Thanks for the advice. I installed 4.7.0-040700.201608021801 and it
doesn't make any difference.
I did discover, though, that with either kernel, if you give
intel_backlight a brightness of 0, the backlight switches off
completely.
** Tags added: kernel-bug-exists-upstream
** Changed in: linux (Ubuntu)
Status: Incomplete => Confirmed
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https://bugs.launchpad.net/bugs/1608745
Title:
Backlight uncontrollable on Samsung NP740UE3 since upgrade to Xenial
Status in linux package in Ubuntu:
Confirmed
Bug description:
Stopped working since I upgraded from 14.04 to 16.04 - now stuck at
full brightness. The only subdirectory in /sys/class/backlight is
intel_backlight and while the function keys control the value in
actual_brightness it has no effect.
If I boot with the previous kernel (3.13.0-34) there are two more
subdirectories: acpi_video0 and acpi_video0. Either of these can be
used to control the brightness by writing to the brightness entry,
though the function keys no longer control it because they change
values in intel_backlight instead.
If I give the Xenial kernel the parameter acpi_backlight=video, those
two subdirectories also appear and are controllable, though the
function keys still try to control intel_backlight.
Seems to be similar to
https://bugzilla.kernel.org/show_bug.cgi?id=108971. From that I have
tried acpi_backlight=native and acpi_backlight="!Windows 2012" and
neither has any effect, nor does video.use_bios_initial or
acpi_osi=Linux.
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-31-generic 4.4.0-31.50
ProcVersionSignature: Ubuntu 4.4.0-31.50-generic 4.4.13
Uname: Linux 4.4.0-31-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: matthew 3526 F.... pulseaudio
CurrentDesktop: Unity
Date: Tue Aug 2 01:41:24 2016
HibernationDevice: RESUME=UUID=0adbc2db-fe30-4c7e-9189-6e241093a9db
MachineType: SAMSUNG ELECTRONICS CO., LTD. 740U
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-31-generic
root=UUID=11a96955-be22-4e0d-ba57-9da738ace79d ro quiet splash vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-4.4.0-31-generic N/A
linux-backports-modules-4.4.0-31-generic N/A
linux-firmware 1.157.2
SourcePackage: linux
UpgradeStatus: Upgraded to xenial on 2016-08-01 (0 days ago)
dmi.bios.date: 02/26/2014
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P07ABW.065.140226.dg
dmi.board.asset.tag: No Asset Tag
dmi.board.name: NP740U3E-S02UK
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.:bvrP07ABW.065.140226.dg:bd02/26/2014:svnSAMSUNGELECTRONICSCO.,LTD.:pn740U:pvrNP740U3E-S02UK:rvnSAMSUNGELECTRONICSCO.,LTD.:rnNP740U3E-S02UK:rvrSEC_SW_REVISION_1234567890ABCD:cvnSAMSUNGELECTRONICSCO.,LTD.:ct9:cvrN/A:
dmi.product.name: 740U
dmi.product.version: NP740U3E-S02UK
dmi.sys.vendor: SAMSUNG ELECTRONICS CO., LTD.
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