Comment 56 for bug 1510344

Well there are really two problems here as I understand it.
I can however confirm that that the first problem (backlight turns on on it's own at boot) is fixed by this patch. So that's a definite improvement.

The second problem (backlight turns on on it's own after unlock) I can still reproduce. Here is my reproduce scenario.
1) Install patched u-s-d from patch in #55.
2) Turn on backlight with hotkey.
3) Shutdown machine.
4) Turn on machine.
5) Log in.
6) Turn off backlight with hotkey.
7) Lock machine (ctrl-alt-l), wait for screensaver to kick in.
8) unlock machine
9) Notice that backlight turned back on.