source: rtems-docs/c-user/config/index.rst @ a9e6a1d

.. SPDX-License-Identifier: CC-BY-SA-4.0

.. Copyright (C) 2010 Gedare Bloom
.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR)

.. index:: configuring a system
.. _Configuring a System:

Configuring a System
********************

.. toctree::

    intro
    general
    classic-api
    classic-init-task

POSIX API Configuration
=======================

The parameters in this section are used to configure resources for the POSIX
API supported by RTEMS.  Most POSIX API objects are available by default since
RTEMS 5.1.  The queued signals and timers are only available if RTEMS was built
with the ``--enable-posix`` build configuration option.

.. index:: CONFIGURE_MAXIMUM_POSIX_KEYS

.. _CONFIGURE_MAXIMUM_POSIX_KEYS:

CONFIGURE_MAXIMUM_POSIX_KEYS
----------------------------

CONSTANT:
    ``CONFIGURE_MAXIMUM_POSIX_KEYS``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Zero or positive.

DEFAULT VALUE:
    The default value is 0.

DESCRIPTION:
    ``CONFIGURE_MAXIMUM_POSIX_KEYS`` is the maximum number of POSIX API Keys
    that can be concurrently active.

NOTES:
    This object class can be configured in unlimited allocation mode.

.. index:: CONFIGURE_MAXIMUM_POSIX_KEY_VALUE_PAIRS

.. _CONFIGURE_MAXIMUM_POSIX_KEY_VALUE_PAIRS:

CONFIGURE_MAXIMUM_POSIX_KEY_VALUE_PAIRS
---------------------------------------

CONSTANT:
    ``CONFIGURE_MAXIMUM_POSIX_KEY_VALUE_PAIRS``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Zero or positive.

DEFAULT VALUE:
    The default value is
    :ref:`CONFIGURE_MAXIMUM_POSIX_KEYS <CONFIGURE_MAXIMUM_POSIX_KEYS>` *
    :ref:`CONFIGURE_MAXIMUM_TASKS <CONFIGURE_MAXIMUM_TASKS>` +
    :ref:`CONFIGURE_MAXIMUM_POSIX_THREADS <CONFIGURE_MAXIMUM_POSIX_THREADS>`.

DESCRIPTION:
    ``CONFIGURE_MAXIMUM_POSIX_KEY_VALUE_PAIRS`` is the maximum number of key
    value pairs used by POSIX API Keys that can be concurrently active.

NOTES:
    This object class can be configured in unlimited allocation mode.

    A key value pair is created by :c:func:`pthread_setspecific` if the value
    is not :c:macro:`NULL`, otherwise it is deleted.

.. index:: CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUES

.. _CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUES:

CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUES
--------------------------------------

CONSTANT:
    ``CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUES``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Zero or positive.

DEFAULT VALUE:
    The default value is 0.

DESCRIPTION:
    ``CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUES`` is the maximum number of POSIX
    API Message Queues that can be concurrently active.

NOTES:
    This object class can be configured in unlimited allocation mode.  You have
    to account for the memory used to store the messages of each message queue,
    see :ref:`CONFIGURE_MESSAGE_BUFFER_MEMORY`.

.. index:: CONFIGURE_MAXIMUM_POSIX_QUEUED_SIGNALS

.. _CONFIGURE_MAXIMUM_POSIX_QUEUED_SIGNALS:

CONFIGURE_MAXIMUM_POSIX_QUEUED_SIGNALS
--------------------------------------

CONSTANT:
    ``CONFIGURE_MAXIMUM_POSIX_QUEUED_SIGNALS``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Zero or positive.

DEFAULT VALUE:
    The default value is 0.

DESCRIPTION:
    ``CONFIGURE_MAXIMUM_POSIX_QUEUED_SIGNALS`` is the maximum number of POSIX
    API Queued Signals that can be concurrently active.

NOTES:
    Unlimited objects are not available for queued signals.

    Queued signals are only available if RTEMS was built with the
    ``--enable-posix`` build configuration option.

.. index:: CONFIGURE_MAXIMUM_POSIX_SEMAPHORES

.. _CONFIGURE_MAXIMUM_POSIX_SEMAPHORES:

CONFIGURE_MAXIMUM_POSIX_SEMAPHORES
----------------------------------

CONSTANT:
    ``CONFIGURE_MAXIMUM_POSIX_SEMAPHORES``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Zero or positive.

DEFAULT VALUE:
    The default value is 0.

DESCRIPTION:
    ``CONFIGURE_MAXIMUM_POSIX_SEMAPHORES`` is the maximum number of POSIX API
    Named Semaphores that can be concurrently active.

NOTES:
    This object class can be configured in unlimited allocation mode.

    Named semaphores are created with ``sem_open()``.  Semaphores initialized
    with ``sem_init()`` are not affected by this configuration option since the
    storage space for these semaphores is user-provided.

.. index:: CONFIGURE_MAXIMUM_POSIX_TIMERS

.. _CONFIGURE_MAXIMUM_POSIX_TIMERS:

CONFIGURE_MAXIMUM_POSIX_TIMERS
------------------------------

CONSTANT:
    ``CONFIGURE_MAXIMUM_POSIX_TIMERS``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Zero or positive.

DEFAULT VALUE:
    The default value is 0.

DESCRIPTION:
    ``CONFIGURE_MAXIMUM_POSIX_TIMERS`` is the maximum number of POSIX API
    Timers that can be concurrently active.

NOTES:
    This object class can be configured in unlimited allocation mode.

    Timers are only available if RTEMS was built with the
    ``--enable-posix`` build configuration option.

.. index:: CONFIGURE_MAXIMUM_POSIX_THREADS

.. _CONFIGURE_MAXIMUM_POSIX_THREADS:

CONFIGURE_MAXIMUM_POSIX_THREADS
-------------------------------

CONSTANT:
    ``CONFIGURE_MAXIMUM_POSIX_THREADS``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Zero or positive.

DEFAULT VALUE:
    The default value is 0.

DESCRIPTION:
    ``CONFIGURE_MAXIMUM_POSIX_THREADS`` is the maximum number of POSIX API
    Threads that can be concurrently active.

NOTES:
    This object class can be configured in unlimited allocation mode.

    This calculations for the required memory in the RTEMS Workspace for
    threads assume that each thread has a minimum stack size and has floating
    point support enabled.  The configuration parameter
    ``CONFIGURE_EXTRA_TASK_STACKS`` is used to specify thread stack
    requirements *ABOVE* the minimum size required.  See :ref:`Reserve
    Task/Thread Stack Memory Above Minimum` for more information about
    ``CONFIGURE_EXTRA_TASK_STACKS``.

    The maximum number of Classic API Tasks is specified by
    :ref:`CONFIGURE_MAXIMUM_TASKS <CONFIGURE_MAXIMUM_TASKS>`.

    All POSIX threads have floating point enabled.

.. index:: CONFIGURE_MINIMUM_POSIX_THREAD_STACK_SIZE
.. index:: minimum POSIX thread stack size

.. _CONFIGURE_MINIMUM_POSIX_THREAD_STACK_SIZE:

CONFIGURE_MINIMUM_POSIX_THREAD_STACK_SIZE
-----------------------------------------

CONSTANT:
    ``CONFIGURE_MINIMUM_POSIX_THREAD_STACK_SIZE``

DATA TYPE:
    Unsigned integer (``size_t``).

RANGE:
    Positive.

DEFAULT VALUE:
    The default value is two times the value of
    :ref:`CONFIGURE_MINIMUM_TASK_STACK_SIZE <CONFIGURE_MINIMUM_TASK_STACK_SIZE>`.

DESCRIPTION:
    This configuration parameter defines the minimum stack size in bytes for
    every POSIX thread in the system.

NOTES:
    None.

POSIX Initialization Thread Configuration
=========================================

The ``<rtems/confdefs.h>`` configuration system can automatically generate a
POSIX Initialization Threads Table named ``POSIX_Initialization_threads`` with
a single entry.  The following parameters control the generation of that table.

.. index:: CONFIGURE_POSIX_INIT_THREAD_ENTRY_POINT

.. _CONFIGURE_POSIX_INIT_THREAD_ENTRY_POINT:

CONFIGURE_POSIX_INIT_THREAD_ENTRY_POINT
---------------------------------------

CONSTANT:
    ``CONFIGURE_POSIX_INIT_THREAD_ENTRY_POINT``

DATA TYPE:
    POSIX thread function pointer (``void *(*entry_point)(void *)``).

RANGE:
    Undefined or a valid POSIX thread function pointer.

DEFAULT VALUE:
    The default value is ``POSIX_Init``.

DESCRIPTION:
    ``CONFIGURE_POSIX_INIT_THREAD_ENTRY_POINT`` is the entry point
    (a.k.a. function name) of the single initialization thread defined by the
    POSIX API Initialization Threads Table.

NOTES:
    The user must implement the function ``POSIX_Init`` or the function name
    provided in this configuration parameter.

.. index:: CONFIGURE_POSIX_INIT_THREAD_STACK_SIZE

.. _CONFIGURE_POSIX_INIT_THREAD_STACK_SIZE:

CONFIGURE_POSIX_INIT_THREAD_STACK_SIZE
--------------------------------------

CONSTANT:
    ``CONFIGURE_POSIX_INIT_THREAD_STACK_SIZE``

DATA TYPE:
    Unsigned integer (``size_t``).

RANGE:
    Zero or positive.

DEFAULT VALUE:
    The default value is 2 \* RTEMS_MINIMUM_STACK_SIZE.

DESCRIPTION:
    ``CONFIGURE_POSIX_INIT_THREAD_STACK_SIZE`` is the stack size of the single
    initialization thread defined by the POSIX API Initialization Threads
    Table.

NOTES:
    If the stack size specified is greater than the configured minimum, it must
    be accounted for in ``CONFIGURE_EXTRA_TASK_STACKS``.  See :ref:`Reserve
    Task/Thread Stack Memory Above Minimum` for more information about
    ``CONFIGURE_EXTRA_TASK_STACKS``.

.. index:: CONFIGURE_POSIX_INIT_THREAD_TABLE

.. _CONFIGURE_POSIX_INIT_THREAD_TABLE:

CONFIGURE_POSIX_INIT_THREAD_TABLE
---------------------------------

CONSTANT:
    ``CONFIGURE_POSIX_INIT_THREAD_TABLE``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This field is not defined by default, as the user MUST select their own API
    for initialization tasks.

DESCRIPTION:
    ``CONFIGURE_POSIX_INIT_THREAD_TABLE`` is defined if the user wishes to use
    a POSIX API Initialization Threads Table.  The table built by
    ``<rtems/confdefs.h>`` specifies the parameters for a single thread. This
    is sufficient for applications which initialization the system from a
    single task.

    By default, this field is not defined as the user MUST select their own API
    for initialization tasks.

NOTES:
    The application may choose to use the initialization tasks or threads table
    from another API.

    A compile time error will be generated if the user does not configure any
    initialization tasks or threads.

Task Stack Allocator Configuration
==================================

RTEMS allows the application or BSP to define its own allocation and
deallocation methods for task stacks. This can be used to place task stacks in
special areas of memory or to utilize a Memory Management Unit so that stack
overflows are detected in hardware.

.. index:: CONFIGURE_TASK_STACK_ALLOCATOR
.. index:: task stack allocator

.. _CONFIGURE_TASK_STACK_ALLOCATOR:

CONFIGURE_TASK_STACK_ALLOCATOR
------------------------------

CONSTANT:
    ``CONFIGURE_TASK_STACK_ALLOCATOR``

DATA TYPE:
    Function pointer.

RANGE:
    Undefined or valid function pointer.

DEFAULT VALUE:
    The default value is ``_Workspace_Allocate``, which indicates that task
    stacks will be allocated from the RTEMS Workspace.

DESCRIPTION:
    ``CONFIGURE_TASK_STACK_ALLOCATOR`` may point to a user provided routine to
    allocate task stacks.

NOTES:
    A correctly configured system must configure the following to be consistent:

- ``CONFIGURE_TASK_STACK_ALLOCATOR_INIT``

- ``CONFIGURE_TASK_STACK_ALLOCATOR``

- ``CONFIGURE_TASK_STACK_DEALLOCATOR``

.. index:: CONFIGURE_TASK_STACK_ALLOCATOR_INIT

.. _CONFIGURE_TASK_STACK_ALLOCATOR_INIT:

CONFIGURE_TASK_STACK_ALLOCATOR_INIT
-----------------------------------

CONSTANT:
    ``CONFIGURE_TASK_STACK_ALLOCATOR_INIT``

DATA TYPE:
    Function pointer.

RANGE:
    Undefined, NULL or valid function pointer.

DEFAULT VALUE:
    The default value is NULL, which indicates that task stacks will be
    allocated from the RTEMS Workspace.

DESCRIPTION:
    ``CONFIGURE_TASK_STACK_ALLOCATOR_INIT`` configures the initialization
    method for an application or BSP specific task stack allocation
    implementation.

NOTES:
    A correctly configured system must configure the following to be consistent:

- ``CONFIGURE_TASK_STACK_ALLOCATOR_INIT``

- ``CONFIGURE_TASK_STACK_ALLOCATOR``

- ``CONFIGURE_TASK_STACK_DEALLOCATOR``

.. index:: CONFIGURE_TASK_STACK_DEALLOCATOR
.. index:: task stack deallocator

.. _CONFIGURE_TASK_STACK_DEALLOCATOR:

CONFIGURE_TASK_STACK_DEALLOCATOR
--------------------------------

CONSTANT:
    ``CONFIGURE_TASK_STACK_DEALLOCATOR``

DATA TYPE:
    Function pointer.

RANGE:
    Undefined or valid function pointer.

DEFAULT VALUE:
    The default value is ``_Workspace_Free``, which indicates that task stacks
    will be allocated from the RTEMS Workspace.

DESCRIPTION:
    ``CONFIGURE_TASK_STACK_DEALLOCATOR`` may point to a user provided routine
    to free task stacks.

NOTES:
    A correctly configured system must configure the following to be consistent:

- ``CONFIGURE_TASK_STACK_ALLOCATOR_INIT``

- ``CONFIGURE_TASK_STACK_ALLOCATOR``

- ``CONFIGURE_TASK_STACK_DEALLOCATOR``

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`.

Filesystem Configuration
========================

By default, the In-Memory Filesystem (IMFS) is used as the base filesystem (also
known as root filesystem).  In order to save some memory for your application,
you can disable the filesystem support with the
:ref:`CONFIGURE_APPLICATION_DISABLE_FILESYSTEM` configuration option.
Alternatively, you can strip down the features of the base filesystem with the
:ref:`CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM` and
:ref:`CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM` configuration options.  These
three configuration options are mutually exclusive.  They are intended for an
advanced application configuration.

Features of the IMFS can be disabled and enabled with the following
configuration options:

* :ref:`CONFIGURE_IMFS_DISABLE_CHMOD`

* :ref:`CONFIGURE_IMFS_DISABLE_CHOWN`

* :ref:`CONFIGURE_IMFS_DISABLE_LINK`

* :ref:`CONFIGURE_IMFS_DISABLE_MKNOD`

* :ref:`CONFIGURE_IMFS_DISABLE_MKNOD_FILE`

* :ref:`CONFIGURE_IMFS_DISABLE_MOUNT`

* :ref:`CONFIGURE_IMFS_DISABLE_READDIR`

* :ref:`CONFIGURE_IMFS_DISABLE_READLINK`

* :ref:`CONFIGURE_IMFS_DISABLE_RENAME`

* :ref:`CONFIGURE_IMFS_DISABLE_RMNOD`

* :ref:`CONFIGURE_IMFS_DISABLE_SYMLINK`

* :ref:`CONFIGURE_IMFS_DISABLE_UNMOUNT`

* :ref:`CONFIGURE_IMFS_DISABLE_UTIME`

* :ref:`CONFIGURE_IMFS_ENABLE_MKFIFO`

.. index:: CONFIGURE_APPLICATION_DISABLE_FILESYSTEM

.. _CONFIGURE_APPLICATION_DISABLE_FILESYSTEM:

CONFIGURE_APPLICATION_DISABLE_FILESYSTEM
----------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_DISABLE_FILESYSTEM``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default. If no other root file system configuration
    parameters are specified, the IMFS will be used as the root file system.

DESCRIPTION:
    This configuration parameter is defined if the application dose not intend
    to use any kind of filesystem support. This include the device
    infrastructure necessary to support ``printf()``.

NOTES:
    None.

.. index:: CONFIGURE_IMFS_ENABLE_MKFIFO

.. _CONFIGURE_IMFS_ENABLE_MKFIFO:

CONFIGURE_IMFS_ENABLE_MKFIFO
----------------------------

CONSTANT:
    ``CONFIGURE_IMFS_ENABLE_MKFIFO``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to make FIFOs
    is enabled in the root IMFS.

.. index:: CONFIGURE_IMFS_DISABLE_CHMOD

.. _CONFIGURE_IMFS_DISABLE_CHMOD:

CONFIGURE_IMFS_DISABLE_CHMOD
----------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_CHMOD``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to change
    the mode is disabled in the root IMFS.

.. index:: CONFIGURE_IMFS_DISABLE_CHOWN

.. _CONFIGURE_IMFS_DISABLE_CHOWN:

CONFIGURE_IMFS_DISABLE_CHOWN
----------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_CHOWN``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to change
    the owner is disabled in the root IMFS.

.. index:: CONFIGURE_IMFS_DISABLE_LINK

.. _CONFIGURE_IMFS_DISABLE_LINK:

CONFIGURE_IMFS_DISABLE_LINK
---------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_LINK``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to create
    hard links is disabled in the root IMFS.

.. index:: CONFIGURE_IMFS_DISABLE_MKNOD

.. _CONFIGURE_IMFS_DISABLE_MKNOD:

CONFIGURE_IMFS_DISABLE_MKNOD
----------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_MKNOD``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to make
    directories, devices, regular files and FIFOs is disabled in the root IMFS.

.. index:: CONFIGURE_IMFS_DISABLE_MKNOD_FILE

.. _CONFIGURE_IMFS_DISABLE_MKNOD_FILE:

CONFIGURE_IMFS_DISABLE_MKNOD_FILE
---------------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_MKNOD_FILE``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to make
    regular files is disabled in the root IMFS.

.. index:: CONFIGURE_IMFS_DISABLE_MOUNT

.. _CONFIGURE_IMFS_DISABLE_MOUNT:

CONFIGURE_IMFS_DISABLE_MOUNT
----------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_MOUNT``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to mount
    other file systems is disabled in the root IMFS.

.. index:: CONFIGURE_IMFS_DISABLE_READDIR

.. _CONFIGURE_IMFS_DISABLE_READDIR:

CONFIGURE_IMFS_DISABLE_READDIR
------------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_READDIR``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to read a
    directory is disabled in the root IMFS.  It is still possible to open nodes
    in a directory.

.. index:: CONFIGURE_IMFS_DISABLE_READLINK

.. _CONFIGURE_IMFS_DISABLE_READLINK:

CONFIGURE_IMFS_DISABLE_READLINK
-------------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_READLINK``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to read
    symbolic links is disabled in the root IMFS.

.. index:: CONFIGURE_IMFS_DISABLE_RENAME

.. _CONFIGURE_IMFS_DISABLE_RENAME:

CONFIGURE_IMFS_DISABLE_RENAME
-----------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_RENAME``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to rename
    nodes is disabled in the root IMFS.

.. index:: CONFIGURE_IMFS_DISABLE_RMNOD

.. _CONFIGURE_IMFS_DISABLE_RMNOD:

CONFIGURE_IMFS_DISABLE_RMNOD
----------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_RMNOD``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to remove
    nodes is disabled in the root IMFS.

.. index:: CONFIGURE_IMFS_DISABLE_SYMLINK

.. _CONFIGURE_IMFS_DISABLE_SYMLINK:

CONFIGURE_IMFS_DISABLE_SYMLINK
------------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_SYMLINK``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to create
    symbolic links is disabled in the root IMFS.

.. index:: CONFIGURE_IMFS_DISABLE_UNMOUNT

.. _CONFIGURE_IMFS_DISABLE_UNMOUNT:

CONFIGURE_IMFS_DISABLE_UNMOUNT
------------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_UNMOUNT``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to unmount
    file systems is disabled in the root IMFS.

.. index:: CONFIGURE_IMFS_DISABLE_UTIME

.. _CONFIGURE_IMFS_DISABLE_UTIME:

CONFIGURE_IMFS_DISABLE_UTIME
----------------------------

CONSTANT:
    ``CONFIGURE_IMFS_DISABLE_UTIME``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the support to change
    times is disabled in the root IMFS.

.. index:: CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK

.. _CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK:

CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK
--------------------------------------

CONSTANT:
    ``CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Valid values for this configuration parameter are a power of two (2)
    between 16 and 512 inclusive.  In other words, valid values are 16, 32, 64,
    128, 256,and 512.

DEFAULT VALUE:
    The default IMFS block size is 128 bytes.

DESCRIPTION:
    This configuration parameter specifies the block size for in-memory files
    managed by the IMFS. The configured block size has two impacts. The first
    is the average amount of unused memory in the last block of each file. For
    example, when the block size is 512, on average one-half of the last block
    of each file will remain unused and the memory is wasted. In contrast, when
    the block size is 16, the average unused memory per file is only 8
    bytes. However, it requires more allocations for the same size file and
    thus more overhead per block for the dynamic memory management.

    Second, the block size has an impact on the maximum size file that can be
    stored in the IMFS. With smaller block size, the maximum file size is
    correspondingly smaller. The following shows the maximum file size possible
    based on the configured block size:

    - when the block size is 16 bytes, the maximum file size is 1,328 bytes.

    - when the block size is 32 bytes, the maximum file size is 18,656 bytes.

    - when the block size is 64 bytes, the maximum file size is 279,488 bytes.

    - when the block size is 128 bytes, the maximum file size is 4,329,344 bytes.

    - when the block size is 256 bytes, the maximum file size is 68,173,568 bytes.

    - when the block size is 512 bytes, the maximum file size is 1,082,195,456
      bytes.

.. index:: CONFIGURE_MAXIMUM_DEVICES

.. _CONFIGURE_MAXIMUM_DEVICES:

CONFIGURE_MAXIMUM_DEVICES
-------------------------

CONSTANT:
    ``CONFIGURE_MAXIMUM_DEVICES``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Positive.

DEFAULT VALUE:
    If ``BSP_MAXIMUM_DEVICES`` is defined, then the default value is
    ``BSP_MAXIMUM_DEVICES``, otherwise the default value is 4.

DESCRIPTION:
    ``CONFIGURE_MAXIMUM_DEVICES`` is defined to the number of individual
    devices that may be registered in the device file system (devFS).

NOTES:
    This option is specific to the device file system (devFS) and should not be
    confused with the ``CONFIGURE_MAXIMUM_DRIVERS`` option.  This parameter
    only impacts the devFS and thus is only used by ``<rtems/confdefs.h>`` when
    ``CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM`` is specified.

.. index:: CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM

.. _CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM:

CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM
--------------------------------------

CONSTANT:
    ``CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default. If no other root file system configuration
    parameters are specified, the IMFS will be used as the root file system.

DESCRIPTION:
    This configuration parameter is defined if the application wishes to use
    the device-only filesytem as the root file system.

NOTES:
    The device-only filesystem supports only device nodes and is smaller in
    executable code size than the full IMFS and miniIMFS.

    The devFS is comparable in functionality to the pseudo-filesystem name
    space provided before RTEMS release 4.5.0.

.. index:: CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM

.. _CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM:

CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM
-----------------------------------------

CONSTANT:
    ``CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    In case this configuration option is defined, then the following
    configuration options will be defined as well

    - ``CONFIGURE_IMFS_DISABLE_CHMOD``,

    - ``CONFIGURE_IMFS_DISABLE_CHOWN``,

    - ``CONFIGURE_IMFS_DISABLE_UTIME``,

    - ``CONFIGURE_IMFS_DISABLE_LINK``,

    - ``CONFIGURE_IMFS_DISABLE_SYMLINK``,

    - ``CONFIGURE_IMFS_DISABLE_READLINK``,

    - ``CONFIGURE_IMFS_DISABLE_RENAME``, and

    - ``CONFIGURE_IMFS_DISABLE_UNMOUNT``.

Block Device Cache Configuration
================================

This section defines Block Device Cache (bdbuf) related configuration
parameters.

.. index:: CONFIGURE_APPLICATION_NEEDS_LIBBLOCK

.. _CONFIGURE_APPLICATION_NEEDS_LIBBLOCK:

CONFIGURE_APPLICATION_NEEDS_LIBBLOCK
------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_LIBBLOCK``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    Provides a Block Device Cache configuration.

NOTES:
    Each option of the Block Device Cache configuration can be explicitly set
    by the user with the configuration options below.  The Block Device Cache
    is used for example by the RFS and DOSFS file systems.

.. index:: CONFIGURE_BDBUF_CACHE_MEMORY_SIZE

.. _CONFIGURE_BDBUF_CACHE_MEMORY_SIZE:

CONFIGURE_BDBUF_CACHE_MEMORY_SIZE
---------------------------------

CONSTANT:
    ``CONFIGURE_BDBUF_CACHE_MEMORY_SIZE``

DATA TYPE:
    Unsigned integer (``size_t``).

RANGE:
    Positive.

DEFAULT VALUE:
    The default value is 32768 bytes.

DESCRIPTION:
    Size of the cache memory in bytes.

NOTES:
    None.

.. index:: CONFIGURE_BDBUF_BUFFER_MAX_SIZE

.. _CONFIGURE_BDBUF_BUFFER_MAX_SIZE:

CONFIGURE_BDBUF_BUFFER_MAX_SIZE
-------------------------------

CONSTANT:
    ``CONFIGURE_BDBUF_BUFFER_MAX_SIZE``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    It must be positive and an integral multiple of the buffer minimum size.

DEFAULT VALUE:
    The default value is 4096 bytes.

DESCRIPTION:
    Defines the maximum size of a buffer in bytes.

NOTES:
    None.

.. index:: CONFIGURE_BDBUF_BUFFER_MIN_SIZE

.. _CONFIGURE_BDBUF_BUFFER_MIN_SIZE:

CONFIGURE_BDBUF_BUFFER_MIN_SIZE
-------------------------------

CONSTANT:
    ``CONFIGURE_BDBUF_BUFFER_MIN_SIZE``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Positive.

DEFAULT VALUE:
    The default value is 512 bytes.

DESCRIPTION:
    Defines the minimum size of a buffer in bytes.

NOTES:
    None.

.. index:: CONFIGURE_BDBUF_MAX_READ_AHEAD_BLOCKS

.. _CONFIGURE_BDBUF_MAX_READ_AHEAD_BLOCKS:

CONFIGURE_BDBUF_MAX_READ_AHEAD_BLOCKS
-------------------------------------

CONSTANT:
    ``CONFIGURE_BDBUF_MAX_READ_AHEAD_BLOCKS``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Positive.

DEFAULT VALUE:
    The default value is 0.

DESCRIPTION:
    Defines the maximum blocks per read-ahead request.

NOTES:
    A value of 0 disables the read-ahead task (default).  The read-ahead task
    will issue speculative read transfers if a sequential access pattern is
    detected.  This can improve the performance on some systems.

.. index:: CONFIGURE_BDBUF_MAX_WRITE_BLOCKS

.. _CONFIGURE_BDBUF_MAX_WRITE_BLOCKS:

CONFIGURE_BDBUF_MAX_WRITE_BLOCKS
--------------------------------

CONSTANT:
    ``CONFIGURE_BDBUF_MAX_WRITE_BLOCKS``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Positive.

DEFAULT VALUE:
    The default value is 16.

DESCRIPTION:
    Defines the maximum blocks per write request.

NOTES:
    None.

.. index:: CONFIGURE_BDBUF_READ_AHEAD_TASK_PRIORITY

.. _CONFIGURE_BDBUF_READ_AHEAD_TASK_PRIORITY:

CONFIGURE_BDBUF_READ_AHEAD_TASK_PRIORITY
----------------------------------------

CONSTANT:
    ``CONFIGURE_BDBUF_READ_AHEAD_TASK_PRIORITY``

DATA TYPE:
    Task priority (``rtems_task_priority``).

RANGE:
    Valid task priority.

DEFAULT VALUE:
    The default value is 15.

DESCRIPTION:
    Defines the read-ahead task priority.

NOTES:
    None.

.. index:: CONFIGURE_BDBUF_TASK_STACK_SIZE

.. _CONFIGURE_BDBUF_TASK_STACK_SIZE:

CONFIGURE_BDBUF_TASK_STACK_SIZE
-------------------------------

CONSTANT:
    ``CONFIGURE_BDBUF_TASK_STACK_SIZE``

DATA TYPE:
    Unsigned integer (``size_t``).

RANGE:
    Zero or positive.

DEFAULT VALUE:
    The default value is RTEMS_MINIMUM_STACK_SIZE.

DESCRIPTION:
    Defines the task stack size of the Block Device Cache tasks in bytes.

NOTES:
    None.

.. index:: CONFIGURE_SWAPOUT_BLOCK_HOLD

.. _CONFIGURE_SWAPOUT_BLOCK_HOLD:

CONFIGURE_SWAPOUT_BLOCK_HOLD
----------------------------

CONSTANT:
    ``CONFIGURE_SWAPOUT_BLOCK_HOLD``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Positive.

DEFAULT VALUE:
    The default value is 1000 milliseconds.

DESCRIPTION:
    Defines the swapout task maximum block hold time in milliseconds.

NOTES:
    None.

.. index:: CONFIGURE_SWAPOUT_SWAP_PERIOD

.. _CONFIGURE_SWAPOUT_SWAP_PERIOD:

CONFIGURE_SWAPOUT_SWAP_PERIOD
-----------------------------

CONSTANT:
    ``CONFIGURE_SWAPOUT_SWAP_PERIOD``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Positive.

DEFAULT VALUE:
    The default value is 250 milliseconds.

DESCRIPTION:
    Defines the swapout task swap period in milliseconds.

NOTES:
    None.

.. index:: CONFIGURE_SWAPOUT_TASK_PRIORITY

.. _CONFIGURE_SWAPOUT_TASK_PRIORITY:

CONFIGURE_SWAPOUT_TASK_PRIORITY
-------------------------------

CONSTANT:
    ``CONFIGURE_SWAPOUT_TASK_PRIORITY``

DATA TYPE:
    Task priority (``rtems_task_priority``).

RANGE:
    Valid task priority.

DEFAULT VALUE:
    The default value is 15.

DESCRIPTION:
    Defines the swapout task priority.

NOTES:
    None.

.. index:: CONFIGURE_SWAPOUT_WORKER_TASK_PRIORITY

.. _CONFIGURE_SWAPOUT_WORKER_TASK_PRIORITY:

CONFIGURE_SWAPOUT_WORKER_TASK_PRIORITY
--------------------------------------

CONSTANT:
    ``CONFIGURE_SWAPOUT_WORKER_TASK_PRIORITY``

DATA TYPE:
    Task priority (``rtems_task_priority``).

RANGE:
    Valid task priority.

DEFAULT VALUE:
    The default value is 15.

DESCRIPTION:
    Defines the swapout worker task priority.

NOTES:
    None.

.. index:: CONFIGURE_SWAPOUT_WORKER_TASKS

.. _CONFIGURE_SWAPOUT_WORKER_TASKS:

CONFIGURE_SWAPOUT_WORKER_TASKS
------------------------------

CONSTANT:
    ``CONFIGURE_SWAPOUT_WORKER_TASKS``

DATA TYPE:
    Unsigned integer (``size_t``).

RANGE:
    Zero or positive.

DEFAULT VALUE:
    The default value is 0.

DESCRIPTION:
    Defines the swapout worker task count.

NOTES:
    None.

BSP Related Configuration Options
=================================

This section describes configuration options related to the BSP.  Some
configuration options may have a BSP-specific setting which is defined by
``<bsp.h>``.  The BSP-specific settings can be disabled by the
:ref:`CONFIGURE_DISABLE_BSP_SETTINGS` configuration option.

.. index:: BSP_IDLE_TASK_BODY

.. _BSP_IDLE_TASK_BODY:

BSP_IDLE_TASK_BODY
------------------

CONSTANT:
    ``BSP_IDLE_TASK_BODY``

DATA TYPE:
    Function pointer.

RANGE:
    Undefined or valid function pointer.

DEFAULT VALUE:
    This option is BSP specific.

DESCRIPTION:
    If ``BSP_IDLE_TASK_BODY`` is defined by the BSP and
    ``CONFIGURE_IDLE_TASK_BODY`` is not defined by the application, then this
    BSP specific idle task body will be used.

NOTES:
    As it has knowledge of the specific CPU model, system controller logic, and
    peripheral buses, a BSP specific IDLE task may be capable of turning
    components off to save power during extended periods of no task activity

.. index:: BSP_IDLE_TASK_STACK_SIZE

.. _BSP_IDLE_TASK_STACK_SIZE:

BSP_IDLE_TASK_STACK_SIZE
------------------------

CONSTANT:
    ``BSP_IDLE_TASK_STACK_SIZE``

DATA TYPE:
    Unsigned integer (``size_t``).

RANGE:
    Undefined or positive.

DEFAULT VALUE:
    This option is BSP specific.

DESCRIPTION:
    If ``BSP_IDLE_TASK_STACK_SIZE`` is defined by the BSP and
    ``CONFIGURE_IDLE_TASK_STACK_SIZE`` is not defined by the application, then
    this BSP suggested idle task stack size will be used.

NOTES:
    The order of precedence for configuring the IDLE task stack size is:

    - RTEMS default minimum stack size.

    - If defined, then ``CONFIGURE_MINIMUM_TASK_STACK_SIZE``.

    - If defined, then the BSP specific ``BSP_IDLE_TASK_SIZE``.

    - If defined, then the application specified ``CONFIGURE_IDLE_TASK_SIZE``.

.. index:: BSP_INITIAL_EXTENSION

.. _BSP_INITIAL_EXTENSION:

BSP_INITIAL_EXTENSION
---------------------

CONSTANT:
    ``BSP_INITIAL_EXTENSION``

DATA TYPE:
    List of user extension initializers (``rtems_extensions_table``).

RANGE:
    Undefined or a list of user extension initializers.

DEFAULT VALUE:
    This option is BSP specific.

DESCRIPTION:
    If ``BSP_INITIAL_EXTENSION`` is defined by the BSP, then this BSP specific
    initial extension will be placed as the last entry in the initial extension
    table.

NOTES:
    None.

.. index:: BSP_INTERRUPT_STACK_SIZE

.. _BSP_INTERRUPT_STACK_SIZE:

BSP_INTERRUPT_STACK_SIZE
------------------------

CONSTANT:
    ``BSP_INTERRUPT_STACK_SIZE``

DATA TYPE:
    Unsigned integer (``size_t``).

RANGE:
    Undefined or positive.

DEFAULT VALUE:
    This option is BSP specific.

DESCRIPTION:
    If ``BSP_INTERRUPT_STACK_SIZE`` is defined by the BSP and
    ``CONFIGURE_INTERRUPT_STACK_SIZE`` is not defined by the application, then
    this BSP specific interrupt stack size will be used.

NOTES:
    None.

.. index:: BSP_MAXIMUM_DEVICES

.. _BSP_MAXIMUM_DEVICES:

BSP_MAXIMUM_DEVICES
-------------------

CONSTANT:
    ``BSP_MAXIMUM_DEVICES``

DATA TYPE:
    Unsigned integer (``size_t``).

RANGE:
    Undefined or positive.

DEFAULT VALUE:
    This option is BSP specific.

DESCRIPTION:
    If ``BSP_MAXIMUM_DEVICES`` is defined by the BSP and
    ``CONFIGURE_MAXIMUM_DEVICES`` is not defined by the application, then this
    BSP specific maximum device count will be used.

NOTES:
    This option is specific to the device file system (devFS) and should not be
    confused with the ``CONFIGURE_MAXIMUM_DRIVERS`` option.  This parameter
    only impacts the devFS and thus is only used by ``<rtems/confdefs.h>`` when
    ``CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM`` is specified.

.. index:: CONFIGURE_BSP_PREREQUISITE_DRIVERS

.. _CONFIGURE_BSP_PREREQUISITE_DRIVERS:

CONFIGURE_BSP_PREREQUISITE_DRIVERS
----------------------------------

CONSTANT:
    ``CONFIGURE_BSP_PREREQUISITE_DRIVERS``

DATA TYPE:
    List of device driver initializers (``rtems_driver_address_table``).

RANGE:
    Undefined or array of device drivers.

DEFAULT VALUE:
    This option is BSP specific.

DESCRIPTION:
    ``CONFIGURE_BSP_PREREQUISITE_DRIVERS`` is defined if the BSP has device
    drivers it needs to include in the Device Driver Table.  This should be
    defined to the set of device driver entries that will be placed in the
    table at the *FRONT* of the Device Driver Table and initialized before any
    other drivers *INCLUDING* any application prerequisite drivers.

NOTES:
    ``CONFIGURE_BSP_PREREQUISITE_DRIVERS`` is typically used by BSPs to
    configure common infrastructure such as bus controllers or probe for
    devices.

.. index:: CONFIGURE_DISABLE_BSP_SETTINGS

.. _CONFIGURE_DISABLE_BSP_SETTINGS:

CONFIGURE_DISABLE_BSP_SETTINGS
------------------------------

CONSTANT:
    ``CONFIGURE_DISABLE_BSP_SETTINGS``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    All BSP specific configuration settings can be disabled by the application
    with the ``CONFIGURE_DISABLE_BSP_SETTINGS`` option.

NOTES:
    None.

.. index:: CONFIGURE_MALLOC_BSP_SUPPORTS_SBRK

.. _CONFIGURE_MALLOC_BSP_SUPPORTS_SBRK:

CONFIGURE_MALLOC_BSP_SUPPORTS_SBRK
----------------------------------

CONSTANT:
    ``CONFIGURE_MALLOC_BSP_SUPPORTS_SBRK``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This option is BSP specific.

DESCRIPTION:
    This configuration parameter is defined by a BSP to indicate that it does
    not allocate all available memory to the C Program Heap used by the Malloc
    Family of routines.

    If defined, when ``malloc()`` is unable to allocate memory, it will call
    the BSP supplied ``sbrk()`` to obtain more memory.

NOTES:
    This parameter should not be defined by the application. Only the BSP knows
    how it allocates memory to the C Program Heap.

Idle Task Configuration
=======================

This section defines the IDLE task related configuration parameters supported
by ``<rtems/confdefs.h>``.

.. index:: CONFIGURE_IDLE_TASK_BODY

.. _CONFIGURE_IDLE_TASK_BODY:

CONFIGURE_IDLE_TASK_BODY
------------------------

CONSTANT:
    ``CONFIGURE_IDLE_TASK_BODY``

DATA TYPE:
    Function pointer.

RANGE:
    Undefined or valid function pointer.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_IDLE_TASK_BODY`` is set to the function name corresponding to
    the application specific IDLE thread body.  If not specified, the BSP or
    RTEMS default IDLE thread body will be used.

NOTES:
    None.

.. index:: CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION

.. _CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION:

CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION
-------------------------------------------

CONSTANT:
    ``CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default, the user is assumed to provide one or more
    initialization tasks.

DESCRIPTION:
    ``CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION`` is set to indicate that the
    user has configured *NO* user initialization tasks or threads and that the
    user provided IDLE task will perform application initialization and then
    transform itself into an IDLE task.

NOTES:
    If you use this option be careful, the user IDLE task *CANNOT* block at all
    during the initialization sequence.  Further, once application
    initialization is complete, it must make itself preemptible and enter an
    IDLE body loop.

    The IDLE task must run at the lowest priority of all tasks in the system.

.. index:: CONFIGURE_IDLE_TASK_STACK_SIZE

.. _CONFIGURE_IDLE_TASK_STACK_SIZE:

CONFIGURE_IDLE_TASK_STACK_SIZE
------------------------------

CONSTANT:
    ``CONFIGURE_IDLE_TASK_STACK_SIZE``

DATA TYPE:
    Unsigned integer (``size_t``).

RANGE:
    Undefined or positive.

DEFAULT VALUE:
    The default value is RTEMS_MINIMUM_STACK_SIZE.

DESCRIPTION:
    ``CONFIGURE_IDLE_TASK_STACK_SIZE`` is set to the desired stack size for the
    IDLE task.

NOTES:
    None.

General Scheduler Configuration
===============================

This section defines the configuration parameters related to selecting a
scheduling algorithm for an application.  A scheduler configuration is optional
and only necessary in very specific circumstances.  A normal application
configuration does not need any of the configuration options described in this
section.  By default, the :ref:`Deterministic Priority Scheduler
<SchedulerPriority>` algorithm is used in uniprocessor configurations.  In case
SMP is enabled and the configured maximum processors
(:ref:`CONFIGURE_MAXIMUM_PROCESSORS <CONFIGURE_MAXIMUM_PROCESSORS>`) is greater
than one, then the :ref:`Earliest Deadline First (EDF) SMP Scheduler
<SchedulerSMPEDF>` is selected as the default scheduler algorithm.

For the :ref:`schedulers built into
RTEMS <SchedulingConcepts>`, the configuration is straightforward.  All that is
required is to define the configuration macro which specifies which scheduler
you want for in your application.

The pluggable scheduler interface also enables the user to provide their own
scheduling algorithm.  If you choose to do this, you must define multiple
configuration macros.

.. index:: CONFIGURE_SCHEDULER_CBS

.. _CONFIGURE_SCHEDULER_CBS:

CONFIGURE_SCHEDULER_CBS
-----------------------

CONSTANT:
    ``CONFIGURE_SCHEDULER_CBS``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    If defined, then the :ref:`Constant Bandwidth Server (CBS) Scheduler
    <SchedulerCBS>` algorithm is made available to the application.

NOTES:
    This scheduler configuration option is an advanced configuration option.
    Think twice before you use it.

    In case no explicit :ref:`clustered scheduler configuration
    <ConfigurationSchedulersClustered>` is present, then it is used as the
    scheduler for exactly one processor.

.. index:: CONFIGURE_SCHEDULER_EDF

.. _CONFIGURE_SCHEDULER_EDF:

CONFIGURE_SCHEDULER_EDF
-----------------------

CONSTANT:
    ``CONFIGURE_SCHEDULER_EDF``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    If defined, then the :ref:`Earliest Deadline First (EDF) Scheduler
    <SchedulerEDF>` algorithm is made available to the application.

NOTES:
    This scheduler configuration option is an advanced configuration option.
    Think twice before you use it.

    In case no explicit :ref:`clustered scheduler configuration
    <ConfigurationSchedulersClustered>` is present, then it is used as the
    scheduler for exactly one processor.

.. index:: CONFIGURE_SCHEDULER_EDF_SMP

.. _CONFIGURE_SCHEDULER_EDF_SMP:

CONFIGURE_SCHEDULER_EDF_SMP
---------------------------

CONSTANT:
    ``CONFIGURE_SCHEDULER_EDF_SMP``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    If defined, then the :ref:`Earliest Deadline First (EDF) SMP Scheduler
    <SchedulerSMPEDF>` algorithm is made available to the application.

NOTES:
    This scheduler configuration option is an advanced configuration option.
    Think twice before you use it.

    This scheduler algorithm is only available when RTEMS is built with SMP
    support enabled.

    In case no explicit :ref:`clustered scheduler configuration
    <ConfigurationSchedulersClustered>` is present, then it is used as the
    scheduler for up to 32 processors.

    This scheduler algorithm is the default in SMP configurations if
    :ref:`CONFIGURE_MAXIMUM_PROCESSORS <CONFIGURE_MAXIMUM_PROCESSORS>` is
    greater than one.

.. index:: CONFIGURE_SCHEDULER_NAME

.. _CONFIGURE_SCHEDULER_NAME:

CONFIGURE_SCHEDULER_NAME
------------------------

CONSTANT:
    ``CONFIGURE_SCHEDULER_NAME``

DATA TYPE:
    RTEMS Name (``rtems_name``).

RANGE:
    Any value.

DEFAULT VALUE:
    The default name is

      - ``"MEDF"`` for the :ref:`EDF SMP Scheduler <SchedulerSMPEDF>`,
      - ``"MPA "`` for the :ref:`Arbitrary Processor Affinity Priority SMP Scheduler <SchedulerSMPPriorityAffinity>`,
      - ``"MPD "`` for the :ref:`Deterministic Priority SMP Scheduler <SchedulerSMPPriority>`,
      - ``"MPS "`` for the :ref:`Simple Priority SMP Scheduler <SchedulerSMPPrioritySimple>`,
      - ``"UCBS"`` for the :ref:`Uniprocessor CBS Scheduler <SchedulerCBS>`,
      - ``"UEDF"`` for the :ref:`Uniprocessor EDF Scheduler <SchedulerEDF>`,
      - ``"UPD "`` for the :ref:`Uniprocessor Deterministic Priority Scheduler <SchedulerPriority>`, and
      - ``"UPS "`` for the :ref:`Uniprocessor Simple Priority Scheduler <SchedulerPrioritySimple>`.

DESCRIPTION:
    Schedulers can be identified via ``rtems_scheduler_ident``.  The name of
    the scheduler is determined by the configuration.

NOTES:
    This scheduler configuration option is an advanced configuration option.
    Think twice before you use it.

.. index:: CONFIGURE_SCHEDULER_PRIORITY

.. _CONFIGURE_SCHEDULER_PRIORITY:

CONFIGURE_SCHEDULER_PRIORITY
----------------------------

CONSTANT:
    ``CONFIGURE_SCHEDULER_PRIORITY``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is defined by default.  This is the default scheduler and specifying
    this configuration parameter is redundant.

DESCRIPTION:
    If defined, then the :ref:`Deterministic Priority Scheduler
    <SchedulerPriority>` algorithm is made available to the application.

NOTES:
    This scheduler configuration option is an advanced configuration option.
    Think twice before you use it.

    In case no explicit :ref:`clustered scheduler configuration
    <ConfigurationSchedulersClustered>` is present, then it is used as the
    scheduler for exactly one processor.

    This scheduler algorithm is the default when
    :ref:`CONFIGURE_MAXIMUM_PROCESSORS <CONFIGURE_MAXIMUM_PROCESSORS>` is
    exactly one.

    The memory allocated for this scheduler depends on the
    :ref:`CONFIGURE_MAXIMUM_PRIORITY` configuration option.

.. index:: CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP

.. _CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP:

CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP
-----------------------------------------

CONSTANT:
    ``CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    If defined, then the :ref:`Arbitrary Processor Affinity SMP Scheduler
    <SchedulerSMPPriorityAffinity>` algorithm is made available to the
    application.

NOTES:
    This scheduler configuration option is an advanced configuration option.
    Think twice before you use it.

    This scheduler algorithm is only available when RTEMS is built with SMP
    support enabled.

    In case no explicit :ref:`clustered scheduler configuration
    <ConfigurationSchedulersClustered>` is present, then it is used as the
    scheduler for up to 32 processors.

    The memory allocated for this scheduler depends on the
    :ref:`CONFIGURE_MAXIMUM_PRIORITY` configuration option.

.. index:: CONFIGURE_SCHEDULER_PRIORITY_SMP

.. _CONFIGURE_SCHEDULER_PRIORITY_SMP:

CONFIGURE_SCHEDULER_PRIORITY_SMP
--------------------------------

CONSTANT:
    ``CONFIGURE_SCHEDULER_PRIORITY_SMP``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    If defined, then the :ref:`Deterministic Priority SMP Scheduler
    <SchedulerSMPPriority>` algorithm is made available to the application.

NOTES:
    This scheduler configuration option is an advanced configuration option.
    Think twice before you use it.

    This scheduler algorithm is only available when RTEMS is built with SMP
    support enabled.

    In case no explicit :ref:`clustered scheduler configuration
    <ConfigurationSchedulersClustered>` is present, then it is used as the
    scheduler for up to 32 processors.

    The memory allocated for this scheduler depends on the
    :ref:`CONFIGURE_MAXIMUM_PRIORITY` configuration option.

.. index:: CONFIGURE_SCHEDULER_SIMPLE

.. _CONFIGURE_SCHEDULER_SIMPLE:

CONFIGURE_SCHEDULER_SIMPLE
--------------------------

CONSTANT:
    ``CONFIGURE_SCHEDULER_SIMPLE``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    If defined, then the :ref:`Simple Priority Scheduler
    <SchedulerPrioritySimple>` algorithm is made available to the application.

NOTES:
    This scheduler configuration option is an advanced configuration option.
    Think twice before you use it.

    In case no explicit :ref:`clustered scheduler configuration
    <ConfigurationSchedulersClustered>` is present, then it is used as the
    scheduler for exactly one processor.

.. index:: CONFIGURE_SCHEDULER_SIMPLE_SMP

.. _CONFIGURE_SCHEDULER_SIMPLE_SMP:

CONFIGURE_SCHEDULER_SIMPLE_SMP
------------------------------

CONSTANT:
    ``CONFIGURE_SCHEDULER_SIMPLE_SMP``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    If defined, then the :ref:`Simple Priority SMP Scheduler
    <SchedulerSMPPrioritySimple>` algorithm is made available to the
    application.

NOTES:
    This scheduler configuration option is an advanced configuration option.
    Think twice before you use it.

    This scheduler algorithm is only available when RTEMS is built with SMP
    support enabled.

    In case no explicit :ref:`clustered scheduler configuration
    <ConfigurationSchedulersClustered>` is present, then it is used as the
    scheduler for up to 32 processors.

.. index:: CONFIGURE_SCHEDULER_USER

.. _CONFIGURE_SCHEDULER_USER:

CONFIGURE_SCHEDULER_USER
------------------------

CONSTANT:
    ``CONFIGURE_SCHEDULER_USER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    RTEMS allows the application to provide its own task/thread scheduling
    algorithm. In order to do this, one must define
    ``CONFIGURE_SCHEDULER_USER`` to indicate the application provides its own
    scheduling algorithm. If ``CONFIGURE_SCHEDULER_USER`` is defined then the
    following additional macros must be defined:

    - ``CONFIGURE_SCHEDULER`` must be defined to a static definition of
      the scheduler data structures of the user scheduler.

    - ``CONFIGURE_SCHEDULER_TABLE_ENTRIES`` must be defined to a scheduler
      table entry initializer for the user scheduler.

    - ``CONFIGURE_SCHEDULER_USER_PER_THREAD`` must be defined to the type of
      the per-thread information of the user scheduler.

NOTES:
    This scheduler configuration option is an advanced configuration option.
    Think twice before you use it.

    At this time, the mechanics and requirements for writing a new scheduler
    are evolving and not fully documented.  It is recommended that you look at
    the existing Deterministic Priority Scheduler in
    ``cpukit/score/src/schedulerpriority*.c`` for guidance.  For guidance on
    the configuration macros, please examine ``cpukit/sapi/include/confdefs.h``
    for how these are defined for the Deterministic Priority Scheduler.

.. _ConfigurationSchedulersClustered:

Clustered Scheduler Configuration
=================================

A clustered scheduler configuration is optional.  It is an advanced
configuration area and only necessary in specific circumstances.

Clustered scheduling helps to control the worst-case latencies in a
multiprocessor system (SMP).  The goal is to reduce the amount of shared state
in the system and thus prevention of lock contention.  Modern multiprocessor
systems tend to have several layers of data and instruction caches.  With
clustered scheduling it is possible to honour the cache topology of a system
and thus avoid expensive cache synchronization traffic.

We have clustered scheduling in case the set of processors of a system is
partitioned into non-empty pairwise-disjoint subsets.  These subsets are called
clusters.  Clusters with a cardinality of one are partitions.  Each cluster is
owned by exactly one scheduler.

In order to use clustered scheduling the application designer has to answer two
questions.

#. How is the set of processors partitioned into clusters?

#. Which scheduler algorithm is used for which cluster?

The schedulers are statically configured.

Configuration Step 1 - Scheduler Algorithms
-------------------------------------------

Firstly, the application must select which scheduling algorithms are available
with the following defines

- :ref:`CONFIGURE_SCHEDULER_EDF_SMP <CONFIGURE_SCHEDULER_EDF_SMP>`,

- :ref:`CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP <CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP>`,

- :ref:`CONFIGURE_SCHEDULER_PRIORITY_SMP <CONFIGURE_SCHEDULER_PRIORITY_SMP>`, and

- :ref:`CONFIGURE_SCHEDULER_SIMPLE_SMP <CONFIGURE_SCHEDULER_SIMPLE_SMP>`.

This is necessary to calculate the per-thread overhead introduced by the
scheduler algorithms.  After these definitions the configuration file must
``#include <rtems/scheduler.h>`` to have access to scheduler-specific
configuration macros.

It is possible to make more than one scheduler algorithm available to the
application.  For example a :ref:`Simple Priority SMP Scheduler
<SchedulerSMPPrioritySimple>` could be used in a partition for low latency
tasks in addition to an :ref:`EDF SMP Scheduler <SchedulerSMPEDF>` for a
general-purpose cluster.  Since the per-thread overhead depends on the
scheduler algorithm only the scheduler algorithms used by the application
should be configured.

Configuration Step 2 - Schedulers
---------------------------------

Each scheduler needs some data structures.  Use the following macros to create
the scheduler data structures for a particular scheduler identified in the
configuration by ``name``.

- ``RTEMS_SCHEDULER_EDF_SMP(name, max_cpu_count)``,

- ``RTEMS_SCHEDULER_PRIORITY_AFFINITY_SMP(name, prio_count)``,

- ``RTEMS_SCHEDULER_PRIORITY_SMP(name, prio_count)``, and

- ``RTEMS_SCHEDULER_SIMPLE_SMP(name)``.

The ``name`` parameter is used as part of a designator for scheduler-specific
data structures, so the usual C/C++ designator rules apply.  This ``name`` is
not the scheduler object name.  Additional parameters are scheduler-specific.

.. _ConfigurationSchedulerTable:

Configuration Step 3 - Scheduler Table
--------------------------------------

The schedulers are registered in the system via the scheduler table.  To
populate the scheduler table define ``CONFIGURE_SCHEDULER_TABLE_ENTRIES`` to a
list of the following scheduler table entry initializers

- ``RTEMS_SCHEDULER_TABLE_EDF_SMP(name, obj_name)``,

- ``RTEMS_SCHEDULER_TABLE_PRIORITY_AFFINITY_SMP(name, obj_name)``,

- ``RTEMS_SCHEDULER_TABLE_PRIORITY_SMP(name, obj_name)``, and

- ``RTEMS_SCHEDULER_TABLE_SIMPLE_SMP(name, obj_name)``.

The ``name`` parameter must correspond to the parameter defining the scheduler
data structures of configuration step 2.  The ``obj_name`` determines the
scheduler object name and can be used in :ref:`rtems_scheduler_ident()
<rtems_scheduler_ident>` to get the scheduler object identifier.  The scheduler
index is defined by the index of the scheduler table.  It is a configuration
error to add a scheduler multiple times to the scheduler table.

Configuration Step 4 - Processor to Scheduler Assignment
--------------------------------------------------------

The last step is to define which processor uses which scheduler.  For this
purpose a scheduler assignment table must be defined.  The entry count of this
table must be equal to the configured maximum processors
(:ref:`CONFIGURE_MAXIMUM_PROCESSORS <CONFIGURE_MAXIMUM_PROCESSORS>`).  A
processor assignment to a scheduler can be optional or mandatory.  The boot
processor must have a scheduler assigned.  In case the system needs more
mandatory processors than available then a fatal run-time error will occur.  To
specify the scheduler assignments define
``CONFIGURE_SCHEDULER_ASSIGNMENTS`` to a list of

- ``RTEMS_SCHEDULER_ASSIGN(scheduler_index, attr)`` and

- ``RTEMS_SCHEDULER_ASSIGN_NO_SCHEDULER``

macros.  The ``scheduler_index`` parameter must be a valid index into the
scheduler table defined by configuration step 3.  The ``attr`` parameter
defines the scheduler assignment attributes.  By default, a scheduler
assignment to a processor is optional.  For the scheduler assignment attribute
use one of the mutually exclusive variants

- ``RTEMS_SCHEDULER_ASSIGN_DEFAULT``,

- ``RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY``, and

- ``RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL``.

It is possible to add/remove processors to/from schedulers at run-time, see
:ref:`rtems_scheduler_add_processor() <rtems_scheduler_add_processor>` and
:ref:`rtems_scheduler_remove_processor() <rtems_scheduler_remove_processor>`.

Configuration Example
---------------------

The following example shows a scheduler configuration for a hypothetical
product using two chip variants.  One variant has four processors which is used
for the normal product line and another provides eight processors for the
high-performance product line.  The first processor performs hard-real time
control of actuators and sensors.  The second processor is not used by RTEMS at
all and runs a Linux instance to provide a graphical user interface.  The
additional processors are used for a worker thread pool to perform data
processing operations.

The processors managed by RTEMS use two Deterministic Priority SMP schedulers
capable of dealing with 256 priority levels.  The scheduler with index zero has
the name ``"IO "``.  The scheduler with index one has the name ``"WORK"``.  The
scheduler assignments of the first, third and fourth processor are mandatory,
so the system must have at least four processors, otherwise a fatal run-time
error will occur during system startup.  The processor assignments for the
fifth up to the eighth processor are optional so that the same application can
be used for the normal and high-performance product lines.  The second
processor has no scheduler assigned and runs Linux.  A hypervisor will ensure
that the two systems cannot interfere in an undesirable way.

.. code-block:: c

    #define CONFIGURE_MAXIMUM_PROCESSORS 8
    #define CONFIGURE_MAXIMUM_PRIORITY 255

    /* Configuration Step 1 - Scheduler Algorithms */
    #define CONFIGURE_SCHEDULER_PRIORITY_SMP
    #include <rtems/scheduler.h>

    /* Configuration Step 2 - Schedulers */
    RTEMS_SCHEDULER_PRIORITY_SMP(io, CONFIGURE_MAXIMUM_PRIORITY + 1);
    RTEMS_SCHEDULER_PRIORITY_SMP(work, CONFIGURE_MAXIMUM_PRIORITY + 1);

    /* Configuration Step 3 - Scheduler Table */
    #define CONFIGURE_SCHEDULER_TABLE_ENTRIES \
      RTEMS_SCHEDULER_TABLE_PRIORITY_SMP( \
        io, \
         rtems_build_name('I', 'O', ' ', ' ') \
      ), \
      RTEMS_SCHEDULER_TABLE_PRIORITY_SMP( \
        work, \
        rtems_build_name('W', 'O', 'R', 'K') \
      )

    /* Configuration Step 4 - Processor to Scheduler Assignment */
    #define CONFIGURE_SCHEDULER_ASSIGNMENTS \
      RTEMS_SCHEDULER_ASSIGN(0, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY), \
      RTEMS_SCHEDULER_ASSIGN_NO_SCHEDULER, \
      RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY), \
      RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY), \
      RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL), \
      RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL), \
      RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL), \
      RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL)

Configuration Errors
--------------------

In case one of the scheduler indices in ``CONFIGURE_SCHEDULER_ASSIGNMENTS``
is invalid a link-time error will occur with an undefined reference to
``RTEMS_SCHEDULER_INVALID_INDEX``.

Some fatal errors may occur in case of scheduler configuration inconsistencies
or a lack of processors on the system.  The fatal source is
``RTEMS_FATAL_SOURCE_SMP``.

- ``SMP_FATAL_BOOT_PROCESSOR_NOT_ASSIGNED_TO_SCHEDULER`` - the boot processor
  must have a scheduler assigned.

- ``SMP_FATAL_MANDATORY_PROCESSOR_NOT_PRESENT`` - there exists a mandatory
  processor beyond the range of physically or virtually available processors.
  The processor demand must be reduced for this system.

- ``SMP_FATAL_START_OF_MANDATORY_PROCESSOR_FAILED`` - the start of a mandatory
  processor failed during system initialization.  The system may not have this
  processor at all or it could be a problem with a boot loader for example.
  Check the ``CONFIGURE_SCHEDULER_ASSIGNMENTS`` definition.

- ``SMP_FATAL_MULTITASKING_START_ON_UNASSIGNED_PROCESSOR`` - it is not allowed
  to start multitasking on a processor with no scheduler assigned.

Device Driver Configuration
===========================

This section defines the configuration parameters related to the automatic
generation of a Device Driver Table.  As ``<rtems/confdefs.h>`` only is aware
of a small set of standard device drivers, the generated Device Driver Table is
suitable for simple applications with no custom device drivers.

Note that network device drivers are not configured in the Device Driver Table.

.. index:: CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER

.. _CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER:

CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER
------------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER`` is defined when the
    application does *NOT* want the Clock Device Driver and is *NOT* using the
    Timer Driver.  The inclusion or exclusion of the Clock Driver must be
    explicit in user applications.

NOTES:
    This configuration parameter is intended to prevent the common user error
    of using the Hello World example as the baseline for an application and
    leaving out a clock tick source.

.. index:: CONFIGURE_APPLICATION_EXTRA_DRIVERS

.. _CONFIGURE_APPLICATION_EXTRA_DRIVERS:

CONFIGURE_APPLICATION_EXTRA_DRIVERS
-----------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_EXTRA_DRIVERS``

DATA TYPE:
    device driver entry structures

RANGE:
    Undefined or set of device driver entry structures

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_APPLICATION_EXTRA_DRIVERS`` is defined if the application has
    device drivers it needs to include in the Device Driver Table.  This should
    be defined to the set of device driver entries that will be placed in the
    table at the *END* of the Device Driver Table.

NOTES:
    None.

.. index:: CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER:

CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER
----------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER`` is defined if the application
    wishes to include the Clock Device Driver.

NOTES:
    This device driver is responsible for providing a regular interrupt which
    invokes a clock tick directive.

    If neither the Clock Driver not Benchmark Timer is enabled and the
    configuration parameter
    ``CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER`` is not defined, then a
    compile time error will occur.

.. index:: CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER:

CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER
------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER`` is defined if the
    application wishes to include the Console Device Driver.

NOTES:
    This device driver is responsible for providing the :file:`/dev/console`
    device file.  This device is used to initialize the standard input, output,
    and error file descriptors.

    BSPs should be constructed in a manner that allows ``printk()`` to work
    properly without the need for the console driver to be configured.

    The

    * ``CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER``,

    * ``CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER``, and

    * ``CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER``

    configuration options are mutually exclusive.

.. index:: CONFIGURE_APPLICATION_NEEDS_FRAME_BUFFER_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_FRAME_BUFFER_DRIVER:

CONFIGURE_APPLICATION_NEEDS_FRAME_BUFFER_DRIVER
-----------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_FRAME_BUFFER_DRIVER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_APPLICATION_NEEDS_FRAME_BUFFER_DRIVER`` is defined if the
    application wishes to include the BSP's Frame Buffer Device Driver.

NOTES:
    Most BSPs do not include support for a Frame Buffer Device Driver. This is
    because many boards do not include the required hardware.

    If this is defined and the BSP does not have this device driver, then the
    user will get a link time error for an undefined symbol.

.. index:: CONFIGURE_APPLICATION_NEEDS_NULL_DRIVER
.. index:: /dev/null

.. _CONFIGURE_APPLICATION_NEEDS_NULL_DRIVER:

CONFIGURE_APPLICATION_NEEDS_NULL_DRIVER
---------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_NULL_DRIVER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    This configuration variable is specified to enable ``/dev/null`` device driver.

NOTES:
    This device driver is supported by all BSPs.

.. index:: CONFIGURE_APPLICATION_NEEDS_RTC_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_RTC_DRIVER:

CONFIGURE_APPLICATION_NEEDS_RTC_DRIVER
--------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_RTC_DRIVER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_APPLICATION_NEEDS_RTC_DRIVER`` is defined if the application
    wishes to include the Real-Time Clock Driver.

NOTES:
    Most BSPs do not include support for a real-time clock. This is because
    many boards do not include the required hardware.

    If this is defined and the BSP does not have this device driver, then the
    user will get a link time error for an undefined symbol.

.. index:: CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER:

CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER
-------------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER`` is defined if the
    application wishes to include the Simple Console Device Driver.

NOTES:
    This device driver is responsible for providing the :file:`/dev/console`
    device file.  This device is used to initialize the standard input, output,
    and error file descriptors.

    This device driver reads via ``getchark()``.

    This device driver writes via ``rtems_putc()``.

    The Termios framework is not used.  There is no support to change device
    settings, e.g. baud, stop bits, parity, etc.

    The

    * ``CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER``,

    * ``CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER``, and

    * ``CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER``

    configuration options are mutually exclusive.

.. index:: CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER:

CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER
------------------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER`` is defined if
    the application wishes to include the Simple Task Console Device Driver.

NOTES:
    This device driver is responsible for providing the :file:`/dev/console`
    device file.  This device is used to initialize the standard input, output,
    and error file descriptors.

    This device driver reads via ``getchark()``.

    This device driver writes into a write buffer.  The count of characters
    written into the write buffer is returned.  It might be less than the
    requested count, in case the write buffer is full.  The write is
    non-blocking and may be called from interrupt context.  A dedicated task
    reads from the write buffer and outputs the characters via
    ``rtems_putc()``.  This task runs with the least important priority.  The
    write buffer size is 2047 characters and it is not configurable.

    Use ``fsync(STDOUT_FILENO)`` or ``fdatasync(STDOUT_FILENO)`` to drain the
    write buffer.

    The Termios framework is not used.  There is no support to change device
    settings, e.g.  baud, stop bits, parity, etc.

    The

    * ``CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER``,

    * ``CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER``, and

    * ``CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER``

    configuration options are mutually exclusive.

.. index:: CONFIGURE_APPLICATION_NEEDS_STUB_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_STUB_DRIVER:

CONFIGURE_APPLICATION_NEEDS_STUB_DRIVER
---------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_STUB_DRIVER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_APPLICATION_NEEDS_STUB_DRIVER`` is defined if the application
    wishes to include the Stub Device Driver.

NOTES:
    This device driver simply provides entry points that return successful and
    is primarily a test fixture. It is supported by all BSPs.

.. index:: CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER:

CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER
----------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER`` is defined if the application
    wishes to include the Timer Driver.  This device driver is used to
    benchmark execution times by the RTEMS Timing Test Suites.

NOTES:
    If neither the Clock Driver not Benchmark Timer is enabled and the
    configuration parameter
    ``CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER`` is not defined, then a
    compile time error will occur.

.. index:: CONFIGURE_APPLICATION_NEEDS_WATCHDOG_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_WATCHDOG_DRIVER:

CONFIGURE_APPLICATION_NEEDS_WATCHDOG_DRIVER
-------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_WATCHDOG_DRIVER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_APPLICATION_NEEDS_WATCHDOG_DRIVER`` is defined if the
    application wishes to include the Watchdog Driver.

NOTES:
    Most BSPs do not include support for a watchdog device driver. This is
    because many boards do not include the required hardware.

    If this is defined and the BSP does not have this device driver, then the
    user will get a link time error for an undefined symbol.

.. index:: CONFIGURE_APPLICATION_NEEDS_ZERO_DRIVER
.. index:: /dev/zero

.. _CONFIGURE_APPLICATION_NEEDS_ZERO_DRIVER:

CONFIGURE_APPLICATION_NEEDS_ZERO_DRIVER
---------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_ZERO_DRIVER``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    This configuration variable is specified to enable ``/dev/zero`` device driver.

NOTES:
    This device driver is supported by all BSPs.

.. index:: CONFIGURE_APPLICATION_PREREQUISITE_DRIVERS

.. _CONFIGURE_APPLICATION_PREREQUISITE_DRIVERS:

CONFIGURE_APPLICATION_PREREQUISITE_DRIVERS
------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_PREREQUISITE_DRIVERS``

DATA TYPE:
    device driver entry structures

RANGE:
    Undefined or set of device driver entry structures

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_APPLICATION_PREREQUISITE_DRIVERS`` is defined if the
    application has device drivers it needs to include in the Device Driver
    Table.  This should be defined to the set of device driver entries that
    will be placed in the table at the *FRONT* of the Device Driver Table and
    initialized before any other drivers *EXCEPT* any BSP prerequisite drivers.

NOTES:
    In some cases, it is used by System On Chip BSPs to support peripheral
    buses beyond those normally found on the System On Chip. For example, this
    is used by one RTEMS system which has implemented a SPARC/ERC32 based board
    with VMEBus. The VMEBus Controller initialization is performed by a device
    driver configured via this configuration parameter.

.. index:: CONFIGURE_MAXIMUM_DRIVERS

.. _CONFIGURE_MAXIMUM_DRIVERS:

CONFIGURE_MAXIMUM_DRIVERS
-------------------------

CONSTANT:
    ``CONFIGURE_MAXIMUM_DRIVERS``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Zero or positive.

DEFAULT VALUE:
    This is computed by default, and is set to the number of device drivers
    configured using the ``CONFIGURE_APPLICATIONS_NEEDS_XXX_DRIVER``
    configuration parameters.

DESCRIPTION:
    ``CONFIGURE_MAXIMUM_DRIVERS`` is defined as the number of device drivers
    per node.

NOTES:
    If the application will dynamically install device drivers, then this
    configuration parameter must be larger than the number of statically
    configured device drivers. Drivers configured using the
    ``CONFIGURE_APPLICATIONS_NEEDS_XXX_DRIVER`` configuration parameters are
    statically installed.

Multiprocessing Configuration
=============================

This section defines the multiprocessing related system configuration
parameters supported by ``<rtems/confdefs.h>``.  They are only used if RTEMS
was built with the ``--enable-multiprocessing`` build configuration option.
The multiprocessing (MPCI) support must not be confused with the SMP support.

Additionally, this class of Configuration Constants are only applicable if
``CONFIGURE_MP_APPLICATION`` is defined.

.. index:: CONFIGURE_MP_APPLICATION

.. _CONFIGURE_MP_APPLICATION:

CONFIGURE_MP_APPLICATION
------------------------

CONSTANT:
    ``CONFIGURE_MP_APPLICATION``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    This configuration parameter must be defined to indicate that the
    application intends to be part of a multiprocessing
    configuration. Additional configuration parameters are assumed to be
    provided.

NOTES:
    This has no impact unless RTEMS was built with the
    ``--enable-multiprocessing`` build configuration option.

.. index:: CONFIGURE_MP_MAXIMUM_GLOBAL_OBJECTS

.. _CONFIGURE_MP_MAXIMUM_GLOBAL_OBJECTS:

CONFIGURE_MP_MAXIMUM_GLOBAL_OBJECTS
-----------------------------------

CONSTANT:
    ``CONFIGURE_MP_MAXIMUM_GLOBAL_OBJECTS``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Positive.

DEFAULT VALUE:
    The default value is 32.

DESCRIPTION:
    ``CONFIGURE_MP_MAXIMUM_GLOBAL_OBJECTS`` is the maximum number of
    concurrently active global objects in a multiprocessor system.

NOTES:
    This value corresponds to the total number of objects which can be created
    with the ``RTEMS_GLOBAL`` attribute.

.. index:: CONFIGURE_MP_MAXIMUM_NODES

.. _CONFIGURE_MP_MAXIMUM_NODES:

CONFIGURE_MP_MAXIMUM_NODES
--------------------------

CONSTANT:
    ``CONFIGURE_MP_MAXIMUM_NODES``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Positive.

DEFAULT VALUE:
    The default value is 2.

DESCRIPTION:
    ``CONFIGURE_MP_MAXIMUM_NODES`` is the maximum number of nodes in a
    multiprocessor system.

NOTES:
    None.

.. index:: CONFIGURE_MP_MAXIMUM_PROXIES

.. _CONFIGURE_MP_MAXIMUM_PROXIES:

CONFIGURE_MP_MAXIMUM_PROXIES
----------------------------

CONSTANT:
    ``CONFIGURE_MP_MAXIMUM_PROXIES``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Undefined or positive.

DEFAULT VALUE:
    The default value is 32.

DESCRIPTION:
    ``CONFIGURE_MP_MAXIMUM_PROXIES`` is the maximum number of concurrently
    active thread/task proxies on this node in a multiprocessor system.

NOTES:
    Since a proxy is used to represent a remote task/thread which is blocking
    on this node. This configuration parameter reflects the maximum number of
    remote tasks/threads which can be blocked on objects on this node.

.. COMMENT: XXX - add xref to proxy discussion in MP chapter

.. index:: CONFIGURE_MP_MPCI_TABLE_POINTER

.. _CONFIGURE_MP_MPCI_TABLE_POINTER:

CONFIGURE_MP_MPCI_TABLE_POINTER
-------------------------------

CONSTANT:
    ``CONFIGURE_MP_MPCI_TABLE_POINTER``

DATA TYPE:
    pointer to ``rtems_mpci_table``

RANGE:
    undefined or valid pointer

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    ``CONFIGURE_MP_MPCI_TABLE_POINTER`` is the pointer to the MPCI
    Configuration Table.  The default value of this field is``&MPCI_table``.

NOTES:
    RTEMS provides a Shared Memory MPCI Device Driver which can be used on any
    Multiprocessor System assuming the BSP provides the proper set of
    supporting methods.

.. index:: CONFIGURE_MP_NODE_NUMBER

.. _CONFIGURE_MP_NODE_NUMBER:

CONFIGURE_MP_NODE_NUMBER
------------------------

CONSTANT:
    ``CONFIGURE_MP_NODE_NUMBER``

DATA TYPE:
    Unsigned integer (``uint32_t``).

RANGE:
    Positive.

DEFAULT VALUE:
    The default value is ``NODE_NUMBER``, which is assumed to be set by the
    compilation environment.

DESCRIPTION:
    ``CONFIGURE_MP_NODE_NUMBER`` is the node number of this node in a
    multiprocessor system.

NOTES:
    In the RTEMS Multiprocessing Test Suite, the node number is derived from
    the Makefile variable ``NODE_NUMBER``. The same code is compiled with the
    ``NODE_NUMBER`` set to different values. The test programs behave
    differently based upon their node number.

PCI Library Configuration
=========================

This section defines the system configuration parameters supported by
``rtems/confdefs.h`` related to configuring the PCI Library for RTEMS.

The PCI Library startup behaviour can be configured in four different ways
depending on how ``CONFIGURE_PCI_CONFIG_LIB`` is defined:

.. index:: PCI_LIB_AUTO

``PCI_LIB_AUTO``
  Used to enable the PCI auto configuration software. PCI will be automatically
  probed, PCI buses enumerated, all devices and bridges will be initialized
  using Plug & Play software routines. The PCI device tree will be populated
  based on the PCI devices found in the system, PCI devices will be configured
  by allocating address region resources automatically in PCI space according
  to the BSP or host bridge driver set up.

.. index:: PCI_LIB_READ

``PCI_LIB_READ``
  Used to enable the PCI read configuration software. The current PCI
  configuration is read to create the RAM representation (the PCI device tree)
  of the PCI devices present. PCI devices are assumed to already have been
  initialized and PCI buses enumerated, it is therefore required that a BIOS or
  a boot loader has set up configuration space prior to booting into RTEMS.

.. index:: PCI_LIB_STATIC

``PCI_LIB_STATIC``
  Used to enable the PCI static configuration software. The user provides a PCI
  tree with information how all PCI devices are to be configured at compile
  time by linking in a custom ``struct pci_bus pci_hb`` tree. The static PCI
  library will not probe PCI for devices, instead it will assume that all
  devices defined by the user are present, it will enumerate the PCI buses and
  configure all PCI devices in static configuration accordingly. Since probe
  and allocation software is not needed the startup is faster, has smaller
  footprint and does not require dynamic memory allocation.

.. index:: PCI_LIB_PERIPHERAL

``PCI_LIB_PERIPHERAL``
  Used to enable the PCI peripheral configuration. It is similar to
  ``PCI_LIB_STATIC``, but it will never write the configuration to the PCI
  devices since PCI peripherals are not allowed to access PCI configuration
  space.

Note that selecting ``PCI_LIB_STATIC`` or ``PCI_LIB_PERIPHERAL`` but not
defining ``pci_hb`` will reuslt in link errors. Note also that in these modes
Plug & Play is not performed.

Event Recording Configuration
=============================

.. index:: CONFIGURE_RECORD_EXTENSIONS_ENABLED

.. _CONFIGURE_RECORD_EXTENSIONS_ENABLED:

CONFIGURE_RECORD_EXTENSIONS_ENABLED
-----------------------------------

CONSTANT:
    ``CONFIGURE_RECORD_EXTENSIONS_ENABLED``

DATA TYPE:
    Boolean feature macro.

RANGE:
    Defined or undefined.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    If defined and :ref:`CONFIGURE_RECORD_PER_PROCESSOR_ITEMS
    <CONFIGURE_RECORD_PER_PROCESSOR_ITEMS>` is also defined properly, then the
    record extensions are enabled.

NOTES:
    The record extensions capture thread create, start, restart, delete,
    switch, begin, exitted and terminate events.

.. index:: CONFIGURE_RECORD_PER_PROCESSOR_ITEMS

.. _CONFIGURE_RECORD_PER_PROCESSOR_ITEMS:

CONFIGURE_RECORD_PER_PROCESSOR_ITEMS
------------------------------------

CONSTANT:
    ``CONFIGURE_RECORD_PER_PROCESSOR_ITEMS``

DATA TYPE:
    Unsigned integer (``unsigned int``).

RANGE:
    A power of two greater than or equal to 16.

DEFAULT VALUE:
    This is not defined by default.

DESCRIPTION:
    If defined, then a record item buffer of the specified item count is
    statically allocated for each configured processor
    (:ref:`CONFIGURE_MAXIMUM_PROCESSORS <CONFIGURE_MAXIMUM_PROCESSORS>`).

NOTES:
    None.

.. _ConfigAda:

Ada Configuration
=================

The GNU Ada runtime library (libgnarl) uses threads, mutexes, condition
variables, and signals from the pthreads API.  It uses also thread-local storage
for the Ada Task Control Block (ATCB).  From these resources only the threads
need to be accounted for in the configuration.  You should include the Ada tasks
in your setting of the :ref:`CONFIGURE_MAXIMUM_POSIX_THREADS` configuration
option.

Obsolete Configuration Options
==============================

.. index:: CONFIGURE_BDBUF_BUFFER_COUNT

CONFIGURE_BDBUF_BUFFER_COUNT
----------------------------

This configuration option was introduced in RTEMS 4.7.0 and is obsolete since
RTEMS 4.10.0.

.. index:: CONFIGURE_BDBUF_BUFFER_SIZE

CONFIGURE_BDBUF_BUFFER_SIZE
---------------------------

This configuration option was introduced in RTEMS 4.7.0 and is obsolete since
RTEMS 4.10.0.

.. index:: CONFIGURE_DISABLE_CLASSIC_API_NOTEPADS

CONFIGURE_DISABLE_CLASSIC_API_NOTEPADS
--------------------------------------

This configuration option was introduced in RTEMS 4.9.0 and is obsolete since
RTEMS 5.1.

.. index:: CONFIGURE_ENABLE_GO

CONFIGURE_ENABLE_GO
-------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_GNAT_RTEMS

CONFIGURE_GNAT_RTEMS
--------------------

This configuration option was present in all RTEMS versions since at 1997 and is
obsolete since RTEMS 5.1.  See also :ref:`ConfigAda`.

.. index:: CONFIGURE_HAS_OWN_CONFIGURATION_TABLE

CONFIGURE_HAS_OWN_CONFIGURATION_TABLE
-------------------------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_HAS_OWN_BDBUF_TABLE

CONFIGURE_HAS_OWN_BDBUF_TABLE
-----------------------------

This configuration option was introduced in RTEMS 4.7.0 and is obsolete since
RTEMS 4.10.0.

.. index:: CONFIGURE_HAS_OWN_DEVICE_DRIVER_TABLE

CONFIGURE_HAS_OWN_DEVICE_DRIVER_TABLE
-------------------------------------

This configuration option was present in all RTEMS versions since at least 1995
and is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_HAS_OWN_INIT_TASK_TABLE

.. _CONFIGURE_HAS_OWN_INIT_TASK_TABLE:

CONFIGURE_HAS_OWN_INIT_TASK_TABLE
---------------------------------

This configuration option was present in all RTEMS versions since at least 1995
and is obsolete since RTEMS 5.1.  If you used this configuration option or you
think that there should be a way to configure more than one Classic API
initialization task, then please ask on the :r:list:`users`.

.. index:: CONFIGURE_HAS_OWN_MOUNT_TABLE

CONFIGURE_HAS_OWN_MOUNT_TABLE
-----------------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_HAS_OWN_MULTIPROCESSING_TABLE

CONFIGURE_HAS_OWN_MULTIPROCESSING_TABLE
---------------------------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS

CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS
--------------------------------

This configuration option was present in all RTEMS versions since at 1998 and is
obsolete since RTEMS 5.1.  See also :ref:`CONFIGURE_MAXIMUM_FILE_DESCRIPTORS`.

.. index:: CONFIGURE_MAXIMUM_ADA_TASKS

CONFIGURE_MAXIMUM_ADA_TASKS
---------------------------

This configuration option was present in all RTEMS versions since at 1997 and is
obsolete since RTEMS 5.1.  See also :ref:`ConfigAda`.

.. index:: CONFIGURE_MAXIMUM_FAKE_ADA_TASKS

CONFIGURE_MAXIMUM_FAKE_ADA_TASKS
--------------------------------

This configuration option was present in all RTEMS versions since at 1997 and is
obsolete since RTEMS 5.1.  See also :ref:`ConfigAda`.

.. index:: CONFIGURE_MAXIMUM_GO_CHANNELS

CONFIGURE_MAXIMUM_GO_CHANNELS
-----------------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_MAXIMUM_GOROUTINES

CONFIGURE_MAXIMUM_GOROUTINES
----------------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_MAXIMUM_MRSP_SEMAPHORES

CONFIGURE_MAXIMUM_MRSP_SEMAPHORES
---------------------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_NUMBER_OF_TERMIOS_PORTS

CONFIGURE_NUMBER_OF_TERMIOS_PORTS
---------------------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_MAXIMUM_POSIX_BARRIERS

CONFIGURE_MAXIMUM_POSIX_BARRIERS
--------------------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_MAXIMUM_POSIX_CONDITION_VARIABLES

CONFIGURE_MAXIMUM_POSIX_CONDITION_VARIABLES
-------------------------------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUE_DESCRIPTORS

CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUE_DESCRIPTORS
-------------------------------

This configuration option was introduced in RTEMS 4.10.0 and is obsolete since
RTEMS 5.1.

.. index:: CONFIGURE_MAXIMUM_POSIX_MUTEXES

CONFIGURE_MAXIMUM_POSIX_MUTEXES
-------------------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_MAXIMUM_POSIX_RWLOCKS

CONFIGURE_MAXIMUM_POSIX_RWLOCKS
-------------------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_MAXIMUM_POSIX_SPINLOCKS

CONFIGURE_MAXIMUM_POSIX_SPINLOCKS
---------------------------------

This configuration option is obsolete since RTEMS 5.1.

.. index:: CONFIGURE_POSIX_HAS_OWN_INIT_THREAD_TABLE

.. _CONFIGURE_POSIX_HAS_OWN_INIT_THREAD_TABLE:

CONFIGURE_POSIX_HAS_OWN_INIT_THREAD_TABLE
-----------------------------------------

This configuration option was present in all RTEMS versions since at least 1995
and is obsolete since RTEMS 5.1.  If you used this configuration option or you
think that there should be a way to configure more than one POSIX initialization
thread, then please ask on the  :r:list:`users`.

.. index:: CONFIGURE_SMP_APPLICATION

CONFIGURE_SMP_APPLICATION
-------------------------

This configuration option was introduced in RTEMS 4.11.0 and is obsolete since
RTEMS 5.1.

.. index:: CONFIGURE_SMP_MAXIMUM_PROCESSORS

CONFIGURE_SMP_MAXIMUM_PROCESSORS
--------------------------------

This configuration option was introduced in RTEMS 4.11.0 and is obsolete since
RTEMS 5.1.  See also :ref:`CONFIGURE_MAXIMUM_PROCESSORS`.

.. index:: CONFIGURE_TERMIOS_DISABLED

CONFIGURE_TERMIOS_DISABLED
--------------------------

This configuration option is obsolete since RTEMS 5.1.