Add support for fixed time brightness fading

Previously display brightness fading was done using constant velocity
or in constant time without considering the type of transition that
was taking place. This made large changes like changing brightness
settings or display dimming take a long time and/or easy to miss.

Now separate fade durations are used when:
- blanking screen
- unblanking screen
- dimming screen
- other display state changes
- adjusting to ambient light / brightness setting changes

The values can be changed via mcetool options
      --set-brightness-fade-def=<msecs>
      --set-brightness-fade-dim=<msecs>
      --set-brightness-fade-als=<msecs>
      --set-brightness-fade-blank=<msecs>
      --set-brightness-fade-unblank=<msecs>

Setting a value to zero disables fading and immediate transition is made.

Also prefers direct sysfs manipulation for brightness control over using
android hal via libhybris since the latter introduces some overhead and
does not provide a way to read current backlight brightness level.

[mce] Add support for fixed time brightness fading. Fixes JB#21713

builtin-gconf.c

@@ -1228,6 +1228,36 @@ static const setting_t gconf_defaults[] =
     .type = "i",
     .def  = "30",
   },
+  {
+    // MCE_GCONF_BRIGHTNESS_FADE_DEF @ modules/display.h
+    .key  = "/system/osso/dsm/display/brightness_fade_def",
+    .type = "i",
+    .def  = "150",
+  },
+  {
+    // MCE_GCONF_BRIGHTNESS_FADE_DIM @ modules/display.h
+    .key  = "/system/osso/dsm/display/brightness_fade_dim",
+    .type = "i",
+    .def  = "1000",
+  },
+  {
+    // MCE_GCONF_BRIGHTNESS_FADE_ALS @ modules/display.h
+    .key  = "/system/osso/dsm/display/brightness_fade_als",
+    .type = "i",
+    .def  = "600",
+  },
+  {
+    // MCE_GCONF_BRIGHTNESS_FADE_BLANK @ modules/display.h
+    .key  = "/system/osso/dsm/display/brightness_fade_blank",
+    .type = "i",
+    .def  = "100",
+  },
+  {
+    // MCE_GCONF_BRIGHTNESS_FADE_UNBLANK @ modules/display.h
+    .key  = "/system/osso/dsm/display/brightness_fade_unblank",
+    .type = "i",
+    .def  = "90",
+  },
   {
     // MCE_GCONF_TK_AUTO_BLANK_DISABLE_PATH @ tklock.h
     .key  = "/system/osso/dsm/locks/tklock_blank_disable",

inifiles/mce.ini

@@ -191,52 +191,6 @@ BacklightFadeInTime=250
 #                                           625, 750, 875, 1000
 BacklightFadeOutTime=1000
 
-[Display]
-
-# Policy for display brightness increase
-# Note: for displays that use hardware-driven fading this setting
-#       does not have any effect
-#
-# direct - Instantly switch to the new brightness level
-# steptime - Fade to the new value with fixed step-time
-#             (larger difference in brightness == longer fadetime)
-# constanttime - Fade to the new value with constant time
-BrightnessIncreasePolicy=constanttime
-
-# Step-time for brightness increase
-#
-# Steptime in milliseconds, default 5;
-#                           valid values: 5, 10, 20, 30, 40, 50
-StepTimeIncrease=5
-
-# Constant time for brightness increase
-#
-# Constant time in milliseconds, default: 2000
-#                           valid values: 2000-5000
-ConstantTimeIncrease=2000
-
-# Policy for display brightness decrease
-# Note: for displays that use hardware-driven fading this setting
-#       does not have any effect
-#
-# direct - Instantly switch to the new brightness level
-# steptime - Fade to the new value with fixed step-time
-#             (larger difference in brightness == longer fadetime)
-# constanttime - Fade to the new value with constant time
-BrightnessDecreasePolicy=constanttime
-
-# Step-time for brightness decrease
-#
-# Steptime in milliseconds, default 10;
-#                           valid values: 5, 10, 20, 30, 40, 50
-StepTimeDecrease=10
-
-# Constant time for brightness decrease
-#
-# Constant time in milliseconds, default: 3000
-#                           valid values: 2000-5000
-ConstantTimeDecrease=3000
-
 [LED]
 
 # A list of all pattern names that should be configured