presence: Add redundancy policy interface

Add a redundancy policy interface class.  Redundancy policies
introduce the concept of multiple presence sensors for a given
fan.  A redundancy model implementation determines how the
distinct sensors making up the redundancy set are controlled
and how their feedbacks determine the overall fan presence state
reflected in the inventory.

Change-Id: Ibb5f71b3189dbb253bb669691e8016cda83a6ebb
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>

1 files changed, 110 insertions, 0 deletions

diff --git a/presence/rpolicy.hpp b/presence/rpolicy.hpp
new file mode 100644
index 0000000..34beb77
--- /dev/null
+++ b/presence/rpolicy.hpp
@@ -0,0 +1,110 @@
+#pragma once
+
+#include "fan.hpp"
+
+namespace phosphor
+{
+namespace fan
+{
+namespace presence
+{
+
+/**
+ * @class RedundancyPolicy
+ * @brief Redundancy policy interface.
+ *
+ * Provide concrete implementations of RedundancyPolicy to realize
+ * new redundancy logic.
+ *
+ * A fan can have multiple ways to detect whether or not it is present.
+ * The redundancy policy encapsulates the logic to aggregate those
+ * inputs into a single yes or no the fan is present.
+ */
+class RedundancyPolicy
+{
+    public:
+        RedundancyPolicy(const RedundancyPolicy&) = default;
+        RedundancyPolicy& operator=(const RedundancyPolicy&) = default;
+        RedundancyPolicy(RedundancyPolicy&&) = default;
+        RedundancyPolicy& operator=(RedundancyPolicy&&) = default;
+        virtual ~RedundancyPolicy() = default;
+
+        /**
+         * @brief Construct a new Redundancy Policy.
+         *
+         * @param[in] fan - The fan associated with this policy.
+         */
+        explicit RedundancyPolicy(const Fan& f) : fan(f) {}
+
+        /**
+         * @brief stateChanged
+         *
+         * Typically invoked by presence sensors to signify
+         * a change of presence.  Implementations should update
+         * the inventory and execute their policy logic.
+         *
+         * @param[in] present - The new state of the sensor.
+         */
+        virtual void stateChanged(bool present) = 0;
+
+        /**
+         * @brief monitor
+         *
+         * Implementations should start monitoring the sensors
+         * associated with the fan.
+         */
+        virtual void monitor() = 0;
+
+    protected:
+        /** @brief Fan name and inventory path. */
+        const Fan& fan;
+};
+
+/**
+ * @class PolicyAccess
+ * @brief Policy association.
+ *
+ * PolicyAccess can be used to associate a redundancy policy
+ * with something else.
+ *
+ * Wrap the type to be associated with a policy with PolicyAccess.
+ *
+ * @tparam T - The type to associate with a redundancy policy.
+ * @tparam Policy - An array type where the policy is stored.
+ */
+template <typename T, typename Policy>
+class PolicyAccess : public T
+{
+    public:
+        PolicyAccess() = default;
+        PolicyAccess(const PolicyAccess&) = default;
+        PolicyAccess& operator=(const PolicyAccess&) = default;
+        PolicyAccess(PolicyAccess&&) = default;
+        PolicyAccess& operator=(PolicyAccess&&) = default;
+        ~PolicyAccess() = default;
+
+        /**
+         * @brief Construct a new PolicyAccess wrapped object.
+         *
+         * @param[in] index - The array index in Policy.
+         * @tparam Args - Forwarded to wrapped type constructor.
+         */
+        template <typename...Args>
+        PolicyAccess(size_t index, Args&&...args) :
+            T(std::forward<Args>(args)...), policy(index) {}
+
+    private:
+        /**
+         * @brief Get the associated policy.
+         */
+        RedundancyPolicy& getPolicy() override
+        {
+            return *Policy::get()[policy];
+        }
+
+        /** The associated policy index. */
+        size_t policy;
+};
+} // namespace presence
+} // namespace fan
+} // namespace phosphor