uORB: ack uorb topic

Add uorb interface to just acknowledge the updates for next poll
without needs to copy data from all the updated topics.

platforms/common/uORB/Subscription.hpp

@@ -143,6 +143,17 @@ class Subscription
 		return valid() ? Manager::orb_data_copy(_node, dst, _last_generation, true) : false;
 	}
 
+	void ack()
+	{
+		if (!valid()) {
+			subscribe();
+		}
+
+		if (valid()) {
+			Manager::orb_data_ack(_node, _last_generation);
+		}
+	}
+
 	/**
 	 * Copy the struct
 	 * @param dst The uORB message struct we are updating.

platforms/common/uORB/SubscriptionInterval.hpp

@@ -100,6 +100,17 @@ class SubscriptionInterval
 		return false;
 	}
 
+	/**
+	 * Acknowledge a new update.
+	 */
+	void ack()
+	{
+		_subscription.ack();
+		const hrt_abstime now = hrt_absolute_time();
+		// shift last update time forward, but don't let it get further behind than the interval
+		_last_update = math::constrain(_last_update + _interval_us, now - _interval_us, now);
+	}
+
 	/**
 	 * Copy the struct if updated.
 	 * @param dst The destination pointer where the struct will be copied.

platforms/common/uORB/uORB.cpp

@@ -130,6 +130,11 @@ int orb_check(orb_sub_t handle, bool *updated)
 	return uORB::Manager::get_instance()->orb_check(handle, updated);
 }
 
+int orb_ack(orb_sub_t handle)
+{
+	return uORB::Manager::get_instance()->orb_ack(handle);
+}
+
 int orb_exists(const struct orb_metadata *meta, int instance)
 {
 	return uORB::Manager::orb_exists(meta, instance);

platforms/common/uORB/uORB.h

@@ -246,6 +246,8 @@ extern int	orb_copy(const struct orb_metadata *meta, orb_sub_t handle, void *buf
  */
 extern int	orb_check(orb_sub_t handle, bool *updated) __EXPORT;
 
+extern int	orb_ack(orb_sub_t handle) __EXPORT;
+
 /**
  * @see uORB::Manager::orb_exists()
  */

platforms/common/uORB/uORBDeviceNode.hpp

@@ -219,6 +219,8 @@ class DeviceNode
 	 */
 	bool copy(void *dst, orb_advert_t &handle, unsigned &generation);
 
+	void ack(unsigned &generation) { generation = _generation.load(); }
+
 	static bool register_callback(orb_advert_t &node_handle, SubscriptionCallback *callback_sub, int8_t poll_lock,
 				      hrt_abstime last_update, uint32_t interval_us, uorb_cb_handle_t &cb_handle)
 	{

platforms/common/uORB/uORBManager.cpp

@@ -365,6 +365,12 @@ int uORB::Manager::orb_check(orb_sub_t handle, bool *updated)
 	return PX4_OK;
 }
 
+int uORB::Manager::orb_ack(orb_sub_t handle)
+{
+	((uORB::SubscriptionInterval *)handle)->ack();
+	return PX4_OK;
+}
+
 int uORB::Manager::orb_set_interval(orb_sub_t handle, unsigned interval)
 {
 	((uORB::SubscriptionInterval *)handle)->set_interval_us(interval * 1000);

platforms/common/uORB/uORBManager.hpp

@@ -291,6 +291,9 @@ class Manager
 	 */
 	static int  orb_check(orb_sub_t handle, bool *updated);
 
+
+	static int  orb_ack(orb_sub_t handle);
+
 	/**
 	 * Check if a topic has already been created and published (advertised)
 	 *
@@ -356,6 +359,11 @@ class Manager
 
 	static uint8_t orb_get_queue_size(const orb_advert_t &node_handle) {return node(node_handle)->get_queue_size();}
 
+	static void orb_data_ack(orb_advert_t &node_handle, unsigned &generation)
+	{
+		node(node_handle)->ack(generation);
+	}
+
 	static bool orb_data_copy(orb_advert_t &node_handle, void *dst, unsigned &generation,
 				  bool only_if_updated)
 	{