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bertos/mware/event.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 2003, 2004, 2005 Develer S.r.l. (http://www.develer.com/)
+ * Copyright 1999, 2001, 2003 Bernie Innocenti <bernie@codewiz.org>
+ * -->
+ *
+ * \defgroup event_handling Event handling module
+ * \ingroup core
+ * \{
+ *
+ * \brief Events handling
+ *
+ * This module implements a common system for executing
+ * a user defined action calling a hook function.
+ *
+ *
+ *  Device drivers often need to wait the completion of some event, usually to
+ *  allow the hardware to accomplish some asynchronous task.
+ *
+ *  A common approach is to place a busy wait with a cpu_relax() loop that invokes
+ *  the architecture-specific instructions to say that we're not doing much with
+ *  the processor.
+ *
+ *  Although technically correct, the busy loop degrades the overall system
+ *  performance in presence of multiple processes and power consumption.
+ *
+ *  With the kernel the natural way to implement such wait/complete mechanism is to
+ *  use signals via sig_wait() and sig_post()/sig_send().
+ *
+ *  However, signals in BeRTOS are only available in presence of the kernel (that
+ *  is just a compile-time option). This means that each device driver must provide
+ *  two different interfaces to implement the wait/complete semantic: one with the
+ *  kernel and another without the kernel.
+ *
+ *  The purpose of the completion events is to provide a generic interface to
+ *  implement a synchronization mechanism to block the execution of code until a
+ *  specific event happens.
+ *
+ *  This interface does not depend on the presence of the kernel and it
+ *  automatically uses the appropriate event backend to provide the same
+ *  behaviour with or without the kernel.
+ *
+ *  Example usage (wait for a generic device driver initialization):
+ *  \code
+ *  static Event e;
+ *
+ *  static void irq_handler(void)
+ *  {
+ *      // Completion event has happened, resume the execution of init()
+ *      event_do(&e);
+ *  }
+ *
+ *  static void init(void)
+ *  {
+ *      // Declare the generic completion event
+ *      event_initGeneric(&e);
+ *      // Submit the hardware initialization request
+ *      async_hw_init();
+ *      // Wait for the completion of the event
+ *      event_wait(&e);
+ *  }
+ *  \endcode
+ *
+ * Example usage: wait multiple generic events via event_select()
+ * \code
+ * Event ev1;
+ * Event ev2;
+ *
+ * void event_notifier(void)
+ * {
+ *      Event *evs[] = { &ev1, &ev2 };
+ *
+ *      event_initGeneric(&ev1);
+ *      event_initGeneric(&ev2);
+ *
+ *      while (1)
+ *      {
+ *              int id = event_select(evs, countof(evs),
+ *                                      ms_to_ticks(100));
+ *              if (id < 0)
+ *              {
+ *                      kprintf("no IRQ\n");
+ *                      continue;
+ *              }
+ *              kprintf("IRQ %d happened\n", id);
+ *      }
+ * }
+ *
+ * void irq1_handler(void)
+ * {
+ *      // do something
+ *      ...
+ *
+ *      // notify the completion of event 1
+ *      event_do(&ev1);
+ * }
+ *
+ * void irq2_handler(void)
+ * {
+ *      // do something
+ *      ...
+ *
+ *      // notify the completion of event 2
+ *      event_do(&ev2);
+ * }
+ * \endcode
+ *
+ * \author Bernie Innocenti <bernie@codewiz.org>
+ *
+ * $WIZ$ module_name = "event"
+ */
+
+#ifndef KERN_EVENT_H
+#define KERN_EVENT_H
+
+#include "cfg/cfg_proc.h"
+#include "cfg/cfg_signal.h"
+#include "cfg/cfg_timer.h"
+#include <cfg/compiler.h>
+
+#include <cpu/power.h> /* cpu_relax() */
+
+#if CONFIG_KERN && CONFIG_KERN_SIGNALS
+#include <kern/signal.h>
+/* Forward decl */
+struct Process;
+#endif
+
+typedef struct Event
+{
+	void (*action)(struct Event *);
+	union
+	{
+#if CONFIG_KERN && CONFIG_KERN_SIGNALS
+		struct
+		{
+			struct Process *sig_proc;  /* Process to be signalled */
+			sigbit_t        sig_bit;   /* Signal to send */
+			Signal          sig;       /* Local signal structure (used by generic event) */
+		} Sig;
+#endif
+		struct
+		{
+			Hook  func;         /* Pointer to softint hook */
+			void *user_data;    /* Data to be passed back to user hook */
+		} Int;
+
+		struct
+		{
+			bool completed;             /* Generic event completion */
+		} Gen;
+	} Ev;
+} Event;
+
+void event_hook_ignore(Event *event);
+void event_hook_signal(Event *event);
+void event_hook_softint(Event *event);
+void event_hook_generic(Event *event);
+void event_hook_generic_signal(Event *event);
+
+/** Initialize the event \a e as a no-op */
+#define event_initNone(e) \
+	((e)->action = event_hook_ignore)
+
+/** Same as event_initNone(), but returns the initialized event */
+INLINE Event event_createNone(void)
+{
+	Event e;
+	e.action = event_hook_ignore;
+	return e;
+}
+
+/** Initialize the event \a e with a software interrupt (call function \a f, with parameter \a u) */
+#define event_initSoftint(e,f,u) \
+	((e)->action = event_hook_softint,(e)->Ev.Int.func = (f), (e)->Ev.Int.user_data = (u))
+
+/** Same as event_initSoftint(), but returns the initialized event */
+INLINE Event event_createSoftint(Hook func, void *user_data)
+{
+	Event e;
+	e.action = event_hook_softint;
+	e.Ev.Int.func = func;
+	e.Ev.Int.user_data = user_data;
+	return e;
+}
+
+#if CONFIG_KERN && CONFIG_KERN_SIGNALS
+/** Initialize the event \a e with a signal (send signal \a s to process \a p) */
+#define event_initSignal(e,p,s) \
+	((e)->action = event_hook_signal,(e)->Ev.Sig.sig_proc = (p), (e)->Ev.Sig.sig_bit = (s))
+
+/** Same as event_initSignal(), but returns the initialized event */
+INLINE Event event_createSignal(struct Process *proc, sigbit_t bit)
+{
+	Event e;
+	e.action = event_hook_signal;
+	e.Ev.Sig.sig_proc = proc;
+	e.Ev.Sig.sig_bit = bit;
+	return e;
+}
+
+/**
+ * Signal used to implement generic events.
+ */
+#define EVENT_GENERIC_SIGNAL	SIG_SYSTEM6
+
+/** Initialize the generic sleepable event \a e */
+#define event_initGeneric(e)					\
+	((e)->action = event_hook_generic_signal,		\
+		(e)->Ev.Sig.sig_proc = proc_current(),		\
+		(e)->Ev.Sig.sig_bit = EVENT_GENERIC_SIGNAL,	\
+		(e)->Ev.Sig.sig.wait = 0, (e)->Ev.Sig.sig.recv = 0)
+#else
+#define event_initGeneric(e) \
+	((e)->action = event_hook_generic, (e)->Ev.Gen.completed = false)
+#endif
+
+/**
+ * Create a generic sleepable event.
+ *
+ * \return the properly initialized generic event structure.
+ */
+INLINE Event event_createGeneric(void)
+{
+	Event e;
+	event_initGeneric(&e);
+	return e;
+}
+
+/**
+ * Wait the completion of event \a e.
+ *
+ * This function releases the CPU the application is configured to use
+ * the kernel, otherwise it's just a busy wait.
+ * \note It's forbidden to use this function inside irq handling functions.
+ */
+INLINE void event_wait(Event *e)
+{
+#if CONFIG_KERN_SIGNALS
+	e->Ev.Sig.sig_proc = proc_current();
+	sig_waitSignal(&e->Ev.Sig.sig, EVENT_GENERIC_SIGNAL);
+#else
+	while (ACCESS_SAFE(e->Ev.Gen.completed) == false)
+		cpu_relax();
+	e->Ev.Gen.completed = false;
+	MEMORY_BARRIER;
+#endif
+}
+
+/**
+ * Wait for multiple events
+ *
+ * On success return the offset in the \a evs vector of the Event that
+ * happened, -1 if the timeout expires.
+ *
+ * NOTE: timeout == 0 means no timeout.
+ *
+ * \attention The API is work in progress and may change in future versions.
+ */
+int event_select(Event **evs, int n, ticks_t timeout);
+
+/**
+ * Wait the completion of event \a e or \a timeout elapses.
+ *
+ * \note It's forbidden to use this function inside irq handling functions.
+ */
+bool event_waitTimeout(Event *e, ticks_t timeout);
+
+/**
+ * Trigger an event.
+ *
+ * Execute the callback function associated with event \a e.
+ *
+ * This function can be used also in interrupt routines, but only if the
+ * event was created as a signal or generic event.
+ */
+INLINE void event_do(struct Event *e)
+{
+	e->action(e);
+}
+
+/** \} */
+
+#endif /* KERN_EVENT_H */