Brightness not changing on some devices

Question

I got problem with brightness. On most devices it works, but i got problem with Nexus 5 and SGS4. Brightness just don't changing. Here is the my function:

@Nullable
private Integer setBrightness(int brightness) {
    ContentResolver cResolver;
    if (ContextCompat.checkSelfPermission(getContext(),
            android.Manifest.permission.WRITE_SETTINGS)
            != PackageManager.PERMISSION_GRANTED) {
        if (ActivityCompat.shouldShowRequestPermissionRationale(getActivity(),
                android.Manifest.permission.WRITE_SETTINGS)) {
        } else {
            ActivityCompat.requestPermissions(getActivity(),
                    new String[]{android.Manifest.permission.WRITE_SETTINGS}, 0);
        }
        return null;
    } else {

        cResolver = getContext().getContentResolver();

        int prevBrg;
        try
        {
            Settings.System.putInt(cResolver,
                    Settings.System.SCREEN_BRIGHTNESS_MODE, Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL);
            prevBrg = Settings.System.getInt(cResolver, Settings.System.SCREEN_BRIGHTNESS);
        }
        catch (Settings.SettingNotFoundException e)
        {
            Log.e("Error", "Cannot access system brightness");
            e.printStackTrace();
            return null;
        }

        Settings.System.putInt(cResolver, Settings.System.SCREEN_BRIGHTNESS, brightness);


        return prevBrg;

    }
}

Logcat now not detecting any problems and app keeps workig. What do i do wrong?