplayPort.

  DisplayPort 1.2 is enabled on the display containing the hub and the
  second display lights up fine but just works as a clone of the first
  display, without ever showing up in xrandr, dmesg or any other useful
  logs I could find.

  My understanding of MST is that the second display should show up as
  DP2 on my laptop so I can configure it as I would any other display.

  UPDATE: Updated the bug report after it was pointed out that the
  original test hardware, a Lenovo x230 isn't DP 1.2 capable. The same
  test on hardware also fails, due to missing support for MST in the
  driver.

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