Public bug reported:
Followed instructions here:
https://wiki.ubuntu.com/Kernel/Debugging/Backlight
Category: Backlight control does not work, but there are entries in
/sys/class/backlight
System: Samsung NT200B5C-STW/R notebook, Lubuntu 17.04 x64
More info:
- Dimming the screen in the BIOS using the function keys works as expected, so
doesn't appear to be a hardware issue.
- After installing Lubuntu 17.04 x64, the screen is at full brightness.
- Attempting to dim the screen using the function keys does not work.
However the brightness applet is displayed and
/sys/class/backlight/intel_backlight/brightness file is modified.
However, at lower settings, instead of dimming, the backlight appears to
switch on and off continuously. If the brightness is set back up to
100%, the flashing ceases. The on off cycling appears to increase in
frequency the lower the brightness setting.
- Ran all debugging info commands. Note that dsdt.dat is lowercase. See
backlight.zip (attached as one zip as the site isn't allowing multiple
attachments for some reason)
- Setting acpi_backlight=vendor
... No change
- /sys/class/backlight/intel_backlight/brightness is present.
... Changing the number has the same effect as using the Fn keys. Values lower
than 100% cause the screen to cycle on and off continuously.
- Kernel param: video.use_bios_initial_backlight=0
... same behavior.
- Kernal param: acpi_osi=
... same behavior
- Kernel version is: 4.10.0-19-generic
- Kernel param: acpi.brightness_switch_enabled=0
... same behavior
- $ dmesg | grep 'ACPI: Video'
[ 2.481461] ACPI: Video Device [PEGP] (multi-head: yes rom: yes post: no)
[ 2.482043] ACPI: Video Device [GFX0] (multi-head: yes rom: no post: no)
- $ lspci |grep VGA
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor
Graphics Controller (rev 09)
ProblemType: Bug
DistroRelease: Ubuntu 17.04
Package: linux-image-4.10.0-19-generic 4.10.0-19.21 [modified:
boot/vmlinuz-4.10.0-19-generic]
ProcVersionSignature: Ubuntu 4.10.0-19.21-generic 4.10.8
Uname: Linux 4.10.0-19-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version
k4.10.0-19-generic.
ApportVersion: 2.20.4-0ubuntu4
Architecture: amd64
ArecordDevices:
**** List of CAPTURE Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC269VC Analog [ALC269VC Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: flgc 1174 F.... pulseaudio
Card0.Amixer.info:
Card hw:0 'PCH'/'HDA Intel PCH at 0xf7e30000 irq 34'
Mixer name : 'Realtek ALC269VC'
Components : 'HDA:10ec0269,144dc0e4,00100202
HDA:80862806,80860101,00100000'
Controls : 28
Simple ctrls : 11
CurrentDesktop: LXDE
Date: Sun Apr 23 20:10:20 2017
HibernationDevice: RESUME=UUID=145d228c-4542-4aab-901e-894d929d2085
InstallationDate: Installed on 2017-04-23 (0 days ago)
InstallationMedia: Lubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412)
MachineType: SAMSUNG ELECTRONICS CO., LTD. 400B4C/400B5C/200B4C/200B5C
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.10.0-19-generic.efi.signed
root=UUID=3312063b-5d45-48b3-9e73-34065c10b162 ro quiet splash vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-4.10.0-19-generic N/A
linux-backports-modules-4.10.0-19-generic N/A
linux-firmware 1.164
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/14/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P05AAZ.033.130814.dg
dmi.board.asset.tag: No Asset Tag
dmi.board.name: SAMSUNG_NP1234567890
dmi.board.vendor: SAMSUNG ELECTRONICS CO., LTD.
dmi.board.version: SEC_SW_REVISION_1234567890ABCD
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 9
dmi.chassis.vendor: SAMSUNG ELECTRONICS CO., LTD.
dmi.chassis.version: N/A
dmi.modalias:
dmi:bvnAmericanMegatrendsInc.:bvrP05AAZ.033.130814.dg:bd08/14/2013:svnSAMSUNGELECTRONICSCO.,LTD.:pn400B4C/400B5C/200B4C/200B5C:pvrP05AAZ:rvnSAMSUNGELECTRONICSCO.,LTD.:rnSAMSUNG_NP1234567890:rvrSEC_SW_REVISION_1234567890ABCD:cvnSAMSUNGELECTRONICSCO.,LTD.:ct9:cvrN/A:
dmi.product.name: 400B4C/400B5C/200B4C/200B5C
dmi.product.version: P05AAZ
dmi.sys.vendor: SAMSUNG ELECTRONICS CO., LTD.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 backlight-bug zesty
** Attachment added: "All debug info"
https://bugs.launchpad.net/bugs/1685620/+attachment/4866853/+files/backlight.zip
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https://bugs.launchpad.net/bugs/1685620
Title:
Screen flashes continuously when brightness set to lower than 100%
using fn keys on Samsung NT200B5C-STW/R laptop running Lubuntu 17.04
x64
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