link-dupont really nailed it! I am having the same issue on an HP Elitebook 8770w with ONLY an NVIDIA Quadro K3000M, using the proprietary driver version 387.34 on Fedora 27, Kernel 4.14.3-300
I tried all: acpi_backlight=video acpi_backlight=vendor acpi_backlight=native to no avail, so removed all of that and installed inotify-tools, I do have /sys/class/backlight/acpi_video0 so I ended up with the following script in /home/YOURUSERHERE/Scripts/backlight_inotify.sh #!/bin/sh path=/sys/class/backlight/acpi_video0 luminance() { read -r level < "$path"/actual_brightness factor=$((100 / max)) printf '%d\n' "$((level * factor))" } read -r max < "$path"/max_brightness nvidia-settings -n -a BacklightBrightness="$(luminance)" inotifywait -me modify --format '' "$path"/actual_brightness | while read; do nvidia-settings -n -a BacklightBrightness="$(luminance)" done And then created file brightnessfix.desktop under /home/YOURUSERHERE/.config/autostart [Desktop Entry] Name=Brightness Fix Exec=/home/YOURUSERHERE/Scripts/backlight_inotify.sh Terminal=false Type=Application Name[en_US]=backlightfix.desktop It is a very effective workaround, thanks. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to nvidia-graphics-drivers-352 in Ubuntu. https://bugs.launchpad.net/bugs/1518473 Title: /sys/class/backlight/acpi_video0/brightness is broken Status in System76: Triaged Status in nvidia-graphics-drivers-352 package in Ubuntu: Confirmed Bug description: With nvidia-352 (and for that matter nvidia-346), the /sys/class/backlight interface is broken. Writing to /sys/class/backlight/acpi_video0/brightness has no effect, and reading from it returns a value that does not necessarily reflect the current brightness. I don't know when exactly this broke in the Nvidia driver, but I do know that not that long ago it worked because the system76-driver uses this to restore the previous backlight brightness level during boot. I believe this still worked with nvidia-343 and perhaps also worked in early nvidia-346 versions. This problem is somewhat masked because with Ubuntu (Unity), unity- settings-daemon has two code paths for setting the brightness: 1) Using /sys/class/backlight 2) Using xrandr, which as far as I can tell takes (roughly) the same approach as the `xbacklight` command line tool However, approach (2) does not work with Ubuntu GNOME because gnome- settings-daemon has dropped this code (it dropped gnome-settings- daemon/gsd-rr*). I've started digging into the dkms module source code, but haven't come up with anything yet. Of course, there is a chance the problem is in the closed proprietary bits. ProblemType: Bug DistroRelease: Ubuntu 15.10 Package: nvidia-352 352.63-0ubuntu0.15.10.1 ProcVersionSignature: Ubuntu 4.2.0-18.22-generic 4.2.3 Uname: Linux 4.2.0-18-generic x86_64 NonfreeKernelModules: nvidia .proc.driver.nvidia.registry: Binary: "" .proc.driver.nvidia.version: NVRM version: NVIDIA UNIX x86_64 Kernel Module 352.63 Sat Nov 7 21:25:42 PST 2015 GCC version: gcc version 5.2.1 20151010 (Ubuntu 5.2.1-22ubuntu2) ApportVersion: 2.19.1-0ubuntu5 Architecture: amd64 CurrentDesktop: Unity Date: Fri Nov 20 15:01:42 2015 DistUpgraded: Fresh install DistroCodename: wily DistroVariant: ubuntu DkmsStatus: bbswitch, 0.7, 4.2.0-18-generic, x86_64: installed fwts-efi-runtime-dkms, 15.09.00, 4.2.0-18-generic, x86_64: installed nvidia-352, 352.63, 4.2.0-18-generic, x86_64: installed GraphicsCard: NVIDIA Corporation GM204M [GeForce GTX 970M] [10de:1618] (rev a1) (prog-if 00 [VGA controller]) Subsystem: CLEVO/KAPOK Computer Device [1558:7701] MachineType: System76, Inc. Serval WS ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.2.0-18-generic.efi.signed root=UUID=d68b8062-f67c-495c-8c16-f2e11d9a9916 ro quiet splash SourcePackage: nvidia-graphics-drivers-352 UdevLog: Error: [Errno 2] No such file or directory: '/var/log/udev' UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 06/09/2015 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: 1.03.03RSY2 dmi.board.asset.tag: Tag 12345 dmi.board.name: Serval WS dmi.board.vendor: System76, Inc. dmi.board.version: serw8-17g dmi.chassis.asset.tag: No Asset Tag dmi.chassis.type: 9 dmi.chassis.vendor: System76, Inc. dmi.chassis.version: Serval WS dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr1.03.03RSY2:bd06/09/2015:svnSystem76,Inc.:pnServalWS:pvrserw8-17g:rvnSystem76,Inc.:rnServalWS:rvrserw8-17g:cvnSystem76,Inc.:ct9:cvrServalWS: dmi.product.name: Serval WS dmi.product.version: serw8-17g dmi.sys.vendor: System76, Inc. modified.conffile..etc.modprobe.d.nvidia.352.hybrid.conf: [deleted] version.compiz: compiz 1:0.9.12.2+15.10.20151015-0ubuntu1 version.ia32-libs: ia32-libs N/A version.libdrm2: libdrm2 2.4.64-1 version.libgl1-mesa-dri: libgl1-mesa-dri 11.0.2-1ubuntu4 version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A version.libgl1-mesa-glx: libgl1-mesa-glx 11.0.2-1ubuntu4 version.nvidia-graphics-drivers: nvidia-graphics-drivers-* N/A version.xserver-xorg-core: xserver-xorg-core 2:1.17.2-1ubuntu9 version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.9.2-1ubuntu1 version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.5.0+git20150819-0ubuntu1 version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20150808-0ubuntu4 version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.11-1ubuntu3 xserver.bootTime: Fri Nov 20 08:41:35 2015 xserver.configfile: default xserver.errors: xserver.logfile: /var/log/Xorg.0.log xserver.outputs: xserver.version: 2:1.17.2-1ubuntu9 To manage notifications about this bug go to: https://bugs.launchpad.net/system76/+bug/1518473/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp