Ubuntu

Laptop backlight adjustment problem

Asked by Evo_nilsen

Hi,
After installing ububtu 6.10(edgy) on my compaq evo n800v everything works fine, except for the backlight adjustment hotkeys (Fn+f7/f8)
They work untill gnome comes up, then they dont work anymore. Syslog does not show them as unrecognized events (some other shortkeys show there), xev does not show them either (byt shows the multimedia player shortkeys). I believe the bios grabs these keys directly, and sends acpi events to the kernel, but these are dropped somwhere along the way. Fn+f3(suspend) works fine, Fn+f2(bluetooth on/off) also works, but these dont generate xev events, so i assume they are bios handled. Hovever, when the lid_close button is pressed, edgu fades down the backlight before turning off, so the kernel has control of the backilght. How do i get it to recognize the bios events?

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Evo_nilsen (svennils) said : 		#1

Correction: on lid_close the screen is faded, not the backlight itself. So i dont know if the kernel has control of the backlight. Only that it blocks bios control.

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Evo_nilsen (svennils) said : 		#2

More info: kernel remembers the brightness setting on battery, and on ac. I just unplugged the ac adapter to move the machine, and got full brightness. Kernel has backlight control, it just won't let me adjust it inside gnome.

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Murat Gunes (mgunes) said : 		#3

See if changing the "Plug and Play OS", "Device configuration by BIOS" or equivalent option in your BIOS setup changes anything. I used all Ubuntu versions up to Breezy on the same laptop and the keys used to work fine without any configuration.

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Evo_nilsen (svennils) said : 		#4

Unfortunately my bios does not have this option, only numlock at boot, boot order and other unimportant things.

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Evo_nilsen (svennils) said : 		#5

Since this works in every oyher os i've tried (slackware from 2.2.14 till 2.6.11.7, windoze 2k, xp, 2003 adv.server, and at boot time,) it seems that the bios is normally capable of handling the backlight itself. It should be possible to tell the kernel to leave this part of acpi alone. But how?

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Evo_nilsen (svennils) said : 		#6

t seems i have a set of scripts in the /etc/acpi directory, doing various things like volume up/down etc. Including brightness up-down, for different hardware (sony, panasonic etc) The sony scripts write to /proc/acpi/sony/brightness. Hovever, the proc/acpi/sony folder is empty on this installation, and as far as i can tell, no other proc file within acpi has anything to do with the backlight setting.
Just the usual stuff like battery status and temp.zones etc. Does the kernel detect the wrong acpi devices, and therefore freak out?

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Murat Gunes (mgunes) said : 		#7

Someone else confirms your problem: http://ubuntuforums.org/showpost.php?p=2306616&postcount=11

This is definitely a regression in either Dapper or Edgy. I'll take a look once I get hold of a N800V, within a month or so.

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Murat Gunes (mgunes) said : 		#8

Does the "Brightness" slider in gnome-power-manager work, by the way?

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Evo_nilsen (svennils) said : 		#9

Hmm, where in power manager is the brightness slider located? Assuming you meant the power manager icon displaying battery status in the taskbar. Or started from the preferneces menu.

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Alan Pope 🍺🐧🐱 🦄 (popey) said : 		#10

It isnt in power manager, it is a separate applet you can add to the panel. It is written by the same guy as the power applet though.

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Murat Gunes (mgunes) said : 		#11

It's in System / Preferences / Power Manager.

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Murat Gunes (mgunes) said : 		#12

Actually, System / Preferences / Power Management. It may help isolate the problem.

One more thing: what's your BIOS version? I'll check against the computer where the keys worked fine.

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lostangel78 (lostangel78) said : 		#13

Try typing the following command in a terminal:

xgamma -gamma 0.75

If that doesn't work you need to install xgamma from the repos.

I have posted my own solution here on setting it up:

http://ubuntuforums.org/showthread.php?p=4168042#post4168042

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