https://bugzilla.kernel.org/show_bug.cgi?id=34582
Summary: ACPI/backlight causes black screen on boot (etc!)
Product: ACPI
Version: 2.5
Kernel Version: 2.6.39-rc5
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Power-Video
AssignedTo: [email protected]
ReportedBy: [email protected]
Regression: No
Created an attachment (id=56732)
--> (https://bugzilla.kernel.org/attachment.cgi?id=56732)
Dmesg
This is a HP Touchsmart tm2 2010eg.
The bug splits in multiple parts, all having to do with faulty ACPI and
backlight support. Users with KMS enabled/vgaswitcheroo enabled experience all
of them. Users without KMS and/or vgaswitcheroo might experience only parts of.
---
With KMS on the screen turns blank on boot and backlight has to be brought back
on through the laptop-mounted control keys. This happens at about 5 to 7.9
seconds in the attached dmesg, I can't tell exactly where, because it passes by
to quickly.
---
The brightness interface in /sys/class/backlight/acpi_video*/brightness does
not sync with the real brightness, which in turn can only set by the hardware
keys.
If the brightness is decreased by those keys, the value in ./brightness
decreases, too. Same with increasing it. But the value has not the correct
absolute value. Values can be written to ./brightness and are accepted, so that
the read-out value changes, but the real brightness does not change.
---
xrandr rotating the screen to "Normal" rotation resets the backlight to 10.
This is about the only "software driven" way that the brightness ever changes.
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