Comment 8 for bug 1263498

Hello,

I have Asus R510L with Nvidia GeForce 840M and the problem exists. I use Ubuntu 14.04 and Unity.
1) I cannot modify brightness using Fn keys.
2) I also cannot change brightness using "System Settings" -> "Brightness and lock" -> "Brightness" slider

% uname -a
Linux lap 3.13.0-37-generic #64-Ubuntu SMP Mon Sep 22 21:28:38 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
% sudo lspci -v| sed -ne '/NVIDIA/,/^$/ { p; }'
04:00.0 3D controller: NVIDIA Corporation GM108M [GeForce 840M] (rev a2)
    Subsystem: ASUSTeK Computer Inc. Device 131d
    Flags: bus master, fast devsel, latency 0, IRQ 70
    Memory at f6000000 (32-bit, non-prefetchable) [size=16M]
    Memory at e0000000 (64-bit, prefetchable) [size=256M]
    Memory at f0000000 (64-bit, prefetchable) [size=32M]
    I/O ports at c000 [size=128]
    [virtual] Expansion ROM at f7000000 [disabled] [size=512K]
    Capabilities: [60] Power Management version 3
    Capabilities: [68] MSI: Enable+ Count=1/1 Maskable- 64bit+
    Capabilities: [78] Express Endpoint, MSI 00
    Capabilities: [100] Virtual Channel
    Capabilities: [250] Latency Tolerance Reporting
    Capabilities: [258] L1 PM Substates
    Capabilities: [128] Power Budgeting <?>
    Capabilities: [600] Vendor Specific Information: ID=0001 Rev=1 Len=024 <?>
    Kernel driver in use: nvidia

% COLUMNS=120 dpkg -l | grep nvidia
ii nvidia-331-updates 331.38-0ubuntu7.1 amd64 NVIDIA binary driver - version 331.38
ii nvidia-common 1:0.2.91.7 amd64 transitional package for ubuntu-drivers-common
ii nvidia-libopencl1-331-up 331.38-0ubuntu7.1 amd64 NVIDIA OpenCL Driver and ICD Loader library
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

Information from nvidia-xconfig:
  Operating System: Linux-x86_64
  NVIDIA Driver Version: 331.38

Let me know if further information is needed.

If someone knows the workaround I will be grateful for information.

Best Regards,
Paweł