Right, so I have re-tested having installed the 4.2.0-040200rc7-generic
kernel. The behaviour seems to be identical to the stock Ubuntu 15.04
kernel.
A few things I have noticed having carried out several reboots and
suspends in the process of testing this. These apply to both the stock
kernel and the 4.2 kernel:
With kernel parameter acpi_backlight=vendor
1. On first boot the brightness of the screen is about 60% brightness and
attempts to change the brightness setting via the hotkeys causes the brightness
level notification to flicker and the brightness level cannot be altered
2. After a suspend the brightness returns to about 100% and using the hotkeys
may then work (i.e brightness controls have been properly restored). This
occurs on about 2 in 3 wakes from suspend, the other 1 in 3 the brighness is
100% but control over brightness still non-functional
with no acpi_backlight kernel param
1. The initial boot brightness is approximately the same as above. Attempts to
change this successfully move the brightness level in the indicator, but have
no impact on the actual screen brighness.
2. wake from suspend results in the 100% brightness as above, but no control of
screen brightness still
Not sure if any of that actually helps any...
Let me know if I can extract any further useful information to help with
debugging.
** Changed in: linux (Ubuntu)
Status: Incomplete => Confirmed
** Tags added: kernel-bug-exists-upstream
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https://bugs.launchpad.net/bugs/1485246
Title:
Backlight issue - Samsung Chronos 7 (model - NP770Z5E)
Status in linux package in Ubuntu:
Confirmed
Bug description:
Control of screen backlight is broken with a default clean install of
Ubuntu 15.04 on my Samsung Series 7 Laptop (NP770Z5E). Setting kernel
parameter 'acpi_backlight=vendor' fixes the issue after two reboots.
Debugging information attached as per -
https://wiki.ubuntu.com/Kernel/Debugging/Backlight
ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: linux-image-3.19.0-25-generic 3.19.0-25.26
ProcVersionSignature: Ubuntu 3.19.0-25.26-generic 3.19.8-ckt2
Uname: Linux 3.19.0-25-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.2
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: mark 1699 F.... pulseaudio
Date: Sat Aug 15 21:36:20 2015
HibernationDevice: RESUME=UUID=c4899b44-3e19-4e62-921d-cf0a1cef97ec
InstallationDate: Installed on 2015-08-12 (3 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
MachineType: SAMSUNG ELECTRONICS CO., LTD. 770Z5E/780Z5E
ProcFB:
0 inteldrmfb
1 radeondrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.19.0-25-generic
root=UUID=5a02817b-1f9b-4abc-93a3-b10d5d9278ed ro quiet splash
acpi_backlight=vendor vt.handoff=7
PulseList:
Error: command ['pacmd', 'list'] failed with exit code 1: Home directory not
accessible: Permission denied
No PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
linux-restricted-modules-3.19.0-25-generic N/A
linux-backports-modules-3.19.0-25-generic N/A
linux-firmware 1.143.3
SourcePackage: linux
UdevLog: Error: [Errno 2] No such file or directory: '/var/log/udev'
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/05/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P05ABU.142.130905.SK
dmi.board.asset.tag: No Asset Tag
dmi.board.name: NP770Z5E-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.:bvrP05ABU.142.130905.SK:bd09/05/2013:svnSAMSUNGELECTRONICSCO.,LTD.:pn770Z5E/780Z5E:pvrP05ABU:rvnSAMSUNGELECTRONICSCO.,LTD.:rnNP770Z5E-S02UK:rvrSEC_SW_REVISION_1234567890ABCD:cvnSAMSUNGELECTRONICSCO.,LTD.:ct9:cvrN/A:
dmi.product.name: 770Z5E/780Z5E
dmi.product.version: P05ABU
dmi.sys.vendor: SAMSUNG ELECTRONICS CO., LTD.
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