mavlink & system: add events interface

- sending protocol
- uorb event message & template methods for argument packing
- libevents submodule to send common events and handle json files
- cmake maintains a list of all (PX4) source files for the current build
  (PX4 modules + libs), which is used to extract event metadata and
  generate a json file

cmake/px4_add_board.cmake

@@ -215,8 +215,12 @@ function(px4_add_board)
 	set(config_romfs_extra_dependencies)
 	# additional embedded metadata
 	if (NOT CONSTRAINED_FLASH AND NOT EXTERNAL_METADATA AND NOT ${PX4_BOARD_LABEL} STREQUAL "test")
-		list(APPEND romfs_extra_files ${PX4_BINARY_DIR}/parameters.json.xz)
-		list(APPEND romfs_extra_dependencies parameters_xml)
+		list(APPEND romfs_extra_files
+			${PX4_BINARY_DIR}/parameters.json.xz
+			${PX4_BINARY_DIR}/events/all_events.json.xz)
+		list(APPEND romfs_extra_dependencies
+			parameters_xml
+			events_json)
 	endif()
 	list(APPEND romfs_extra_files ${PX4_BINARY_DIR}/component_general.json.xz)
 	list(APPEND romfs_extra_dependencies component_general_json)

cmake/px4_add_library.cmake

@@ -30,6 +30,7 @@
 # POSSIBILITY OF SUCH DAMAGE.
 #
 ############################################################################
+include(px4_list_make_absolute)
 
 #=============================================================================
 #
@@ -52,4 +53,6 @@ function(px4_add_library target)
 	endif()
 
 	set_property(GLOBAL APPEND PROPERTY PX4_MODULE_PATHS ${CMAKE_CURRENT_SOURCE_DIR})
+	px4_list_make_absolute(ABS_SRCS ${CMAKE_CURRENT_SOURCE_DIR} ${ARGN})
+	set_property(GLOBAL APPEND PROPERTY PX4_SRC_FILES ${ABS_SRCS})
 endfunction()

cmake/px4_add_module.cmake

@@ -30,6 +30,7 @@
 # POSSIBILITY OF SUCH DAMAGE.
 #
 ############################################################################
+include(px4_list_make_absolute)
 
 #=============================================================================
 #
@@ -156,6 +157,8 @@ function(px4_add_module)
 		target_link_libraries(${MODULE} PRIVATE prebuild_targets parameters_interface px4_layer px4_platform systemlib)
 		set_property(GLOBAL APPEND PROPERTY PX4_MODULE_LIBRARIES ${MODULE})
 		set_property(GLOBAL APPEND PROPERTY PX4_MODULE_PATHS ${CMAKE_CURRENT_SOURCE_DIR})
+		px4_list_make_absolute(ABS_SRCS ${CMAKE_CURRENT_SOURCE_DIR} ${SRCS})
+		set_property(GLOBAL APPEND PROPERTY PX4_SRC_FILES ${ABS_SRCS})
 	endif()
 
 	# set defaults if not set

cmake/px4_list_make_absolute.cmake

@@ -0,0 +1,58 @@
+############################################################################
+#
+# Copyright (c) 2020 PX4 Development Team. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name PX4 nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+############################################################################
+
+# cmake include guard
+if(px4_list_make_absolute_included)
+	return()
+endif(px4_list_make_absolute_included)
+set(px4_list_make_absolute_included true)
+
+#=============================================================================
+#
+#	px4_list_make_absolute
+#
+#	prepend a prefix to each element in a list, if the element is not an abolute
+#	path
+#
+function(px4_list_make_absolute var prefix)
+	set(list_var "")
+	foreach(f ${ARGN})
+		if(IS_ABSOLUTE ${f})
+			list(APPEND list_var "${f}")
+		else()
+			list(APPEND list_var "${prefix}/${f}")
+		endif()
+	endforeach(f)
+	set(${var} "${list_var}" PARENT_SCOPE)
+endfunction()
+