Public bug reported:
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
** Affects: system76
Importance: Undecided
Status: New
** Affects: nvidia-graphics-drivers-352 (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug ubuntu wily
** Also affects: system76
Importance: Undecided
Status: New
** Description changed:
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
+ 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)
+ 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
+ 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]
+ 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
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https://bugs.launchpad.net/bugs/1518473
Title:
/sys/class/backlight/acpi_video0/brightness is broken
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