c-user: Clarify message buffer configuration

The help macro CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE() is not a
configuration option.  Move it into the documentatation of the
CONFIGURE_MESSAGE_BUFFER_MEMORY configuration option.  Move this option
to the general system configuration group.

Update #3836.

c-user/config/general.rst

@@ -324,6 +324,79 @@ NOTES:
     Typically the memory allocation will be too low when an application does
     not account for all message queue buffers or task stacks.
 
+.. index:: CONFIGURE_MESSAGE_BUFFER_MEMORY
+.. index:: configure message queue buffer memory
+.. index:: CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE
+.. index:: memory for a single message queue's buffers
+
+.. _CONFIGURE_MESSAGE_BUFFER_MEMORY:
+
+CONFIGURE_MESSAGE_BUFFER_MEMORY
+-------------------------------
+
+CONSTANT:
+    ``CONFIGURE_MESSAGE_BUFFER_MEMORY``
+
+DATA TYPE:
+    integer summation macro
+
+RANGE:
+    undefined (zero) or calculation resulting in a positive integer
+
+DEFAULT VALUE:
+    The default value is zero.
+
+DESCRIPTION:
+    The value of this configuration option defines the number of bytes
+    resereved for message queue buffers in the RTEMS Workspace.
+
+NOTES:
+    The configuration options :ref:`CONFIGURE_MAXIMUM_MESSAGE_QUEUES` and
+    :ref:`CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUES` define only how many message
+    queues can be created by the application.  The memory for the message
+    buffers is configured by this option.  For each message queue you have to
+    reserve some memory for the message buffers.  The size dependes on the
+    maximum number of pending messages and the maximum size of the messages of
+    a message queue.  Use the ``CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE()`` macro
+    to specify the message buffer memory for each message queue and sum them up
+    to define the value for ``CONFIGURE_MAXIMUM_MESSAGE_QUEUES``.
+
+    The interface for the ``CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE()`` help
+    macro is as follows:
+
+    .. code-block:: c
+
+        CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE( max_messages, max_msg_size )
+
+    Where ``max_messages`` is the maximum number of pending messages and
+    ``max_msg_size`` is the maximum size in bytes of the messages of the
+    corresponding message queue.  Both parameters shall be compile time
+    constants.  Not using this help macro (e.g. just using
+    ``max_messages * max_msg_size``) may result in an underestimate of the
+    RTEMS Workspace size.
+
+    The following example illustrates how the
+    `CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE()` help macro can be used to assist in
+    calculating the message buffer memory required.  In this example, there are
+    two message queues used in this application.  The first message queue has a
+    maximum of 24 pending messages with the message structure defined by the
+    type ``one_message_type``.  The other message queue has a maximum of 500
+    pending messages with the message structure defined by the type
+    ``other_message_type``.
+
+    .. code-block:: c
+
+        #define CONFIGURE_MESSAGE_BUFFER_MEMORY ( \
+            CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE( \
+              24, \
+              sizeof( one_message_type ) \
+            ) \
+            + CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE( \
+              500, \
+              sizeof( other_message_type ) \
+            ) \
+          )
+
 .. index:: CONFIGURE_MICROSECONDS_PER_TICK
 .. index:: tick quantum
 

c-user/config/index.rst

@@ -17,7 +17,6 @@ Configuring a System
     posix-api
     posix-init-thread
     task-stack-alloc
-    msg-queue-buffer
     filesystem
     bdbuf
     bsp-related

c-user/config/msg-queue-buffer.rst

@@ -1,93 +0,0 @@
-.. SPDX-License-Identifier: CC-BY-SA-4.0
-
-.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR)
-
-Message Queue Buffer Configuration
-==================================
-
-This section describes the configuration parameters related to specifying the
-amount of memory reserved for message queue message buffers.  See
-:ref:`CONFIGURE_MAXIMUM_MESSAGE_QUEUES` and
-:ref:`CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUES`.
-
-.. index:: CONFIGURE_MESSAGE_BUFFER_MEMORY
-.. index:: configure message queue buffer memory
-
-.. _CONFIGURE_MESSAGE_BUFFER_MEMORY:
-
-CONFIGURE_MESSAGE_BUFFER_MEMORY
--------------------------------
-
-CONSTANT:
-    ``CONFIGURE_MESSAGE_BUFFER_MEMORY``
-
-DATA TYPE:
-    integer summation macro
-
-RANGE:
-    undefined (zero) or calculation resulting in a positive integer
-
-DEFAULT VALUE:
-    This is not defined by default, and zero (0) memory is reserved.
-
-DESCRIPTION:
-    This macro is set to the number of bytes the application requires to be
-    reserved for pending Classic API Message Queue buffers.
-
-NOTES:
-    The following illustrates how the help macro
-    :ref:`CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE` can be used to assist in
-    calculating the message buffer memory required.  In this example, there are
-    two message queues used in this application.  The first message queue has
-    maximum of 24 pending messages with the message structure defined by the
-    type ``one_message_type``.  The other message queue has maximum of 500
-    pending messages with the message structure defined by the type
-    ``other_message_type``.
-
-    .. code-block:: c
-
-        #define CONFIGURE_MESSAGE_BUFFER_MEMORY \
-                    (CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE( \
-                         24, sizeof(one_message_type) \
-                     ) + \
-                     CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE( \
-                         500, sizeof(other_message_type) \
-                     )
-
-.. index:: CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE
-.. index:: memory for a single message queue's buffers
-
-.. _CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE:
-
-CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE
------------------------------------
-
-CONSTANT:
-    ``CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE(max_messages, size_per)``
-
-DATA TYPE:
-    Unsigned integer (``size_t``).
-
-RANGE:
-    Positive.
-
-DEFAULT VALUE:
-    The default value is None.
-
-DESCRIPTION:
-    This is a helper macro which is used to assist in computing the total
-    amount of memory required for message buffers.  Each message queue will
-    have its own configuration with maximum message size and maximum number of
-    pending messages.
-
-    The interface for this macro is as follows:
-
-    .. code-block:: c
-
-        CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE(max_messages, size_per)
-
-    Where ``max_messages`` is the maximum number of pending messages and
-    ``size_per`` is the size in bytes of the user message.
-
-NOTES:
-    This macro is only used in support of :ref:`CONFIGURE_MESSAGE_BUFFER_MEMORY`.