[ltp] Prevent brightness change for AC events

[Vincent Bernat]

 =E2=9D=A6 12 juillet 2014 11:24 +0200, Jochen Spieker <ml@well-adjusted.de=
>=C2=A0:

>> The kernel going berserk over the mess that Win8 ACPI firmware did to AC=
PI
>> backlight control.
>>=20
>> There are fixes going around the linux-acpi ML for this stuff.  Try remo=
ving
>> the ACPI video module, maybe it helps...
>
> Which one would that be?
>
> $ lsmod | grep -e video -e acpi
> uvcvideo               79003  0=20
> videobuf2_vmalloc      12816  1 uvcvideo
> videobuf2_memops       12519  1 videobuf2_vmalloc
> videobuf2_core         35303  1 uvcvideo
> videodev              122144  2 uvcvideo,videobuf2_core
> media                  18303  2 uvcvideo,videodev
> thinkpad_acpi          65023  1=20
> nvram                  13034  1 thinkpad_acpi
> rfkill                 18867  5 cfg80211,thinkpad_acpi,bluetooth
> video                  17804  1 i915
> snd 61100 19
> snd_hda_codec_realtek,snd_hwdep,snd_timer,snd_hda_codec_hdmi,snd_pcm,snd_=
hda_codec_generic,snd_hda_codec,snd_hda_intel,thinkpad_acpi
> i2c_core               41916  6 drm,i915,i2c_i801,drm_kms_helper,i2c_algo=
_bit,videodev
> usbcore               162603  7 uas,btusb,uvcvideo,usb_storage,ehci_hcd,e=
hci_pci,xhci_hcd
> thermal_sys            27642  5
> video,intel_powerclamp,thermal,processor,x86_pkg_temp_thermal

It's "video":

filename:       /lib/modules/3.14-1-amd64/kernel/drivers/acpi/video.ko
license:        GPL
description:    ACPI Video Driver
author:         Bruno Ducrot
alias:          acpi*:LNXVIDEO:*
depends:        thermal_sys
intree:         Y
vermagic:       3.14-1-amd64 SMP mod_unload modversions
parm:           brightness_switch_enabled:bool
parm:           allow_duplicates:bool
parm:           use_native_backlight:int

Maybe loading it with brightness_switch to N? As I cannot unload it
without rebooting, I cannot test right now.
--=20
Make sure input cannot violate the limits of the program.
            - The Elements of Programming Style (Kernighan & Plauger)