Ubuntu
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  1. Bug #853244
  2. Comment #0

Comment 0 for bug 853244

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Alkis Georgopoulos (alkisg) wrote : Acer Aspire 5742Z brightness keys not working

In 2.6.32 (Lucid) there's an /sys/devices/virtual/backlight/acpi_video0 interface for Aspire 5742Z, and brightness hotkeys do modify the values of the files in that dir, but the actual laptop brightness isn't changed.

In 3.0.0-9 (Oneiric beta 1) there's no /sys/devices/virtual/backlight interface at all.

If I boot with acpi=off, the brightness keys correctly modify brightness, but of course I lose all other ACPI functionality.

I tried some of the other acpi-related kernel parameters (acpi_backlight=vendor etc) mentioned in
 * https://wiki.ubuntu.com/Kernel/Debugging/Backlight
 * https://wiki.ubuntu.com/DebuggingACPI
 * www.kernel.org/doc/Documentation/kernel-parameters.txt
 * http://www.lesswatts.org/projects/acpi/debug.php
to no avail, brightness only works with acpi=off or acpi=ht.

I tried the fwts tool for ACPI testing, and it produced some errors, I'm attaching the output.
I also tried playing with acpiexec, but calling the _BCM method didn't change the brightness either.

`ubuntu-bug linux` doesn't work from the oneiric beta live CD, I'll manually attach lspci etc as well.