# Introduction

Swampd's primary function is to drive the fans of a system given various inputs.

# Layout

The code is broken out into modules as follows:

* `dbus` - Any read or write interface that uses dbus primarily.
* `experiments` - Small execution paths that allow for fan examination
including how quickly fans respond to changes.
* `ipmi` - Manual control for any zone is handled by receiving an IPMI message.
This holds the ipmid provider for receiving those messages and sending them
onto swampd.
* `notimpl` - These are read-only and write-only interface implementations that
can be dropped into a pluggable sensor to make it complete.
* `pid` - This contains all the PID associated code, including the zone
definition, controller definition, and the PID computational code.
* `scripts` - This contains the scripts that convert YAML into C++.
* `sensors` - This contains a couple of sensor types including the pluggable
sensor's definition.  It also holds the sensor manager.
* `sysfs` - This contains code that reads from or writes to sysfs.
* `threads` - Most of swampd's threads run in this method where there's just a
dbus bus that we manage.


# Design

One defines a series of sensors and a series of PIDs that utilize those sensors
as inputs (and outputs).

 The thermal PID

 set-point -------->|---|---> RPM
 current value ---->|___|

 The fan PID

 set-point -------->|---|---> pwm%
 current value ---->|___|

 How to get set-point for fan PIDs

 thermal-out ----->|-----|
 thermal-out ----->|     |-----> RPM
 thermal-out ----->| MAX |
 thermal-out ----->|_____|