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Diffstat (limited to 'c-user/partition')
| -rw-r--r-- | c-user/partition/background.rst | 50 | ||||
| -rw-r--r-- | c-user/partition/directives.rst | 349 | ||||
| -rw-r--r-- | c-user/partition/index.rst | 15 | ||||
| -rw-r--r-- | c-user/partition/introduction.rst | 19 | ||||
| -rw-r--r-- | c-user/partition/operations.rst | 55 |
5 files changed, 488 insertions, 0 deletions
diff --git a/c-user/partition/background.rst b/c-user/partition/background.rst new file mode 100644 index 0000000..ce38fc7 --- /dev/null +++ b/c-user/partition/background.rst @@ -0,0 +1,50 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR) + +Background +========== + +.. index:: partition, definition + +Partition Manager Definitions +----------------------------- + +A partition is a physically contiguous memory area divided into fixed-size +buffers that can be dynamically allocated and deallocated. + +.. index:: buffers, definition + +Partitions are managed and maintained as a list of buffers. Buffers are +obtained from the front of the partition's free buffer chain and returned to +the rear of the same chain. When a buffer is on the free buffer chain, RTEMS +uses two pointers of memory from each buffer as the free buffer chain. When a +buffer is allocated, the entire buffer is available for application use. +Therefore, modifying memory that is outside of an allocated buffer could +destroy the free buffer chain or the contents of an adjacent allocated buffer. + +.. index:: partition attribute set, building + +Building a Partition Attribute Set +---------------------------------- + +In general, an attribute set is built by a bitwise OR of the desired attribute +components. The set of valid partition attributes is provided in the following +table: + +.. list-table:: + :class: rtems-table + + * - ``RTEMS_LOCAL`` + - local partition (default) + * - ``RTEMS_GLOBAL`` + - global partition + +Attribute values are specifically designed to be mutually exclusive, therefore +bitwise OR and addition operations are equivalent as long as each attribute +appears exactly once in the component list. An attribute listed as a default +is not required to appear in the attribute list, although it is a good +programming practice to specify default attributes. If all defaults are +desired, the attribute ``RTEMS_DEFAULT_ATTRIBUTES`` should be specified on this +call. The attribute_set parameter should be ``RTEMS_GLOBAL`` to indicate that +the partition is to be known globally. diff --git a/c-user/partition/directives.rst b/c-user/partition/directives.rst new file mode 100644 index 0000000..f81c37f --- /dev/null +++ b/c-user/partition/directives.rst @@ -0,0 +1,349 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR) + +Directives +========== + +This section details the partition 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 partition +.. index:: rtems_partition_create + +.. _rtems_partition_create: + +PARTITION_CREATE - Create a partition +------------------------------------- + +CALLING SEQUENCE: + .. code-block:: c + + rtems_status_code rtems_partition_create( + rtems_name name, + void *starting_address, + uintptr_t length, + size_t buffer_size, + rtems_attribute attribute_set, + rtems_id *id + ); + +DIRECTIVE STATUS CODES: + .. list-table:: + :class: rtems-table + + * - ``RTEMS_SUCCESSFUL`` + - partition created successfully + * - ``RTEMS_INVALID_NAME`` + - invalid partition ``name`` + * - ``RTEMS_TOO_MANY`` + - too many partitions created + * - ``RTEMS_INVALID_ADDRESS`` + - ``starting_address`` is not on a pointer size boundary + * - ``RTEMS_INVALID_ADDRESS`` + - ``starting_address`` is NULL + * - ``RTEMS_INVALID_ADDRESS`` + - ``id`` is NULL + * - ``RTEMS_INVALID_SIZE`` + - ``length`` or ``buffer_size`` is 0 + * - ``RTEMS_INVALID_SIZE`` + - ``length`` is less than the ``buffer_size`` + * - ``RTEMS_INVALID_SIZE`` + - ``buffer_size`` is not an integral multiple of the pointer size + * - ``RTEMS_INVALID_SIZE`` + - ``buffer_size`` is less than two times the pointer size + * - ``RTEMS_TOO_MANY`` + - too many global objects + +DESCRIPTION: + This directive creates a partition of fixed size buffers from a physically + contiguous memory space which starts at starting_address and is length + bytes in size. Each allocated buffer is to be of ``buffer_size`` in bytes. + The assigned partition id is returned in ``id``. This partition id is used + to access the partition with other partition related directives. For + control and maintenance of the partition, RTEMS allocates a PTCB from the + local PTCB free pool and initializes it. + +NOTES: + This directive may cause the calling task to be preempted due to an + obtain and release of the object allocator mutex. + + The partition buffer area specified by the ``starting_address`` must be + properly aligned. It must be possible to directly store target + architecture pointers and the also the user data. For example, if the user + data contains some long double or vector data types, the partition buffer + area and the buffer size must take the alignment of these types into + account which is usually larger than the pointer alignment. A cache line + alignment may be also a factor. + + The ``buffer_size`` parameter must be an integral multiple of the pointer + size on the target architecture. Additionally, ``buffer_size`` must be + large enough to hold two pointers on the target architecture. This is + required for RTEMS to manage the buffers when they are free. + + Memory from the partition is not used by RTEMS to store the Partition + Control Block. + + The following partition attribute constants are defined by RTEMS: + + .. list-table:: + :class: rtems-table + + * - ``RTEMS_LOCAL`` + - local partition (default) + * - ``RTEMS_GLOBAL`` + - global partition + + The PTCB for a global partition is allocated on the local node. The memory + space used for the partition must reside in shared memory. Partitions + should not be made global unless remote tasks must interact with the + partition. This is to avoid the overhead incurred by the creation of a + global partition. When a global partition is created, the partition's name + and id must be transmitted to every node in the system for insertion in the + local copy of the global object table. + + The total number of global objects, including partitions, is limited by the + maximum_global_objects field in the Configuration Table. + +EXAMPLE: + .. code-block:: c + + #include <rtems.h> + #include <rtems/chain.h> + + #include <assert.h> + + typedef struct { + char less; + short more; + } item; + + union { + item data; + rtems_chain_node node; + } items[ 13 ]; + + rtems_id create_partition(void) + { + rtems_id id; + rtems_status_code sc; + + sc = rtems_partition_create( + rtems_build_name( 'P', 'A', 'R', 'T' ), + items, + sizeof( items ), + sizeof( items[ 0 ] ), + RTEMS_DEFAULT_ATTRIBUTES, + &id + ); + assert(sc == RTEMS_SUCCESSFUL); + + return id; + } + +.. raw:: latex + + \clearpage + +.. index:: get ID of a partition +.. index:: obtain ID of a partition +.. index:: rtems_partition_ident + +.. _rtems_partition_ident: + +PARTITION_IDENT - Get ID of a partition +--------------------------------------- + +CALLING SEQUENCE: + .. code-block:: c + + rtems_status_code rtems_partition_ident( + rtems_name name, + uint32_t node, + rtems_id *id + ); + +DIRECTIVE STATUS CODES: + .. list-table:: + :class: rtems-table + + * - ``RTEMS_SUCCESSFUL`` + - partition identified successfully + * - ``RTEMS_INVALID_ADDRESS`` + - ``id`` is NULL + * - ``RTEMS_INVALID_NAME`` + - partition name not found + * - ``RTEMS_INVALID_NODE`` + - invalid node id + +DESCRIPTION: + This directive obtains the partition id associated with the partition name. + If the partition name is not unique, then the partition id will match one + of the partitions with that name. However, this partition id is not + guaranteed to correspond to the desired partition. The partition id is + used with other partition related directives to access the partition. + +NOTES: + This directive will not cause the running task to be preempted. + + If node is ``RTEMS_SEARCH_ALL_NODES``, all nodes are searched with the + local node being searched first. All other nodes are searched with the + lowest numbered node searched first. + + If node is a valid node number which does not represent the local node, + then only the partitions exported by the designated node are searched. + + This directive does not generate activity on remote nodes. It accesses + only the local copy of the global object table. + +.. raw:: latex + + \clearpage + +.. index:: delete a partition +.. index:: rtems_partition_delete + +.. _rtems_partition_delete: + +PARTITION_DELETE - Delete a partition +------------------------------------- + +CALLING SEQUENCE: + .. code-block:: c + + rtems_status_code rtems_partition_delete( + rtems_id id + ); + +DIRECTIVE STATUS CODES: + .. list-table:: + :class: rtems-table + + * - ``RTEMS_SUCCESSFUL`` + - partition deleted successfully + * - ``RTEMS_INVALID_ID`` + - invalid partition id + * - ``RTEMS_RESOURCE_IN_USE`` + - buffers still in use + * - ``RTEMS_ILLEGAL_ON_REMOTE_OBJECT`` + - cannot delete remote partition + +DESCRIPTION: + This directive deletes the partition specified by id. The partition cannot + be deleted if any of its buffers are still allocated. The PTCB for the + deleted partition is reclaimed by RTEMS. + +NOTES: + This directive may cause the calling task to be preempted due to an + obtain and release of the object allocator mutex. + + The calling task does not have to be the task that created the partition. + Any local task that knows the partition id can delete the partition. + + When a global partition is deleted, the partition id must be transmitted to + every node in the system for deletion from the local copy of the global + object table. + + The partition must reside on the local node, even if the partition was + created with the ``RTEMS_GLOBAL`` option. + +.. raw:: latex + + \clearpage + +.. index:: get buffer from partition +.. index:: obtain buffer from partition +.. index:: rtems_partition_get_buffer + +.. _rtems_partition_get_buffer: + +PARTITION_GET_BUFFER - Get buffer from a partition +-------------------------------------------------- + +CALLING SEQUENCE: + .. code-block:: c + + rtems_status_code rtems_partition_get_buffer( + rtems_id id, + void **buffer + ); + +DIRECTIVE STATUS CODES: + .. list-table:: + :class: rtems-table + + * - ``RTEMS_SUCCESSFUL`` + - buffer obtained successfully + * - ``RTEMS_INVALID_ADDRESS`` + - ``buffer`` is NULL + * - ``RTEMS_INVALID_ID`` + - invalid partition id + * - ``RTEMS_UNSATISFIED`` + - all buffers are allocated + +DESCRIPTION: + This directive allows a buffer to be obtained from the partition specified + in id. The address of the allocated buffer is returned in buffer. + +NOTES: + This directive will not cause the running task to be preempted. + + All buffers begin on a four byte boundary. + + A task cannot wait on a buffer to become available. + + Getting a buffer from a global partition which does not reside on the local + node will generate a request telling the remote node to allocate a buffer + from the specified partition. + +.. raw:: latex + + \clearpage + +.. index:: return buffer to partitition +.. index:: rtems_partition_return_buffer + +.. _rtems_partition_return_buffer: + +PARTITION_RETURN_BUFFER - Return buffer to a partition +------------------------------------------------------ + +CALLING SEQUENCE: + .. code-block:: c + + rtems_status_code rtems_partition_return_buffer( + rtems_id id, + void *buffer + ); + +DIRECTIVE STATUS CODES: + .. list-table:: + :class: rtems-table + + * - ``RTEMS_SUCCESSFUL`` + - buffer returned successfully + * - ``RTEMS_INVALID_ADDRESS`` + - ``buffer`` is NULL + * - ``RTEMS_INVALID_ID`` + - invalid partition id + * - ``RTEMS_INVALID_ADDRESS`` + - buffer address not in partition + +DESCRIPTION: + This directive returns the buffer specified by buffer to the partition + specified by id. + +NOTES: + This directive will not cause the running task to be preempted. + + Returning a buffer to a global partition which does not reside on the local + node will generate a request telling the remote node to return the buffer + to the specified partition. + + Returning a buffer multiple times is an error. It will corrupt the + internal state of the partition. diff --git a/c-user/partition/index.rst b/c-user/partition/index.rst new file mode 100644 index 0000000..c8e7348 --- /dev/null +++ b/c-user/partition/index.rst @@ -0,0 +1,15 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +.. Copyright (C) 2020 embedded brains GmbH (http://www.embedded-brains.de) + +.. index:: partitions + +Partition Manager +***************** + +.. toctree:: + + introduction + background + operations + directives diff --git a/c-user/partition/introduction.rst b/c-user/partition/introduction.rst new file mode 100644 index 0000000..dd51d30 --- /dev/null +++ b/c-user/partition/introduction.rst @@ -0,0 +1,19 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR) + +Introduction +============ + +The partition manager provides facilities to dynamically allocate memory in +fixed-size units. The directives provided by the partition manager are: + +- :ref:`rtems_partition_create` + +- :ref:`rtems_partition_ident` + +- :ref:`rtems_partition_delete` + +- :ref:`rtems_partition_get_buffer` + +- :ref:`rtems_partition_return_buffer` diff --git a/c-user/partition/operations.rst b/c-user/partition/operations.rst new file mode 100644 index 0000000..d0eff5b --- /dev/null +++ b/c-user/partition/operations.rst @@ -0,0 +1,55 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR) + +Operations +========== + +Creating a Partition +-------------------- + +The ``rtems_partition_create`` directive creates a partition with a +user-specified name. The partition's name, starting address, length and buffer +size are all specified to the ``rtems_partition_create`` directive. RTEMS +allocates a Partition Control Block (PTCB) from the PTCB free list. This data +structure is used by RTEMS to manage the newly created partition. The number +of buffers in the partition is calculated based upon the specified partition +length and buffer size. If successful,the unique partition ID is returned to +the calling task. + +Obtaining Partition IDs +----------------------- + +When a partition is created, RTEMS generates a unique partition ID and assigned +it to the created partition until it is deleted. The partition ID may be +obtained by either of two methods. First, as the result of an invocation of +the ``rtems_partition_create`` directive, the partition ID is stored in a user +provided location. Second, the partition ID may be obtained later using the +``rtems_partition_ident`` directive. The partition ID is used by other +partition manager directives to access this partition. + +Acquiring a Buffer +------------------ + +A buffer can be obtained by calling the ``rtems_partition_get_buffer`` +directive. If a buffer is available, then it is returned immediately with a +successful return code. Otherwise, an unsuccessful return code is returned +immediately to the caller. Tasks cannot block to wait for a buffer to become +available. + +Releasing a Buffer +------------------ + +Buffers are returned to a partition's free buffer chain with the +``rtems_partition_return_buffer`` directive. This directive returns an error +status code if the returned buffer was not previously allocated from this +partition. + +Deleting a Partition +-------------------- + +The ``rtems_partition_delete`` directive allows a partition to be removed and +returned to RTEMS. When a partition is deleted, the PTCB for that partition is +returned to the PTCB free list. A partition with buffers still allocated +cannot be deleted. Any task attempting to do so will be returned an error +status code. |