nanostack-hal: modify eventloop to allow running it in a main thread

The separate eventloop thread may not be necessary on all uses, as one
can use the existing main thread for event dispatching. Add a
conditional nanostack-hal.event-loop-dispatch-from-application, which
disables the thread creation.

Note: the ns_hal_init must be ran from the same thread which will be
used to execute the event loop later.

Author: TeroJaasko

features/FEATURE_COMMON_PAL/nanostack-hal-mbed-cmsis-rtos/mbed_lib.json

@@ -13,5 +13,10 @@
             "help": "Make critical section API usable from interrupt context. Else a mutex is used as locking primitive.",
             "value": false
         }
+        ,
+        "event-loop-dispatch-from-application": {
+            "help": "Application is responsible of message dispatch loop. Else launch a separate thread for event-loop.",
+            "value": false
+        }
     }
 }

features/FEATURE_COMMON_PAL/nanostack-hal-mbed-cmsis-rtos/ns_event_loop.c

@@ -14,6 +14,9 @@
 
 #define TRACE_GROUP "evlp"
 
+
+#if !MBED_CONF_NANOSTACK_HAL_EVENT_LOOP_DISPATCH_FROM_APPLICATION
+
 static void event_loop_thread(void *arg);
 
 static uint64_t event_thread_stk[MBED_CONF_NANOSTACK_HAL_EVENT_LOOP_THREAD_STACK_SIZE/8];
@@ -26,6 +29,8 @@ static const osThreadAttr_t event_thread_attr = {
     .cb_mem = &event_thread_tcb,
     .cb_size = sizeof event_thread_tcb,
 };
+#endif
+
 static osThreadId_t event_thread_id;
 static mbed_rtos_storage_mutex_t event_mutex;
 static const osMutexAttr_t event_mutex_attr = {
@@ -78,22 +83,37 @@ void eventOS_scheduler_idle(void)
     eventOS_scheduler_mutex_wait();
 }
 
+#if !MBED_CONF_NANOSTACK_HAL_EVENT_LOOP_DISPATCH_FROM_APPLICATION
 static void event_loop_thread(void *arg)
 {
     (void)arg;
     eventOS_scheduler_mutex_wait();
     eventOS_scheduler_run(); //Does not return
 }
+#endif
 
-void ns_event_loop_thread_create(void)
+// This is used to initialize the lock used by event loop even
+// if it is not ran in a separate thread.
+void ns_event_loop_init(void)
 {
     event_mutex_id = osMutexNew(&event_mutex_attr);
     MBED_ASSERT(event_mutex_id != NULL);
 
+#if MBED_CONF_NANOSTACK_HAL_EVENT_LOOP_DISPATCH_FROM_APPLICATION
+    // The thread id of the current thread is stored so it can be used to signal
+    // the waiting thread from other threads or from a interrupt.
+    event_thread_id = osThreadGetId();
+#endif
+}
+
+#if !MBED_CONF_NANOSTACK_HAL_EVENT_LOOP_DISPATCH_FROM_APPLICATION
+void ns_event_loop_thread_create(void)
+{
     event_thread_id = osThreadNew(event_loop_thread, NULL, &event_thread_attr);
     MBED_ASSERT(event_thread_id != NULL);
 }
 
 void ns_event_loop_thread_start(void)
 {
 }
+#endif

features/FEATURE_COMMON_PAL/nanostack-hal-mbed-cmsis-rtos/ns_event_loop.h

@@ -6,6 +6,7 @@
 extern "C" {
 #endif
 
+void ns_event_loop_init(void);
 void ns_event_loop_thread_create(void);
 void ns_event_loop_thread_start(void);
 

features/FEATURE_COMMON_PAL/nanostack-hal-mbed-cmsis-rtos/ns_hal_init.c

@@ -32,10 +32,19 @@ void ns_hal_init(void *heap, size_t h_size, void (*passed_fptr)(heap_fail_t), me
     ns_dyn_mem_init(heap, h_size, passed_fptr, info_ptr);
     platform_timer_enable();
     eventOS_scheduler_init();
+
     // We do not initialise randlib, as it should be done after
     // RF driver has started, to get MAC address and RF noise as seed.
     // We do not initialise trace - left to application.
+
+    // Prepare the event loop lock which is used even if the loop
+    // is not ran in a separate thread.
+    ns_event_loop_init();
+
+#if !MBED_CONF_NANOSTACK_HAL_EVENT_LOOP_DISPATCH_FROM_APPLICATION
     ns_event_loop_thread_create();
     ns_event_loop_thread_start();
+#endif
+
     initted = true;
 }