[ltp] Prevent brightness change for AC events

[Jochen Spieker]

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Vincent Bernat:
>  =E2=9D=A6 12 juillet 2014 11:24 +0200, Jochen Spieker <ml@well-adjusted.=
de>=C2=A0:
>=20
>>> The kernel going berserk over the mess that Win8 ACPI firmware did to A=
CPI
>>> backlight control.
>>>=20
>>> There are fixes going around the linux-acpi ML for this stuff.  Try rem=
oving
>>> the ACPI video module, maybe it helps...
>>=20
>> Which one would that be?
>=20
> It's "video":

Thanks. I don't know how I can rmmod it, though. i915 depends on it and
I usually prefer to run X. :)

> Maybe loading it with brightness_switch to N? As I cannot unload it
> without rebooting, I cannot test right now.

I googled a bit and think this should be the correct syntax:

options video brightness_switch_enabled=3D0

I updated the initramfs, rebooted and it appears the setting is applied:

$ cat parameters/brightness_switch_enabled=20
N

I just don't see any difference. The Ubuntu wiki suggested to use these
boot parameters:

thinkpad-acpi.brightness_enable=3D1 acpi_backlight=3Dvendor

The first one generates a warning by thinkpad-acpi ("Unsupported
brightness interface"), but the second one appears to do what I want.

Thanks for the pointers!
J.
--=20
I will not admit to failure even when I know I am terribly mistaken and
have offended others.
[Agree]   [Disagree]
                 <http://www.slowlydownward.com/NODATA/data_enter2.html>

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