Android 以双击亮屏为例，上层控制驱动节点的流程

1、双击屏幕时，tp报上来的事件设定为KeyEvent.KEYCODE_U，则在PhoneWindowManager中可以增加监听，只要正常上报该事件，按以下的执行则能实现双击亮屏的功能。

ALPS_R0MP1/frameworks / base/services/core/java/com/android/server/policy/PhoneWindowManager.java
 
    @Override
    public int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags) {
 
 
    ......//省略大量代码
    case KeyEvent.KEYCODE_U:{
                if (SystemProperties.getBoolean("ro.hct_double_click_brighten_screen_support", false)) {
                    result &= ~ACTION_PASS_TO_USER;
                    if (down) {
                        isWakeKey = true;
                    }
                }
                break;
            }
}

2、实现功能后则需要添加按钮控制，以达到不需要时关闭该功能后节省点的目的，UI具体实现代码如下：

ALPS_R0MP1/vendor/mediatek/proprietary/packages / apps/MtkSettings/src/com/android/settings/gestures/WakeUpSwitchController.java
 
package com.android.settings.gestures;
import android.content.Context;
import android.os.SystemProperties;
import android.os.UserHandle;
import android.provider.Settings;
 
import androidx.preference.Preference;
import androidx.preference.PreferenceScreen;
import androidx.preference.SwitchPreference;
import com.android.settings.core.TogglePreferenceController;
 
public class WakeUpSwitchController extends TogglePreferenceController {
    private final Context mContext;
    private static final int MY_USER_ID = UserHandle.myUserId();
    private final String WAKE_UP_SWITHCH_MOD = "wake_up_switch_mod";
    public WakeUpSwitchController(Context context, String preferenceKey) {
        super(context, preferenceKey);
        mContext = context;
    }
    @Override
    public boolean isChecked() {
        return Settings.System.getIntForUser(mContext.getContentResolver(),
                WAKE_UP_SWITHCH_MOD,
                0, MY_USER_ID) != 0;
    }
    @Override
    public boolean setChecked(boolean isChecked) {
        Settings.System.putIntForUser(mContext.getContentResolver(), WAKE_UP_SWITHCH_MOD,
                isChecked ? 1 : 0, MY_USER_ID);
        //通过这只prop值，来控制驱动节点
        SystemProperties.set("persist.vendor.hct.gesturewake", isChecked ? "1" : "0");
        return true;
    }
    @Override
    public int getAvailabilityStatus() {
        return SystemProperties.getBoolean("ro.hct_double_click_brighten_screen_support", false) ? AVAILABLE : UNSUPPORTED_ON_DEVICE;
    }
}

3、通过对目标prop值的监听来控制tp的节点，具体实现如下：

ALPS_R0MP1/device / mediatek/mt6779/init.mt6779.rc
 
 
#gesturewake
    chown root system /sys/bus/i2c/devices/0-0038/fts_gesture_mode  //修改节点文件所有类型
    chmod 0777 /sys/bus/i2c/devices/0-0038/fts_gesture_mode         //修改节点文件读写权限
on property:persist.vendor.hct.gesturewake=*                        //监听prop并将其写入节点(类似ContentProvider功能)
    write /sys/bus/i2c/devices/0-0038/fts_gesture_mode ${persist.vendor.hct.gesturewake}
 
 
----------
ALPS_R0MP1/device / mediatek/sepolicy/basic/non_plat/file.te
 
#gesturewake
type hct_gesture_mode, fs_type, sysfs_type;         //定义节点文件属性
 
----------
ALPS_R0MP1/device / mediatek/sepolicy/basic/non_plat/file_contexts
 
#gesturewake
/sys/bus/i2c/devices/0-0038/fts_gesture_mode u:object_r:hct_gesture_mode:s0     //定义节点文件
 
----------
ALPS_R0MP1/device / mediatek/sepolicy/basic/non_plat/property_contexts
 
#=============gesture wake==============
persist.vendor.hct.gesturewake u:object_r:system_prop:s0            //定义prop属性
 
 
----------
ALPS_R0MP1/device / mediatek/sepolicy/basic/non_plat/system_app.te
 
#gesturewake
allow system_app system_prop:property_service set;
allow system_app hct_gesture_mode:file { write read getattr open };     //允许系统app读写该prop