https://bugzilla.kernel.org/show_bug.cgi?id=55701
Summary: Backlight control not functioning anymore on Acer
Aspire V5 since kernel 3.7
Product: ACPI
Version: 2.5
Kernel Version: 3.7.x - 3.8.x
Platform: All
OS/Version: Linux
Tree: Fedora
Status: NEW
Severity: normal
Priority: P1
Component: Power-Video
AssignedTo: [email protected]
ReportedBy: [email protected]
Regression: Yes
Created an attachment (id=96051)
--> (https://bugzilla.kernel.org/attachment.cgi?id=96051)
generated with acpidump
Acer Aspire V5-571G
Fedora 18
With kernel 3.6.x on Fedora 17 the backlight control (via the Fn keys) of this
laptop functioned when adding acpi_osi=Linux acpi_backlight=vendor to the grub
command line, and I found I could also modify the backlight by echoing values
to /sys/class/backlight/intel_backlight.
Since moving to kernel 3.7 in Fedora 18 (and also now at kernel 3.8) the
backlight control doesn't function anymore, and there is no more
/sys/class/backlight/intel_backlight file, only an acpi_video0 file. Echoing
to that file doesn't change anything to the backlight.
I've tried with various values of acpi_osi, but none work:
- with no value given: only /sys/class/backlight/acpi_video0
- with acpi_osi=Linux acpi_backlight=vendor: /sys/class/backlight is empty
- with acpi_osi=Linux: only /sys/class/backlight/acpi_video0
- with acpi_osi="!Windows 2012": only /sys/class/backlight/acpi_video0
I've experimented a bit further by installing old kernels and booting from
them, and found:
- kernel-3.6.11-5.fc17.x86_64.rpm: backlight control worked, intel_backlight
file present
- kernel-3.7.2-201.fc18.x86_64.rpm: backlight control doesn't work,
intel_backlight file not present
These tests are both done with 'acpi_osi=Linux acpi_backlight=vendor'. So
something was broken between kernel 3.6 and 3.7.
I'm attaching dmesg on both kernels, and acpidump.
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