Brightness control via ACPI in HP notebooks

Bug #82188 reported by grybba on 2007-01-29
Affects Status Importance Assigned to Milestone
hal (Ubuntu)

Bug Description

I own a HP notebook model nx7400 EY505ES with BIOS F.08 and neither ubuntu edgy nor feisty recognizes the brightness control of the built in LCD. The brightness of the LCD can be easily changed via writing to the file:
/proc/acpi/video/C080/C13F/brightness. The file contains:
levels: 100 51 30 37 44 51 58 65 72 79 86 93 100
current: 51
The brightness can be changed via issuing
sudo bash
echo 51 > brightness
The numbers echoed into the file have to come from the list, and the number 100 is impossible to enter this way. Is there a way to make the ubuntu aware of these possibility?

grybba (grybba) wrote :

This is a zipped /proc directory. I will be happy to run any tests or submit a DSDT or help in any other way.

grybba (grybba) wrote :
Chris Burgan (cburgan) wrote :

Thanks for the report,

Just for clarification, what you're trying to say is that going through gnome System > Preferences > Power Management doesn't have any options to adjust the brightness? Is that what your issue is? I just want to classify this in the right area by pinpointing where else you're trying to change the brightness that it's not recognized.

grybba (grybba) wrote :

Yes, I would like the power managment to be able to adjust the brightness if running on batteries. For example there is a simple Power Manager in Kubuntu, and, in general, it allows to setup brightness if running on batteries. This tool does not allow to set up brightness on my notebook - I've checked some forums and found out that the reason is that the HAL is not recognizing the possibility of adjusting brightness. I guessed that making hald aware of it would solve the problem.

Chris Burgan (cburgan) wrote :

You're correct actually and as such this bug becomes a duplicate of bug #68617

The good news is that there is a fix, located in that report or even nicer in this page:

Hope this works out for you. If by chance it doesn't, I'll glady remove the duplicate status.

grybba (grybba) wrote :

This fix does not work for me and I think that my problem is located in a different place. I do not have a possibility to adjust brightness in Power Management in Gnome - it seems that Ubuntu is unaware of the fact that the brightness of my LCD can be changed using ACPI. I assume that if HAL knew about the ACPI possibility of adjusting brightness via writing to the file, an appropriate slider would appear in Power Management but there is nothing like this in there. So this definitely not a duplicate of a bug #68617. Please do remove the duplicate flag as the bug is still valid.

grybba (grybba) wrote :

I just wanted to add that all the HP notebook users would be extremely happy if this thing would get fixed. Running the LCD all the time at the full brightness really decreases the battery life and is, together with the suspend issue, one of the two remaining problems with Ubuntu on HP laptops - otherwise it is just perfect ;).

Chris Burgan (cburgan) wrote :

Removed the duplicate status, sorry. I thought they were essentially the same problem. In fact I just tried the solution with an Acer Laptop suffering from the same symptoms and met the same results.

jiasheng (jiasheng-shi) wrote :

I think I have the same problem with you. My laptop is HP dv2210us which is a model of dv2000z series. I cannot adjust the LCD brightness through Fn keys. Moreover, there is no brightness slider in gnome-power-management. I then install Kubuntu which I use more often before, however, the kpowersave report that HAL cannot recognize my hardware when I try to adjust the LCD brightness.

thekimera (thekymera) wrote :

Hi, I have a laptop HP DV2000 series (dv2033ea) and when I upgrade the bios, I have this problem! If I increase or decrease the bright, with Fn keys, bright comes to MAX and i cant decrease it. It's really a problem for me, becouse my laptop battery is not too biger...and i cant use it for more than 1,5 hours,

sampsa (sampsa-hamalainen) wrote :

I can confirm this problem on an intel core 2 duo dv2100t with bios versions f.22-f.26. The older versions of the bios (f.11 and f.12) work perfectly but intel's VT virtualization is disabled in them.

Downgrading the bios will probably solve the problem.The older bios versions are not listed on HP's site any more, but they still have them on their ftp-server. The f.12, which is the newest version with which brightness adjustments work for me, can be downloaded from

thekimera (thekymera) wrote :

Hey really thank you for this information, but i tried and the installer said that it's not for my notebook, but I have a pavilion dv2000, there's any way to force??

Hi, finally I could downgrade the firmware, but not with this version of bios, I search in this ftp and find the bios f.13 and it allow me to downgrade it without problems.
Here you have the link for bios Phoenix F.13 from the hp fpt:

lostangel78 (lostangel78) wrote :

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:

sampsa (sampsa-hamalainen) wrote :

I tried a newer BIOS (f.39) again in the hope that bug would have been fixed, as the older bioses cause other bugs for me, but the brighness adjustment still will not work.

I think the bug actually isn't in hal but in the kernel (acpi module?). It seems that the /proc/acpi interface is deprecated and hal won't be supporting it in the future. At least according to this thread on the hal mailing list
If I understood correctly the kernel should supply a /sys/class/backlight directory to control the lcd backlight brightness.

On my laptop (HP dv2100t) with the f.39 BIOS I too can control the brightness like grybba explained through
but my /sys/class/backlight directory is empty and thus hal can't control the brigthtness.

If the others suffering from this bug also have no /sys/class/backlight, but can control the brightness via /proc then in my understanding this bug should be assigned to the kernel.

If there is any further information on my system you need, just let me know. I'll happily run some tests.

grybba (grybba) on 2008-05-01
Changed in hal:
status: New → Confirmed

I think this is related to, except for the drivers involved. Actually looks like the drivers are not working correctly, but APCI is, so why not just use ACPI in hal for changing the brightness?

Przemek K. (azrael) wrote :

Can you check if this bug is still present in Ubuntu 9.10 Karmic Koala?

Mahmoud Kassem (mmkassem) wrote :

Using Ubuntu 10.04, HP laptop display brightness can be adjusted from Power Management (System > Preferences > Power Management) or using the command line but can not be adjusted with Fn key on Ubuntu 10.04.

/proc/acpi/video/VGA/LCD# echo 50 > brightness

Mahmoud can you confirm this bug is fixed? Thank you for helping us!

Changed in hal (Ubuntu):
status: Confirmed → Incomplete
Launchpad Janitor (janitor) wrote :

[Expired for hal (Ubuntu) because there has been no activity for 60 days.]

Changed in hal (Ubuntu):
status: Incomplete → Expired
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