Brightness control doesn't work on HP dv7t laptop

[DoYouKubuntu]

I am completely unable to control the brightness on my new HP dv7t laptop; neither its brightness control buttons nor any software solution I've tried has worked. Here's my card's specs:

Intel(R) HD Graphics 3000 [HDMI, VGA]

Note that sometimes the onscreen display comes on when I attempt to adjust the brightness, whether via the buttons or software...and sometimes it doesn't. I have no idea why. But one thing that's consistent is that I cannot adjust the brightness! Any ideas?

[Snowhog]

Re: Brightness control doesn't work on HP dv7t laptop

You can try adding noapic to the line GRUB_CMDLINE_LINUX="" in /etc/default/grub so that it reads:

GRUB_CMDLINE_LINUX="noapic"

Save and close the file and then in a console type:

sudo update-grub

Reboot and see if the brightness controls (fn+f2 and fn+f3 here on my Pavilion g7) work. Be warned, that if it works, you may loose keyboard control of the wireless function key.

[DoYouKubuntu]

Re: Brightness control doesn't work on HP dv7t laptop

You can try adding noapic to the line GRUB_CMDLINE_LINUX="" in /etc/default/grub so that it reads:

GRUB_CMDLINE_LINUX="noapic"

Save and close the file and then in a console type:

sudo update-grub

Reboot and see if the brightness controls (fn+f2 and fn+f3 here on my Pavilion g7) work. Be warned, that if it works, you may loose keyboard control of the wireless function key.

Okay, I did the above--and I did not lose anything! I gained control of brightness, but NOT via the keys on the laptop. I can now go to System Settings | Display and Monitor | Gamma and adjust the brightness up/down from there. It's a hassle, but at least it works! Thanks for the point in the right direction. I hadn't even thought about noapic in years...I remember one of my earlier laptops had some kind of issue that I solved by adding noapic to it during installation, but that was a while back!

[Snowhog]

Re: Brightness control doesn't work on HP dv7t laptop

Well, good. I had similar issues with my HP g7 'initially', and tried several kernel= options. You might want to try this (as apposed to, or in addition to):

acpi.power_nocheck=1
acpi=noirq

[SteveRiley]

Re: Brightness control doesn't work on HP dv7t laptop

Some nVidia cards require adding a line to /etc/X11/xorg.conf in the "DEVICE" section:

Option "RegistryDwords" "EnableBrightnessControl=1"

I wonder whether that might work on Intel graphics chips too?

Also, I just noticed a page about debugging backlight problems in the Kubuntu wiki.