Problem with LCD backlight remaining on during ACPI sleep

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Revision as of 05:56, 14 May 2005 by 69.142.223.199 (Talk)

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Problem description

On some models the LCD backlight remains on during ACPI sleep.

Affected Models

(according to the relevant bug on the Kernel bug tracker (bug 2576))

ACPI Daemon Solution

The T30 ACPI Sleeping page describes in detail how to use an acpi event handler to sleep the T30 automatically when the lid is closed or Fn-F4 is triggered. This is the proper method for sleeping your T30 when using APCI.

Partial solution

If the ThinkPad has a radeon video chip, then switching off the light with the command

 radeontool light off

will work, but only in a text-mode virtual terminal. If X is running, the light apparently comes back on when the kernel switches to text mode prior to sleeping. The solution in that case it to switch to a text mode console first.

I use the following script to suspend my machine. The hwclock lines compensate for the clock running at double speed during suspend (this is fixed in the 2.6.11 release candidate kernels, various distributions may backport the fix).

logger "Software suspend to ram."
sync
FGCONSOLE=`fgconsole`
/sbin/hwclock --systohc
chvt 1
radeontool light off
echo -n 3 >/proc/acpi/sleep
/sbin/hwclock --adjust
/sbin/hwclock --hctosys
logger "Woke up from suspend."
radeontool light on
chvt $FGCONSOLE

Improvements are clearly possible. :-)