Re: 8086:2a42 [Asus UL80VT] Backlight control does not work with Intel integrated card, but there are entries in /sys/class/backlight

[Guillaume Millet <gmillet@crans.org>]

https://bugzilla.kernel.org/show_bug.cgi?id=66501

Le 04/12/2013 02:16, Aaron Lu a écrit :
> On 12/03/2013 06:10 PM, Guillaume Millet wrote:
>> Le 03/12/2013 05:25, Aaron Lu a écrit :
>>> On 12/03/2013 12:53 AM, Guillaume Millet wrote:
>>>> Hello, I report an issue, in attempting to follow the instructions at
>>>> https://wiki.ubuntu.com/Bugs/Upstream/kernel#KernelTeam.2BAC8-KernelTeamBugPolicies.Overview_on_Reporting_Bugs_Upstream
>>>>
>>>> [1.] 8086:2a42 [Asus UL80VT] Backlight control does not work with Intel
>>>> integrated card, but there are entries in /sys/class/backlight
>>>>
>>>> [2.] The screen brightness control has apparently never worked
>>>> off-the-shelf on this laptop, Asus UL80VT-A1, which is an NVIDIA Optimus
>>>> laptop (2 graphic cards). The use of the discrete Nvidia card is managed
>>>> by Bumblebee (https://wiki.ubuntu.com/Bumblebee). It used to work with
>>>> the workaround suggested at
>>>> http://wiki.daviddarts.com/Ubuntu_Maverick_on_the_Asus_UL30VT#Screen_Brightness
>>>> which modifies asus-brn-down.sh to use the "setpci" method.
>>>> Hotkeys are detected, showkey -s returns 0xe0 0x4c 0xe0 0xcc for Fn+F5
>>>> and 0xe0 0x54 0xe0 0xd4 for Fn+F6.
>>>> When the hotkeys are triggered, there is no brightness change but the
>>>> KDE notification pops up with 3 or 4 levels.
>>>>
>>>> [X.] Other notes
>>>> $ ls /sys/class/backlight/
>>>> acpi_video0  acpi_video1  intel_backlight
>>>>
>>>> $ cat /sys/class/backlight/intel_backlight/max_brightness
>>>> 2583660
>>>>
>>>> $ cat /sys/class/backlight/intel_backlight/brightness
>>>> 121584
>>> With v3.12, does the intel_backlight interface work?
>>> You can verify this by echoing some value to the brightness file and see
>>> if it has any effect. The value can be echoed is 0 - max_brightness. Be
>>> careful with very small values, it will black your screen.
>>>
>>> If it works, you can specify intel_backlight as the control interface
>>> for X by creating a xorg.conf file like this:
>>> $ cat /etc/Xorg/Xorg.conf
>>> Section "Device"
>>>           Option     "Backlight"	"intel_backlight"
>>> 	Identifier  "Card0"
>>> 	Driver      "intel"
>>> 	BusID       "PCI:0:2:0"
>>> EndSection
>>
>> The intel_backlight interface does work, by echoing a value between 0
>> and 2583660.
>> The control interface for X also works with that addition in
>> /etc/X11/xorg.conf (Kubuntu).
>>
>> Wow, the issue was immediately solved by posting here. Thanks Aaron Lu!
>> After, (out of curiosity) what should be modified so that X
>> automatically detect the correct control interface, in case of a new
>> installation for example ?
>
> Please file a bug to https://bugzilla.kernel.org, choose
> ACPI-Power/Video category.
>
> Please provide these information when filing the bug:
> 1 attach dmesg.
> 2 attach acpidump output.
> 3 attach dmidecode output.
> 4 of those backlight control interfaces, which works and which don't.
> 5 attach /var/log/Xorg.0.log when you do not use the customized xorg.conf,
>    I want to know which interface is picked up by X driver by default.
>
> Thanks,
> Aaron
>
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