Implement median filtering for ALS data

Earlier, when fixed time ALS sampling was possible, mce used median
filtering to prevent adjusting display brightness due to short lived
sensor noise. The feature got removed while adapting to sensor drivers
that report only changes that are significant enough.

User timer based approach to resample waveform obtained by tracking
changes reported by the ambient light sensor. Apply 9 slot moving
window median filtering on top of that and feed the results in to
brightness evaluation state machines.

To avoid unnecessary processing, the timer is stopped when no ALS
changes are noticed i.e. when all of the history data is the same.

The median filter can be enabled via:
  mcetool --set-als-input-filter=<disabled|median>

And the sample time can be adjusted via:
  mcetool --set-als-sample-time=<50...1000>

[mce] Implement median filtering for ALS data

.depend

@@ -4,6 +4,7 @@ builtin-gconf.o:\
 	mce-dbus.h\
 	mce-io.h\
 	mce-log.h\
+	modules/filter-brightness-als.h\
 	modules/memnotify.h\
 	powerkey.h\
 
@@ -13,6 +14,7 @@ builtin-gconf.pic.o:\
 	mce-dbus.h\
 	mce-io.h\
 	mce-log.h\
+	modules/filter-brightness-als.h\
 	modules/memnotify.h\
 	powerkey.h\
 

builtin-gconf.c

@@ -25,6 +25,7 @@
 #include "powerkey.h"
 
 #include "modules/memnotify.h"
+#include "modules/filter-brightness-als.h"
 
 #include <stdlib.h>
 #include <string.h>
@@ -1082,6 +1083,18 @@ static const setting_t gconf_defaults[] =
     .type = "b",
     .def  = "true",
   },
+  {
+    // MCE_GCONF_DISPLAY_ALS_INPUT_FILTER @ modules/display.h
+    .key  = "/system/osso/dsm/display/als_input_filter",
+    .type = "s",
+    .def  = ALS_INPUT_FILTER_DEFAULT,
+  },
+  {
+    // MCE_GCONF_DISPLAY_ALS_SAMPLE_TIME @ modules/display.h
+    .key  = "/system/osso/dsm/display/als_sample_time",
+    .type = "i",
+    .def  = G_STRINGIFY(ALS_SAMPLE_TIME_DEFAULT),
+  },
   {
     // MCE_GCONF_DISPLAY_COLOR_PROFILE @ modules/display.h
     .key  = "/system/osso/dsm/display/color_profile",

modules/display.h

@@ -105,6 +105,12 @@
 /** Path to the ALS enabled GConf setting */
 #define MCE_GCONF_DISPLAY_ALS_ENABLED                   MCE_GCONF_DISPLAY_PATH "/als_enabled"
 
+/** ALS input filter GConf setting */
+#define MCE_GCONF_DISPLAY_ALS_INPUT_FILTER              MCE_GCONF_DISPLAY_PATH "/als_input_filter"
+
+/** ALS sample time GConf setting */
+#define MCE_GCONF_DISPLAY_ALS_SAMPLE_TIME               MCE_GCONF_DISPLAY_PATH "/als_sample_time"
+
 /** Path to the color profile GConf setting */
 #define MCE_GCONF_DISPLAY_COLOR_PROFILE                 MCE_GCONF_DISPLAY_PATH "/color_profile"