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bertos/mware/resource.h

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+/**
+ * \file
+ * <!--
+ * This file is part of BeRTOS.
+ *
+ * Bertos is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As a special exception, you may use this file as part of a free software
+ * library without restriction.  Specifically, if other files instantiate
+ * templates or use macros or inline functions from this file, or you compile
+ * this file and link it with other files to produce an executable, this
+ * file does not by itself cause the resulting executable to be covered by
+ * the GNU General Public License.  This exception does not however
+ * invalidate any other reasons why the executable file might be covered by
+ * the GNU General Public License.
+ *
+ * Copyright 2006 Develer S.r.l. (http://www.develer.com/)
+ * All Rights Reserved.
+ * -->
+ *
+ * \brief TODO:
+ *
+ *
+ * \author Bernie Innocenti <bernie@codewiz.org>
+ * \author Stefano Fedrigo <aleph@develer.com>
+ */
+
+#ifndef MWARE_RESOURCE_H
+#define MWARE_RESOURCE_H
+
+#include <drv/timer.h> // time_t
+#include <kern/sem.h>
+
+#warning FIXME:Revise me!
+
+/*
+ * Abstract locking primitives used by host OS.
+ */
+typedef Semaphore ResourceLock;
+#define ResMan_sleep()         timer_delay(1)
+#define ResMan_time_t          mtime_t
+
+
+
+// Forward decl
+struct Observer;
+
+/**
+ * Hold context information for a resource such as an audio channel.
+ *
+ * Each driver registers one or more Resource instances with the
+ * ResMan using ResMan_Register().
+ *
+ * Clients can then allocate the resource through ResMan_Alloc()
+ * providing a desired priority and an Observer for asynchronous
+ * notification.
+ *
+ * Allocated resources can be stolen by other clients asking for a
+ * higher priority.  ResMan notifies a preemption request by invoking
+ * the Observer of the current owner.
+ *
+ * The Observer callback must take whatever action is needed to
+ * release the resource as soon as possible to avoid blocking the
+ * new owner.
+ */
+typedef struct Resource
+{
+//Private
+	/// Control access to fields below.
+	Semaphore lock;
+
+	/// Pointer to current owner's observer.  NULL if resource is free.
+	struct Observer *owner;
+
+	/// Priority of current owner (higher values mean higher priority).
+	int pri;
+
+	/// Queue of processes waiting to obtain the resource.
+	List queue;
+} Resource;
+
+/// Event sent by ResMan to owners when to request resource release.
+enum { EVENT_RELEASE = 1 };
+
+/// Try to allocate a resource \a res with priority \a pri for at most \a timeout ticks.
+bool ResMan_Alloc(Resource *res, int pri, ResMan_time_t timeout, struct Observer *releaseRequest);
+
+/// Free resource \a res.  Will eventually wake-up other queued owners.
+void ResMan_Free(Resource *res);
+
+void ResMan_Init(Resource *res);
+
+#endif /* MWARE_RESOURCE_H */