Also of possible interest. On my system I have three devices of class "backlight":
> ls -l /sys/class/backlight/ total 0 lrwxrwxrwx 1 root root 0 Jun 12 14:17 acpi_video0 -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0 lrwxrwxrwx 1 root root 0 Jun 12 13:39 acpi_video1 -> ../../devices/pci0000:00/0000:00:02.0/backlight/acpi_video1 lrwxrwxrwx 1 root root 0 Jun 12 14:17 intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight Each of these devices has a file inside called "brightness". The way these files change is interesting and suggests there is a probelem/confusion/interaction among acpi_video0 and acpi_video1 I could see what happens with the following command: watch -d -n 0.1 "cat /sys/class/backlight/acpi_video0/brightness && cat /sys/class/backlight/acpi_video1/brightness && cat /sys/class/backlight/intel_backlight/brightness" then watching how the values change in reaction to brightness keypresses. The intel_backlight/brightness value stands fixed at 497 The acpi_video0/brightness and acpi_video1/brightness values are normally not the same. e.g. the following happens: Values are: 6 -- 7 then I do one Fn+ArrowUP keypress for increasing brighness. After 1s, values become (but brightness does not change): 8 -- 7 Then after 1s and at 0.5s intervals, they change to 8 -- 9 8 -- 10 8 -- 11 One thing it always happens is that after a single keypress of brightness up (down), the first value acpi_video0/brightness gets the value of acpi_video1/brightness plus (minus) one, respectively. Then acpi_video1/brightness continues to change in the same direction. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to gnome-power-manager in Ubuntu. https://bugs.launchpad.net/bugs/847001 Title: Adjusting display brightness is very slow on several Dell laptops Status in “gnome-power-manager” package in Ubuntu: Confirmed Bug description: Changing the brightness via FN key combination or via the brightness applet is very slow. the CPUs don't seem to go to 100%, but the adjustment process seems relatively slow. The mouse cursor is also sluggish. Reinstalled the OS twice, but not because of this issue and the problem seems to persist. ProblemType: Bug DistroRelease: Ubuntu 11.04 Package: gnome-power-manager 2.32.0-2ubuntu2.1 ProcVersionSignature: Ubuntu 2.6.38-11.48-generic 2.6.38.8 Uname: Linux 2.6.38-11-generic x86_64 Architecture: amd64 Date: Sun Sep 11 15:29:02 2011 GnomeSessionIdleInhibited: No GnomeSessionInhibitors: None GnomeSessionSuspendInhibited: No InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427) MachineType: Dell Inc. Latitude E5410 ProcEnviron: LANGUAGE=en_US:en LANG=en_US.UTF-8 SHELL=/bin/bash ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-11-generic root=UUID=0dfaacc9-c19d-425b-963d-dabb87ae18bc ro quiet splash vt.handoff=7 SourcePackage: gnome-power-manager UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 01/28/2011 dmi.bios.vendor: Dell Inc. dmi.bios.version: A09 dmi.board.name: 05C67D dmi.board.vendor: Dell Inc. dmi.board.version: A00 dmi.chassis.type: 9 dmi.chassis.vendor: Dell Inc. dmi.modalias: dmi:bvnDellInc.:bvrA09:bd01/28/2011:svnDellInc.:pnLatitudeE5410:pvr0001:rvnDellInc.:rn05C67D:rvrA00:cvnDellInc.:ct9:cvr: dmi.product.name: Latitude E5410 dmi.product.version: 0001 dmi.sys.vendor: Dell Inc. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-power-manager/+bug/847001/+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
