/**
* \file
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* Copyright 2004 Develer S.r.l. (http://www.develer.com/)
* Copyright 1999,2001 Bernie Innocenti <bernie@codewiz.org>
*
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*
*
* \defgroup kern_msg Message box IPC
* \ingroup kern
* \{
*
* \brief Simple inter-process messaging system
*
* This module implements a common system for executing
* a user defined action calling a hook function.
*
* A message port is an abstraction used to exchange information
* asynchronously between processes or other entities such as
* interrupts and call-back functions.
*
* This form of IPC is higher-level than bare signals and
* semaphores, because it sets a policy for exchanging
* structured data with well-defined synchronization and
* ownership semantics.
*
* Before using it, a message port must be initialized by
* calling msg_initPort(), which associates the port with
* an Event object, which can be setup to signal a process
* or invoke a call-back hook.
*
* A process or interrupt routine can deliver messages to any
* message port by calling msg_put(). By sending a message,
* the sender temporarly or permanently transfers ownership
* of its associated data to the receiver.
*
* Queuing a message to a port automatically triggers the
* associated Event to notify the receiver. When the
* receiver wakes up, it usually invokes msg_get() to pick
* the next message from the port.
*
* \note
* When you put a message into a port, such message becomes
* unavailable until you retrieve it using msg_get(), eg.
* you must not delete it or put it into another port.
*
* Message ports can hold any number of pending messages,
* and receivers usually process them in FIFO order.
* Other scheduling policies are possible, but not implemented
* in this API.
*
* After the receiver has done processing a message, it replies
* it back to the sender with msg_reply(), which transfer
* ownership back to the original sender. Replies are delivered
* to a reply port, which is nothing more than another MsgPort
* structure designated by the sender.
*
* Returning messages to senders is not mandatory, but it provides
* a convenient way to provide some kind of result and simplify
* the resource allocation scheme at the same time.
*
* When using signals to receive messages in a process, you
* call sig_wait() in an event-loop to wake up when messages
* are delivered to any of your ports. When your process
* wakes up with the port signal active, multiple messages
* may already have queued up at the message port, and the
* process must process them all before returning to sleep.
* Signals don't keep a nesting count.
*
* A simple message loop works like this:
*
* \code
* // Our message port.
* static MsgPort test_port;
*
* // A test message with two parameters and a result.
* typedef struct
* {
* Msg msg;
*
* int x, y;
* int result;
* } TestMsg;
*
*
* PROC_DEFINE_STACK(sender_stack, KERN_MINSTACKSIZE);
*
* // A process that sends two messages and waits for replies.
* static void sender_proc(void)
* {
* MsgPort test_reply_port;
* TestMsg msg1;
* TestMsg msg2;
* Msg *reply;
*
* msg_initPort(&test_reply_port,
* event_createSignal(proc_current(), SIG_SINGLE);
*
* // Fill-in first message and send it out.
* msg1.x = 3;
* msg1.y = 2;
* msg1.msg.replyPort = &test_reply_port;
* msg_put(&test_port, &msg1.msg);
*
* // Fill-in second message and send it out too.
* msg2.x = 5;
* msg2.y = 4;
* msg2.msg.replyPort = &test_reply_port;
* msg_put(&test_port, &msg2.msg);
*
* // Wait for a reply...
* sig_wait(SIG_SINGLE);
*
reply = containerof(msg_get(&test_reply_port), TestMsg, msg);
* ASSERT(reply != NULL);
* ASSERT(reply->result == 5);
*
* // Get reply to second message.
* while (!(reply = containerof(msg_get(&test_reply_port), TestMsg, msg)))
* {
* // Not yet, be patient and wait some more.
* sig_wait(SIG_SINGLE);
* }
*
* ASSERT(reply->result == 9);
* }
*
*
* // Receive messages and do something boring with them.
* static void receiver_proc(void)
* {
* msg_initPort(&test_port,
* event_createSignal(proc_current(), SIG_EXAMPLE);
*
* proc_new(sender_proc, NULL,sizeof(sender_stack), sender_stack);
*
* for (;;)
* {
* sigmask_t sigs = sig_wait(SIG_EXAMPLE | more_signals);
*
* if (sigs & SIG_EXAMPLE)
* {
* TestMsg *emsg;
* while((emsg = containerof(msg_get(&test_port), TestMsg, msg)))
* {
* // Do something with the message
* emsg->result = emsg->x + emsg->y;
* msg_reply(emsg->msg);
* }
* }
* }
* }
* \endcode
*
* \author Bernie Innocenti <bernie@codewiz.org>
*
* $WIZ$ module_name = "msg"
* $WIZ$ module_depends = "event", "signal", "kernel"
*/
#ifndef KERN_MSG_H
#define KERN_MSG_H
#include <mware/event.h>
#include <struct/list.h>
#include <kern/proc.h>
typedef struct MsgPort
{
List queue; /**< Messages queued at this port. */
Event event; /**< Event to trigger when a message arrives. */
} MsgPort;
typedef struct Msg
{
Node link; /**< Link into message port queue. */
MsgPort *replyPort; /**< Port to which the msg is to be replied. */
/* User data may follow */
} Msg;
/**
* Lock a message port.
*
* This is required before reading or manipulating
* any field of the MsgPort structure.
*
* \note Ports may be locked multiple times and each
* call to msg_lockPort() must be paired with
* a corresponding call to msg_unlockPort().
*
* \todo Add a configurable policy for locking against
* interrupts and locking with semaphorse.
*
* \see msg_unlockPort()
*/
INLINE void msg_lockPort(UNUSED_ARG(MsgPort *, port))
{
proc_forbid();
}
/**
* Unlock a message port.
*
* \see msg_lockPort()
*/
INLINE void msg_unlockPort(UNUSED_ARG(MsgPort *, port))
{
proc_permit();
}
/** Initialize a message port */
INLINE void msg_initPort(MsgPort *port, Event event)
{
LIST_INIT(&port->queue);
port->event = event;
}
/** Queue \a msg into \a port, triggering the associated event */
INLINE void msg_put(MsgPort *port, Msg *msg)
{
msg_lockPort(port);
ADDTAIL(&port->queue, &msg->link);
msg_unlockPort(port);
event_do(&port->event);
}
/**
* Get the first message from the queue of \a port.
*
* \return Pointer to the message or NULL if the port was empty.
*/
INLINE Msg *msg_get(MsgPort *port)
{
Msg *msg;
msg_lockPort(port);
msg = (Msg *)list_remHead(&port->queue);
msg_unlockPort(port);
return msg;
}
/** Peek the first message in the queue of \a port, or NULL if the port is empty. */
INLINE Msg *msg_peek(MsgPort *port)
{
Msg *msg;
msg_lockPort(port);
msg = (Msg *)port->queue.head.succ;
if (LIST_EMPTY(&port->queue))
msg = NULL;
msg_unlockPort(port);
return msg;
}
/** Send back (reply) \a msg to its sender. */
INLINE void msg_reply(Msg *msg)
{
msg_put(msg->replyPort, msg);
}
/** \} */ //defgroup kern_msg
int msg_testRun(void);
int msg_testSetup(void);
int msg_testTearDown(void);
#endif /* KERN_MSG_H */