Bug 95021

Summary:	Auto backlight control. Modprobe samsung_laptop returns "ERROR...No such device" on Samsung XE700T
Product:	Platform Specific/Hardware	Reporter:	Ovi (bernovy)
Component:	IA-64	Assignee:	platform_ia-64
Status:	NEW ---
Severity:	normal
Priority:	P1
Hardware:	Intel
OS:	Linux
URL:	http://ubuntuforums.org/showthread.php?t=2216224&page=2
Kernel Version:	3.16.0-31-generic	Subsystem:
Regression:	No	Bisected commit-id:

Description Ovi 2015-03-18 03:35:13 UTC

Please see the full description on: http://ubuntuforums.org/showthread.php?t=2216224&page=2

I posted on ubuntu forum after trying numerous ineffective solutions to a backlight auto-dimming issue. After running through a troubleshooting process which is described on the page linked above, I was advised by Toz to submit a kernel bug.

sudo dmidecode -s system-manufacturer
SAMSUNG ELECTRONICS CO., LTD.
sudo dmidecode -s system-product-name
700T1C
sudo dmidecode -s system-version
P10AAT

sudo modprobe samsung_laptop
modprobe: ERROR: could not insert 'samsung_laptop': No such device

cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-3.16.0-31-generic.efi.signed root=/dev/mapper/ubuntu--vg-root ro acpi_osi=Linux quiet splash vt.handoff=7

lsb_release -rd
Description: Ubuntu 14.04.2 LTS
Release: 14.04

Summary:
I can't control the brightness from my settings or by manually changing the values in ../intel_backlight/brightness.
My auto brightness seems to have a mind of its own and unfortunately for me I can't fix it with the "acpi_osi=" trick. Since the auto brightness flickers up and down every few seconds, its so frustrating that I can barely use my tablet. I tried my best to fix in the last 4 days since I re-installed Ubuntu, but regardless of what I tried, I simply can't stabilize it, nevermind control it. At this state I would be delighted if I could just set it to one value at boot.

After running a few commands as advised by Toz, the flickering seems to have stopped while the tablet is plugged in, but while the settings value shows my screen at max brightness, its definitely not as bright as in Windows. (and I definitely don't want to use Windows as my main OS).

I would like to be able to control the brightness manually in the power settings or by setting it at boot in rc.local.

PS: btw the controls for gyro, accelometer and rotation don't seem to be functional in Ubuntu, even if they show up in lsmod as loaded. Could these be because of the missing samsung_laptop module?

I hope this helps. If you require further info, please get in touch.
Thanks!

Comment 1 Ovi 2015-03-18 05:45:48 UTC

Edit: I updated to 3.19.1 kernel. My screen is now much brighter but the backlight problem is still present. I still can't control the screen brightness from Power Settings menu and the manual value update in intel_backlight makes no difference (however I do have different minimum values now):

cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-3.19.1-031901-generic root=/dev/mapper/ubuntu--vg-root ro acpi_osi=Linux quiet splash vt.handoff=7

/sys/class/backlight/intel_backlight
2928
4648
2928

However, modprobe result is the same on 3.19.1 as on 3.16:
sudo modprobe samsung_laptop
modprobe: ERROR: could not insert 'samsung_laptop': No such device