.. SPDX-License-Identifier: CC-BY-SA-4.0 .. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR) Directives ========== This section details the region manager's directives. A subsection is dedicated to each of this manager's directives and describes the calling sequence, related constants, usage, and status codes. .. raw:: latex \clearpage .. index:: create a region .. _rtems_region_create: REGION_CREATE - Create a region ------------------------------- CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_region_create( rtems_name name, void *starting_address, uintptr_t length, uintptr_t page_size, rtems_attribute attribute_set, rtems_id *id ); DIRECTIVE STATUS CODES: .. list-table:: :class: rtems-table * - ``RTEMS_SUCCESSFUL`` - region created successfully * - ``RTEMS_INVALID_NAME`` - invalid region name * - ``RTEMS_INVALID_ADDRESS`` - ``id`` is NULL * - ``RTEMS_INVALID_ADDRESS`` - ``starting_address`` is NULL * - ``RTEMS_TOO_MANY`` - too many regions created * - ``RTEMS_INVALID_SIZE`` - invalid page size * - ``RTEMS_INVALID_SIZE`` - the memory area defined by the starting address and the length parameters is too small DESCRIPTION: This directive creates a region from a contiguous memory area which starts at starting_address and is length bytes long. The memory area must be large enough to contain some internal region administration data. Segments allocated from the region will be a multiple of page_size bytes in length. The specified page size will be aligned to an architecture-specific minimum alignment if necessary. The assigned region id is returned in id. This region id is used as an argument to other region related directives to access the region. For control and maintenance of the region, RTEMS allocates and initializes an RNCB from the RNCB free pool. Thus memory from the region is not used to store the RNCB. However, some overhead within the region is required by RTEMS each time a segment is constructed in the region. Specifying ``RTEMS_PRIORITY`` in attribute_set causes tasks waiting for a segment to be serviced according to task priority. Specifying ``RTEMS_FIFO`` in attribute_set or selecting ``RTEMS_DEFAULT_ATTRIBUTES`` will cause waiting tasks to be serviced in First In-First Out order. NOTES: This directive will obtain the allocator mutex and may cause the calling task to be preempted. The following region attribute constants are defined by RTEMS: .. list-table:: :class: rtems-table * - ``RTEMS_FIFO`` - tasks wait by FIFO (default) * - ``RTEMS_PRIORITY`` - tasks wait by priority .. raw:: latex \clearpage .. index:: get ID of a region .. index:: obtain ID of a region .. index:: rtems_region_ident .. _rtems_region_ident: REGION_IDENT - Get ID of a region --------------------------------- CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_region_ident( rtems_name name, rtems_id *id ); DIRECTIVE STATUS CODES: .. list-table:: :class: rtems-table * - ``RTEMS_SUCCESSFUL`` - region identified successfully * - ``RTEMS_INVALID_ADDRESS`` - ``id`` is NULL * - ``RTEMS_INVALID_NAME`` - region name not found DESCRIPTION: This directive obtains the region id associated with the region name to be acquired. If the region name is not unique, then the region id will match one of the regions with that name. However, this region id is not guaranteed to correspond to the desired region. The region id is used to access this region in other region manager directives. NOTES: This directive will not cause the running task to be preempted. .. raw:: latex \clearpage .. index:: delete a region .. index:: rtems_region_delete .. _rtems_region_delete: REGION_DELETE - Delete a region ------------------------------- CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_region_delete( rtems_id id ); DIRECTIVE STATUS CODES: .. list-table:: :class: rtems-table * - ``RTEMS_SUCCESSFUL`` - region deleted successfully * - ``RTEMS_INVALID_ID`` - invalid region id * - ``RTEMS_RESOURCE_IN_USE`` - segments still in use DESCRIPTION: This directive deletes the region specified by id. The region cannot be deleted if any of its segments are still allocated. The RNCB for the deleted region is reclaimed by RTEMS. NOTES: This directive will obtain the allocator mutex and may cause the calling task to be preempted. The calling task does not have to be the task that created the region. Any local task that knows the region id can delete the region. .. raw:: latex \clearpage .. index:: add memory to a region .. index:: region, add memory .. index:: rtems_region_extend .. _rtems_region_extend: REGION_EXTEND - Add memory to a region -------------------------------------- CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_region_extend( rtems_id id, void *starting_address, uintptr_t length ); DIRECTIVE STATUS CODES: .. list-table:: :class: rtems-table * - ``RTEMS_SUCCESSFUL`` - region extended successfully * - ``RTEMS_INVALID_ADDRESS`` - ``starting_address`` is NULL * - ``RTEMS_INVALID_ID`` - invalid region id * - ``RTEMS_INVALID_ADDRESS`` - invalid address of area to add DESCRIPTION: This directive adds the memory area which starts at :c:data:`starting_address` for :c:data:`length` bytes to the region specified by :c:data:`id`. There are no alignment requirements for the memory area. The memory area must be big enough to contain some maintenance blocks. It must not overlap parts of the current heap memory areas. Disconnected memory areas added to the heap will lead to used blocks which cover the gaps. Extending with an inappropriate memory area will corrupt the heap resulting in undefined behaviour. NOTES: This directive will obtain the allocator mutex and may cause the calling task to be preempted. The calling task does not have to be the task that created the region. Any local task that knows the region identifier can extend the region. .. raw:: latex \clearpage .. index:: get segment from region .. index:: rtems_region_get_segment .. _rtems_region_get_segment: REGION_GET_SEGMENT - Get segment from a region ---------------------------------------------- CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_region_get_segment( rtems_id id, uintptr_t size, rtems_option option_set, rtems_interval timeout, void **segment ); DIRECTIVE STATUS CODES: .. list-table:: :class: rtems-table * - ``RTEMS_SUCCESSFUL`` - segment obtained successfully * - ``RTEMS_INVALID_ADDRESS`` - ``segment`` is NULL * - ``RTEMS_INVALID_ID`` - invalid region id * - ``RTEMS_INVALID_SIZE`` - request is for zero bytes or exceeds the size of maximum segment which is possible for this region * - ``RTEMS_UNSATISFIED`` - segment of requested size not available * - ``RTEMS_TIMEOUT`` - timed out waiting for segment * - ``RTEMS_OBJECT_WAS_DELETED`` - region deleted while waiting DESCRIPTION: This directive obtains a variable size segment from the region specified by ``id``. The address of the allocated segment is returned in segment. The ``RTEMS_WAIT`` and ``RTEMS_NO_WAIT`` components of the options parameter are used to specify whether the calling tasks wish to wait for a segment to become available or return immediately if no segment is available. For either option, if a sufficiently sized segment is available, then the segment is successfully acquired by returning immediately with the ``RTEMS_SUCCESSFUL`` status code. If the calling task chooses to return immediately and a segment large enough is not available, then an error code indicating this fact is returned. If the calling task chooses to wait for the segment and a segment large enough is not available, then the calling task is placed on the region's segment wait queue and blocked. If the region was created with the ``RTEMS_PRIORITY`` option, then the calling task is inserted into the wait queue according to its priority. However, if the region was created with the ``RTEMS_FIFO`` option, then the calling task is placed at the rear of the wait queue. The timeout parameter specifies the maximum interval that a task is willing to wait to obtain a segment. If timeout is set to ``RTEMS_NO_TIMEOUT``, then the calling task will wait forever. NOTES: This directive will obtain the allocator mutex and may cause the calling task to be preempted. The actual length of the allocated segment may be larger than the requested size because a segment size is always a multiple of the region's page size. The following segment acquisition option constants are defined by RTEMS: .. list-table:: :class: rtems-table * - ``RTEMS_WAIT`` - task will wait for segment (default) * - ``RTEMS_NO_WAIT`` - task should not wait A clock tick is required to support the timeout functionality of this directive. .. raw:: latex \clearpage .. index:: return segment to region .. index:: rtems_region_return_segment .. _rtems_region_return_segment: REGION_RETURN_SEGMENT - Return segment to a region -------------------------------------------------- CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_region_return_segment( rtems_id id, void *segment ); DIRECTIVE STATUS CODES: .. list-table:: :class: rtems-table * - ``RTEMS_SUCCESSFUL`` - segment returned successfully * - ``RTEMS_INVALID_ADDRESS`` - ``segment`` is NULL * - ``RTEMS_INVALID_ID`` - invalid region id * - ``RTEMS_INVALID_ADDRESS`` - segment address not in region DESCRIPTION: This directive returns the segment specified by segment to the region specified by id. The returned segment is merged with its neighbors to form the largest possible segment. The first task on the wait queue is examined to determine if its segment request can now be satisfied. If so, it is given a segment and unblocked. This process is repeated until the first task's segment request cannot be satisfied. NOTES: This directive will cause the calling task to be preempted if one or more local tasks are waiting for a segment and the following conditions exist: - a waiting task has a higher priority than the calling task - the size of the segment required by the waiting task is less than or equal to the size of the segment returned. .. raw:: latex \clearpage .. index:: get size of segment .. index:: rtems_region_get_segment_size .. _rtems_region_get_segment_size: REGION_GET_SEGMENT_SIZE - Obtain size of a segment -------------------------------------------------- CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_region_get_segment_size( rtems_id id, void *segment, uintptr_t *size ); DIRECTIVE STATUS CODES: .. list-table:: :class: rtems-table * - ``RTEMS_SUCCESSFUL`` - segment obtained successfully * - ``RTEMS_INVALID_ADDRESS`` - ``segment`` is NULL * - ``RTEMS_INVALID_ADDRESS`` - ``size`` is NULL * - ``RTEMS_INVALID_ID`` - invalid region id * - ``RTEMS_INVALID_ADDRESS`` - segment address not in region DESCRIPTION: This directive obtains the size in bytes of the specified segment. NOTES: The actual length of the allocated segment may be larger than the requested size because a segment size is always a multiple of the region's page size. .. raw:: latex \clearpage .. index:: resize segment .. index:: rtems_region_resize_segment .. _rtems_region_resize_segment: REGION_RESIZE_SEGMENT - Change size of a segment ------------------------------------------------ CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_region_resize_segment( rtems_id id, void *segment, uintptr_t new_size, uintptr_t *old_size ); DIRECTIVE STATUS CODES: .. list-table:: :class: rtems-table * - ``RTEMS_SUCCESSFUL`` - segment obtained successfully * - ``RTEMS_INVALID_ADDRESS`` - ``segment`` is NULL * - ``RTEMS_INVALID_ADDRESS`` - ``old_size`` is NULL * - ``RTEMS_INVALID_ID`` - invalid region id * - ``RTEMS_INVALID_ADDRESS`` - segment address not in region * - ``RTEMS_UNSATISFIED`` - unable to make segment larger DESCRIPTION: This directive is used to increase or decrease the size of a segment. When increasing the size of a segment, it is possible that there is not memory available contiguous to the segment. In this case, the request is unsatisfied. NOTES: This directive will obtain the allocator mutex and may cause the calling task to be preempted. If an attempt to increase the size of a segment fails, then the application may want to allocate a new segment of the desired size, copy the contents of the original segment to the new, larger segment and then return the original segment. .. raw:: latex \clearpage .. index:: obtain region information .. index:: rtems_region_get_information .. _rtems_region_get_information: REGION_GET_INFORMATION - Get region information ----------------------------------------------- CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_region_get_information( rtems_id id, Heap_Information_block *the_info ); DIRECTIVE STATUS CODES: .. list-table:: :class: rtems-table * - ``RTEMS_SUCCESSFUL`` - information obtained successfully * - ``RTEMS_INVALID_ADDRESS`` - ``the_info`` is NULL * - ``RTEMS_INVALID_ID`` - invalid region id DESCRIPTION: This directive is used to obtain information about the used and free memory in the region specified by ``id``. This is a snapshot at the time of the call. The information will be returned in the structure pointed to by ``the_info``. NOTES: This directive will obtain the allocator mutex and may cause the calling task to be preempted. This is primarily intended as a mechanism to obtain a diagnostic information. This method forms am O(n) scan of the free and an O(n) scan of the used blocks in the region to calculate the information provided. Given that the execution time is driven by the number of used and free blocks, it can take a non-deterministic time to execute. .. raw:: latex \clearpage .. index:: obtain region information on free blocks .. index:: rtems_region_get_free_information .. _rtems_region_get_free_information: REGION_GET_FREE_INFORMATION - Get region free information --------------------------------------------------------- CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_region_get_free_information( rtems_id id, Heap_Information_block *the_info ); DIRECTIVE STATUS CODES: .. list-table:: :class: rtems-table * - ``RTEMS_SUCCESSFUL`` - information obtained successfully * - ``RTEMS_INVALID_ADDRESS`` - ``the_info`` is NULL * - ``RTEMS_INVALID_ID`` - invalid region id DESCRIPTION: This directive is used to obtain information about the free memory in the region specified by ``id``. This is a snapshot at the time of the call. The information will be returned in the structure pointed to by ``the_info``. NOTES: This directive will obtain the allocator mutex and may cause the calling task to be preempted. This uses the same structure to return information as the ``rtems_region_get_information`` directive but does not fill in the used information. This is primarily intended as a mechanism to obtain a diagnostic information. This method forms am O(n) scan of the free in the region to calculate the information provided. Given that the execution time is driven by the number of used and free blocks, it can take a non-deterministic time to execute. Typically, there are many used blocks and a much smaller number of used blocks making a call to this directive less expensive than a call to ``rtems_region_get_information``.