LinuxQuestions.org - L501x Brightness

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L501x Brightness

Hi everyone!
Recently I came out with a brand new Dell laptop. Just beautiful and powerful I must say. A Dell XPS 15 (formerly L501X).
The first thing to do when you receive a ready-to-go computer is just format it all, while downloading the latest slack on the old one thinking about all the new possibilities that new box will give you (just the old ones but a little bit faster :D).
Well... installed my slackware64 13.1, upgraded to -current. Just ~20 recompiles of latest 2.6.37 kernel just to see your desktop working as it should. But there is always something that goes wrong; in this is case is brightness controls with Fn + F4/F5.
It just doesn't work!
I compiled the kernel with dell_wmi and dell_laptop extras. Neither just seem to do anything meaningful.
With a fresh boot, pressing Fn + F4 cause the brightness to be slightly reduced, subsequents tries just spit out tons of:

Code:

Jan 10 10:58:02 xpsbox logger: ACPI group video / action brightnessdown is not defined

Jan 10 10:58:02 xpsbox logger: ACPI group PNP0C14:00 / action 000000d0 is not defined

...and the brightness is locked to the top value.

Googling around I've found that Mr. Kamal Mostafa (http://ubuntuforums.org/showthread.php?t=1636959) developed a fix for ubuntu kernel. I tried to apply that (outdated) patch manually to a 2.6.37 kernel but the API probably changed, probably I did it wrong... it didn't fix the issue.
My accelerated desktop is working with i915 driver with modesetting enabled by default, without any nvidia driver (is a double GPU system: i3 integrated one and nvidia [HybridPower]).
This is really driving me mad!!
Any hint for applying that patch or anything else would be really appreciated.
Any information you eventually need, just ask.
Thank you in advance.

Greetings,

Karimo

I want that laptop... when the 1080p screen becomes available again (supposed to be in a few weeks).

Edit: Ha! Just checked Dell's site, and the 1080p screen is back.

I'm glad I read about Nvidia's Optimus technology on NVnews.net... they have no plans to support switchable graphics in Linux, so you'll be stuck with Intel graphics only. Unless someone creates a hack or BIOS option to treat the Nvidia GPU as the primary video option...

The laptop is really great, I assure you.
Yeah... I'm stuck with the intel graphic, but really it is not a problem: the full-effected accelerated kde just works great!!
Let me know if you manage to solve your future brightness problem ;)

Regards,

Karimo

Hi. Thinking about buying a Dell XPS 15 with the i7 cpu (and the 1080p screen). Talked to this Dell tech and he said that this processor does not have the build inn graphics that you would have with the i3 and i5 cpus. And that it then should run only with the Nvidia graphics. Any thoughts on that?

And by the way, is everything else working with this laptop running linux? Sound, wifi etc...

hi,
are you using kde daemon for power management? i had the same problem (hp probook laptop), but now i use guidance power manager in kde and the brightness keys work (almost) fine.

I've tried to uncheck the "Let PowerDevil manage screen powersaving" in the Power Management System Setting of KDE but nothing solved.
More practically I think is not a KDE issue, is a kernel problem:

Code:

root@xpsbox:/sys/class/backlight/acpi_video0# ls -l

total 0

-r--r--r-- 1 root root 4096 Jan 11 16:33 actual_brightness

-rw-r--r-- 1 root root 4096 Jan 11 16:43 bl_power

-rw-r--r-- 1 root root 4096 Jan 11 16:43 brightness

lrwxrwxrwx 1 root root    0 Jan 11 16:33 device -> ../../../LNXSYSTM:00/device:00/PNP0A08:00/device:01/LNXVIDEO:00/device:02/

-r--r--r-- 1 root root 4096 Jan 11 16:33 max_brightness

drwxr-xr-x 2 root root    0 Jan 11 16:43 power/

lrwxrwxrwx 1 root root    0 Jan 11  2011 subsystem -> ../../../../class/backlight/

-rw-r--r-- 1 root root 4096 Jan 11  2011 uevent

root@xpsbox:/sys/class/backlight/acpi_video0# cat actual_brightness 

15

root@xpsbox:/sys/class/backlight/acpi_video0# echo 5 >brightness 

root@xpsbox:/sys/class/backlight/acpi_video0# cat actual_brightness 

5

root@xpsbox:/sys/class/backlight/acpi_video0#

DOING THIS THE BRIGHTNESS DOES NOT CHANGE! Argh....
There is a driver that I'm missing? A patch or something?

what i did to make brightness control work:
system settings » shortcuts and gesturers » global keyboard shortcuts » from the "KDE component" drop-down list select "guidance power manager" » reassign Fn+Fx to their respective actions.

@doomey: thanks for the hint, but is a kernel issue for sure. Giudance showing the reduced/increased brightness dialog but nothing happens. Still messages from ACPI notifying that brightnessdown/brightnessup actions are not defined.

I've discovered that the computer naturally can change display brightness.
Infact before loading that driver, the kernel is still able to change brightness.
So: how to maintain the bios-driven functionality overriding the i915 drm driver?

Separate post?