https://bugzilla.novell.com/show_bug.cgi?id=308264#c33
Adam Martinson changed:
What |Removed |Added
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CC| |loki1984@vfemail.net
--- Comment #33 from Adam Martinson 2007-10-08 15:56:31 MST ---
Add the X41 Tablet to the list (technically the first Lenovo Thinkpad). For
me, Fn+Home/End always works for changing the brightness, but thinkpad_acpi,
and consequently kpowersave, etc have problems with it. After installation
kpowersave claimed controlling brightness was not supported for my hardware,
and indeed the /proc/acpi/ibm/brightness and
/sys/class/backlight/thinkpad_screen interfaces were missing. grep
thinkpad_acpi /var/log/boot.msg produced:
<6>thinkpad_acpi: ThinkPad ACPI Extras v0.14
<6>thinkpad_acpi: http://ibm-acpi.sf.net/
<6>thinkpad_acpi: ThinkPad BIOS 75ET35WW (1.06 ), EC 75HT18WW-1.00
<6>thinkpad_acpi: IBM ThinkPad X41 Tablet
<3>thinkpad_acpi: CMOS NVRAM (5) and EC (0) do not agree on display brightness
level
It seems that Fn+Home/End use the NVRAM interface, and this works even in the
BIOS before the OS is loaded. If you make a note of the EC setting, reboot,
and before the OS loads, use Fn+Home/End to make the NVRAM setting match the
EC setting, then the thinkpad_acpi module will load without errors. You can
also use Fn+Home/End to change the brightness to the same level as the EC on a
running system, and then reinsert the thinkpad_acpi module. After this the
/sys and /proc interfaces will be there, and everything works fine until you
use Fn+Home/End to change the brightness. As soon as you do, cat
/proc/acpi/ibm/brightness returns:
level: unreadable
cat /sys/class/backlight/thinkpad_screen/actual_brightness returns:
-5
If you use Fn+Home/End to change it the brightness back, then you can use the
/proc and /sys interfaces again, and everything works normally. Using the
/proc and /sys interfaces to control the brightness properly updates both the
NVRAM and EC, but Fn+Home/End only update the NVRAM. Hopefully this info is
helpful. ~Loki
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