nanokernel: Add generic fifo routine

Adds the following generic fifo routine:
	nano_fifo_get_wait_timeout()

That routine is a convenience wrapper for invoking the task or fiber
specific implementation.

Change-Id: I9bd709ea416db834e2a0c5de81257c363e7db066
Signed-off-by: Peter Mitsis <peter.mitsis@windriver.com>

include/nanokernel.h

@@ -399,6 +399,24 @@ extern void *nano_fifo_get(struct nano_fifo *fifo);
  */
 extern void *nano_fifo_get_wait(struct nano_fifo *fifo);
 
+/**
+ *
+ * @brief Get the head element of a fifo, poll/pend with timeout if empty
+ *
+ * This is a convenience wrapper for the execution context-specific APIs. This
+ * is helpful whenever the exact execution context is not known, but should be
+ * avoided when the context is known up-front (to avoid unnecessary overhead).
+ *
+ * @warning It's only valid to call this API from a fiber or a task.
+ *
+ * @param fifo FIFO on which to interact.
+ * @param timeout Timeout measured in ticks
+ *
+ * @return Pointer to head element in the list
+ */
+extern void *nano_fifo_get_wait_timeout(struct nano_fifo *fifo,
+		int32_t timeout);
+
 /*
  * methods for ISRs
  */

kernel/nanokernel/nano_fifo.c

@@ -150,8 +150,11 @@ void nano_task_fifo_put(struct nano_fifo *fifo, void *data)
 void nano_fifo_put(struct nano_fifo *fifo, void *data)
 {
 	static void (*func[3])(struct nano_fifo *fifo, void *data) = {
-		nano_isr_fifo_put, nano_fiber_fifo_put, nano_task_fifo_put
+		nano_isr_fifo_put,
+		nano_fiber_fifo_put,
+		nano_task_fifo_put
 	};
+
 	func[sys_execution_context_type_get()](fifo, data);
 }
 
@@ -259,8 +262,11 @@ void *nano_task_fifo_get_wait(struct nano_fifo *fifo)
 void *nano_fifo_get_wait(struct nano_fifo *fifo)
 {
 	static void *(*func[3])(struct nano_fifo *fifo) = {
-		NULL, nano_fiber_fifo_get_wait, nano_task_fifo_get_wait
+		NULL,
+		nano_fiber_fifo_get_wait,
+		nano_task_fifo_get_wait
 	};
+
 	return func[sys_execution_context_type_get()](fifo);
 }
 
@@ -340,4 +346,15 @@ void *nano_task_fifo_get_wait_timeout(struct nano_fifo *fifo,
 	irq_unlock(key);
 	return NULL;
 }
+
+void *nano_fifo_get_wait_timeout(struct nano_fifo *fifo, int32_t timeout)
+{
+	static void *(*func[3])(struct nano_fifo *, int32_t) = {
+		NULL,
+		nano_fiber_fifo_get_wait_timeout,
+		nano_task_fifo_get_wait_timeout
+	};
+
+	return func[sys_execution_context_type_get()](fifo, timeout);
+}
 #endif /* CONFIG_NANO_TIMEOUTS */