Add stepwise controller

This adds the ability to use stepwise curves alongside
pid control. This creates a base controller class that
pidcontroller and stepwise controller inherit from.

Note: Hysteresis to come in follow-on patch

Tested-by:
Created a stepwise controller and noticed that when it
crossed a threshold that it contributed to the pwm setting.

Change-Id: I6cf842f80eaccafc905d620970afe91e2092d568
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/pid/stepwisecontroller.cpp b/pid/stepwisecontroller.cpp
new file mode 100644
index 0000000..cea21e5
--- /dev/null
+++ b/pid/stepwisecontroller.cpp
@@ -0,0 +1,75 @@
+/*
+// Copyright (c) 2018 Intel Corporation
+//
+// 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.
+*/
+
+#include "stepwisecontroller.hpp"
+
+#include "ec/stepwise.hpp"
+#include "util.hpp"
+#include "zone.hpp"
+
+#include <algorithm>
+#include <chrono>
+#include <iostream>
+#include <map>
+#include <memory>
+#include <thread>
+#include <vector>
+
+void StepwiseController::process(void)
+{
+    // Get input value
+    float input = input_proc();
+
+    // Calculate new output
+    float output = ec::stepwise(get_stepwise_info(), input);
+
+    // Output new value
+    output_proc(output);
+
+    return;
+}
+
+std::unique_ptr<Controller> StepwiseController::CreateStepwiseController(
+    ZoneInterface* owner, const std::string& id,
+    const std::vector<std::string>& inputs, const ec::StepwiseInfo& initial)
+{
+    // StepwiseController currently only supports precisely one input.
+    if (inputs.size() != 1)
+    {
+        return nullptr;
+    }
+
+    auto thermal = std::make_unique<StepwiseController>(id, inputs, owner);
+
+    ec::StepwiseInfo& info = thermal->get_stepwise_info();
+
+    info = initial;
+
+    return thermal;
+}
+
+float StepwiseController::input_proc(void)
+{
+    double value = _owner->getCachedValue(_inputs.at(0));
+    return static_cast<float>(value);
+}
+
+void StepwiseController::output_proc(float value)
+{
+    _owner->addRPMSetPoint(value);
+
+    return;
+}