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[Ara Pulido <ara@xxxxxxxxxx>]

** Also affects: xserver-xorg-video-intel (Ubuntu Trusty)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1405325

Title:
  [I+N] Split screen after setting the monitors configuration to
  extended

Status in HWE Next Project:
  Triaged
Status in xserver-xorg-video-intel package in Ubuntu:
  New
Status in xserver-xorg-video-intel source package in Trusty:
  New

Bug description:
  Steps:
  1. Install trusty image and log in to system
  2. Connect an external DP monitor.
  3. Press the display hot key to change the monitors configuration

  Actual result:
  Split screen after set the monitors configuration to extended mode.

  Expected result:
  The video signal can be mirrored, extended, displayed on external or onboard only.

  [Analysis from NVIDIA]
  I tracked down the culprit to an Ubuntu patch applied to xf86-video-intel 2.99.910: patches/10-handle-rotated-slaves.diff. That patch is a cherry-pick of upstream commit a45b2ea11c15f35c36330ff27cb45854a29c2e2c. The Ubuntu version of the patch is significantly different from the upstream commit, so somebody must have done quite a bit of porting. Either they messed it up during porting, or they missed cherry-picking another upstream commit that fixes the problem.

  It looks like what's happening is that the Intel driver is applying
  the RandR CRTC offset even though it's actually scanning out from a
  CRTC-sized private scanout buffer. Since it's a linear buffer, this
  shifts all of the lines over by however many pixels the CRTC offset is
  set to, wrapping lines around in the process.

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