Button Backlight Control

NOTE: This does not affect XOS 8.0 and newer.

We made a new implementation of button backlight control.

It is relatively easy to set it up, here we'll show you how to do that.

First create the file xoshw/ButtonBacklightControl.java in your device tree with following content:

/*
 * Copyright (C) 2016-2017 halogenOS
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.halogenos.hardware.buttons;

import org.halogenos.hardware.buttons.IButtonBacklightControl;

/**
 * This class is supposed to control button backlight
 */
public class ButtonBacklightControl extends IButtonBacklightControl {
    
    public ButtonBacklightControl() {
        
    }

}

Inside of public ButtonBacklightControl()... you will have to specify some things which are device-specific. First of all, the CONTROL_TYPE needs to be specified.

Control type	Description
CONTROL_TYPE = CONTROL_TYPE_FULL	Brightness can be changed seamlessly.
CONTROL_TYPE = CONTROL_TYPE_PARTIAL	Only 3 brightness modes, On, Dimmed and Off.
CONTROL_TYPE = CONTROL_TYPE_SWITCH	Backlight can only be turned on and off, no brightness change is possible.
CONTROL_TYPE = CONTROL_TYPE_NONE	No backlight. If you don't have backlight, you don't need this file, CONTROL_TYPE_NONE would be default.

Then you will have some optional things which you can also set:

Config variable	Description
BUTTON_BACKLIGHT_PATH	The path to the button backlight control folder, where the control files are stored. Default is /sys/class/leds/button-backlight/ and should work on any device.
BUTTON_BACKLIGHT_PATHS	Array of paths
MAXIMUM_BRIGHTNESS	In case you have to specify the brightness manually, specify it here. This value is usually auto-detected.

You can see an example here: https://github.com/halogenOS/android_device_oneplus_oneplus2/blob/XOS-7.1/xoshw/ButtonBacklightControl.java