Re: 2.6.25-rc1 regression - IBM ACPI backlight

From: Lukas Hejtmanek
Date: Fri Feb 15 2008 - 06:02:33 EST


On Thu, Feb 14, 2008 at 10:24:52AM -0200, Henrique de Moraes Holschuh wrote:
> > as of 2.6.25-rc1, there is no more /sys/class/backlight/acpi_video1 which
> > controlled LVDS backlight on Lenovo ThinkPad T61. There is still
> > acpi_video0 which seems to have sane values but echo N > brightness has no
> > effect at all.
> >
> > thinkpad_acpi module reports that ACPI controlled backlight is present.
>
> Please report this to linux-acpi @ vger . kernel . org...
>
> It is likely caused by the stuff to locate and disable the unused video
> device in the DSDT (apparently it got the wrong device?!).
>
> However, BEFORE reporting to linux-acpi, please test it in single user mode
> without X *ever* being loaded on that boot. New X disables the BIOS
> brightness changes that ACPI uses.

2.6.24 kernel has two acpi_video[01]. 2.6.25-rc1 does not, it contains only
acpi_video0 (even in text mode in single user without X being loaded) which
does not work at all.

--
Lukáš Hejtmánek
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