Bug#830814: ThinkPad x260 keyboard backlight state not restored

[Joonas Kylmälä]

Package: gnome-settings-daemon
Version: 3.20.1-2
Severity: normal

When I resume Lenovo ThinkPad x260 from resume the keyboard
backlight's state doesn't get restored. So for example if the keyboard
is off (brightness is 0, the scale is 0-2) when going to sleep then
when resuming the keyboard backlight will be turned on (brightness =
1). So also if the brightness = 2 when going to sleep it will be
changed to 1 when resuming. I already faced this same bug in the
Fedora GNU/Linux distribution and filed the bug to
<https://bugzilla.redhat.com/show_bug.cgi?id=1348156>. There might be
some useful info to solve this problem.

In ubuntu they have made a patch to the same problem (included already
to Debian sid):
<https://code.launchpad.net/~3v1n0/unity-settings-daemon/kbd-brightness-update>.
And the bug report for this patch:
<https://bugs.launchpad.net/dell-sputnik/+bug/1510344>. But for
ThinkPad 260 it didn't work.

Quote from Redhat Bugzilla:

"For me, x260 thinkpad, changing the line in gsd-power-manger.c to
         if (manager->priv->kbd_brightness_now < 0) {
didn't fix the problem."

"So the bug in my case is not in that particular piece of code because
it sets the kb backlight to max and for me it sets it to 1 (my kb
backlight is in scale of 0-2). It sets it to 1 nevertheless if it's
before going to sleep 0 or 2."

The ThinkPad x260's keyboard backlight is controlled with the module
thinkpad_acpi, in case that the bug might be there.

System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.6.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)