cannot control screen brightness with kubuntu 12.10 beta 2

[John_kubuntu]

And part three of my testing feedback.
Most of my problems over the years were with linux on the laptop, and kubuntu 12.10
is no exception. Again, feedback intended in a positive way!

I never was able to control the screen brightness of my Dell Inspiron laptop.
The quick buttons do bring up the on screen display, but the screen brightness is not reacting.
I tried fiddling in the past with boot options, did not try it now.
Too difficult with the gazillion files needed by grub2.
Is this a bug I should file against kde?
Not sure.

[SteveRiley]

Yes, Google shows lots of ideas for getting screen brightness to work on Inspirons. Don't be afraid of trying kernel boot options. The procedure is:

1. Using your favorite text editor, open /etc/default/grub with elevated privileges

2. Find the line that starts with GRUB_CMDLINE_LINUX_DEFAULT

3. Place the desired parameters between the quotes. For example:

GRUB_CMDLINE_LINUX_DEFAULT="alice bob_c=1 foo.bar=0"

4. Run

sudo update-grub

That's all there is to it.

[John_kubuntu]

Yes, Google shows lots of ideas for getting screen brightness to work on Inspirons. Don't be afraid of trying kernel boot options. The procedure is:

1. Using your favorite text editor, open /etc/default/grub with elevated privileges

2. Find the line that starts with GRUB_CMDLINE_LINUX_DEFAULT

3. Place the desired parameters between the quotes. For example:

GRUB_CMDLINE_LINUX_DEFAULT="alice bob_c=1 foo.bar=0"

4. Run

sudo update-grub

That's all there is to it.

Steve, you're doing pretty good solving my problems!

I put the following line in /etc/default/grub

GRUB_CMDLINE_LINUX_DEFAULT="acpi_osi=Linux acpi_backlight=vendor"

And now I can control the brightness of the display using the standard keyboard shortcuts!!!

BTW my laptop is a DELL studio XPS, with nvidea/intel 915 graphics.
The combination of these graphic cards is apparently the problem.

[SteveRiley]

BTW my laptop is a DELL studio XPS, with nvidea/intel 915 graphics.
The combination of these graphic cards is apparently the problem.

Ugh, is that thing configured with Optimus? I have that on my T520. nVidia Quadro 4200M and Intel HD 3000. No matter how I configure the firmware setting, whether in "Optimus" mode or "discrete," the nVidia binary blob refuses to load. This is a known issue. So I use the Nouveau driver when the laptop is docked, because I need to drive two digital monitors (the Intel chip isn't wired to allow this). When the laptop isn't docked, I switch the graphics setting in the firmware to "integrated" so that I use the Intel driver, which is more stable.

Supposedly full Optimus support with the nVidia blob should be here Real Soon Now...

[John_kubuntu]

It has Optimus under Windows, an Nvidea card plus the build-in intel graphics
(i5 processor, the last predecessor of sandy bridge, don't know the i9xx umber).
Since Dell has a locked Phoenix BIOS (to reduce the cost of customer service, had I known before buying it!)
I cannot switch of the nvidea card or configure anything related to graphics.

Linux uses only use the intel graphic, ignoring the nvidea card.
I had hoped to be able to switch it completely off to save power, but no sigar :-(
Perhaps I will physically remove it one of these days :-)
Basically I choose for a laptop that does not support gaming, but I had to buy the nvidea card anyway

[SteveRiley]

Well, don't despair. Nouveau already appears able to understand Optimus, but I experience occasional X crashes when I do things like, oh, dial my VoIP phone.

Don't even think about physically removing the nVidia chip. It's most likely soldered directly to the motherboard!