http://bugzilla.kernel.org/show_bug.cgi?id=12235
Summary: /sys/devices/virtual/backlight/acpi_video0/brightness
has it backwards
Product: ACPI
Version: 2.5
KernelVersion: 2.6.28-rc8
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Power-Video
AssignedTo: acpi_power-vi...@kernel-bugs.osdl.org
ReportedBy: khashayar.li...@gmail.com
Latest working kernel version:
2.6.27
Earliest failing kernel version:
probably 2.6.28-rc1, but could be later in the release candidates.
Distribution:
Ubuntu 8.10
Hardware Environment:
Asus, N20A, all intel.
Problem Description:
If the laptop loads the video module at boot time,
/sys/devices/virtual/backlight/acpi_video0/brightness is created. However, it's
all backwards, confusing applications like gnome-power-manager and the likes
(well, that basically means hal). Echoing 0 to 'brightness' raises the
backlight of this laptop to maximum. Echoing 13 to it, takes the backlight to a
minimum.
actual_brightness' seems to stay at 0 at all times.
If I disalllow the video module to be loaded at boot time, there's no backlight
interface in /sys/class/backlight/*. But, nevertheless, the xbacklight utility
and hal seem to be able to control the backlight just fine. In this latter
case, withouth the video module loaded, xbacklight & hal handle the backlight
correctly, i.e. less means lower backlight, and more means brighter backlight.
I just confirmed this problem exists with the latest git from Linus' tree, as
well as the rc8 patch.
If I remember correctly, the 2.6.27-series created an interface under
/sys/devices/platform/asus-laptop/ for controlling backlight which worked just
fine.
Please let me know what additional information to post. I'd love to have this
fixed before the 2.6.28 release.
-----
http://dl.getdropbox.com/u/175461/lspci-nnvv.output
http://dl.getdropbox.com/u/175461/dmidecode.output
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