ipmi: Break circular dependency between IpmiDD and IpmiRP

Previously IpmiDD depended on IpmiRP to acquire IpmiRP's message queue
for IpmiDD to enqueue hardware state change events. IpmiRP in-turn
depends on IpmiDD for shutdown event handling, calling through
IpmiDD::handleShutdown() in IpmiRP::shutdownNow().

Break the circular dependency by asynchronously publishing hardware
state change events from IpmiDD on a queue owned by IpmiDD. IpmiRP
consumes messages from IpmiDD's event queue and republishes them on its
own internal queue for consumption by the state management task. This is
a little inefficient but provides for greater design clarity in the face
of a lack of a select() or poll() style interface that would allow
listening for messages on multiple message queues.

Change-Id: I3c3c3209d515ec9e90c04630779624bf85e953b1
Signed-off-by: Andrew Jeffery <andrewrj@au1.ibm.com>
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/65936
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP Build CI <op-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP HW <op-hw-jenkins+hostboot@us.ibm.com>
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Reviewed-by: Corey V. Swenson <cswenson@us.ibm.com>
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>

1 files changed, 20 insertions, 1 deletions

diff --git a/src/usr/ipmi/ipmidd.H b/src/usr/ipmi/ipmidd.H
index cb72d0076..ef6ed814f 100644
--- a/src/usr/ipmi/ipmidd.H
+++ b/src/usr/ipmi/ipmidd.H
@@ -5,7 +5,7 @@
 /*                                                                        */
 /* OpenPOWER HostBoot Project                                             */
 /*                                                                        */
-/* Contributors Listed Below - COPYRIGHT 2011,2016                        */
+/* Contributors Listed Below - COPYRIGHT 2011,2018                        */
 /* [+] International Business Machines Corp.                              */
 /*                                                                        */
 /*                                                                        */
@@ -112,6 +112,15 @@ class IpmiDD
     void handleShutdown(void);
 
     /**
+     * @brief Get the queue on which IpmiDD publishes hardware events
+     *
+     * The events on the queue are consumed by IpmiRP. This "publish" approach
+     * avoids circular dependencies between the two components.
+     */
+    msg_q_t eventQueue(void)
+        { return iv_eventQ; }
+
+    /**
      * @brief Constructor
      *
      * @parm void
@@ -156,6 +165,16 @@ class IpmiDD
      */
     bool iv_eagains;
 
+    /**
+     * @brief Publishes changes to device state
+     *
+     * To clarify, IpmiDD does not consume any messages from this queue. The
+     * queue exists purely for the purpose of another component to consume IPMI
+     * hardware events (currently, IpmiRP). IpmiDD performs an asynchronous
+     * msg_send() to deliver the events to the listening task.
+     */
+    msg_q_t iv_eventQ;
+
     // Disallow copying this class.
     IpmiDD& operator=(const IpmiDD&);
     IpmiDD(const IpmiDD&);