platform: x86: dell-laptop: Add support for keyboard backlight

This patch adds the support for the configuration of the keyboard
backlight on supported Dell laptops.

With this patch it is possible to set:
* keyboard backlight level
* timeout after which the backlight will be automatically turned off
* input activity triggers (keyboard, touchpad, mouse) that enable the backlight
* ambient light settings

The settings are exposed via /sys/class/leds/dell::kbd_backlight/

The code is based on the newly released documentation by Dell in the
libsmbios project.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>

1 files changed, 69 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-platform-dell-laptop b/Documentation/ABI/testing/sysfs-platform-dell-laptop
new file mode 100644
index 000000000000..8c6a0b8e1131
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-platform-dell-laptop
@@ -0,0 +1,69 @@
+What:           /sys/class/leds/dell::kbd_backlight/als_enabled
+Date:           December 2014
+KernelVersion:  3.19
+Contact:        Gabriele Mazzotta <gabriele.mzt@gmail.com>,
+                Pali Rohár <pali.rohar@gmail.com>
+Description:
+                This file allows to control the automatic keyboard
+                illumination mode on some systems that have an ambient
+                light sensor. Write 1 to this file to enable the auto
+                mode, 0 to disable it.
+
+What:           /sys/class/leds/dell::kbd_backlight/als_setting
+Date:           December 2014
+KernelVersion:  3.19
+Contact:        Gabriele Mazzotta <gabriele.mzt@gmail.com>,
+                Pali Rohár <pali.rohar@gmail.com>
+Description:
+                This file allows to specifiy the on/off threshold value,
+                as reported by the ambient light sensor.
+
+What:           /sys/class/leds/dell::kbd_backlight/start_triggers
+Date:           December 2014
+KernelVersion:  3.19
+Contact:        Gabriele Mazzotta <gabriele.mzt@gmail.com>,
+                Pali Rohár <pali.rohar@gmail.com>
+Description:
+                This file allows to control the input triggers that
+                turn on the keyboard backlight illumination that is
+                disabled because of inactivity.
+                Read the file to see the triggers available. The ones
+                enabled are preceded by '+', those disabled by '-'.
+
+                To enable a trigger, write its name preceded by '+' to
+                this file. To disable a trigger, write its name preceded
+                by '-' instead.
+
+                For example, to enable the keyboard as trigger run:
+                    echo +keyboard > /sys/class/leds/dell::kbd_backlight/start_triggers
+                To disable it:
+                    echo -keyboard > /sys/class/leds/dell::kbd_backlight/start_triggers
+
+                Note that not all the available triggers can be configured.
+
+What:           /sys/class/leds/dell::kbd_backlight/stop_timeout
+Date:           December 2014
+KernelVersion:  3.19
+Contact:        Gabriele Mazzotta <gabriele.mzt@gmail.com>,
+                Pali Rohár <pali.rohar@gmail.com>
+Description:
+                This file allows to specify the interval after which the
+                keyboard illumination is disabled because of inactivity.
+                The timeouts are expressed in seconds, minutes, hours and
+                days, for which the symbols are 's', 'm', 'h' and 'd'
+                respectively.
+
+                To configure the timeout, write to this file a value along
+                with any the above units. If no unit is specified, the value
+                is assumed to be expressed in seconds.
+
+                For example, to set the timeout to 10 minutes run:
+                    echo 10m > /sys/class/leds/dell::kbd_backlight/stop_timeout
+
+                Note that when this file is read, the returned value might be
+                expressed in a different unit than the one used when the timeout
+                was set.
+
+                Also note that only some timeouts are supported and that
+                some systems might fall back to a specific timeout in case
+                an invalid timeout is written to this file.