Comment 3 for bug 1349282

An I+N machine, Lenovo ThinkPad T440p (CID 201309-14169),
could not reproduce this issue.

However,
I tested this fix by the following steps:

1. install Ubuntu 14.04.1 on Lenovo ThinkPad T440p (CID 201309-14169)
2. sudo apt-get install ubuntu-drivers-common ( to be the latest version 1:0.2.91.6)
3. sudo reboot
4. sudo apt-get install nvidia-331-updates (version: 331.38-0ubuntu7.1)
5. sudo reboot
6. sudo dkms remove bbswitch/0.7 --all
7. reboot
8. /var/log/gpu-manager.log now will tell you 'Is nvidia enabled? no'
9. enabled the proposed pocket via software center
10. sudo apt-get install ubuntu-drivers-common ( to upgrade ubuntu-drivers-common)
11. reboot
12. /var/log/gpu-manager.log now will tell you 'Is nvidia enabled? yes'

--------------------
apt-cache policy ubuntu-drivers-common
The following is the snapshot of the test environment:
ubuntu-drivers-common:
  Installed: 1:0.2.91.7
  Candidate: 1:0.2.91.7
  Version table:
 *** 1:0.2.91.7 0
        500 http://tw.archive.ubuntu.com/ubuntu/ trusty-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     1:0.2.91.6 0
        500 http://tw.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
     1:0.2.91.4 0
        500 http://tw.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages

dpkg -l | grep -e nvidia -e bbsw
ii bbswitch-dkms 0.7-2ubuntu1 amd64 Interface for toggling the power on nVidia Optimus video cards
ii nvidia-331-updates 331.38-0ubuntu7.1 amd64 NVIDIA binary driver - version 331.38
ii nvidia-libopencl1-331-updates 331.38-0ubuntu7.1 amd64 NVIDIA OpenCL Driver and ICD Loader library
ii nvidia-opencl-icd-331-updates 331.38-0ubuntu7.1 amd64 NVIDIA OpenCL ICD
ii nvidia-prime 0.6.2 amd64 Tools to enable NVIDIA's Prime
ii nvidia-settings 331.20-0ubuntu8 amd64 Tool for configuring the NVIDIA graphics driver

dkms status
fwts-efi-runtime-dkms, 14.08.00, 3.13.0-36-generic, x86_64: installed
nvidia-331-updates, 331.38, 3.13.0-36-generic, x86_64: installed

lsmod | grep bb (could not found anything)

ubuntu@201309-14169:~$ ls /proc/acpi/
ac_adapter battery button ibm wakeup