Maybe we'll never know for sure, but as long as we're not missing an obvious answer then I'm fine with that.
]]>I would like to know what system component is cranking up the brightness when I open the lid.
Good question. Sadly i don't know but it seems it could also be the thinkpad-acpi kernel module (https://github.com/torvalds/linux/blob/ … d-acpi.txt). Didn't check but i wouldn't be suprised if that is even active before any actual acpi packages get installed. I am just guessing here but in my opinion it's either that or the i915 module as both include brightness controls or very maybe the BIOS but my bet would be on one of the first two.
]]>So although I now have a workaround (thank you, devuser!), the main reason I opened the thread is that I would like to know what system component is cranking up the brightness when I open the lid. I know it's not UPower and not acpi (since it wasn't even installed). How do I find out if the culprit is X, the kernel, i915, or something else?
]]>I have a T400 with integrated Intel grapics, libreboot, MATE, and lightdm. In my Devuan Jessie partition, which is quite a vanilla installation using the default kernel (version 3.16.51-3+deb8u1), I've noticed that if I turn the display brightness down, close laptop lid, then open laptop lid, brightness automatically changes itself to maximum. How can I prevent this?
Some details:
-acpi is not installed
-I have IgnoreLid=true in /etc/UPower/Upower.conf
-using i915.panel_ignore_lid=1 and i915.panel_ignore_lid=-2 kernel boot options have no effect