https://bugzilla.kernel.org/show_bug.cgi?id=41672
Summary: backlight control will not work on Lenovo V570
Product: ACPI
Version: 2.5
Kernel Version: 3.1-rc3 and others
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: ACPICA-Core
AssignedTo: acpi_acpica-c...@kernel-bugs.osdl.org
ReportedBy: wf...@virginia.edu
Regression: No
No backlight options will be available on a Lenovo V570. I've tried it with
several different kernel versions including 3.1-rc3. In all cases dmesg has
the error ACPI Error: Current brightness invalid.
It appears the kernel believes the machine is multi-headed. It does the right
thing for the first head it sees and then gets the invalid brightness on the
second head which causes it to assume acpi brightness won't work. The laptop
has the standard external D-sub connector for an external monitor, but there is
nothing connected to it. In fact, if I make the ugly hack of commenting out
the multihead check in acpi_video_bus_check() then backlight control works
fine.
I'll attach the acpidump, dmesg, and ugly hack.
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