From 9ae5a34d17b1134b0dd88457d3efe4745ee4e1fe Mon Sep 17 00:00:00 2001
From: "Arun Kumar K.R" <akumarkr@codeaurora.org>
Date: Wed, 23 Aug 2017 13:46:03 +0530
Subject: [PATCH] liblights: Enable button backlight conditionally

Check for the existence of button backlight node before
enabling that in the HAL.

Change-Id: I66828d67dbabffdb694da55d4a3d12246fb7a66f
Crs-fixed: 2093165
---
 liblight/lights.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/liblight/lights.c b/liblight/lights.c
index 3b5068cf..15db827b 100644
--- a/liblight/lights.c
+++ b/liblight/lights.c
@@ -361,8 +361,14 @@ static int open_lights(const struct hw_module_t* module, char const* 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))
-        set_light = set_light_buttons;
+    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