[ltp] RFC : a hotkey, backlight, and bluetooth driver for SL series thinkpads

[Alexandre Rostovtsev]

Please see if the following works.
Make sure lenovo-sl-laptop is loaded with the "control_backlight=1"
module parameter
echo 0 > /sys/module/video/parameters/brightness_switch_enabled
and then restart the X server

The problem is that the ACPI video driver implements its own
brightness switch mechanism, driven by ACPI events; except it doesn't
work quite right, because the SL series uses the ACPI interface in
non-standard ways. I implemented backlight brightness by reading from
the hkey embedded controller. So if you allow the ACPI brightness
switch, each time you press the brightness change key, both drivers
try to change the brightness, and that can make the screen skip some
brightness levels.

-Alexandre