doc: lib: bluetooth: add GATT queue documentation

Add documentation for BLE GATT queue.

Signed-off-by: Eivind Jølsgard <eivind.jolsgard@nordicsemi.no>

Author: eivindj-nordic

doc/nrf-bm/api/api.rst

@@ -105,6 +105,8 @@ Bare Metal Zephyr Memory Storage (ZMS)
    :inner:
    :members:
 
+.. _api_ble_gatt_queue:
+
 GATT Queue
 ==========
 

doc/nrf-bm/libraries/bluetooth/ble_gatt_queue.rst

@@ -0,0 +1,76 @@
+.. _lib_ble_gatt_queue:
+
+Bluetooth: GATT Queue
+#####################
+
+.. contents::
+   :local:
+   :depth: 2
+
+The Bluetooth Low Energy® GATT Queue library can be used to buffer ``BLE GATT`` requests if the SoftDevice is not able to process them immediately.
+
+Overview
+********
+
+The GATT Queue library temporarily stores GATT requests if the SoftDevice is currently busy.
+Once the SoftDevice is available, as indicated by a Bluetooth LE event, the library retries the request.
+This library can be used in a multiple connections scenario.
+
+The library currently handles the following types of GATT requests:
+
+* Read Characteristic or Descriptor (see ``sd_ble_gattc_read``).
+* Write Characteristic Value or Descriptor (see ``sd_ble_gattc_write``).
+* Primary Service Discovery (see ``sd_ble_gattc_primary_services_discover``).
+* Characteristic Discovery (see ``sd_ble_gattc_characteristics_discover``).
+* Descriptor Discovery (see ``sd_ble_gattc_descriptors_discover``).
+* Notify or Indicate an attribute value (see ``sd_ble_gatts_hvx``).
+
+The GATT Queue can be used with Bluetooth LE service clients and other Bluetooth LE libraries that issue GATT requests to the SoftDevice.
+
+Configuration
+*************
+
+The library is enabled and configured using the Kconfig system.
+Set the :kconfig:option:`CONFIG_BLE_GATT_QUEUE` Kconfig option to enable the library.
+
+You can add an instance of the library to your application using the :c:macro:`BLE_GQ_DEF` macro.
+To add an instance that does not use the default parameters, use the :c:macro:`BLE_GQ_CUSTOM_DEF` macro.
+
+The library exposes the following Kconfig options for the default configuration:
+
+* :kconfig:option:`CONFIG_BLE_GQ_MAX_CONNECTIONS` - Sets the maximum number of simultaneous connections that the GATT queue instance can manage.
+* :kconfig:option:`CONFIG_BLE_GQ_QUEUE_SIZE` - Sets the maximum number of requests that can be queued for each connection that has been registered to the GATT queue instance.
+* :kconfig:option:`CONFIG_BLE_GQ_HEAP_SIZE` - Sets the heap size for storing additional data that can be of variable size.
+  The heap is used for storing the data of Write, Notify, and Indicate requests.
+
+Initialization
+==============
+
+The library does not require other initialization than adding a library instance as described above.
+
+Usage
+*****
+
+After defining a Bluetooth LE Gatt Queue (``BLE GQ``) instance, make sure to register a connection handle by calling the :c:func:`ble_gq_conn_handle_register` function.
+The ``BLE GQ`` instance can now handle GATT requests associated with the handle until the connection is no longer valid (for example, after a disconnect event occurs).
+
+To add a GATT request to the ``BLE GQ`` instance, call the :c:func:`ble_gq_item_add` function.
+This function adds a request to the ``BLE GQ`` instance and allocates necessary memory for the data that can be held within the request descriptor.
+If the SoftDevice is free and the queue is empty, the request is processed immediately.
+Otherwise, the request is queued and processed later.
+
+Dependencies
+************
+
+This library uses the following |BMshort| libraries:
+
+* SoftDevice - :kconfig:option:`CONFIG_SOFTDEVICE`
+* SoftDevice handler - :kconfig:option:`CONFIG_NRF_SDH`
+
+API documentation
+*****************
+
+| Header file: :file:`include/bm/bluetooth/ble_gq.h`
+| Source files: :file:`lib/bluetooth/ble_gq/`
+
+:ref:`Bluetooth LE GATT Queue library API reference <api_ble_gatt_queue>`

doc/nrf-bm/release_notes/release_notes_changelog.rst

@@ -134,5 +134,6 @@ Documentation
 
 * Added documentation for the :ref:`lib_bm_timer` library.
 * Added documentation for the :ref:`lib_ble_adv`.
+* Added documentation for the :ref:`lib_ble_gatt_queue` library.
 * Added documentation for the :ref:`lib_event_scheduler` library.
 * Added documentation for the :ref:`lib_sensorsim` library.