4 * This file is part of BeRTOS.
6 * Bertos is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
20 * As a special exception, you may use this file as part of a free software
21 * library without restriction. Specifically, if other files instantiate
22 * templates or use macros or inline functions from this file, or you compile
23 * this file and link it with other files to produce an executable, this
24 * file does not by itself cause the resulting executable to be covered by
25 * the GNU General Public License. This exception does not however
26 * invalidate any other reasons why the executable file might be covered by
27 * the GNU General Public License.
29 * Copyright 2004 Develer S.r.l. (http://www.develer.com/)
30 * Copyright 1999,2001 Bernardo Innocenti <bernie@develer.com>
35 * This module implements a common system for executing
36 * a user defined action calling a hook function.
40 * \author Bernardo Innocenti <bernie@develer.com>
42 * \brief Simple inter-process messaging system
44 * Handle queues of messages associated an action.
46 * A message port is an abstraction used to exchange information
47 * asynchronously between processes or other entities such as
48 * interrupts and call-back functions.
50 * This form of IPC is higher-level than bare signals and
51 * semaphores, because it sets a policy for exchanging
52 * structured data with well-defined synchronization and
53 * ownership semantics.
55 * Before using it, a message port must be initialized by
56 * calling msg_initPort(), which associates the port with
57 * an Event object, which can be setup to signal a process
58 * or invoke a call-back hook.
60 * A process or interrupt routine can deliver messages to any
61 * message port by calling msg_put(). By sending a message,
62 * the sender temporarly or permanently transfers ownership
63 * of its associated data to the receiver.
65 * Queuing a message to a port automatically triggers the
66 * associated Event to notify the receiver. When the
67 * receiver wakes up, it usually invokes msg_get() to pick
68 * the next message from the port.
70 * Message ports can hold any number of pending messages,
71 * and receivers usually process them in FIFO order.
72 * Other scheduling policies are possible, but not implemented
75 * After the receiver has done processing a message, it replies
76 * it back to the sender with msg_reply(), which transfer
77 * ownership back to the original sender. Replies are delivered
78 * to a reply port, which is nothing more than another MsgPort
79 * structure designated by the sender.
81 * Returning messages to senders is not mandatory, but it provides
82 * a convenient way to provide some kind of result and simplify
83 * the resource allocation scheme at the same time.
85 * When using signals to receive messages in a process, you
86 * call sig_wait() in an event-loop to wake up when messages
87 * are delivered to any of your ports. When your process
88 * wakes up with the port signal active, multiple messages
89 * may already have queued up at the message port, and the
90 * process must process them all before returning to sleep.
91 * Signals don't keep a nesting count.
93 * A simple message loop works like this:
96 * // Our message port.
97 * static MsgPort test_port;
99 * // A test message with two parameters and a result.
109 * // A process that sends two messages and waits for replies.
110 * static void sender_proc(void)
112 * MsgPort test_reply_port;
117 * msg_initPort(&reply_port,
118 * event_createSignal(proc_current(), SIGF_SINGLE);
120 * // Fill-in first message and send it out.
123 * msg1.msg.replyPort = &test_reply_port;
124 * msg_put(&test_port, &msg1);
126 * // Fill-in second message and send it out too.
129 * msg2.msg.replyPort = &test_reply_port;
130 * msg_put(&test_port, &msg1);
132 * // Wait for a reply...
133 * sig_wait(SIG_SINGLE);
135 * reply = (TestMsg *)msg_get(&test_reply_port);
136 * ASSERT(reply != NULL);
137 * ASSERT(reply->result == 5);
139 * // Get reply to second message.
140 * while (!(reply = (TestMsg *)msg_get(&test_reply_port))
142 * // Not yet, be patient and wait some more.
143 * sig_wait(SIG_SINGLE);
146 * ASSERT(reply->result == 9);
150 * // Receive messages and do something boring with them.
151 * static void receiver_proc(void)
153 * msg_initPort(&test_port,
154 * event_createSignal(proc_current(), SIGF_EXAMPLE);
156 * proc_new(sender_proc, (iptr_t)&test_port,
157 * sender_stack, sizeof(sender_stack);
161 * sigmask_t sigs = sig_wait(SIGF_EXAMPLE | more_signals);
163 * if (sigs & SIGF_EXAMPLE)
166 * while (emsg = (TestMsg *)msg_get(&test_port)
168 * // Do something with the message
169 * emsg->result = emsg->x + emsg->y;
170 * msg_reply((Msg *)msg);
184 #include <mware/list.h>
187 typedef struct MsgPort
189 List queue; /**< Messages queued at this port. */
190 Event event; /**< Event to trigger when a message arrives. */
196 Node link; /**< Link into message port queue. */
197 MsgPort *replyPort; /**< Port to which the msg is to be replied. */
198 /* User data may follow */
203 * Lock a message port.
205 * This is required before reading or manipulating
206 * any field of the MsgPort structure.
208 * \note Ports may be locked multiple times and each
209 * call to msg_lockPort() must be paired with
210 * a corresponding call to msg_unlockPort().
212 * \todo Add a configurable policy for locking against
213 * interrupts and locking with semaphorse.
215 * \see msg_unlockPort()
217 INLINE void msg_lockPort(MsgPort *port)
223 * Unlock a message port.
225 * \see msg_lockPort()
227 INLINE void msg_unlockPort(MsgPort *port)
233 /** Initialize a message port */
234 INLINE void msg_initPort(MsgPort *port, Event event)
236 LIST_INIT(&port->queue);
240 /** Queue \a msg into \a port, triggering the associated event */
241 INLINE void msg_put(MsgPort *port, Msg *msg)
244 ADDTAIL(&port->queue, &msg->link);
245 msg_portUnlock(port);
247 event_do(&port->event);
251 * Get the first message from the queue of \a port.
253 * \return Pointer to the message or NULL if the port was empty.
255 INLINE Msg *msg_get(MsgPort *port)
260 msg = (Msg *)REMHEAD(&port->queue);
261 msg_portUnlock(port);
266 /** Peek the first message in the queue of \a port, or NULL if the port is empty. */
267 INLINE Msg *msg_peek(MsgPort *port)
272 msg = (Msg *)port->queue.head;
273 if (ISLISTEMPTY(&port->queue))
275 msg_portUnlock(port);
280 /** Send back (reply) \a msg to its sender. */
281 INLINE void msg_reply(Msg *msg)
283 msg_put(msg->replyPort, msg);
286 #endif /* KERN_MSG_H */