Public bug reported: 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. ** Affects: linux (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug xenial -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1608745 Title: Backlight uncontrollable on Samsung NP740UE3 since upgrade to Xenial To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1608745/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
