[Bug 81515] [IVB Regression] Backlight is not adjustable and set at maximum level in kernels 3.16-rcX on HD 4000

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=81515

Aaron Lu <aaron.lu at intel.com> changed:

           What    |Removed                     |Added
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                 CC|                            |jwrdegoede at fedoraproject.or
                   |                            |g, rjw at sisk.pl

--- Comment #16 from Aaron Lu <aaron.lu at intel.com> ---
EC is abbreviated for embedded controller, wikipedia has explanation for it if
you are interested. For win8, I mean its ACPI table has a query of
_OSI("Windows 2012"), which means the BIOS is Win8 aware, though it doesn't
necessarily mean the laptop is actually running Win8.

We have believed for Win8 aware BIOS, it will not have a working backlight
interface and the GPU's raw interface will do the job. So we are disabling the
ACPI backlight interface if the BIOS is Win8 aware since v3.16. This is not the
case for your laptop and that's because your laptop is actually a Win7 one but
your BIOS somehow has the _OSI("Windows 2012") call.

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