https://bugzilla.kernel.org/show_bug.cgi?id=72491
Bug ID: 72491
Summary: acpi backlight does not expose full brightness on
Haswell-ULT
Product: ACPI
Version: 2.5
Kernel Version: 3.13.6-1-ARCH
Hardware: All
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Config-Other
Assignee: acpi_config-ot...@kernel-bugs.osdl.org
Reporter: nico-bugzilla.kernel....@schottelius.org
Regression: No
When trying to increase the backlight to the maximum via acpi, it only reaches
765 of 937 as seen in the intel driver.
How to reproduce:
% xbacklight -set 100
% cat
/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight/brightness
765
% cat
/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight/max_brightness
937
echo'ing 937 > the brightness file increases the backlight a lot and imho this
maximum value should be exposed via ACPI.
This is a follow up of a bug reported at x.org:
https://bugs.freedesktop.org/show_bug.cgi?id=75085
Background information:
Lenovo Yoga 2 Pro
[18:50] artist:intel_backlight% lspci
00:00.0 Host bridge: Intel Corporation Haswell-ULT DRAM Controller (rev 09)
00:02.0 VGA compatible controller: Intel Corporation Haswell-ULT Integrated
Graphics Controller (rev 09)
00:03.0 Audio device: Intel Corporation Device 0a0c (rev 09)
00:04.0 Signal processing controller: Intel Corporation Device 0a03 (rev 09)
00:14.0 USB controller: Intel Corporation Lynx Point-LP USB xHCI HC (rev 04)
00:16.0 Communication controller: Intel Corporation Lynx Point-LP HECI #0 (rev
04)
00:1b.0 Audio device: Intel Corporation Lynx Point-LP HD Audio Controller (rev
04)
00:1c.0 PCI bridge: Intel Corporation Lynx Point-LP PCI Express Root Port 1
(rev e4)
00:1d.0 USB controller: Intel Corporation Lynx Point-LP USB EHCI #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation Lynx Point-LP LPC Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation Lynx Point-LP SATA Controller 1
[AHCI mode] (rev 04)
00:1f.3 SMBus: Intel Corporation Lynx Point-LP SMBus Controller (rev 04)
00:1f.6 Signal processing controller: Intel Corporation Lynx Point-LP Thermal
(rev 04)
01:00.0 Network controller: Intel Corporation Wireless 7260 (rev 6b)
[18:52] artist:intel_backlight% X -version
X.Org X Server 1.15.0
Release Date: 2013-12-27
X Protocol Version 11, Revision 0
Build Operating System: Linux 3.12.5-1-ARCH x86_64
Current Operating System: Linux artist 3.13.6-1-ARCH #1 SMP PREEMPT Fri Mar 7
22:47:48 CET 2014 x86_64
Kernel command line: BOOT_IMAGE=/vmlinuz-linux root=/dev/mapper/root rw
cryptdevice=/dev/sda3:root quiet
Build Date: 09 January 2014 08:47:24AM
Current version of pixman: 0.32.4
Before reporting problems, check http://wiki.x.org
to make sure that you have the latest version.
[18:53] artist:intel_backlight% pacman -Q | grep -e xorg -e "^linux "
linux 3.13.6-1
xorg-bdftopcf 1.0.4-1
xorg-font-util 1.3.0-1
xorg-font-utils 7.6-3
xorg-fonts-100dpi 1.0.1-4
xorg-fonts-75dpi 1.0.3-1
xorg-fonts-alias 1.0.3-1
xorg-fonts-encodings 1.0.4-3
xorg-fonts-misc 1.0.1-2
xorg-luit 1.1.1-2
xorg-mkfontdir 1.0.7-1
xorg-mkfontscale 1.1.1-1
xorg-server 1.15.0-5
xorg-server-common 1.15.0-5
xorg-server-devel 1.15.0-5
xorg-server-xnest 1.15.0-5
xorg-setxkbmap 1.3.0-1
xorg-util-macros 1.18.0-1
xorg-xauth 1.0.8-1
xorg-xbacklight 1.2.0-1
xorg-xdpyinfo 1.3.1-1
xorg-xev 1.2.1-1
xorg-xinit 1.3.3-3
xorg-xinput 1.6.1-1
xorg-xkbcomp 1.2.4-1
xorg-xkill 1.0.4-1
xorg-xrandr 1.4.1-1
xorg-xrdb 1.1.0-1
xorg-xset 1.2.3-1
xorg-xsetroot 1.1.1-1
xorg-xwd 1.0.6-1
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