301 lines
8.1 KiB
C
301 lines
8.1 KiB
C
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/**
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* \file
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* <!--
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* This file is part of BeRTOS.
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*
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* Bertos is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* As a special exception, you may use this file as part of a free software
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* library without restriction. Specifically, if other files instantiate
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* templates or use macros or inline functions from this file, or you compile
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* this file and link it with other files to produce an executable, this
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* file does not by itself cause the resulting executable to be covered by
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* the GNU General Public License. This exception does not however
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* invalidate any other reasons why the executable file might be covered by
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* the GNU General Public License.
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*
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* Copyright 2004 Develer S.r.l. (http://www.develer.com/)
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* Copyright 1999,2001 Bernie Innocenti <bernie@codewiz.org>
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*
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* -->
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*
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*
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* \defgroup kern_msg Message box IPC
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* \ingroup kern
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* \{
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*
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* \brief Simple inter-process messaging system
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*
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* This module implements a common system for executing
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* a user defined action calling a hook function.
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*
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* A message port is an abstraction used to exchange information
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* asynchronously between processes or other entities such as
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* interrupts and call-back functions.
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*
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* This form of IPC is higher-level than bare signals and
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* semaphores, because it sets a policy for exchanging
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* structured data with well-defined synchronization and
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* ownership semantics.
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*
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* Before using it, a message port must be initialized by
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* calling msg_initPort(), which associates the port with
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* an Event object, which can be setup to signal a process
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* or invoke a call-back hook.
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*
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* A process or interrupt routine can deliver messages to any
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* message port by calling msg_put(). By sending a message,
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* the sender temporarly or permanently transfers ownership
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* of its associated data to the receiver.
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*
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* Queuing a message to a port automatically triggers the
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* associated Event to notify the receiver. When the
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* receiver wakes up, it usually invokes msg_get() to pick
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* the next message from the port.
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*
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* \note
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* When you put a message into a port, such message becomes
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* unavailable until you retrieve it using msg_get(), eg.
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* you must not delete it or put it into another port.
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*
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* Message ports can hold any number of pending messages,
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* and receivers usually process them in FIFO order.
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* Other scheduling policies are possible, but not implemented
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* in this API.
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*
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* After the receiver has done processing a message, it replies
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* it back to the sender with msg_reply(), which transfer
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* ownership back to the original sender. Replies are delivered
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* to a reply port, which is nothing more than another MsgPort
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* structure designated by the sender.
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*
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* Returning messages to senders is not mandatory, but it provides
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* a convenient way to provide some kind of result and simplify
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* the resource allocation scheme at the same time.
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*
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* When using signals to receive messages in a process, you
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* call sig_wait() in an event-loop to wake up when messages
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* are delivered to any of your ports. When your process
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* wakes up with the port signal active, multiple messages
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* may already have queued up at the message port, and the
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* process must process them all before returning to sleep.
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* Signals don't keep a nesting count.
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*
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* A simple message loop works like this:
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*
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* \code
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* // Our message port.
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* static MsgPort test_port;
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*
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* // A test message with two parameters and a result.
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* typedef struct
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* {
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* Msg msg;
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*
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* int x, y;
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* int result;
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* } TestMsg;
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*
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*
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* PROC_DEFINE_STACK(sender_stack, KERN_MINSTACKSIZE);
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*
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* // A process that sends two messages and waits for replies.
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* static void sender_proc(void)
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* {
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* MsgPort test_reply_port;
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* TestMsg msg1;
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* TestMsg msg2;
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* Msg *reply;
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*
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* msg_initPort(&test_reply_port,
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* event_createSignal(proc_current(), SIG_SINGLE);
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*
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* // Fill-in first message and send it out.
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* msg1.x = 3;
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* msg1.y = 2;
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* msg1.msg.replyPort = &test_reply_port;
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* msg_put(&test_port, &msg1.msg);
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*
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* // Fill-in second message and send it out too.
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* msg2.x = 5;
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* msg2.y = 4;
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* msg2.msg.replyPort = &test_reply_port;
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* msg_put(&test_port, &msg2.msg);
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*
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* // Wait for a reply...
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* sig_wait(SIG_SINGLE);
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*
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reply = containerof(msg_get(&test_reply_port), TestMsg, msg);
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* ASSERT(reply != NULL);
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* ASSERT(reply->result == 5);
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*
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* // Get reply to second message.
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* while (!(reply = containerof(msg_get(&test_reply_port), TestMsg, msg)))
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* {
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* // Not yet, be patient and wait some more.
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* sig_wait(SIG_SINGLE);
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* }
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*
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* ASSERT(reply->result == 9);
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* }
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*
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*
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* // Receive messages and do something boring with them.
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* static void receiver_proc(void)
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* {
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* msg_initPort(&test_port,
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* event_createSignal(proc_current(), SIG_EXAMPLE);
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*
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* proc_new(sender_proc, NULL,sizeof(sender_stack), sender_stack);
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*
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* for (;;)
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* {
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* sigmask_t sigs = sig_wait(SIG_EXAMPLE | more_signals);
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*
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* if (sigs & SIG_EXAMPLE)
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* {
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* TestMsg *emsg;
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* while((emsg = containerof(msg_get(&test_port), TestMsg, msg)))
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* {
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* // Do something with the message
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* emsg->result = emsg->x + emsg->y;
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* msg_reply(emsg->msg);
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* }
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* }
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* }
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* }
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* \endcode
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*
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* \author Bernie Innocenti <bernie@codewiz.org>
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*
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* $WIZ$ module_name = "msg"
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* $WIZ$ module_depends = "event", "signal", "kernel"
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*/
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#ifndef KERN_MSG_H
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#define KERN_MSG_H
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#include <mware/event.h>
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#include <struct/list.h>
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#include <kern/proc.h>
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typedef struct MsgPort
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{
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List queue; /**< Messages queued at this port. */
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Event event; /**< Event to trigger when a message arrives. */
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} MsgPort;
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typedef struct Msg
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{
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Node link; /**< Link into message port queue. */
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MsgPort *replyPort; /**< Port to which the msg is to be replied. */
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/* User data may follow */
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} Msg;
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/**
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* Lock a message port.
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*
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* This is required before reading or manipulating
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* any field of the MsgPort structure.
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*
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* \note Ports may be locked multiple times and each
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* call to msg_lockPort() must be paired with
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* a corresponding call to msg_unlockPort().
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*
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* \todo Add a configurable policy for locking against
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* interrupts and locking with semaphorse.
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*
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* \see msg_unlockPort()
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*/
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INLINE void msg_lockPort(UNUSED_ARG(MsgPort *, port))
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{
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proc_forbid();
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}
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/**
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* Unlock a message port.
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*
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* \see msg_lockPort()
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*/
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INLINE void msg_unlockPort(UNUSED_ARG(MsgPort *, port))
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{
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proc_permit();
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}
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/** Initialize a message port */
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INLINE void msg_initPort(MsgPort *port, Event event)
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{
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LIST_INIT(&port->queue);
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port->event = event;
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}
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/** Queue \a msg into \a port, triggering the associated event */
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INLINE void msg_put(MsgPort *port, Msg *msg)
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{
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msg_lockPort(port);
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ADDTAIL(&port->queue, &msg->link);
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msg_unlockPort(port);
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event_do(&port->event);
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}
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/**
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* Get the first message from the queue of \a port.
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*
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* \return Pointer to the message or NULL if the port was empty.
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*/
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INLINE Msg *msg_get(MsgPort *port)
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{
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Msg *msg;
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msg_lockPort(port);
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msg = (Msg *)list_remHead(&port->queue);
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msg_unlockPort(port);
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return msg;
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}
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/** Peek the first message in the queue of \a port, or NULL if the port is empty. */
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INLINE Msg *msg_peek(MsgPort *port)
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{
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Msg *msg;
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msg_lockPort(port);
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msg = (Msg *)port->queue.head.succ;
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if (LIST_EMPTY(&port->queue))
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msg = NULL;
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msg_unlockPort(port);
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return msg;
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}
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/** Send back (reply) \a msg to its sender. */
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INLINE void msg_reply(Msg *msg)
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{
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msg_put(msg->replyPort, msg);
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}
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/** \} */ //defgroup kern_msg
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int msg_testRun(void);
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int msg_testSetup(void);
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int msg_testTearDown(void);
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#endif /* KERN_MSG_H */
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