Split document into seperate files by section.

1 files changed, 5016 insertions, 0 deletions

diff --git a/c_user/configuring_a_system.rst b/c_user/configuring_a_system.rst
new file mode 100644
index 0000000..b4d4066
--- /dev/null
+++ b/c_user/configuring_a_system.rst
@@ -0,0 +1,5016 @@
+Configuring a System
+####################
+
+.. COMMENT: === Introduction ===
+
+Introduction
+============
+
+RTEMS must be configured for an application.  This configuration
+encompasses a variety of information including the length of each clock
+tick, the maximum number of each information RTEMS object that can
+be created, the application initialization tasks, the task scheduling
+algorithm to be used, and the device drivers in the application.
+
+Although this information is contained in data structures that are used
+by RTEMS at system initialization time, the data structures themselves
+should only rarely to be generated by hand. RTEMS provides a set of
+macros system which provides a simple standard mechanism to automate
+the generation of these structures.
+.. index:: confdefs.h
+.. index:: confdefs.h
+.. index:: <rtems/confdefs.h>
+.. index:: <rtems/confdefs.h>
+
+The RTEMS header file ``<rtems/confdefs.h>`` is at the core of the
+automatic generation of system configuration. It is based on the idea
+of setting macros which define configuration parameters of interest to
+the application and defaulting or calculating all others. This variety
+of macros can automatically produce all of the configuration data
+required for an RTEMS application.
+
+Trivia: ``confdefs`` is shorthand for a *Configuration Defaults*.
+
+As a general rule, application developers only specify values
+for the configuration parameters of interest to them. They define what
+resources or features they require. In most cases, when a parameter is
+not specified, it defaults to zero (0) instances, a standards compliant
+value, or disabled as appropriate. For example, by default there will be
+256 task priority levels but this can be lowered by the application. This
+number of priority levels is required to be compliant with the RTEID/ORKID
+standards upon which the Classic API is based. There are similar cases
+where the default is selected to be compliant with with the POSIX standard.
+
+For each configuration parameter in the configuration tables, the macro
+corresponding to that field is discussed. The RTEMS Maintainers
+expect that all systems can be easily configured using the``<rtems/confdefs.h>`` mechanism and that using this mechanism will
+avoid internal RTEMS configuration changes impacting applications.
+
+.. COMMENT: === Philosophy ===
+
+Default Value Selection Philosophy
+==================================
+
+The user should be aware that the defaults are intentionally set as
+low as possible.  By default, no application resources are configured.
+The ``<rtems/confdefs.h>`` file ensures that at least one application
+task or thread is configured and that at least one of the initialization
+task/thread tables is configured.
+
+.. COMMENT: === Sizing the RTEMS Workspace ===
+
+Sizing the RTEMS Workspace
+==========================
+
+The RTEMS Workspace is a user-specified block of memory reserved for
+use by RTEMS.  The application should NOT modify this memory.  This area
+consists primarily of the RTEMS data structures whose exact size depends
+upon the values specified in the Configuration Table.  In addition,
+task stacks and floating point context areas are dynamically allocated
+from the RTEMS Workspace.
+
+The ``<rtems/confdefs.h>`` mechanism calculates the size of the RTEMS
+Workspace automatically.  It assumes that all tasks are floating point and
+that all will be allocated the minimum stack space.  This calculation
+includes the amount of memory that will be allocated for internal use
+by RTEMS. The automatic calculation may underestimate the workspace
+size truly needed by the application, in which case one can use the``CONFIGURE_MEMORY_OVERHEAD`` macro to add a value to the estimate. See `Specify Memory Overhead`_ for more details.
+
+The memory area for the RTEMS Workspace is determined by the BSP.  In case the
+RTEMS Workspace is too large for the available memory, then a fatal run-time
+error occurs and the system terminates.
+
+The file ``<rtems/confdefs.h>`` will calculate the value of the``work_space_size`` parameter of the Configuration Table. There
+are many parameters the application developer can specify to
+help ``<rtems/confdefs.h>`` in its calculations.  Correctly
+specifying the application requirements via parameters such as``CONFIGURE_EXTRA_TASK_STACKS`` and ``CONFIGURE_MAXIMUM_TASKS``
+is critical for production software.
+
+For each class of objects, the allocation can operate in one of two ways.
+The default way has an ceiling on the maximum number of object instances
+which can concurrently exist in the system. Memory for all instances of
+that object class is reserved at system initialization.  The second
+way allocates memory for an initial number of objects and increases the
+current allocation by a fixed increment when required. Both ways allocate
+space from inside the RTEMS Workspace.
+
+See `Unlimited Objects`_ for more details about
+the second way, which allows for dynamic allocation of objects and
+therefore does not provide determinism.  This mode is useful mostly for
+when the number of objects cannot be determined ahead of time or when
+porting software for which you do not know the object requirements.
+
+The space needed for stacks and for RTEMS objects will vary from
+one version of RTEMS and from one target processor to another.
+Therefore it is safest to use ``<rtems/confdefs.h>`` and specify
+your application’s requirements in terms of the numbers of objects and
+multiples of ``RTEMS_MINIMUM_STACK_SIZE``, as far as is possible. The
+automatic estimates of space required will in general change when:
+
+- a configuration parameter is changed,
+
+- task or interrupt stack sizes change,
+
+- the floating point attribute of a task changes,
+
+- task floating point attribute is altered,
+
+- RTEMS is upgraded, or
+
+- the target processor is changed.
+
+Failure to provide enough space in the RTEMS Workspace may result in fatal
+run-time errors terminating the system.
+
+.. COMMENT: === Potential Issues ===
+
+Potential Issues with RTEMS Workspace Size Estimation
+=====================================================
+
+The ``<rtems/confdefs.h>`` file estimates the amount of memory
+required for the RTEMS Workspace.  This estimate is only as accurate
+as the information given to ``<rtems/confdefs.h>`` and may be either
+too high or too low for a variety of reasons.  Some of the reasons that``<rtems/confdefs.h>`` may reserve too much memory for RTEMS are:
+
+- All tasks/threads are assumed to be floating point.
+
+Conversely, there are many more reasons that the resource estimate could be
+too low:
+
+- Task/thread stacks greater than minimum size must be
+  accounted for explicitly by developer.
+
+- Memory for messages is not included.
+
+- Device driver requirements are not included.
+
+- Network stack requirements are not included.
+
+- Requirements for add-on libraries are not included.
+
+In general, ``<rtems/confdefs.h>`` is very accurate when given enough
+information.  However, it is quite easy to use a library and forget to
+account for its resources.
+
+.. COMMENT: === Format to be followed for making changes in this file ===
+
+Format to be followed for making changes in this file
+=====================================================
+
+- MACRO NAME
+  Should be alphanumeric. Can have ’_’ (underscore).
+
+- DATA TYPE
+  Please refer to all existing formats.
+
+- RANGE:
+
+  The range depends on the Data Type of the macro.
+
+  - − If the data type is of type task priority, then its value should
+    be an integer in the range of 1 to 255.
+  - − If the data type is an integer, then it can have numbers, characters
+    (in case the value is defined using another macro) and arithmetic operations
+    (+, -, \*, /).
+  - − If the data type is a function pointer the first character
+    should be an alphabet or an underscore. The rest of the string
+    can be alphanumeric.
+  - − If the data type is RTEMS Attributes or RTEMS Mode then
+    the string should be alphanumeric.
+  - − If the data type is RTEMS NAME then the value should be
+    an integer>=0 or RTEMS_BUILD_NAME( ’U’, ’I’, ’1’, ’ ’ )
+
+- DEFAULT VALUE
+
+  The default value should be in the following formats-
+  Please note that the ’.’ (full stop) is necessary.
+
+  - − In case the value is not defined then:
+    This is not defined by default.
+  - − If we know the default value then:
+    The default value is XXX.
+  - − If the default value is BSP Specific then:
+    This option is BSP specific.
+
+- DESCRIPTION
+  The description of the macro. (No specific format)
+
+- NOTES
+  Any further notes. (No specific format)
+
+.. COMMENT: === Configuration Example ===
+
+Configuration Example
+=====================
+
+In the following example, the configuration information for a system
+with a single message queue, four (4) tasks, and a timeslice of
+fifty (50) milliseconds is as follows:
+.. code:: c
+
+    #include <bsp.h>
+    #define CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER
+    #define CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER
+    #define CONFIGURE_MICROSECONDS_PER_TICK   1000 /* 1 millisecond \*/
+    #define CONFIGURE_TICKS_PER_TIMESLICE       50 /* 50 milliseconds \*/
+    #define CONFIGURE_RTEMS_INIT_TASKS_TABLE
+    #define CONFIGURE_MAXIMUM_TASKS 4
+    #define CONFIGURE_MAXIMUM_MESSAGE_QUEUES 1
+    #define CONFIGURE_MESSAGE_BUFFER_MEMORY \\
+    CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE(20, sizeof(struct USER_MESSAGE))
+    #define CONFIGURE_INIT
+    #include <rtems/confdefs.h>
+
+In this example, only a few configuration parameters are specified. The
+impact of these are as follows:
+
+- The example specified ``CONFIGURE_RTEMS_INIT_TASK_TABLE``
+  but did not specify any additional parameters. This results in a
+  configuration of an application which will begin execution of a single
+  initialization task named ``Init`` which is non-preemptible and at
+  priority one (1).
+
+- By specifying ``CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER``,
+  this application is configured to have a clock tick device
+  driver. Without a clock tick device driver, RTEMS has no way to know
+  that time is passing and will be unable to support delays and wall
+  time. Further configuration details about time are
+  provided. Per ``CONFIGURE_MICROSECONDS_PER_TICK`` and``CONFIGURE_TICKS_PER_TIMESLICE``, the user specified they wanted a
+  clock tick to occur each millisecond, and that the length of a timeslice
+  would be fifty (50) milliseconds.
+
+- By specifying ``CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER``,
+  the application will include a console device driver. Although the
+  console device driver may support a combination of multiple serial
+  ports and display and keyboard combinations, it is only required to
+  provide a single device named ``/dev/console``. This device will
+  be used for Standard Input, Output and Error I/O Streams. Thus when``CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER`` is specified, implicitly
+  three (3) file descriptors are reserved for the Standard I/O Streams and
+  those file descriptors are associated with ``/dev/console`` during
+  initialization. All console devices are expected to support the POSIX*termios* interface.
+
+- The example above specifies via ``CONFIGURE_MAXIMUM_TASKS``
+  that the application requires a maximum of four (4)
+  simultaneously existing Classic API tasks. Similarly, by specifying``CONFIGURE_MAXIMUM_MESSAGE_QUEUES``, there may be a maximum of only
+  one (1) concurrently existent Classic API message queues.
+
+- The most surprising configuration parameter in this example is the
+  use of ``CONFIGURE_MESSAGE_BUFFER_MEMORY``. Message buffer memory is
+  allocated from the RTEMS Workspace and must be accounted for. In this
+  example, the single message queue will have up to twenty (20) messages
+  of type ``struct USER_MESSAGE``.
+
+- The ``CONFIGURE_INIT`` constant must be defined in order to
+  make ``<rtems/confdefs.h>`` instantiate the configuration data
+  structures.  This can only be defined in one source file per
+  application that includes ``<rtems/confdefs.h>`` or the symbol
+  table will be instantiated multiple times and linking errors
+  produced.
+
+This example illustrates that parameters have default values. Among
+other things, the application implicitly used the following defaults:
+
+- All unspecified types of communications and synchronization objects
+  in the Classic and POSIX Threads API have maximums of zero (0).
+
+- The filesystem will be the default filesystem which is the In-Memory File
+  System (IMFS).
+
+- The application will have the default number of priority levels.
+
+- The minimum task stack size will be that recommended by RTEMS for
+  the target architecture.
+
+.. COMMENT: === Unlimited Objects ===
+
+
+Unlimited Objects
+-----------------
+
+In real-time embedded systems the RAM is normally a limited, critical
+resource and dynamic allocation is avoided as much as possible to
+ensure predictable, deterministic execution times. For such cases, see `Sizing the RTEMS Workspace`_ for an overview
+of how to tune the size of the workspace.  Frequently when users are
+porting software to RTEMS the precise resource requirements of the
+software is unknown. In these situations users do not need to control
+the size of the workspace very tightly because they just want to get
+the new software to run; later they can tune the workspace size as needed.
+
+The following API-independent object classes can be configured in
+unlimited mode:
+
+- POSIX Keys
+
+- POSIX Key Value Pairs
+
+The following object classes in the Classic API can be configured in
+unlimited mode:
+
+- Tasks
+
+- Timers
+
+- Semaphores
+
+- Message Queues
+
+- Periods
+
+- Barriers
+
+- Partitions
+
+- Regions
+
+- Ports
+
+Additionally, the following object classes from the POSIX API can be
+configured in unlimited mode:
+
+- Threads
+
+- Mutexes
+
+- Condition Variables
+
+- Timers
+
+- Message Queues
+
+- Message Queue Descriptors
+
+- Semaphores
+
+- Barriers
+
+- Read/Write Locks
+
+- Spinlocks
+
+The following object classes can *not* be configured in unlimited mode:
+
+- Drivers
+
+- File Descriptors
+
+- User Extensions
+
+- POSIX Queued Signals
+
+Due to the memory requirements of unlimited objects it is strongly recommended
+to use them only in combination with the unified work areas. See `Separate or Unified Work Areas`_ for more information
+on unified work areas.
+
+The following example demonstrates how the two simple configuration defines for
+unlimited objects and unified works areas can replace many seperate
+configuration defines for supported object classes:
+.. code:: c
+
+    #define CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER
+    #define CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER
+    #define CONFIGURE_UNIFIED_WORK_AREAS
+    #define CONFIGURE_UNLIMITED_OBJECTS
+    #define CONFIGURE_RTEMS_INIT_TASKS_TABLE
+    #define CONFIGURE_INIT
+    #include <rtems/confdefs.h>
+
+Users are cautioned that using unlimited objects is not recommended for
+production software unless the dynamic growth is absolutely required. It
+is generally considered a safer embedded systems programming practice to
+know the system limits rather than experience an out of memory error
+at an arbitrary and largely unpredictable time in the field.
+
+.. COMMENT: === Per Object Class Unlimited Object Instances ===
+
+Per Object Class Unlimited Object Instances
+-------------------------------------------
+.. index:: rtems_resource_unlimited
+
+When the number of objects is not known ahead of time, RTEMS provides an
+auto-extending mode that can be enabled individually for each object
+type by using the macro ``rtems_resource_unlimited``. This takes a value
+as a parameter, and is used to set the object maximum number field in
+an API Configuration table. The value is an allocation unit size. When
+RTEMS is required to grow the object table it is grown by this
+size. The kernel will return the object memory back to the RTEMS Workspace
+when an object is destroyed. The kernel will only return an allocated
+block of objects to the RTEMS Workspace if at least half the allocation
+size of free objects remain allocated. RTEMS always keeps one
+allocation block of objects allocated. Here is an example of using``rtems_resource_unlimited``:
+.. code:: c
+
+    #define CONFIGURE_MAXIMUM_TASKS rtems_resource_unlimited(5)
+
+.. index:: rtems_resource_is_unlimited
+.. index:: rtems_resource_maximum_per_allocation
+
+Object maximum specifications can be evaluated with the``rtems_resource_is_unlimited`` and``rtems_resource_maximum_per_allocation`` macros.
+
+.. COMMENT: === Unlimited Object Instances ===
+
+Unlimited Object Instances
+--------------------------
+
+To ease the burden of developers who are porting new software RTEMS
+also provides the capability to make all object classes listed above
+operate in unlimited mode in a simple manner. The application developer
+is only responsible for enabling unlimited objects and specifying the
+allocation size.
+
+.. COMMENT: === CONFIGURE_UNLIMITED_OBJECTS ===
+
+Enable Unlimited Object Instances
+---------------------------------
+.. index:: CONFIGURE_UNLIMITED_OBJECTS
+
+*CONSTANT:*
+    ``CONFIGURE_UNLIMITED_OBJECTS``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default.
+
+**DESCRIPTION:**
+
+``CONFIGURE_UNLIMITED_OBJECTS`` enables ``rtems_resource_unlimited``
+mode for Classic API and POSIX API objects that do not already have a
+specific maximum limit defined.
+
+**NOTES:**
+
+When using unlimited objects, it is common practice to also specify``CONFIGURE_UNIFIED_WORK_AREAS`` so the system operates with a single
+pool of memory for both RTEMS and application memory allocations.
+
+.. COMMENT: === CONFIGURE_UNLIMITED_ALLOCATION_SIZE ===
+
+Specify Unlimited Objects Allocation Size
+-----------------------------------------
+
+*CONSTANT:*
+    ``CONFIGURE_UNLIMITED_ALLOCATION_SIZE``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Positive.
+
+*DEFAULT VALUE:*
+    If not defined and ``CONFIGURE_UNLIMITED_OBJECTS`` is defined, the
+    default value is eight (8).
+
+**DESCRIPTION:**
+
+``CONFIGURE_UNLIMITED_ALLOCATION_SIZE`` provides an
+allocation size to use for ``rtems_resource_unlimited`` when using``CONFIGURE_UNLIMITED_OBJECTS``.
+
+**NOTES:**
+
+By allowing users to declare all resources as being unlimited
+the user can avoid identifying and limiting the resources used.``CONFIGURE_UNLIMITED_OBJECTS`` does not support varying the allocation
+sizes for different objects; users who want that much control can define
+the ``rtems_resource_unlimited`` macros themselves.
+.. code:: c
+
+    #define CONFIGURE_UNLIMITED_OBJECTS
+    #define CONFIGURE_UNLIMITED_ALLOCATION_SIZE 5
+
+.. COMMENT: === Classic API Configuration ===
+
+Classic API Configuration
+=========================
+
+This section defines the Classic API related system configuration
+parameters supported by ``<rtems/confdefs.h>``.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_TASKS ===
+
+Specify Maximum Classic API Tasks
+---------------------------------
+.. index:: CONFIGURE_MAXIMUM_TASKS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_TASKS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_TASKS`` is the maximum number of Classic API
+Tasks that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+The calculations for the required memory in the RTEMS Workspace
+for tasks assume that each task has a minimum stack size and
+has floating point support enabled.  The configuration parameter``CONFIGURE_EXTRA_TASK_STACKS`` is used to specify task stack
+requirements *ABOVE* the minimum size required.  See `Reserve Task/Thread Stack Memory Above Minimum`_
+for more information about ``CONFIGURE_EXTRA_TASK_STACKS``.
+
+The maximum number of POSIX threads is specified by``CONFIGURE_MAXIMUM_POSIX_THREADS``.
+
+.. COMMENT: XXX - Add xref to CONFIGURE_MAXIMUM_POSIX_THREADS.
+
+A future enhancement to ``<rtems/confdefs.h>`` could be to eliminate
+the assumption that all tasks have floating point enabled. This would
+require the addition of a new configuration parameter to specify the
+number of tasks which enable floating point support.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_TIMERS ===
+
+Specify Maximum Classic API Timers
+----------------------------------
+.. index:: CONFIGURE_MAXIMUM_TIMERS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_TIMERS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_TIMERS`` is the maximum number of Classic API
+Timers that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_SEMAPHORES ===
+
+Specify Maximum Classic API Semaphores
+--------------------------------------
+.. index:: CONFIGURE_MAXIMUM_SEMAPHORES
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_SEMAPHORES``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_SEMAPHORES`` is the maximum number of Classic
+API Semaphores that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_MRSP_SEMAPHORES ===
+
+Specify Maximum Classic API Semaphores usable with MrsP
+-------------------------------------------------------
+.. index:: CONFIGURE_MAXIMUM_MRSP_SEMAPHORES
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_MRSP_SEMAPHORES``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_MRSP_SEMAPHORES`` is the
+maximum number of Classic API Semaphores using the Multiprocessor Resource
+Sharing Protocol (MrsP) that can be concurrently active.
+
+**NOTES:**
+
+This configuration option is only used on SMP configurations.  On uni-processor
+configurations the Priority Ceiling Protocol is used for MrsP semaphores and
+thus no extra memory is necessary.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_MESSAGE_QUEUES ===
+
+Specify Maximum Classic API Message Queues
+------------------------------------------
+.. index:: CONFIGURE_MAXIMUM_MESSAGE_QUEUES
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_MESSAGE_QUEUES``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_MESSAGE_QUEUES`` is the maximum number of Classic
+API Message Queues that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_BARRIERS ===
+
+Specify Maximum Classic API Barriers
+------------------------------------
+.. index:: CONFIGURE_MAXIMUM_BARRIERS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_BARRIERS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_BARRIERS`` is the maximum number of Classic
+API Barriers that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_PERIODS ===
+
+Specify Maximum Classic API Periods
+-----------------------------------
+.. index:: CONFIGURE_MAXIMUM_PERIODS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_PERIODS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_PERIODS`` is the maximum number of Classic
+API Periods that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_PARTITIONS ===
+
+Specify Maximum Classic API Partitions
+--------------------------------------
+.. index:: CONFIGURE_MAXIMUM_PARTITIONS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_PARTITIONS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_PARTITIONS`` is the maximum number of Classic
+API Partitions that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_REGIONS ===
+
+Specify Maximum Classic API Regions
+-----------------------------------
+.. index:: CONFIGURE_MAXIMUM_REGIONS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_REGIONS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_REGIONS`` is the maximum number of Classic
+API Regions that can be concurrently active.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_PORTS ===
+
+Specify Maximum Classic API Ports
+---------------------------------
+.. index:: CONFIGURE_MAXIMUM_PORTS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_PORTS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_PORTS`` is the maximum number of Classic
+API Ports that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_USER_EXTENSIONS ===
+
+Specify Maximum Classic API User Extensions
+-------------------------------------------
+.. index:: CONFIGURE_MAXIMUM_USER_EXTENSIONS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_USER_EXTENSIONS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_USER_EXTENSIONS`` is the maximum number of Classic
+API User Extensions that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === Classic API Initialization Task Configuration ===
+
+Classic API Initialization Tasks Table Configuration
+====================================================
+
+The ``<rtems/confdefs.h>`` configuration system can automatically
+generate an Initialization Tasks Table named``Initialization_tasks`` with a single entry.  The following
+parameters control the generation of that table.
+
+.. COMMENT: === CONFIGURE_RTEMS_INIT_TASKS_TABLE ===
+
+Instantiate Classic API Initialization Task Table
+-------------------------------------------------
+.. index:: CONFIGURE_RTEMS_INIT_TASKS_TABLE
+
+*CONSTANT:*
+    ``CONFIGURE_RTEMS_INIT_TASKS_TABLE``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default.
+
+**DESCRIPTION:**
+
+``CONFIGURE_RTEMS_INIT_TASKS_TABLE`` is defined if the user wishes
+to use a Classic RTEMS API Initialization Task Table. The table built by``<rtems/confdefs.h>`` specifies the parameters for a single task. 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.
+
+.. COMMENT: === CONFIGURE_INIT_TASK_ENTRY_POINT ===
+
+Specifying Classic API Initialization Task Entry Point
+------------------------------------------------------
+.. index:: CONFIGURE_INIT_TASK_ENTRY_POINT
+
+*CONSTANT:*
+    ``CONFIGURE_INIT_TASK_ENTRY_POINT``
+
+*DATA TYPE:*
+    Task entry function pointer (``rtems_task_entry``).
+
+*RANGE:*
+    Valid task entry function pointer.
+
+*DEFAULT VALUE:*
+    The default value is ``Init``.
+
+**DESCRIPTION:**
+
+``CONFIGURE_INIT_TASK_ENTRY_POINT`` is the entry point (a.k.a. function
+name) of the single initialization task defined by the Classic API
+Initialization Tasks Table.
+
+**NOTES:**
+
+The user must implement the function ``Init`` or the function name provided
+in this configuration parameter.
+
+.. COMMENT: === CONFIGURE_INIT_TASK_NAME ===
+
+Specifying Classic API Initialization Task Name
+-----------------------------------------------
+.. index:: CONFIGURE_INIT_TASK_NAME
+
+*CONSTANT:*
+    ``CONFIGURE_INIT_TASK_NAME``
+
+*DATA TYPE:*
+    RTEMS Name (``rtems_name``).
+
+*RANGE:*
+    Any value.
+
+*DEFAULT VALUE:*
+    The default value is ``rtems_build_name( 'U', 'I', '1', ' ' )``.
+
+**DESCRIPTION:**
+
+``CONFIGURE_INIT_TASK_NAME`` is the name of the single initialization
+task defined by the Classic API Initialization Tasks Table.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === CONFIGURE_INIT_TASK_STACK_SIZE ===
+
+Specifying Classic API Initialization Task Stack Size
+-----------------------------------------------------
+.. index:: CONFIGURE_INIT_TASK_STACK_SIZE
+
+*CONSTANT:*
+    ``CONFIGURE_INIT_TASK_STACK_SIZE``
+
+*DATA TYPE:*
+    Unsigned integer (``size_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is RTEMS_MINIMUM_STACK_SIZE.
+
+**DESCRIPTION:**
+
+``CONFIGURE_INIT_TASK_STACK_SIZE`` is the stack size of the single
+initialization task defined by the Classic API Initialization Tasks Table.
+
+**NOTES:**
+
+If the stack size specified is greater than the configured minimum,
+it must be accounted for in ``CONFIGURE_EXTRA_TASK_STACKS``.
+See `Reserve Task/Thread Stack Memory Above Minimum`_ 
+for more information about ``CONFIGURE_EXTRA_TASK_STACKS``.
+
+.. COMMENT: === CONFIGURE_INIT_TASK_PRIORITY ===
+
+Specifying Classic API Initialization Task Priority
+---------------------------------------------------
+.. index:: CONFIGURE_INIT_TASK_PRIORITY
+
+*CONSTANT:*
+    ``CONFIGURE_INIT_TASK_PRIORITY``
+
+*DATA TYPE:*
+    RTEMS Task Priority (``rtems_task_priority``).
+
+*RANGE:*
+    One (1) to CONFIGURE_MAXIMUM_PRIORITY.
+
+*DEFAULT VALUE:*
+    The default value is 1, which is the highest priority in the
+    Classic API.
+
+**DESCRIPTION:**
+
+``CONFIGURE_INIT_TASK_PRIORITY`` is the initial priority of the single
+initialization task defined by the Classic API Initialization Tasks Table.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === CONFIGURE_INIT_TASK_ATTRIBUTES ===
+
+Specifying Classic API Initialization Task Attributes
+-----------------------------------------------------
+.. index:: CONFIGURE_INIT_TASK_ATTRIBUTES
+
+*CONSTANT:*
+    ``CONFIGURE_INIT_TASK_ATTRIBUTES``
+
+*DATA TYPE:*
+    RTEMS Attributes (``rtems_attribute``).
+
+*RANGE:*
+    Valid task attribute sets.
+
+*DEFAULT VALUE:*
+    The default value is ``RTEMS_DEFAULT_ATTRIBUTES``.
+
+**DESCRIPTION:**
+
+``CONFIGURE_INIT_TASK_ATTRIBUTES`` is the task attributes of the single
+initialization task defined by the Classic API Initialization Tasks Table.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === CONFIGURE_INIT_TASK_INITIAL_MODES ===
+
+Specifying Classic API Initialization Task Modes
+------------------------------------------------
+.. index:: CONFIGURE_INIT_TASK_INITIAL_MODES
+
+*CONSTANT:*
+    ``CONFIGURE_INIT_TASK_INITIAL_MODES``
+
+*DATA TYPE:*
+    RTEMS Mode (``rtems_mode``).
+
+*RANGE:*
+    Valid task mode sets.
+
+*DEFAULT VALUE:*
+    The default value is ``RTEMS_NO_PREEMPT``.
+
+**DESCRIPTION:**
+
+``CONFIGURE_INIT_TASK_INITIAL_MODES`` is the initial execution mode of
+the single initialization task defined by the Classic API Initialization
+Tasks Table.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === CONFIGURE_INIT_TASK_ARGUMENTS ===
+
+Specifying Classic API Initialization Task Arguments
+----------------------------------------------------
+.. index:: CONFIGURE_INIT_TASK_ARGUMENTS
+
+*CONSTANT:*
+    ``CONFIGURE_INIT_TASK_ARGUMENTS``
+
+*DATA TYPE:*
+    RTEMS Task Argument (``rtems_task_argument``).
+
+*RANGE:*
+    Complete range of the type.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_INIT_TASK_ARGUMENTS`` is the task argument of the single
+initialization task defined by the Classic API Initialization Tasks Table.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === CONFIGURE_HAS_OWN_INIT_TASK_TABLE ===
+
+Not Using Generated Initialization Tasks Table
+----------------------------------------------
+.. index:: CONFIGURE_HAS_OWN_INIT_TASK_TABLE
+
+*CONSTANT:*
+    ``CONFIGURE_HAS_OWN_INIT_TASK_TABLE``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default.
+
+**DESCRIPTION:**
+
+``CONFIGURE_HAS_OWN_INIT_TASK_TABLE`` is defined if the user wishes
+to define their own Classic API Initialization Tasks Table.  This table
+should be named ``Initialization_tasks``.
+
+**NOTES:**
+
+This is a seldom used configuration parameter. The most likely use case
+is when an application desires to have more than one initialization task.
+
+.. COMMENT: === POSIX API Configuration ===
+
+POSIX API Configuration
+=======================
+
+The parameters in this section are used to configure resources
+for the RTEMS POSIX API.  They are only relevant if the POSIX API
+is enabled at configure time using the ``--enable-posix`` option.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_POSIX_THREADS ===
+
+Specify Maximum POSIX API Threads
+---------------------------------
+.. index:: 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 `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``CONFIGURE_MAXIMUM_TASKS``.
+
+All POSIX threads have floating point enabled.
+
+.. COMMENT: XXX - Add xref to CONFIGURE_MAXIMUM_TASKS.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_POSIX_MUTEXES ===
+
+Specify Maximum POSIX API Mutexes
+---------------------------------
+.. index:: CONFIGURE_MAXIMUM_POSIX_MUTEXES
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_POSIX_MUTEXES``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_POSIX_MUTEXES`` is the maximum number of POSIX
+API Mutexes that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_POSIX_CONDITION_VARIABLES ===
+
+Specify Maximum POSIX API Condition Variables
+---------------------------------------------
+.. index:: CONFIGURE_MAXIMUM_POSIX_CONDITION_VARIABLES
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_POSIX_CONDITION_VARIABLES``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_POSIX_CONDITION_VARIABLES`` is the maximum number
+of POSIX API Condition Variables that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_POSIX_KEYS ===
+
+Specify Maximum POSIX API Keys
+------------------------------
+.. index:: 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.
+
+.. COMMENT: XXX - Key pairs
+
+.. COMMENT: === CONFIGURE_MAXIMUM_POSIX_TIMERS ===
+
+Specify Maximum POSIX API Timers
+--------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_POSIX_QUEUED_SIGNALS ===
+
+Specify Maximum POSIX API Queued Signals
+----------------------------------------
+.. index:: 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:**
+
+None.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUES ===
+
+Specify Maximum POSIX API Message Queues
+----------------------------------------
+.. index:: 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.
+
+.. COMMENT: XXX - memory for buffers note
+
+.. COMMENT: === CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUE_DESCRIPTORS ===
+
+Specify Maximum POSIX API Message Queue Descriptors
+---------------------------------------------------
+.. index:: CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUE_DESCRIPTORS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUE_DESCRIPTORS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    greater than or equal to ``CONFIGURE_MAXIMUM_POSIX_MESSAGES_QUEUES``
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUE_DESCRIPTORS`` is the maximum
+number of POSIX API Message Queue Descriptors that can be concurrently
+active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+``CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUE_DESCRIPTORS`` should be
+greater than or equal to ``CONFIGURE_MAXIMUM_POSIX_MESSAGE_QUEUES``.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_POSIX_SEMAPHORES ===
+
+Specify Maximum POSIX API Semaphores
+------------------------------------
+.. index:: 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 Semaphores that can be concurrently active.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_POSIX_BARRIERS ===
+
+Specify Maximum POSIX API Barriers
+----------------------------------
+.. index:: CONFIGURE_MAXIMUM_POSIX_BARRIERS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_POSIX_BARRIERS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_POSIX_BARRIERS`` is the maximum number of POSIX
+API Barriers that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_POSIX_SPINLOCKS ===
+
+Specify Maximum POSIX API Spinlocks
+-----------------------------------
+.. index:: CONFIGURE_MAXIMUM_POSIX_SPINLOCKS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_POSIX_SPINLOCKS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_POSIX_SPINLOCKS`` is the maximum number of POSIX
+API Spinlocks that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_POSIX_RWLOCKS ===
+
+Specify Maximum POSIX API Read/Write Locks
+------------------------------------------
+.. index:: CONFIGURE_MAXIMUM_POSIX_RWLOCKS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_POSIX_RWLOCKS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_POSIX_RWLOCKS`` is the maximum number of POSIX
+API Read/Write Locks that can be concurrently active.
+
+**NOTES:**
+
+This object class can be configured in unlimited allocation mode.
+
+.. COMMENT: === POSIX Initialization Threads Table Configuration ===
+
+POSIX Initialization Threads Table 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.
+
+.. COMMENT: === CONFIGURE_POSIX_INIT_THREAD_TABLE ===
+
+Instantiate POSIX API Initialization Thread Table
+-------------------------------------------------
+.. index:: CONFIGURE_POSIX_INIT_THREAD_TABLE
+
+*CONSTANT:*
+    .. index:: 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.
+
+.. COMMENT: === CONFIGURE_POSIX_INIT_THREAD_ENTRY_POINT ===
+
+Specifying POSIX API Initialization Thread Entry Point
+------------------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_POSIX_INIT_THREAD_STACK_SIZE ===
+
+Specifying POSIX API Initialization Thread Stack Size
+-----------------------------------------------------
+.. index:: 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 `Reserve Task/Thread Stack Memory Above Minimum`_
+for more information about ``CONFIGURE_EXTRA_TASK_STACKS``.
+
+.. COMMENT: === CONFIGURE_POSIX_HAS_OWN_INIT_THREAD_TABLE ===
+
+Not Using Generated POSIX Initialization Threads Table
+------------------------------------------------------
+.. index:: CONFIGURE_POSIX_HAS_OWN_INIT_THREAD_TABLE
+
+*CONSTANT:*
+    ``CONFIGURE_POSIX_HAS_OWN_INIT_THREAD_TABLE``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default.
+
+**DESCRIPTION:**
+
+``CONFIGURE_POSIX_HAS_OWN_INIT_THREAD_TABLE`` is defined if the
+user wishes to define their own POSIX API Initialization Threads Table.
+This table should be named ``POSIX_Initialization_threads``.
+
+**NOTES:**
+
+This is a seldom used configuration parameter. The most likely use case
+is when an application desires to have more than one initialization task.
+
+.. COMMENT: === Basic System Information ===
+
+Basic System Information
+========================
+
+This section defines the general system configuration parameters supported by``<rtems/confdefs.h>``.
+
+.. COMMENT: === CONFIGURE_UNIFIED_WORK_AREAS ===
+
+
+Separate or Unified Work Areas
+------------------------------
+.. index:: CONFIGURE_UNIFIED_WORK_AREAS
+.. index:: unified work areas
+.. index:: separate work areas
+.. index:: RTEMS Workspace
+.. index:: C Program Heap
+
+*CONSTANT:*
+    ``CONFIGURE_UNIFIED_WORK_AREAS``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default, which specifies that the C Program Heap
+    and the RTEMS Workspace will be separate.
+
+**DESCRIPTION:**
+
+When defined, the C Program Heap and the RTEMS Workspace will be one pool
+of memory.
+
+When not defined, there will be separate memory pools for the RTEMS
+Workspace and C Program Heap.
+
+**NOTES:**
+
+Having separate pools does have some advantages in the event a task blows
+a stack or writes outside its memory area. However, in low memory systems
+the overhead of the two pools plus the potential for unused memory in
+either pool is very undesirable.
+
+In high memory environments, this is desirable when you want to use the
+RTEMS "unlimited" objects option.  You will be able to create objects
+until you run out of all available memory rather then just until you
+run out of RTEMS Workspace.
+
+.. COMMENT: === CONFIGURE_MICROSECONDS_PER_TICK ===
+
+Length of Each Clock Tick
+-------------------------
+.. index:: CONFIGURE_MICROSECONDS_PER_TICK
+.. index:: tick quantum
+
+*CONSTANT:*
+    ``CONFIGURE_MICROSECONDS_PER_TICK``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Positive.
+
+*DEFAULT VALUE:*
+    This is not defined by default. When not defined,
+    the clock tick quantum is configured to be 10,000
+    microseconds which is ten (10) milliseconds.
+
+**DESCRIPTION:**
+
+This constant is  used to specify the length of time between clock ticks.
+
+When the clock tick quantum value is too low, the system will spend so
+much time processing clock ticks that it does not have processing time
+available to perform application work. In this case, the system will
+become unresponsive.
+
+The lowest practical time quantum varies widely based upon the speed
+of the target hardware and the architectural overhead associated with
+interrupts. In general terms, you do not want to configure it lower than
+is needed for the application.
+
+The clock tick quantum should be selected such that it all blocking and
+delay times in the application are evenly divisible by it. Otherwise,
+rounding errors will be introduced which may negatively impact the
+application.
+
+**NOTES:**
+
+This configuration parameter has no impact if the Clock Tick Device
+driver is not configured.
+
+There may be BSP specific limits on the resolution or maximum value of
+a clock tick quantum.
+
+.. COMMENT: === CONFIGURE_TICKS_PER_TIMESLICE ===
+
+Specifying Timeslicing Quantum
+------------------------------
+.. index:: CONFIGURE_TICKS_PER_TIMESLICE
+.. index:: ticks per timeslice
+
+*CONSTANT:*
+    ``CONFIGURE_TICKS_PER_TIMESLICE``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Positive.
+
+*DEFAULT VALUE:*
+    The default value is 50.
+
+**DESCRIPTION:**
+
+This configuration parameter specifies the length of the timeslice
+quantum in ticks for each task.
+
+**NOTES:**
+
+This configuration parameter has no impact if the Clock Tick Device
+driver is not configured.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_PRIORITY ===
+
+Specifying the Number of Thread Priority Levels
+-----------------------------------------------
+.. index:: CONFIGURE_MAXIMUM_PRIORITY
+.. index:: maximum priority
+.. index:: number of priority levels
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_PRIORITY``
+
+*DATA TYPE:*
+    Unsigned integer (``uint8_t``).
+
+*RANGE:*
+    Valid values for this configuration parameter must be one (1) less than
+    than a power of two (2) between 4 and 256 inclusively.  In other words,
+    valid values are 3, 7, 31, 63, 127, and 255.
+
+*DEFAULT VALUE:*
+    The default value is 255, because RTEMS must support 256 priority levels to be
+    compliant with various standards. These priorities range from zero (0) to 255.
+
+**DESCRIPTION:**
+
+This configuration parameter specified the maximum numeric priority
+of any task in the system and one less that the number of priority levels
+in the system.
+
+Reducing the number of priorities in the system reduces the amount of
+memory allocated from the RTEMS Workspace.
+
+**NOTES:**
+
+The numerically greatest priority is the logically lowest priority in
+the system and will thus be used by the IDLE task.
+
+Priority zero (0) is reserved for internal use by RTEMS and is not
+available to applications.
+
+With some schedulers, reducing the number of priorities can reduce the
+amount of memory used by the scheduler. For example, the Deterministic
+Priority Scheduler (DPS) used by default uses three pointers of storage
+per priority level. Reducing the number of priorities from 256 levels
+to sixteen (16) can reduce memory usage by about three (3) kilobytes.
+
+.. COMMENT: === CONFIGURE_MINIMUM_TASK_STACK_SIZE ===
+
+Specifying the Minimum Task Size
+--------------------------------
+.. index:: CONFIGURE_MINIMUM_TASK_STACK_SIZE
+.. index:: minimum task stack size
+
+*CONSTANT:*
+    ``CONFIGURE_MINIMUM_TASK_STACK_SIZE``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Positive.
+
+*DEFAULT VALUE:*
+    This is not defined by default, which sets the executive to the recommended
+    minimum stack size for this processor.
+
+**DESCRIPTION:**
+
+The configuration parameter is set to the number of bytes the application
+wants the minimum stack size to be for every task or thread in the system.
+
+Adjusting this parameter should be done with caution. Examining the actual
+usage using the Stack Checker Usage Reporting facility is recommended.
+
+**NOTES:**
+
+This parameter can be used to lower the minimum from that
+recommended. This can be used in low memory systems to reduce memory
+consumption for stacks. However, this must be done with caution as it
+could increase the possibility of a blown task stack.
+
+This parameter can be used to increase the minimum from that
+recommended. This can be used in higher memory systems to reduce the
+risk of stack overflow without performing analysis on actual consumption.
+
+.. COMMENT: === CONFIGURE_INTERRUPT_STACK_SIZE ===
+
+Configuring the Size of the Interrupt Stack
+-------------------------------------------
+.. index:: CONFIGURE_INTERRUPT_STACK_SIZE
+.. index:: interrupt stack size
+
+*CONSTANT:*
+    ``CONFIGURE_INTERRUPT_STACK_SIZE``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Positive.
+
+*DEFAULT VALUE:*
+    The default value is CONFIGURE_MINIMUM_TASK_STACK_SIZE, which is the minimum
+    interrupt stack size.
+
+**DESCRIPTION:**
+
+``CONFIGURE_INTERRUPT_STACK_SIZE`` is set to the size of the
+interrupt stack.  The interrupt stack size is often set by the BSP but
+since this memory may be allocated from the RTEMS Workspace, it must be
+accounted for.
+
+**NOTES:**
+
+In some BSPs, changing this constant does NOT change the
+size of the interrupt stack, only the amount of memory
+reserved for it.
+
+Patches which result in this constant only being used in memory
+calculations when the interrupt stack is intended to be allocated
+from the RTEMS Workspace would be welcomed by the RTEMS Project.
+
+.. COMMENT: === CONFIGURE_EXTRA_TASK_STACKS ===
+
+
+Reserve Task/Thread Stack Memory Above Minimum
+----------------------------------------------
+.. index:: CONFIGURE_EXTRA_TASK_STACKS
+.. index:: memory for task tasks
+
+*CONSTANT:*
+    ``CONFIGURE_EXTRA_TASK_STACKS``
+
+*DATA TYPE:*
+    Unsigned integer (``size_t``).
+
+*RANGE:*
+    Undefined or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+This configuration parameter is set to the number of bytes the
+applications wishes to add to the task stack requirements calculated
+by ``<rtems/confdefs.h>``.
+
+**NOTES:**
+
+This parameter is very important.  If the application creates tasks with
+stacks larger then the minimum, then that memory is NOT accounted for
+by ``<rtems/confdefs.h>``.
+
+.. COMMENT: === CONFIGURE_ZERO_WORKSPACE_AUTOMATICALLY ===
+
+Automatically Zeroing the RTEMS Workspace and C Program Heap
+------------------------------------------------------------
+.. index:: CONFIGURE_ZERO_WORKSPACE_AUTOMATICALLY
+.. index:: clear C Program Heap
+.. index:: clear RTEMS Workspace
+.. index:: zero C Program Heap
+.. index:: zero RTEMS Workspace
+
+*CONSTANT:*
+    ``CONFIGURE_ZERO_WORKSPACE_AUTOMATICALLY``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default, unless overridden by the BSP.
+    The default is *NOT* to zero out the RTEMS Workspace or C Program Heap.
+
+**DESCRIPTION:**
+
+This macro indicates whether RTEMS should zero the RTEMS Workspace and
+C Program Heap as part of its initialization.  If defined, the memory
+regions are zeroed.  Otherwise, they are not.
+
+**NOTES:**
+
+Zeroing memory can add significantly to system boot time. It is not
+necessary for RTEMS but is often assumed by support libraries.
+
+.. COMMENT: === CONFIGURE_STACK_CHECKER_ENABLED ===
+
+Enable The Task Stack Usage Checker
+-----------------------------------
+.. index:: CONFIGURE_STACK_CHECKER_ENABLED
+
+*CONSTANT:*
+    ``CONFIGURE_STACK_CHECKER_ENABLED``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default, and thus stack checking is disabled.
+
+**DESCRIPTION:**
+
+This configuration parameter is defined when the application wishes to
+enable run-time stack bounds checking.
+
+**NOTES:**
+
+In 4.9 and older, this configuration parameter was named``STACK_CHECKER_ON``.
+
+This increases the time required to create tasks as well as adding
+overhead to each context switch.
+
+.. COMMENT: === CONFIGURE_INITIAL_EXTENSIONS ===
+
+Specify Application Specific User Extensions
+--------------------------------------------
+.. index:: CONFIGURE_INITIAL_EXTENSIONS
+
+*CONSTANT:*
+    ``CONFIGURE_INITIAL_EXTENSIONS``
+
+*DATA TYPE:*
+    List of user extension initializers (``rtems_extensions_table``).
+
+*RANGE:*
+    Undefined or a list of one or more user extensions.
+
+*DEFAULT VALUE:*
+    This is not defined by default.
+
+**DESCRIPTION:**
+
+If ``CONFIGURE_INITIAL_EXTENSIONS`` is defined by the application,
+then this application specific set of initial extensions will be placed
+in the initial extension table.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === Custom Stack Allocator ===
+
+Configuring Custom Task Stack Allocation
+========================================
+
+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.
+
+.. COMMENT: === CONFIGURE_TASK_STACK_ALLOCATOR_INIT ===
+
+Custom Task Stack Allocator Initialization
+------------------------------------------
+.. index:: 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``
+
+.. COMMENT: === CONFIGURE_TASK_STACK_ALLOCATOR ===
+
+Custom Task Stack Allocator
+---------------------------
+.. index:: CONFIGURE_TASK_STACK_ALLOCATOR
+
+.. index:: 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``
+
+.. COMMENT: === CONFIGURE_TASK_STACK_DEALLOCATOR ===
+
+Custom Task Stack Deallocator
+-----------------------------
+.. index:: CONFIGURE_TASK_STACK_DEALLOCATOR
+.. index:: 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``
+
+.. COMMENT: === Classic API Message Buffers ===
+
+Configuring Memory for Classic API Message Buffers
+==================================================
+
+This section describes the configuration parameters related to specifying
+the amount of memory reserved for Classic API Message Buffers.
+
+.. COMMENT: === CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE ===
+
+Calculate Memory for a Single Classic Message API Message Queue
+---------------------------------------------------------------
+.. index:: CONFIGURE_MESSAGE_BUFFERS_FOR_QUEUE
+.. index:: memory for a single message queue’s buffers
+
+*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:: 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 ``CONFIGURE_MESSAGE_BUFFER_MEMORY``.
+
+.. COMMENT: === CONFIGURE_MESSAGE_BUFFER_MEMORY ===
+
+Reserve Memory for All Classic Message API Message Queues
+---------------------------------------------------------
+.. index:: CONFIGURE_MESSAGE_BUFFER_MEMORY
+.. index:: configure message queue 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``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:: 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) \\
+    )
+
+.. COMMENT: === Seldom Used Configuration Parameters ===
+
+Seldom Used Configuration Parameters
+====================================
+
+This section describes configuration parameters supported by``<rtems/confdefs.h>`` which are seldom used by applications. These
+parameters tend to be oriented to debugging system configurations
+and providing work-arounds when the memory estimated by``<rtems/confdefs.h>`` is incorrect.
+
+.. COMMENT: === CONFIGURE_MEMORY_OVERHEAD ===
+
+
+Specify Memory Overhead
+-----------------------
+.. index:: CONFIGURE_MEMORY_OVERHEAD
+
+*CONSTANT:*
+    ``CONFIGURE_MEMORY_OVERHEAD``
+
+*DATA TYPE:*
+    Unsigned integer (``size_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+Thie parameter is set to the number of kilobytes the application wishes
+to add to the requirements calculated by ``<rtems/confdefs.h>``.
+
+**NOTES:**
+
+This configuration parameter should only be used when it is suspected that
+a bug in ``<rtems/confdefs.h>`` has resulted in an underestimation.
+Typically the memory allocation will be too low when an application does
+not account for all message queue buffers or task stacks.
+
+.. COMMENT: === CONFIGURE_HAS_OWN_CONFIGURATION_TABLE ===
+
+Do Not Generate Configuration Information
+-----------------------------------------
+.. index:: CONFIGURE_HAS_OWN_CONFIGURATION_TABLE
+
+*CONSTANT:*
+    ``CONFIGURE_HAS_OWN_CONFIGURATION_TABLE``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default.
+
+**DESCRIPTION:**
+
+This configuration parameter should only be defined if the application
+is providing their own complete set of configuration tables.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === C Library Support Configuration ===
+
+C Library Support Configuration
+===============================
+
+This section defines the file system and IO library
+related configuration parameters supported by``<rtems/confdefs.h>``.
+
+.. COMMENT: === CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS ===
+
+Specify Maximum Number of File Descriptors
+------------------------------------------
+.. index:: CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS
+.. index:: maximum file descriptors
+
+*CONSTANT:*
+    ``CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    If ``CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER`` is defined, then the
+    default value is 3, otherwise the default value is 0.
+    Three file descriptors allows RTEMS to support standard input, output, and
+    error I/O streams on ``/dev/console``.
+
+**DESCRIPTION:**
+
+This configuration parameter is set to the maximum number of file like objects
+that can be concurrently open.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === CONFIGURE_TERMIOS_DISABLED ===
+
+Disable POSIX Termios Support
+-----------------------------
+.. index:: CONFIGURE_TERMIOS_DISABLED
+
+*CONSTANT:*
+    ``CONFIGURE_TERMIOS_DISABLED``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default, and resources are reserved for the
+    termios functionality.
+
+**DESCRIPTION:**
+
+This configuration parameter is defined if the software implementing
+POSIX termios functionality is not going to be used by this application.
+
+**NOTES:**
+
+The termios support library should not be included in an application
+executable unless it is directly referenced by the application or a
+device driver.
+
+.. COMMENT: === CONFIGURE_NUMBER_OF_TERMIOS_PORTS ===
+
+Specify Maximum Termios Ports
+-----------------------------
+.. index:: CONFIGURE_NUMBER_OF_TERMIOS_PORTS
+
+*CONSTANT:*
+    ``CONFIGURE_NUMBER_OF_TERMIOS_PORTS``
+
+*DATA TYPE:*
+    Unsigned integer.
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 1, so a console port can be used.
+
+**DESCRIPTION:**
+
+This configuration parameter is set to the number of ports using the
+termios functionality.  Each concurrently active termios port requires
+resources.
+
+**NOTES:**
+
+If the application will be using serial ports
+including, but not limited to, the Console Device
+(e.g. ``CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER``), then it is
+highly likely that this configuration parameter should NOT be is defined.
+
+.. COMMENT: === File System Configuration Parameters ===
+
+File System Configuration Parameters
+====================================
+
+This section defines File System related configuration parameters.
+
+.. COMMENT: === CONFIGURE_HAS_OWN_MOUNT_TABLE ===
+
+Providing Application Specific Mount Table
+------------------------------------------
+.. index:: CONFIGURE_HAS_OWN_MOUNT_TABLE
+
+*CONSTANT:*
+    ``CONFIGURE_HAS_OWN_MOUNT_TABLE``
+
+*DATA TYPE:*
+    Undefined or an array of type ``rtems_filesystem_mount_table_t``.
+
+*RANGE:*
+    Undefined or an array of type ``rtems_filesystem_mount_table_t``.
+
+*DEFAULT VALUE:*
+    This is not defined by default.
+
+**DESCRIPTION:**
+
+This configuration parameter is defined when the application
+provides their own filesystem mount table.  The mount table is an
+array of ``rtems_filesystem_mount_table_t`` entries pointed
+to by the global variable ``rtems_filesystem_mount_table``.
+The number of entries in this table is in an integer variable named``rtems_filesystem_mount_table_t``.
+
+.. COMMENT: XXX - is the variable name for the count right?
+
+**NOTES:**
+
+None.
+
+.. COMMENT: XXX - Please provide an example
+
+.. COMMENT: === CONFIGURE_USE_DEVFS_AS_BASE_FILESYSTEM ===
+
+Configure devFS as Root File System
+-----------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_DEVICES ===
+
+Specifying Maximum Devices for devFS
+------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_APPLICATION_DISABLE_FILESYSTEM ===
+
+Disable File System Support
+---------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM ===
+
+Use a Root IMFS with a Minimalistic Feature Set
+-----------------------------------------------
+.. index:: 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``.
+
+.. COMMENT: === CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK ===
+
+Specify Block Size for IMFS
+---------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_CHOWN ===
+
+Disable Change Owner Support of Root IMFS
+-----------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_CHMOD ===
+
+Disable Change Mode Support of Root IMFS
+----------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_UTIME ===
+
+Disable Change Times Support of Root IMFS
+-----------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_LINK ===
+
+Disable Create Hard Link Support of Root IMFS
+---------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_SYMLINK ===
+
+Disable Create Symbolic Link Support of Root IMFS
+-------------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_READLINK ===
+
+Disable Read Symbolic Link Support of Root IMFS
+-----------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_RENAME ===
+
+Disable Rename Support of Root IMFS
+-----------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_READDIR ===
+
+Disable Directory Read Support of Root IMFS
+-------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_MOUNT ===
+
+Disable Mount Support of Root IMFS
+----------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_UNMOUNT ===
+
+Disable Unmount Support of Root IMFS
+------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_MKNOD ===
+
+Disable Make Nodes Support of Root IMFS
+---------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_MKNOD_FILE ===
+
+Disable Make Files Support of Root IMFS
+---------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IMFS_DISABLE_RMNOD ===
+
+Disable Remove Nodes Support of Root IMFS
+-----------------------------------------
+.. index:: 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.
+
+.. COMMENT: === Block Device Cache Configuration ===
+
+Block Device Cache Configuration
+================================
+
+This section defines Block Device Cache (bdbuf) related configuration
+parameters.
+
+.. COMMENT: === CONFIGURE_APPLICATION_NEEDS_LIBBLOCK ===
+
+Enable Block Device Cache
+-------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_BDBUF_CACHE_MEMORY_SIZE ===
+
+Size of the Cache Memory
+------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_BDBUF_BUFFER_MIN_SIZE ===
+
+Minimum Size of a Buffer
+------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_BDBUF_BUFFER_MAX_SIZE ===
+
+Maximum Size of a Buffer
+------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_SWAPOUT_SWAP_PERIOD ===
+
+Swapout Task Swap Period
+------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_SWAPOUT_BLOCK_HOLD ===
+
+Swapout Task Maximum Block Hold Time
+------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_SWAPOUT_TASK_PRIORITY ===
+
+Swapout Task Priority
+---------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_BDBUF_MAX_READ_AHEAD_BLOCKS ===
+
+Maximum Blocks per Read-Ahead Request
+-------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_BDBUF_MAX_WRITE_BLOCKS ===
+
+Maximum Blocks per Write Request
+--------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_BDBUF_TASK_STACK_SIZE ===
+
+Task Stack Size of the Block Device Cache Tasks
+-----------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_BDBUF_READ_AHEAD_TASK_PRIORITY ===
+
+Read-Ahead Task Priority
+------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_SWAPOUT_WORKER_TASKS ===
+
+Swapout Worker Task Count
+-------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_SWAPOUT_WORKER_TASK_PRIORITY ===
+
+Swapout Worker Task Priority
+----------------------------
+.. index:: 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.
+
+.. COMMENT: === BSP Specific Settings ===
+
+BSP Specific Settings
+=====================
+
+This section describes BSP specific configuration settings used by``<rtems/confdefs.h>``.  The BSP specific configuration settings are
+defined in ``<bsp.h>``.
+
+.. COMMENT: === Disable BSP Settings ===
+
+Disable BSP Configuration Settings
+----------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_MALLOC_BSP_SUPPORTS_SBRK ===
+
+Specify BSP Supports sbrk()
+---------------------------
+.. index:: 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.
+
+.. COMMENT: === BSP_IDLE_TASK_BODY ===
+
+Specify BSP Specific Idle Task
+------------------------------
+.. index:: 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
+
+.. COMMENT: === BSP_IDLE_TASK_STACK_SIZE ===
+
+Specify BSP Suggested Value for IDLE Task Stack Size
+----------------------------------------------------
+.. index:: 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``.
+
+.. COMMENT: XXX - add cross references to other related values.
+
+.. COMMENT: === BSP_INITIAL_EXTENSION ===
+
+Specify BSP Specific User Extensions
+------------------------------------
+.. index:: 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.
+
+.. COMMENT: === BSP_INTERRUPT_STACK_SIZE ===
+
+Specifying BSP Specific Interrupt Stack Size
+--------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === BSP_MAXIMUM_DEVICES ===
+
+Specifying BSP Specific Maximum Devices
+---------------------------------------
+.. index:: 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.
+
+.. COMMENT: === BSP_ZERO_WORKSPACE_AUTOMATICALLY ===
+
+BSP Recommends RTEMS Workspace be Cleared
+-----------------------------------------
+.. index:: BSP_ZERO_WORKSPACE_AUTOMATICALLY
+
+*CONSTANT:*
+    ``BSP_ZERO_WORKSPACE_AUTOMATICALLY``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This option is BSP specific.
+
+**DESCRIPTION:**
+
+If ``BSP_ZERO_WORKSPACE_AUTOMATICALLY`` is defined by the BSP and``CONFIGURE_ZERO_WORKSPACE_AUTOMATICALLY`` is not defined by the
+application, then the workspace will be zeroed automatically.
+
+**NOTES:**
+
+Zeroing memory can add significantly to system boot time. It is not
+necessary for RTEMS but is often assumed by support libraries.
+
+.. COMMENT: === CONFIGURE_BSP_PREREQUISITE_DRIVERS ===
+
+Specify BSP Prerequisite Drivers
+--------------------------------
+.. index:: 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.
+
+.. COMMENT: === Idle Task Configuration ===
+
+Idle Task Configuration
+=======================
+
+This section defines the IDLE task related configuration parameters
+supported by ``<rtems/confdefs.h>``.
+
+.. COMMENT: === CONFIGURE_IDLE_TASK_BODY ===
+
+Specify Application Specific Idle Task Body
+-------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IDLE_TASK_STACK_SIZE ===
+
+Specify Idle Task Stack Size
+----------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION ===
+
+Specify Idle Task Performs Application Initialization
+-----------------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === Scheduler Algorithm Configuration ===
+
+Scheduler Algorithm Configuration
+=================================
+
+This section defines the configuration parameters related to selecting a
+scheduling algorithm for an application.  For the schedulers built into
+RTEMS, 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 currently available schedulers are:
+
+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.
+
+.. COMMENT: === CONFIGURE_SCHEDULER_PRIORITY ===
+
+Use Deterministic Priority Scheduler
+------------------------------------
+.. index:: 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:**
+
+The Deterministic Priority Scheduler is the default scheduler in RTEMS
+for uni-processor applications and is designed for predictable performance
+under the highest loads.  It can block or unblock a thread in a constant
+amount of time.  This scheduler requires a variable amount of memory
+based upon the number of priorities configured in the system.
+
+**NOTES:**
+
+This scheduler may be explicitly selected by defining``CONFIGURE_SCHEDULER_PRIORITY`` although this is equivalent to the
+default behavior.
+
+.. COMMENT: === CONFIGURE_SCHEDULER_SIMPLE ===
+
+Use Simple Priority Scheduler
+-----------------------------
+.. index:: 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:**
+
+When defined, the Simple Priority Scheduler is used at the thread
+scheduling algorithm. This is an alternative scheduler in RTEMS.
+It is designed to provide the same task scheduling behaviour as the
+Deterministic Priority Scheduler while being simpler in implementation
+and uses less memory for data management.  It maintains a single sorted
+list of all ready threads.  Thus blocking or unblocking a thread is not
+a constant time operation with this scheduler.
+
+This scheduler may be explicitly selected by defining``CONFIGURE_SCHEDULER_SIMPLE``.
+
+**NOTES:**
+
+This scheduler is appropriate for use in small systems where RAM is limited.
+
+.. COMMENT: === CONFIGURE_SCHEDULER_EDF ===
+
+Use Earliest Deadline First Scheduler
+-------------------------------------
+.. index:: 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:**
+
+The Earliest Deadline First Scheduler (EDF) is an alternative scheduler in
+RTEMS for uni-processor applications. The EDF schedules tasks with dynamic
+priorities equal to deadlines. The deadlines are declared using only
+Rate Monotonic manager which handles periodic behavior.  Period is always
+equal to deadline. If a task does not have any deadline declared or the
+deadline is cancelled, the task is considered a background task which is
+scheduled in case no deadline-driven tasks are ready to run.  Moreover,
+multiple background tasks are scheduled according their priority assigned
+upon initialization. All ready tasks reside in a single ready queue.
+
+This scheduler may be explicitly selected by defining``CONFIGURE_SCHEDULER_EDF``.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === CONFIGURE_SCHEDULER_CBS ===
+
+Use Constant Bandwidth Server Scheduler
+---------------------------------------
+.. index:: 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:**
+
+The Constant Bandwidth Server Scheduler (CBS) is an alternative scheduler
+in RTEMS for uni-processor applications. The CBS is a budget aware extension
+of EDF scheduler. The goal of this scheduler is to ensure temporal
+isolation of tasks. The CBS is equipped with a set of additional rules
+and provides with an extensive API.
+
+This scheduler may be explicitly selected by defining``CONFIGURE_SCHEDULER_CBS``.
+
+.. COMMENT: XXX - add cross reference to API chapter
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === CONFIGURE_SCHEDULER_PRIORITY_SMP ===
+
+Use Deterministic Priority SMP Scheduler
+----------------------------------------
+.. index:: 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:**
+
+The Deterministic Priority SMP Scheduler is derived from the Deterministic
+Priority Scheduler but is capable of scheduling threads across multiple
+processors.
+
+In a configuration with SMP enabled at configure time, it may be
+explicitly selected by defining ``CONFIGURE_SCHEDULER_PRIORITY_SMP``.
+
+**NOTES:**
+
+This scheduler is only available when RTEMS is configured with SMP
+support enabled.
+
+This scheduler is currently the default in SMP configurations and is
+only selected when ``CONFIGURE_SMP_APPLICATION`` is defined.
+
+.. COMMENT: === CONFIGURE_SCHEDULER_SIMPLE_SMP ===
+
+Use Simple SMP Priority Scheduler
+---------------------------------
+.. index:: 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:**
+
+The Simple SMP Priority Scheduler is derived from the Simple Priority
+Scheduler but is capable of scheduling threads across multiple processors.
+It is designed to provide the same task scheduling behaviour as the
+Deterministic Priority Scheduler while distributing threads across
+multiple processors.  Being based upon the Simple Priority Scheduler, it also
+maintains a single sorted list of all ready threads.  Thus blocking or
+unblocking a thread is not a constant time operation with this scheduler.
+
+In addition, when allocating threads to processors, the algorithm is not
+constant time. This algorithm was not designed with efficiency as a
+primary design goal.  Its primary design goal was to provide an SMP-aware
+scheduling algorithm that is simple to understand.
+
+In a configuration with SMP enabled at configure time, it may be
+explicitly selected by defining ``CONFIGURE_SCHEDULER_SIMPLE_SMP``.
+
+**NOTES:**
+
+This scheduler is only available when RTEMS is configured with SMP
+support enabled.
+
+.. COMMENT: === Configuring a Scheduler Name ===
+
+Configuring a Scheduler Name
+----------------------------
+.. index:: CONFIGURE_SCHEDULER_NAME
+
+*CONSTANT:*
+    ``CONFIGURE_SCHEDULER_NAME``
+
+*DATA TYPE:*
+    RTEMS Name (``rtems_name``).
+
+*RANGE:*
+    Any value.
+
+*DEFAULT VALUE:*
+    The default name is
+    - ``"UCBS"`` for the Uni-Processor CBS scheduler,
+    - ``"UEDF"`` for the Uni-Processor EDF scheduler,
+    - ``"UPD "`` for the Uni-Processor Deterministic Priority scheduler,
+    - ``"UPS "`` for the Uni-Processor Simple Priority scheduler,
+    - ``"MPA "`` for the Multi-Processor Priority Affinity scheduler, and
+    - ``"MPD "`` for the Multi-Processor Deterministic Priority scheduler, and
+    - ``"MPS "`` for the Multi-Processor Simple Priority scheduler.
+
+**DESCRIPTION:**
+
+Schedulers can be identified via ``rtems_scheduler_ident``.  The name of the scheduler is determined by the configuration.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === Configuring a User Scheduler ===
+
+Configuring a User Provided Scheduler
+-------------------------------------
+.. index:: 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_CONTEXT`` must be defined to a static definition
+  of the scheduler context of the user scheduler.
+
+- ``CONFIGURE_SCHEDULER_CONTROLS`` must be defined to a scheduler
+  control 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:**
+
+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.
+
+.. COMMENT: === Configuring Clustered Schedulers ===
+
+
+Configuring Clustered Schedulers
+--------------------------------
+
+Clustered scheduling helps to control the worst-case latencies in a
+multi-processor system.  The goal is to reduce the amount of shared state in
+the system and thus prevention of lock contention.  Modern multi-processor
+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 instance.  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 is used for which cluster?
+
+**CONFIGURATION:**
+
+The schedulers in an SMP system are statically configured on RTEMS.  Firstly
+the application must select which scheduling algorithms are available with the
+following defines
+
+- ``CONFIGURE_SCHEDULER_PRIORITY_SMP``,
+
+- ``CONFIGURE_SCHEDULER_SIMPLE_SMP``, and
+
+- ``CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP``.
+
+This is necessary to calculate the per-thread overhead introduced by the
+schedulers.  After these definitions the configuration file must ``#include
+<rtems/scheduler.h>`` to have access to scheduler specific configuration macros.
+Each scheduler needs a context to store state information at run-time.  To
+provide a context for each scheduler is the next step.  Use the following
+macros to create scheduler contexts
+
+- ``RTEMS_SCHEDULER_CONTEXT_PRIORITY_SMP(name, prio_count)``,
+
+- ``RTEMS_SCHEDULER_CONTEXT_SIMPLE_SMP(name)``, and
+
+- ``RTEMS_SCHEDULER_CONTEXT_PRIORITY_AFFINITY_SMP(name, prio_count)``.
+
+The ``name`` parameter is used as part of a designator for a global
+variable, so the usual C/C++ designator rules apply.  Additional parameters are
+scheduler specific.  The schedulers are registered in the system via the
+scheduler table.  To create the scheduler table define``CONFIGURE_SCHEDULER_CONTROLS`` to a list of the following scheduler
+control initializers
+
+- ``RTEMS_SCHEDULER_CONTROL_PRIORITY_SMP(name, obj_name)``,
+
+- ``RTEMS_SCHEDULER_CONTROL_SIMPLE_SMP(name, obj_name)``, and
+
+- ``RTEMS_SCHEDULER_CONTROL_PRIORITY_AFFINITY_SMP(name, obj_name)``.
+
+The ``name`` parameter must correspond to the parameter defining the
+scheduler context.  The ``obj_name`` determines the scheduler object name
+and can be used in ``rtems_scheduler_ident()`` to get the scheduler object
+identifier.
+
+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
+(``CONFIGURE_SMP_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_SMP_SCHEDULER_ASSIGNMENTS`` to a list of``RTEMS_SCHEDULER_ASSIGN(index, attr)`` and``RTEMS_SCHEDULER_ASSIGN_NO_SCHEDULER`` macros.  The ``index`` parameter
+must be a valid index into the scheduler table.  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``.
+
+**ERRORS:**
+
+In case one of the scheduler indices in``CONFIGURE_SMP_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``.  None of the errors is internal.
+
+- ``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_SMP_SCHEDULER_ASSIGNMENTS`` definition.
+
+- ``SMP_FATAL_MULTITASKING_START_ON_UNASSIGNED_PROCESSOR`` - it is not
+  allowed to start multitasking on a processor with no scheduler assigned.
+
+**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 scheduler
+instances 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:: c
+
+    #define CONFIGURE_SMP_MAXIMUM_PROCESSORS 8
+    #define CONFIGURE_MAXIMUM_PRIORITY 255
+    /* Make the scheduler algorithm available \*/
+    #define CONFIGURE_SCHEDULER_PRIORITY_SMP
+    #include <rtems/scheduler.h>
+    /* Create contexts for the two scheduler instances \*/
+    RTEMS_SCHEDULER_CONTEXT_PRIORITY_SMP(io, CONFIGURE_MAXIMUM_PRIORITY + 1);
+    RTEMS_SCHEDULER_CONTEXT_PRIORITY_SMP(work, CONFIGURE_MAXIMUM_PRIORITY + 1);
+    /* Define the scheduler table \*/
+    #define CONFIGURE_SCHEDULER_CONTROLS \\
+    RTEMS_SCHEDULER_CONTROL_PRIORITY_SMP( \\
+    io, \\
+    rtems_build_name('I', 'O', ' ', ' ') \\
+    ), \\
+    RTEMS_SCHEDULER_CONTROL_PRIORITY_SMP( \\
+    work, \\
+    rtems_build_name('W', 'O', 'R', 'K') \\
+    )
+    /* Define the processor to scheduler assignments \*/
+    #define CONFIGURE_SMP_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)
+
+.. COMMENT: === SMP Specific Configuration Parameters ===
+
+SMP Specific Configuration Parameters
+=====================================
+
+When RTEMS is configured to support SMP target systems, there are other
+configuration parameters which apply.
+
+.. COMMENT: XXX - add -enable-smp
+
+.. COMMENT: === CONFIGURE_SMP_APPLICATION ===
+
+
+Enable SMP Support for Applications
+-----------------------------------
+.. index:: CONFIGURE_SMP_APPLICATION
+
+*CONSTANT:*
+    ``CONFIGURE_SMP_APPLICATION``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default.
+
+**DESCRIPTION:**
+
+``CONFIGURE_SMP_APPLICATION`` must be defined to enable SMP support for the
+application.
+
+**NOTES:**
+
+This define may go away in the future in case all RTEMS components are SMP
+ready.  This configuration define is ignored on uni-processor configurations.
+
+.. COMMENT: === CONFIGURE_SMP_MAXIMUM_PROCESSORS ===
+
+Specify Maximum Processors in SMP System
+----------------------------------------
+.. index:: CONFIGURE_SMP_MAXIMUM_PROCESSORS
+
+*CONSTANT:*
+    ``CONFIGURE_SMP_MAXIMUM_PROCESSORS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    The default value is 1, (if CONFIGURE_SMP_APPLICATION is defined).
+
+**DESCRIPTION:**
+
+``CONFIGURE_SMP_MAXIMUM_PROCESSORS`` must be set to the number of
+processors in the SMP configuration.
+
+**NOTES:**
+
+If there are more processors available than configured, the rest will be
+ignored.  This configuration define is ignored on uni-processor configurations.
+
+.. COMMENT: === Device Driver Table ===
+
+Device Driver Table
+===================
+
+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.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_DRIVERS ===
+
+Specifying the Maximum Number of Device Drivers
+-----------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER ===
+
+Enable Console Device Driver
+----------------------------
+.. index:: 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 standard input and output
+using */dev/console*.
+
+BSPs should be constructed in a manner that allows ``printk()``
+to work properly without the need for the console driver to be configured.
+
+.. COMMENT: === CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER ===
+
+Enable Clock Driver
+-------------------
+.. index:: 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 the ``rtems_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.
+
+.. COMMENT: === CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER ===
+
+Enable the Benchmark Timer Driver
+---------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER ===
+
+Specify Clock and Benchmark Timer Drivers Are Not Needed
+--------------------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_APPLICATION_NEEDS_RTC_DRIVER ===
+
+Enable Real-Time Clock Driver
+-----------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_APPLICATION_NEEDS_WATCHDOG_DRIVER ===
+
+Enable the Watchdog Device Driver
+---------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_APPLICATION_NEEDS_FRAME_BUFFER_DRIVER ===
+
+Enable the Graphics Frame Buffer Device Driver
+----------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_APPLICATION_NEEDS_STUB_DRIVER ===
+
+Enable Stub Device Driver
+-------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_APPLICATION_PREREQUISITE_DRIVERS ===
+
+Specify Application Prerequisite Device Drivers
+-----------------------------------------------
+.. index:: 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.
+
+.. COMMENT: XXX Add example
+
+.. COMMENT: === CONFIGURE_APPLICATION_EXTRA_DRIVERS ===
+
+Specify Extra Application Device Drivers
+----------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_APPLICATION_NEEDS_NULL_DRIVER ===
+
+Enable /dev/null Device Driver
+------------------------------
+.. index:: CONFIGURE_APPLICATION_NEEDS_NULL_DRIVER
+.. index:: /dev/null
+
+*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.
+
+.. COMMENT: === CONFIGURE_APPLICATION_NEEDS_ZERO_DRIVER ===
+
+Enable /dev/zero Device Driver
+------------------------------
+.. index:: CONFIGURE_APPLICATION_NEEDS_ZERO_DRIVER
+.. index:: /dev/zero
+
+*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.
+
+.. COMMENT: === CONFIGURE_HAS_OWN_DEVICE_DRIVER_TABLE ===
+
+Specifying Application Defined Device Driver Table
+--------------------------------------------------
+.. index:: CONFIGURE_HAS_OWN_DEVICE_DRIVER_TABLE
+
+*CONSTANT:*
+    ``CONFIGURE_HAS_OWN_DEVICE_DRIVER_TABLE``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default, indicating the ``<rtems/confdefs.h>``
+    is providing the device driver table.
+
+**DESCRIPTION:**
+
+``CONFIGURE_HAS_OWN_DEVICE_DRIVER_TABLE`` is defined if the application
+wishes to provide their own Device Driver Table.
+
+The table must be an array of ``rtems_driver_address_table`` entries named``_IO_Driver_address_table``.  The application must also provide a const
+variable ``_IO_Number_of_drivers`` of type ``size_t`` indicating the
+number of entries in the ``_IO_Driver_address_table``.
+
+**NOTES:**
+
+It is expected that there the application would only rarely need to do this.
+
+.. COMMENT: === Multiprocessing Configuration ===
+
+Multiprocessing Configuration
+=============================
+
+This section defines the multiprocessing related system configuration
+parameters supported by ``<rtems/confdefs.h>``.  They are only used
+if the Multiprocessing Support (distinct from the SMP support) is enabled
+at configure time using the ``--enable-multiprocessing`` option.
+
+Additionally, this class of Configuration Constants are only applicable if``CONFIGURE_MP_APPLICATION`` is defined.
+
+.. COMMENT: === CONFIGURE_MP_APPLICATION ===
+
+Specify Application Will Use Multiprocessing
+--------------------------------------------
+.. index:: 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 configured and built using the``--enable-multiprocessing`` option.
+
+.. COMMENT: === CONFIGURE_MP_NODE_NUMBER ===
+
+Configure Node Number in Multiprocessor Configuration
+-----------------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_MP_MAXIMUM_NODES ===
+
+Configure Maximum Node in Multiprocessor Configuration
+------------------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_MP_MAXIMUM_GLOBAL_OBJECTS ===
+
+Configure Maximum Global Objects in Multiprocessor Configuration
+----------------------------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_MP_MAXIMUM_PROXIES ===
+
+Configure Maximum Proxies in Multiprocessor Configuration
+---------------------------------------------------------
+.. index:: 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
+
+.. COMMENT: === CONFIGURE_MP_MPCI_TABLE_POINTER ===
+
+Configure MPCI in Multiprocessor Configuration
+----------------------------------------------
+.. index:: 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.
+
+.. COMMENT: === CONFIGURE_HAS_OWN_MULTIPROCESSING_TABLE ===
+
+Do Not Generate Multiprocessor Configuration Table
+--------------------------------------------------
+.. index:: CONFIGURE_HAS_OWN_MULTIPROCESSING_TABLE
+
+*CONSTANT:*
+    ``CONFIGURE_HAS_OWN_MULTIPROCESSING_TABLE``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default.
+
+**DESCRIPTION:**
+
+``CONFIGURE_HAS_OWN_MULTIPROCESSING_TABLE`` is defined if the
+application wishes to provide their own Multiprocessing Configuration
+Table.  The generated table is named ``Multiprocessing_configuration``.
+
+**NOTES:**
+
+This is a configuration parameter which is very unlikely to be used by
+an application. If you find yourself wanting to use it in an application,
+please reconsider and discuss this on the RTEMS Users mailing list.
+
+.. COMMENT: === Ada Tasks ===
+
+Ada Tasks
+=========
+
+This section defines the system configuration parameters supported
+by ``<rtems/confdefs.h>`` related to configuring RTEMS to support
+a task using Ada tasking with GNAT/RTEMS.
+
+These configuration parameters are only available when RTEMS is built with
+the ``--enable-ada`` configure option and the application specifies``CONFIGURE_GNAT_RTEMS``.
+
+Additionally RTEMS includes an Ada language binding to the Classic
+API which has a test suite. This test suite is enabled only when``--enable-tests`` and ``--enable-expada`` are specified on the
+configure command.
+
+.. COMMENT: === CONFIGURE_GNAT_RTEMS ===
+
+Specify Application Includes Ada Code
+-------------------------------------
+.. index:: CONFIGURE_GNAT_RTEMS
+
+*CONSTANT:*
+    ``CONFIGURE_GNAT_RTEMS``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default.
+
+**DESCRIPTION:**
+
+``CONFIGURE_GNAT_RTEMS`` is defined to inform RTEMS that the GNAT
+Ada run-time is to be used by the application.
+
+**NOTES:**
+
+This configuration parameter is critical as it makes``<rtems/confdefs.h>`` configure the resources (POSIX API Threads,
+Mutexes, Condition Variables, and Keys) used implicitly by the GNAT
+run-time.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_ADA_TASKS ===
+
+Specify the Maximum Number of Ada Tasks.
+----------------------------------------
+.. index:: CONFIGURE_MAXIMUM_ADA_TASKS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_ADA_TASKS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Undefined or positive.
+
+*DEFAULT VALUE:*
+    If ``CONFIGURE_GNAT_RTEMS`` is defined, then the
+    default value is 20, otherwise the default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_ADA_TASKS`` is the number of Ada tasks that can
+be concurrently active in the system.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === CONFIGURE_MAXIMUM_FAKE_ADA_TASKS ===
+
+Specify the Maximum Fake Ada Tasks
+----------------------------------
+.. index:: CONFIGURE_MAXIMUM_FAKE_ADA_TASKS
+
+*CONSTANT:*
+    .. index:: ``CONFIGURE_MAXIMUM_FAKE_ADA_TASKS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 0.
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_FAKE_ADA_TASKS`` is the number of *fake* Ada tasks
+that can be concurrently active in the system.  A *fake* Ada task is
+a non-Ada task that makes calls back into Ada code and thus implicitly
+uses the Ada run-time.
+
+**NOTES:**
+
+None.
+
+.. COMMENT: === PCI Library ===
+
+PCI Library
+===========
+
+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`` is 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`` is 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`` is 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`` is 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.
+
+.. COMMENT: === Go Tasks ===
+
+Go Tasks
+========
+
+.. COMMENT: === CONFIGURE_ENABLE_GO ===
+
+Specify Application Includes Go Code
+------------------------------------
+.. index:: CONFIGURE_ENABLE_GO
+
+*CONSTANT:*
+    ``CONFIGURE_ENABLE_GO``
+
+*DATA TYPE:*
+    Boolean feature macro.
+
+*RANGE:*
+    Defined or undefined.
+
+*DEFAULT VALUE:*
+    This is not defined by default.
+
+**DESCRIPTION:**
+
+``CONFIGURE_ENABLE_GO`` is defined to inform RTEMS that the Go
+run-time is to be used by the application.
+
+**NOTES:**
+
+The Go language support is experimental
+
+.. COMMENT: === CONFIGURE_MAXIMUM_GOROUTINES ===
+
+Specify the maximum number of Go routines
+-----------------------------------------
+.. index:: CONFIGURE_MAXIMUM_GOROUTINES
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_GOROUTINES``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 400
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_GOROUTINES`` is defined to specify the maximum number of
+Go routines.
+
+**NOTES:**
+
+The Go language support is experimental
+
+.. COMMENT: === CONFIGURE_MAXIMUM_GO_CHANNELS ===
+
+Specify the maximum number of Go Channels
+-----------------------------------------
+.. index:: CONFIGURE_MAXIMUM_GO_CHANNELS
+
+*CONSTANT:*
+    ``CONFIGURE_MAXIMUM_GO_CHANNELS``
+
+*DATA TYPE:*
+    Unsigned integer (``uint32_t``).
+
+*RANGE:*
+    Zero or positive.
+
+*DEFAULT VALUE:*
+    The default value is 500
+
+**DESCRIPTION:**
+
+``CONFIGURE_MAXIMUM_GO_CHANNELS`` is defined to specify the maximum number
+of Go channels.
+
+**NOTES:**
+
+The Go language support is experimental
+
+.. COMMENT: === Configuration Data Structures ===
+
+Configuration Data Structures
+=============================
+
+It is recommended that applications be configured using``<rtems/confdefs.h>`` as it is simpler and insulates applications
+from changes in the underlying data structures.  However, it is sometimes
+important to understand the data structures that are automatically filled
+in by the configuration parameters.  This section describes the primary
+configuration data structures.
+
+If the user wishes to see the details of a particular data structure,
+they are are advised to look at the source code. After all, that is one
+of the advantages of RTEMS.
+
+.. COMMENT: COPYRIGHT (c) 1988-2007.
+
+.. COMMENT: On-Line Applications Research Corporation (OAR).
+
+.. COMMENT: All rights reserved.
+