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/controller.hpp b/pid/controller.hpp
index 57ee43f..f52c412 100644
--- a/pid/controller.hpp
+++ b/pid/controller.hpp
@@ -3,57 +3,23 @@
 #include "ec/pid.hpp"
 #include "fan.hpp"
 
-#include <memory>
-#include <vector>
-
-class ZoneInterface;
+#include <string>
 
 /*
- * Base class for PID controllers.  Each PID that implements this needs to
- * provide an input_proc, setpt_proc, and output_proc.
+ * Base class for controllers.  Each controller that implements this needs to
+ * provide an input_proc, process, and output_proc.
  */
-class PIDController
-{
-  public:
-    PIDController(const std::string& id, ZoneInterface* owner) :
-        _owner(owner), _setpoint(0), _id(id)
-    {
-    }
+class ZoneInterface;
 
-    virtual ~PIDController()
-    {
-    }
+struct Controller
+{
+    virtual ~Controller() = default;
 
     virtual float input_proc(void) = 0;
-    virtual float setpt_proc(void) = 0;
+
     virtual void output_proc(float value) = 0;
 
-    void pid_process(void);
+    virtual void process(void) = 0;
 
-    std::string get_id(void)
-    {
-        return _id;
-    }
-    float get_setpoint(void)
-    {
-        return _setpoint;
-    }
-    void set_setpoint(float setpoint)
-    {
-        _setpoint = setpoint;
-    }
-
-    ec::pid_info_t* get_pid_info(void)
-    {
-        return &_pid_info;
-    }
-
-  protected:
-    ZoneInterface* _owner;
-
-  private:
-    // parameters
-    ec::pid_info_t _pid_info;
-    float _setpoint;
-    std::string _id;
+    virtual std::string get_id(void) = 0;
 };