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[Bug 1510344] Re: Keyboard Backlight Turns on at boot


I am working in Dell. I have some digging on this issue. There are two
symptoms reported in the thread – the keyboard backlight unexpectedly
turns ON on boot and after the resume from a screen lock. These are due
to two different causes.

- the backlight unexpectedly turns ON on boot, regardless of the
previous state of brightness. This is an intentional behavior of “unity-
settings-daemon”. This daemon reads the brightness value of
kbd_backlight (via “upowerd”) when system starts up, and turn it on (via
upowerd) if the read value is 0 (which indicates the backlight is off).
Even worse, the daemon does not make this behavior configurable.

- The backlight unexpectedly turns ON after the resume from a screen
lock, regardless of the previous state of brightness. The “unity-
settings-daemon” also deals with power management things. It turns the
backlight off when the system is about to dim screen for power saving
reason. Also, the daemon thought itself as the only S/W piece that can
set the brightness of backlight and no other ones will change it, so it
does not query for the current state of backlight before dimming it. But
the fact is, Dell’s BIOS already dimmed the backlight due to a timeout
of idle. When screen resumes, the daemon resumes the backlight to ON as
it assumed the backlight was ON before dim.

The issue should start happening since the introduce of commit
6cff8d60aa0aba5583ecda09984dbcb2f24cc28d (pointed out in #5), because it
implements a new “kbd_backlight” driver in dell-laptop kernel module. It
it gives the chance to “upowerd” for having the control over the
keyboard backlight hardware on Dell laptops.

The workaround provided in #47 does work because it denies “unity-
settings-daemon” from sending DBUS commands that regarding kbd_backlight
set/get to upowerd.

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  Keyboard Backlight Turns on at boot

Status in Dell Sputnik:
Status in One Hundred Papercuts:
Status in Linux:
Status in linux package in Ubuntu:

Bug description:
  System: Dell XPS 13 9343

  Action: Boot computer

  Expected Behavior: Keyboard backlight would be off when computer is

  Actual Behavior: Keyboard backlight is on at boot

  This did not happen with Ubuntu 15.04

  There are new files in Ubuntu 15.10 -

  cat stop_timeout

   cat start_triggers 
  +keyboard +touchpad

  cat trigger 
  [none] AC-online BAT0-charging-or-full BAT0-charging BAT0-full BAT0-charging-blink-full-solid usb-gadget usb-host cpu0 cpu1 cpu2 cpu3 mmc0 rfkill0

  cat brightness 


  Unsure if these files are important, but included in the report

  ProblemType: Bug
  DistroRelease: Ubuntu 15.10
  Package: linux-image-4.1.0-2-generic 4.1.0-2.2
  ProcVersionSignature: Ubuntu 4.1.0-2.2-generic 4.1.3
  Uname: Linux 4.1.0-2-generic x86_64
  ApportVersion: 2.18-0ubuntu5
  Architecture: amd64
   /dev/snd/controlC1:  ubuntu     2488 F.... pulseaudio
   /dev/snd/controlC0:  ubuntu     2488 F.... pulseaudio
  CasperVersion: 1.362
  CurrentDesktop: Unity
  Date: Tue Oct 27 01:29:47 2015
   enx00249b0981e3  no wireless extensions.
   lo        no wireless extensions.
  LiveMediaBuild: Ubuntu 15.10 "Wily Werewolf" - Alpha amd64 (20150730)
  MachineType: Dell Inc. XPS 13 9343
   PATH=(custom, no user)
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/username.seed boot=casper quiet splash --- cdrom-detect/try-usb=true noprompt
   linux-restricted-modules-4.1.0-2-generic N/A
   linux-backports-modules-4.1.0-2-generic  N/A
   linux-firmware                           1.145
   0: hci0: Bluetooth
   	Soft blocked: no
   	Hard blocked: no
  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: 07/14/2015
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: A05
  dmi.board.name: 0TM99H
  dmi.board.vendor: Dell Inc.
  dmi.board.version: A00
  dmi.chassis.type: 9
  dmi.chassis.vendor: Dell Inc.
  dmi.modalias: dmi:bvnDellInc.:bvrA05:bd07/14/2015:svnDellInc.:pnXPS139343:pvr:rvnDellInc.:rn0TM99H:rvrA00:cvnDellInc.:ct9:cvr:
  dmi.product.name: XPS 13 9343
  dmi.sys.vendor: Dell Inc.

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