diff --git a/light/lights.c b/light/lights.c
index 61c6de2..d86ab97 100644
--- a/light/lights.c
+++ b/light/lights.c
@@ -1,5 +1,7 @@
 /*
- * Copyright (C) 2014 The CyanogenMod Project
+ * Copyright (C) 2014, 2017-2018 The  Linux Foundation. All rights reserved.
+ * Not a contribution
+ * Copyright (C) 2008 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,203 +16,335 @@
  * limitations under the License.
  */
 
-#include <cutils/log.h>
+
+// #define LOG_NDEBUG 0
+
+#include <log/log.h>
+#include <cutils/properties.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <pthread.h>
-#include <stdlib.h>
-#include <string.h>
+
+#include <sys/ioctl.h>
+#include <sys/types.h>
 
 #include <hardware/lights.h>
 
+#ifndef DEFAULT_LOW_PERSISTENCE_MODE_BRIGHTNESS
+#define DEFAULT_LOW_PERSISTENCE_MODE_BRIGHTNESS 0x80
+#endif
+
 /******************************************************************************/
 
-#define MAX_PATH_SIZE 80
-
-#define LED_LIGHT_OFF 0
-#define LED_LIGHT_ON 255
-
-enum {
-    ATTENTION = 0,
-    NOTIFICATION,
-    BATTERY,
-    LIGHT_MAX,
-};
-
 static pthread_once_t g_init = PTHREAD_ONCE_INIT;
 static pthread_mutex_t g_lock = PTHREAD_MUTEX_INITIALIZER;
-static struct light_state_t g_lights[LIGHT_MAX];
+static struct light_state_t g_notification;
+static struct light_state_t g_battery;
+static int g_last_backlight_mode = BRIGHTNESS_MODE_USER;
+static int g_attention = 0;
+static bool g_has_persistence_node = false;
 
-#define LCD_BRIGHTNESS_FILE "/sys/class/backlight/panel0-backlight/brightness"
+char const*const LCD_FILE
+        = "/sys/class/leds/lcd-backlight/brightness";
 
-#define GREEN_LED_BREATH_FILE "/sys/class/leds/green/breath"
-#define GREEN_LED_BRIGHTNESS_FILE "/sys/class/leds/green/brightness"
-#define GREEN_LED_DELAY_OFF_FILE "/sys/class/leds/green/delay_off"
-#define GREEN_LED_DELAY_ON_FILE "/sys/class/leds/green/delay_on"
+char const*const LCD_FILE2
+        = "/sys/class/backlight/panel0-backlight/brightness";
 
-#define RED_LED_BREATH_FILE "/sys/class/leds/red/breath"
-#define RED_LED_BRIGHTNESS_FILE "/sys/class/leds/red/brightness"
-#define RED_LED_DELAY_OFF_FILE "/sys/class/leds/red/delay_off"
-#define RED_LED_DELAY_ON_FILE "/sys/class/leds/red/delay_on"
+char const*const BUTTON_FILE
+        = "/sys/class/leds/button-backlight/brightness";
 
+char const*const PERSISTENCE_FILE
+        = "/sys/class/graphics/fb0/msm_fb_persist_mode";
+
+enum rgb_led {
+    LED_RED = 0,
+    LED_GREEN,
+    LED_BLUE,
+};
+
+char *led_names[] = {
+    "red",
+    "green",
+    "blue",
+};
 /**
  * device methods
  */
 
-void init_globals(void) {
+void init_globals(void)
+{
     // init the mutex
     pthread_mutex_init(&g_lock, NULL);
 }
 
-static int write_int(char const* path, int value) {
+static int write_int(char const* path, int value)
+{
     int fd;
     static int already_warned = 0;
 
     fd = open(path, O_RDWR);
     if (fd >= 0) {
         char buffer[20];
-        int bytes = sprintf(buffer, "%d\n", value);
-        int amt = write(fd, buffer, bytes);
+        int bytes = snprintf(buffer, sizeof(buffer), "%d\n", value);
+        ssize_t amt = write(fd, buffer, (size_t)bytes);
         close(fd);
         return amt == -1 ? -errno : 0;
     } else {
         if (already_warned == 0) {
-            ALOGE("%s: failed to open %s\n", __func__, path);
+            ALOGE("write_int failed to open %s, errno = %d\n", path, errno);
             already_warned = 1;
         }
         return -errno;
     }
 }
 
-static int is_lit(struct light_state_t const* state) {
+static bool file_exists(const char *file)
+{
+    int fd;
+
+    fd = open(file, O_RDWR);
+    if (fd < 0) {
+        ALOGE("failed to open %s, errno=%d\n", file, errno);
+        return false;
+    }
+
+    close(fd);
+    return true;
+}
+
+static int
+is_lit(struct light_state_t const* state)
+{
     return state->color & 0x00ffffff;
 }
 
-static int rgb_to_brightness(struct light_state_t const* state) {
+static int
+rgb_to_brightness(struct light_state_t const* state)
+{
     int color = state->color & 0x00ffffff;
-    return ((77 * ((color >> 16) & 0x00ff)) + (150 * ((color >> 8) & 0x00ff)) +
-            (29 * (color & 0x00ff))) >>
-           8;
+    return ((77*((color>>16)&0x00ff))
+            + (150*((color>>8)&0x00ff)) + (29*(color&0x00ff))) >> 8;
 }
 
-static int set_light_backlight(__attribute__((unused)) struct light_device_t* dev,
-                               struct light_state_t const* state) {
+static int
+set_light_backlight(struct light_device_t* dev,
+        struct light_state_t const* state)
+{
     int err = 0;
     int brightness = rgb_to_brightness(state);
-    pthread_mutex_lock(&g_lock);
-    err = write_int(LCD_BRIGHTNESS_FILE, brightness);
-    pthread_mutex_unlock(&g_lock);
-    return err;
-}
-
-static int set_light_locked(struct light_state_t const* state) {
-    int onMS, offMS;
-    int blink = 0;
-    int brightness_level;
-
-    switch (state->flashMode) {
-        case LIGHT_FLASH_TIMED:
-        case LIGHT_FLASH_HARDWARE:
-            offMS = state->flashOffMS;
-            onMS = state->flashOnMS;
-            break;
-        case LIGHT_FLASH_NONE:
-        default:
-            offMS = 0;
-            onMS = 0;
-            break;
+    unsigned int lpEnabled =
+        state->brightnessMode == BRIGHTNESS_MODE_LOW_PERSISTENCE;
+    if(!dev) {
+        return -1;
     }
 
-    if (onMS != 0 && offMS != 0) blink = 1;
-
-    if (is_lit(state))
-        brightness_level =
-            (state->color & 0xff000000) ? (state->color & 0xff000000) >> 24 : LED_LIGHT_ON;
-    else
-        brightness_level = LED_LIGHT_OFF;
-
-    if (blink) {
-        write_int(GREEN_LED_BREATH_FILE, 1);
-        write_int(GREEN_LED_DELAY_OFF_FILE, offMS);
-        write_int(GREEN_LED_DELAY_ON_FILE, onMS);
-    } else {
-        write_int(GREEN_LED_BRIGHTNESS_FILE, brightness_level);
+    pthread_mutex_lock(&g_lock);
+    // Toggle low persistence mode state
+    bool persistence_mode = ((g_last_backlight_mode != state->brightnessMode && lpEnabled) ||
+                            (!lpEnabled &&
+                            g_last_backlight_mode == BRIGHTNESS_MODE_LOW_PERSISTENCE));
+    bool cannot_handle_persistence = !g_has_persistence_node && persistence_mode;
+    if (g_has_persistence_node) {
+        if (persistence_mode) {
+            if ((err = write_int(PERSISTENCE_FILE, lpEnabled)) != 0) {
+                ALOGE("%s: Failed to write to %s: %s\n", __FUNCTION__,
+                       PERSISTENCE_FILE, strerror(errno));
+            }
+            if (lpEnabled != 0) {
+                brightness = DEFAULT_LOW_PERSISTENCE_MODE_BRIGHTNESS;
+            }
+        }
+        g_last_backlight_mode = state->brightnessMode;
     }
 
-    return 0;
-}
-
-static int handle_led_prioritized_locked(struct light_state_t const* state) {
-    if (is_lit(&g_lights[ATTENTION]))
-        return set_light_locked(&g_lights[ATTENTION]);
-    else if (is_lit(&g_lights[NOTIFICATION]))
-        return set_light_locked(&g_lights[NOTIFICATION]);
-    else
-        return set_light_locked(state);
-}
-
-static int set_light_notifications(__attribute__((unused)) struct light_device_t* dev,
-                                   struct light_state_t const* state) {
-    int err = 0;
-    pthread_mutex_lock(&g_lock);
-    g_lights[NOTIFICATION] = *state;
-    err = handle_led_prioritized_locked(state);
-    pthread_mutex_unlock(&g_lock);
-    return err;
-}
-
-static int set_light_attention(__attribute__((unused)) struct light_device_t* dev,
-                               struct light_state_t const* state) {
-    int err = 0;
-    pthread_mutex_lock(&g_lock);
-    g_lights[ATTENTION] = *state;
-    err = handle_led_prioritized_locked(state);
-    pthread_mutex_unlock(&g_lock);
-    return err;
-}
-
-static int set_light_battery(__attribute__((unused)) struct light_device_t* dev,
-                             struct light_state_t const* state) {
-    int err = 0;
-
-    if (!dev) return -1;
-
-    pthread_mutex_lock(&g_lock);
-
-    int level = (state->color & 0xff000000) >> 24;
-
-    // sanity check
-    if (level < 0)
-        level = 0;
-    else if (level > 100)
-        level = 100;
-
-    // turn led off
-    write_int(GREEN_LED_BRIGHTNESS_FILE, LED_LIGHT_OFF);
-    write_int(RED_LED_BRIGHTNESS_FILE, LED_LIGHT_OFF);
-
-    if (is_lit(state)) {
-        if (level <= 15) {
-            write_int(RED_LED_BRIGHTNESS_FILE, 255);
-        } else if (level <= 99) {
-            write_int(GREEN_LED_BRIGHTNESS_FILE, 255);
-            write_int(RED_LED_BRIGHTNESS_FILE, 255);
+    if (!err) {
+        if (!access(LCD_FILE, F_OK)) {
+            err = write_int(LCD_FILE, brightness);
         } else {
-            write_int(GREEN_LED_BRIGHTNESS_FILE, 255);
+            err = write_int(LCD_FILE2, brightness);
         }
     }
 
     pthread_mutex_unlock(&g_lock);
+    return cannot_handle_persistence ? -ENOSYS : err;
+}
+
+static int set_rgb_led_brightness(enum rgb_led led, int brightness)
+{
+    char file[48];
+
+    snprintf(file, sizeof(file), "/sys/class/leds/%s/brightness", led_names[led]);
+    return write_int(file, brightness);
+}
+
+static int set_rgb_led_timer_trigger(enum rgb_led led, int onMS, int offMS)
+{
+    char file[48];
+    int rc;
+
+    snprintf(file, sizeof(file), "/sys/class/leds/%s/delay_off", led_names[led]);
+    rc = write_int(file, offMS);
+    if (rc < 0)
+        goto out;
+
+    snprintf(file, sizeof(file), "/sys/class/leds/%s/delay_on", led_names[led]);
+    rc = write_int(file, onMS);
+    if (rc < 0)
+        goto out;
+
+    return 0;
+out:
+    ALOGD("%s doesn't support timer trigger\n", led_names[led]);
+    return rc;
+}
+
+static int set_rgb_led_hw_blink(enum rgb_led led, int blink)
+{
+    char file[48];
+
+    snprintf(file, sizeof(file), "/sys/class/leds/%s/breath", led_names[led]);
+    if (!file_exists(file))
+        snprintf(file, sizeof(file), "/sys/class/leds/%s/blink", led_names[led]);
+
+    return write_int(file, blink);
+}
+
+static int
+set_speaker_light_locked(struct light_device_t* dev,
+        struct light_state_t const* state)
+{
+    int red, green, blue;
+    int onMS, offMS;
+    unsigned int colorRGB;
+    int blink = 0;
+    int rc = 0;
+
+    if(!dev) {
+        return -1;
+    }
+
+    colorRGB = state->color;
+    red = (colorRGB >> 16) & 0xFF;
+    green = (colorRGB >> 8) & 0xFF;
+    blue = colorRGB & 0xFF;
+
+    onMS = state->flashOnMS;
+    offMS = state->flashOffMS;
+
+    if (onMS != 0 && offMS != 0)
+        blink = 1;
+
+    switch (state->flashMode) {
+        case LIGHT_FLASH_HARDWARE:
+            if (!!red)
+                rc = set_rgb_led_hw_blink(LED_RED, blink);
+            if (!!green)
+                rc |= set_rgb_led_hw_blink(LED_GREEN, blink);
+            if (!!blue)
+                rc |= set_rgb_led_hw_blink(LED_BLUE, blink);
+            /* fallback to timed blinking if breath is not supported */
+            if (rc == 0)
+                break;
+        case LIGHT_FLASH_TIMED:
+            if (!!red)
+                rc = set_rgb_led_timer_trigger(LED_RED, onMS, offMS);
+            if (!!green)
+                rc |= set_rgb_led_timer_trigger(LED_GREEN, onMS, offMS);
+            if (!!blue)
+                rc |= set_rgb_led_timer_trigger(LED_BLUE, onMS, offMS);
+            /* fallback to constant on if timed blinking is not supported */
+            if (rc == 0)
+                break;
+        case LIGHT_FLASH_NONE:
+        default:
+            rc = set_rgb_led_brightness(LED_RED, red);
+            rc |= set_rgb_led_brightness(LED_GREEN, green);
+            rc |= set_rgb_led_brightness(LED_BLUE, blue);
+            break;
+    }
+
+    ALOGD("set_speaker_light_locked mode=%d, colorRGB=%08X, onMS=%d, offMS=%d, rc=%d\n",
+            state->flashMode, colorRGB, onMS, offMS, rc);
+
+    return rc;
+}
+
+static void
+handle_speaker_battery_locked(struct light_device_t* dev)
+{
+    if (is_lit(&g_battery)) {
+        set_speaker_light_locked(dev, &g_battery);
+    } else {
+        set_speaker_light_locked(dev, &g_notification);
+    }
+}
+
+static int
+set_light_battery(struct light_device_t* dev,
+        struct light_state_t const* state)
+{
+    pthread_mutex_lock(&g_lock);
+    g_battery = *state;
+    handle_speaker_battery_locked(dev);
+    pthread_mutex_unlock(&g_lock);
+    return 0;
+}
+
+static int
+set_light_notifications(struct light_device_t* dev,
+        struct light_state_t const* state)
+{
+    pthread_mutex_lock(&g_lock);
+    g_notification = *state;
+    handle_speaker_battery_locked(dev);
+    pthread_mutex_unlock(&g_lock);
+    return 0;
+}
+
+static int
+set_light_attention(struct light_device_t* dev,
+        struct light_state_t const* state)
+{
+    pthread_mutex_lock(&g_lock);
+    if (state->flashMode == LIGHT_FLASH_HARDWARE) {
+        g_attention = state->flashOnMS;
+    } else if (state->flashMode == LIGHT_FLASH_NONE) {
+        g_attention = 0;
+    }
+    handle_speaker_battery_locked(dev);
+    pthread_mutex_unlock(&g_lock);
+    return 0;
+}
+
+static int
+set_light_buttons(struct light_device_t* dev,
+        struct light_state_t const* state)
+{
+    int err = 0;
+    if(!dev) {
+        return -1;
+    }
+    pthread_mutex_lock(&g_lock);
+    err = write_int(BUTTON_FILE, state->color & 0xFF);
+    pthread_mutex_unlock(&g_lock);
     return err;
 }
 
 /** Close the lights device */
-static int close_lights(struct light_device_t* dev) {
-    if (dev) free(dev);
-
+static int
+close_lights(struct light_device_t *dev)
+{
+    if (dev) {
+        free(dev);
+    }
     return 0;
 }
 
+
 /******************************************************************************/
 
 /**
@@ -219,27 +353,42 @@
 
 /** Open a new instance of a lights device using name */
 static int open_lights(const struct hw_module_t* module, char const* name,
-                       struct hw_device_t** device) {
-    int (*set_light)(struct light_device_t * dev, struct light_state_t const* state);
+        struct hw_device_t** device)
+{
+    int (*set_light)(struct light_device_t* dev,
+            struct light_state_t const* state);
 
-    if (strcmp(LIGHT_ID_BACKLIGHT, name) == 0)
+    if (0 == strcmp(LIGHT_ID_BACKLIGHT, name)) {
+        g_has_persistence_node = !access(PERSISTENCE_FILE, F_OK);
         set_light = set_light_backlight;
-    else if (strcmp(LIGHT_ID_NOTIFICATIONS, name) == 0)
-        set_light = set_light_notifications;
-    else if (strcmp(LIGHT_ID_ATTENTION, name) == 0)
-        set_light = set_light_attention;
-    else if (strcmp(LIGHT_ID_BATTERY, name) == 0)
+    } else if (0 == strcmp(LIGHT_ID_BATTERY, name))
         set_light = set_light_battery;
+    else if (0 == strcmp(LIGHT_ID_NOTIFICATIONS, name))
+        set_light = set_light_notifications;
+    else if (0 == strcmp(LIGHT_ID_BUTTONS, name)) {
+        if (!access(BUTTON_FILE, F_OK)) {
+          // enable light button when the file is present
+          set_light = set_light_buttons;
+        } else {
+          return -EINVAL;
+        }
+    }
+    else if (0 == strcmp(LIGHT_ID_ATTENTION, name))
+        set_light = set_light_attention;
     else
         return -EINVAL;
 
     pthread_once(&g_init, init_globals);
 
-    struct light_device_t* dev = malloc(sizeof(struct light_device_t));
+    struct light_device_t *dev = malloc(sizeof(struct light_device_t));
+
+    if(!dev)
+        return -ENOMEM;
+
     memset(dev, 0, sizeof(*dev));
 
     dev->common.tag = HARDWARE_DEVICE_TAG;
-    dev->common.version = 0;
+    dev->common.version = LIGHTS_DEVICE_API_VERSION_2_0;
     dev->common.module = (struct hw_module_t*)module;
     dev->common.close = (int (*)(struct hw_device_t*))close_lights;
     dev->set_light = set_light;
@@ -249,7 +398,7 @@
 }
 
 static struct hw_module_methods_t lights_module_methods = {
-    .open = open_lights,
+    .open =  open_lights,
 };
 
 /*
@@ -260,7 +409,7 @@
     .version_major = 1,
     .version_minor = 0,
     .id = LIGHTS_HARDWARE_MODULE_ID,
-    .name = "MSM8916 lights Module",
+    .name = "lights Module",
     .author = "Google, Inc.",
     .methods = &lights_module_methods,
-};
+};
\ No newline at end of file