presence: Add presence sensor interface

Prepare to extend the fan presence model to include
sensors of other types with a presence sensor interface
class.

Presence sensors can be both event driven or polled.  Provide
start and stop for the former and present for the latter.

Change-Id: Ia1b91a5e30e27fbe66c6f075e5e5ce620dac997e
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>

1 files changed, 77 insertions, 0 deletions

diff --git a/presence/psensor.hpp b/presence/psensor.hpp
new file mode 100644
index 0000000..096c96c
--- /dev/null
+++ b/presence/psensor.hpp
@@ -0,0 +1,77 @@
+#pragma once
+
+namespace phosphor
+{
+namespace fan
+{
+namespace presence
+{
+
+/**
+ * @class PresenceSensor
+ * @brief PresenceSensor interface.
+ *
+ * Provide concrete implementations of PresenceSensor to realize
+ * new presence detection methods.
+ *
+ * Note that implementations drive the inventory update process via
+ * a redundancy policy (rpolicy.hpp) - it is not enough to implement
+ * the interfaces below.
+ */
+class PresenceSensor
+{
+    public:
+        PresenceSensor(const PresenceSensor&) = default;
+        PresenceSensor& operator=(const PresenceSensor&) = default;
+        PresenceSensor(PresenceSensor&&) = default;
+        PresenceSensor& operator=(PresenceSensor&&) = default;
+        virtual ~PresenceSensor() = default;
+        PresenceSensor() = default;
+
+        /**
+         * @brief start
+         *
+         * Implementations should peform any preparation
+         * for detecting presence.  Typical implementations
+         * might register signal callbacks or start
+         * a polling loop.
+         *
+         * @return The state of the sensor.
+         */
+        virtual bool start() = 0;
+
+        /**
+         * @brief stop
+         *
+         * Implementations should stop issuing presence
+         * state change notifications.  Typical implementations
+         * might de-register signal callbacks or terminate
+         * polling loops.
+         */
+        virtual void stop() = 0;
+
+        /**
+         * @brief Check the sensor.
+         *
+         * Implementations should perform an offline (the start
+         * method has not been invoked) query of the presence
+         * state.
+         *
+         * @return The state of the sensor.
+         */
+        virtual bool present() = 0;
+
+        /**
+         * @brief Mark the sensor as failed.
+         *
+         * Implementations should log an an event if the
+         * system policy requires it.
+         *
+         * Provide a default noop implementation.
+         */
+        virtual void fail() {}
+};
+
+} // namespace presence
+} // namespace fan
+} // namespace phosphor