Some more information: It looks like the default ACPI backlight support
is mis-detecting the range of levels:
[EMAIL PROTECTED]:~# cat /sys/class/backlight/acpi_video0/max_brightness
5
These fake levels 0 to 5 correspond to real levels 1 to 6, omitting the
real minimum (0) and maximum(7).
If I add the backlight_enable=1 module parameter to thinkpad_acpi
("enable thinkpad-specific acpi support despite the fact there seems to
be working generic acpi support"), I get a new entry in sysfs,
/sys/class/backlight/thinkpad_screen/ - this one correctly reports
max_brightness as 7 and allows setting the brightness to the missing
levels.
So, perhaps the real bug is in whatever the default kernel acpi support
uses to decide on the number of levels?
--
Max brightness is not max brightness
https://bugs.launchpad.net/bugs/203096
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