uavobject: Use linker to produce uavobj initcalls

The UAVObject initcall list is now automatically
generated at link time based on the exact set of
UAVObjects linked into the firmware image.

This will allow any subset of UAVObjects to be
used in any firmware image.

The uavobj_initcall() macro automatically adds the
marked function's address into the .initcalluavobj.init
ELF section.

The UAVObjectsInitializeAll() function now simply
iterates over the functions listed in the
.initcalluavobj.init section and calls them.

You can see the contents of this section in the ELF file
like this:
  ./tools/arm-2009q3/bin/arm-none-eabi-objdump \
      --syms -j .initcalluavobj.init \
      ./build/openpilot/OpenPilot.elf

This is fundamentally the same mechanism that the Linux
kernel uses to initialize the specific set of components
that the user has selected in their kernel configuration.

git-svn-id: svn://svn.openpilot.org/OpenPilot/trunk@2630 ebee16cc-31ac-478f-84a7-5cbb03baadba

flight/PiOS/STM32F10x/link_STM3210E_OP_HD_NB.ld

@@ -218,6 +218,16 @@ SECTIONS
     } >FLASH
  
     
+    /* init sections */
+    .initcalluavobj.init :
+    {
+        . = ALIGN(4);
+	__uavobj_initcall_start = .;
+        KEEP(*(.initcalluavobj.init))
+	. = ALIGN(4);
+	__uavobj_initcall_end   = .;
+    } >FLASH
+
     /* the program code is stored in the .text section, which goes to Flash */
     .text :
     {

flight/PiOS/inc/pios_initcall.h

@@ -0,0 +1,65 @@
+/**
+ ******************************************************************************
+ * @addtogroup PIOS PIOS Initcall infrastructure
+ * @{
+ * @addtogroup   PIOS_INITCALL Generic Initcall Macros
+ * @brief Initcall Macros
+ * @{
+ *
+ * @file       pios_initcall.h  
+ * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2011.
+ * @brief      Initcall header
+ * @see        The GNU Public License (GPL) Version 3
+ *
+ *****************************************************************************/
+/* 
+ * This program is free software; you can redistribute it and/or modify 
+ * it under the terms of the GNU General Public License as published by 
+ * the Free Software Foundation; either version 3 of the License, or 
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful, but 
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 
+ * for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along 
+ * with this program; if not, write to the Free Software Foundation, Inc., 
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#ifndef PIOS_INITCALL_H
+#define PIOS_INITCALL_H
+
+/* 
+ * This implementation is heavily based on the Linux Kernel initcall
+ * infrastructure:
+ *   http://lxr.linux.no/#linux/include/linux/init.h
+ *   http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=include/linux/init.h
+ */
+
+/*
+ * Used for initialization calls..
+ */
+typedef int32_t (*initcall_t)(void);
+
+/* initcalls are now grouped by functionality into separate 
+ * subsections. Ordering inside the subsections is determined
+ * by link order.
+ *
+ * The `id' arg to __define_initcall() is needed so that multiple initcalls
+ * can point at the same handler without causing duplicate-symbol build errors.
+ */
+
+#define __define_initcall(level,fn,id) \
+	static initcall_t __initcall_##fn##id __attribute__((__used__)) \
+	__attribute__((__section__(".initcall" level ".init"))) = fn
+
+#define uavobj_initcall(fn)		__define_initcall("uavobj",fn,1)
+
+#endif	/* PIOS_INITCALL_H */
+
+/**
+ * @}
+ * @}
+ */

flight/PiOS/pios.h

@@ -58,6 +58,9 @@
 #include <msd.h>
 #endif
 
+/* Generic initcall infrastructure */
+#include "pios_initcall.h"
+
 /* PIOS Board Specific Device Configuration */
 #include "pios_board.h"
 

flight/UAVObjects/uavobjectsinittemplate.c

@@ -28,13 +28,18 @@
  */
 
 #include "openpilot.h"
-$(OBJINC)
 
 /**
  * Function used to initialize the first instance of each object.
  * This file is automatically updated by the UAVObjectGenerator.
  */
+extern initcall_t __uavobj_initcall_start[], __uavobj_initcall_end[];
+
 void UAVObjectsInitializeAll()
 {
-$(OBJINIT)
+	initcall_t *fn;
+	int32_t ret;
+
+	for (fn = __uavobj_initcall_start; fn < __uavobj_initcall_end; fn++)
+		ret = (*fn)();
 }

flight/UAVObjects/uavobjecttemplate.c

@@ -47,7 +47,7 @@ static UAVObjHandle handle;
  * \return 0 Success
  * \return -1 Failure
  */
-int32_t $(NAME)Initialize()
+int32_t $(NAME)Initialize(void)
 {
 	// Register object with the object manager
 	handle = UAVObjRegister($(NAMEUC)_OBJID, $(NAMEUC)_NAME, $(NAMEUC)_METANAME, 0,
@@ -64,6 +64,8 @@ int32_t $(NAME)Initialize()
 	}
 }
 
+uavobj_initcall($(NAME)Initialize);
+
 /**
  * Initialize object fields and metadata with the default values.
  * If a default value is not specified the object fields