docs/library/openamp: Document the new openamp module.

Signed-off-by: iabdalkader <i.abdalkader@gmail.com>

docs/library/index.rst

@@ -103,6 +103,7 @@ the following libraries.
    micropython.rst
    neopixel.rst
    network.rst
+   openamp.rst
    uctypes.rst
    vfs.rst
 

docs/library/openamp.rst

@@ -0,0 +1,115 @@
+:mod:`openamp` -- provides standard Asymmetric Multiprocessing (AMP) support
+============================================================================
+
+.. module:: openamp
+   :synopsis: provides standard Asymmetric Multiprocessing (AMP) support
+
+The ``openamp`` module provides a standard inter-processor communications infrastructure
+for MicroPython. The module handles all of the details of OpenAMP, such as setting up
+the shared resource table, initializing vrings, etc. It provides an API for using the
+RPMsg bus infrastructure with the `Endpoint` class, and provides processor Life Cycle
+Management (LCM) support, such as loading firmware and starting and stopping a remote
+core, via the `RemoteProc` class.
+
+Example usage::
+
+    import openamp
+
+    def ept_recv_callback(src, data):
+        print("Received message on endpoint", data)
+
+    # Create a new RPMsg endpoint to communicate with the remote core.
+    ept = openamp.Endpoint("vuart-channel", callback=ept_recv_callback)
+
+    # Create a RemoteProc object, load its firmware and start it.
+    rproc = openamp.RemoteProc("virtual_uart.elf") # Or entry point address (ex 0x081E0000)
+    rproc.start()
+
+    while True:
+        if ept.is_ready():
+            ept.send("data")
+
+Functions
+---------
+
+.. function:: new_service_callback(ns_callback)
+
+    Set the new service callback.
+
+    The *ns_callback* argument is a function that will be called when the remote processor
+    announces new services. At that point the host processor can choose to create the
+    announced endpoint, if this particular service is supported, or ignore it if it's
+    not. If this function is not set, the host processor should first register the
+    endpoint locally, and it will be automatically bound when the remote announces
+    the service.
+
+Endpoint class
+--------------
+
+.. class:: Endpoint(name, callback, src=ENDPOINT_ADDR_ANY, dest=ENDPOINT_ADDR_ANY)
+
+   Construct a new RPMsg Endpoint. An endpoint is a bidirectional communication
+   channel between two cores.
+
+   Arguments are:
+
+        - *name* is the name of the endpoint.
+        - *callback* is a function that is called when the endpoint receives data with the
+          source address of the remote point, and the data as bytes passed by reference.
+        - *src* is the endpoint source address. If none is provided one will be assigned
+          to the endpoint by the library.
+        - *dest* is the endpoint destination address. If the endpoint is created from the
+          new_service_callback, this must be provided and it must match the remote endpoint's
+          source address. If the endpoint is registered locally, before the announcement, the
+          destination address will be assigned by the library when the endpoint is bound.
+
+.. method:: Endpoint.deinit()
+
+   Destroy the endpoint and release all of its resources.
+
+.. method:: Endpoint.is_ready()
+
+   Returns True if the endpoint is ready to send (i.e., has both a source and destination addresses)
+
+.. method:: Endpoint.send(src=-1, dest=-1, timeout=-1)
+
+   Send a message to the remote processor over this endpoint.
+
+   Arguments are:
+
+        - *src* is the source endpoint address of the message. If none is provided, the
+          source address the endpoint is bound to is used.
+        - *dest* is the destination endpoint address of the message. If none is provided,
+          the destination address the endpoint is bound to is used.
+        - *timeout* specifies the time in milliseconds to wait for a free buffer. By default
+          the function is blocking.
+
+RemoteProc class
+----------------
+
+.. class:: RemoteProc(entry)
+
+   The RemoteProc object provides processor Life Cycle Management (LCM) support, such as
+   loading firmware, starting and stopping a remote core.
+
+   The *entry* argument can be a path to firmware image, in which case the firmware is
+   loaded from file to its target memory, or an entry point address, in which case the
+   firmware must be loaded already at the given address.
+
+.. method:: RemoteProc.start()
+
+   Starts the remote processor.
+
+.. method:: RemoteProc.stop()
+
+   Stops the remote processor. The exact behavior is platform-dependent. On the STM32H7 for
+   example it's not possible to stop and then restart the Cortex-M4 core, so a complete
+   system reset is performed on a call to this function.
+
+.. method:: RemoteProc.shutdown()
+
+   Shutdown stops the remote processor and releases all of its resources. The exact behavior
+   is platform-dependent, however typically it disables power and clocks to the remote core.
+   This function is also used as the finaliser (i.e., called when ``RemoteProc`` object is
+   collected). Note that on the STM32H7, it's not possible to stop and then restart the
+   Cortex-M4 core, so a complete system reset is performed on a call to this function.