lmdk: How to convert and build loadable modules

How to tutorial

Signed-off-by: Dobrowolski, PawelX <pawelx.dobrowolski@intel.com>

getting_started/loadable_modules/lmdk_user_guide.rst

@@ -7,12 +7,71 @@ What is LMDK
 ************
 
 LMDK(Loadable Module Development Kit) is a standalone package required to build loadable module. It is independent from SOF FW but contains necessary data structures to interact with it.
+Package consists building CMake scripts and headers pack which is generated by python building script by executing it with -p:
+
+.. code-block:: bash
+
+    $ python scripts/lmdk/build_modules.py -l dummy -k "/path/to/signing/key.pem" -p
+
+These headers should be extracted in include directory of lmdk:
+
+.. code-block:: cmake
+    
+    set(LMDK_DIR_INCLUDE ../../../lmdk/include)
+    target_include_directories(up_down_mixer PRIVATE "${LMDK_DIR_INCLUDE}"
+                                                     "${LMDK_DIR_INCLUDE}/sof"
+                                                     "${LMDK_DIR_INCLUDE}/sof/audio"
+                                                     "${LMDK_DIR_INCLUDE}/module/audio")
+
+
+How to prepare MODULE to be loadable
+************************************
+
+Loadable modules are using functions provided by native_system_services which are narrowed to only neccesary and safe functions. For example all dynamic allocations are done on strict size local heap_mem
+declared in a body of the module.
+
+.. code-block:: c
+
+    static struct native_system_service_api* system_service;
+    uint32_t heap_mem[2048] __attribute__((section(".heap_mem"))) __attribute__((aligned(4096)));
+
+Each module also has to declare as a loadable and has prepared manifest which is specific for each.
+
+.. code-block:: c
+
+    DECLARE_LOADABLE_MODULE_API_VERSION(dummy);
+
+    static void* entry_point(void* mod_cfg, void* parent_ppl, void** mod_ptr)
+        {
+            system_service = *(const struct native_system_agent**)mod_ptr;
+
+            return &up_down_mixer_interface;
+        }
+
+        __attribute__((section(".module")))
+        const struct sof_man_module_manifest dummy_module_manifest = {
+            .module = {
+                    .name = "DUMMY",
+                    .uuid = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
+                    .entry_point = (uint32_t)dummyPackageEntryPoint,
+                    .type = {
+                            .load_type = SOF_MAN_MOD_TYPE_MODULE,
+                            .domain_ll = 1
+                    },
+                    .affinity_mask = 3,
+            }
+        };
+
+
 
 How to build
 ************
 
+Using CMake scripts
+===================
 To build example loadable library execute:
-.. code-block:: bash 
+
+.. code-block:: bash
 
     $ cd libraries/example
     $ mkdir build
@@ -23,3 +82,6 @@ To build example loadable library execute:
 
 Here RIMAGE_COMMAND is path to rimage executable binary, SIGNING_KEY is path to
 signing key for rimage. `LMDK <https://github.com/thesofproject/sof/pull/7354>`
+
+Using Python scripts
+====================