https://bugzilla.kernel.org/show_bug.cgi?id=89741
Bug ID: 89741
Summary: Backlight control not working on Acer Aspire 5742
Product: ACPI
Version: 2.5
Kernel Version: 3.18.0-031800-generic
Hardware: Intel
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Power-Video
Assignee: [email protected]
Reporter: [email protected]
Regression: No
Acer Aspire 5742 ("Version: V1.19" from dmidecode)
On 3.16.0-28-generic and 3.18.0-031800-generic backlight control won't work
until "acpi_osi=" is added to the kernel boot params.
Other acpi_backlight or acpi_osi settings didn't have any effect.
$ ls /sys/class/backlight
acpi_video0 intel_backlight
The one that actually changes the brightness is "intel_backlight".
Without "acpi_osi=" acpi_listen detected something like below upon brightness
adjustment keypresses:
video/brightnessdown BRTDN 00000087 00000000
PNP0C14:01 000000bc 00000000
video/switchmode VMOD 00000080 00000000 K
video/brightnessup BRTUP 00000086 00000000
PNP0C14:01 000000bc 00000000
With "acpi_osi=" acpi_listen detects the following:
PNP0C14:01 000000bc 00000000
PNP0C14:01 000000bc 00000000
video/switchmode VMOD 00000080 00000000 K
Also,
# cat /var/log/Xorg.0.log | grep backlight
[ 29.553] (--) intel(0): Found backlight control interface acpi_video0 (type
'firmware') for output LVDS1
There's a similar bug related to Asus - #70241
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