General guidelines for updating FreeRTOS

This file will list the necessary modifications to FreeRTOS package to be used inside PiOS

Brief list of modifications: 
*Add function to get task run time;
*Modified heap_1.c to allow for different alignment for stack and generic malloc;
*Allow heap_1.c for modification of max heap size at runtime;
*use section ".heap" for heap.

Memory manager now handles two different kind of alignments for F1, portBYTE_ALIGNMENT for standard mallocs, and portBYTE_HEAP_ALIGNMENT for stack(aligned) allocs




- include/task.h
add the following declaration: 

	/**
	 * task.h
	 * <PRE>unsigned portBASE_TYPE uxTaskGetRunTime( xTaskHandle xTask );</PRE>
	 *
	 * Returns the run time of selected task
	 *
	 * @param xTask Handle of the task associated with the stack to be checked.
	 * Set xTask to NULL to check the stack of the calling task.
	 *
	 * @return The run time of selected task
	 */
	unsigned portBASE_TYPE uxTaskGetRunTime( xTaskHandle xTask );

it usually is added after the declaration of vTaskGetRunTimeStats.

- task.c
add the following function: 

	#if ( INCLUDE_uxTaskGetRunTime == 1 )
	
	    unsigned portBASE_TYPE uxTaskGetRunTime( xTaskHandle xTask )
	    {
	        unsigned long runTime;
	
	        tskTCB *pxTCB;
	        pxTCB = prvGetTCBFromHandle( xTask );
	        runTime = pxTCB->ulRunTimeCounter;
	        pxTCB->ulRunTimeCounter = 0;
	        return runTime;
	    }
	
	#endif
	/*----------------------------------------------------------*/

it usually is added after the declaration of vTaskGetRunTimeStats.

- STM32F1XX/libraries/FreeRTOS/Source/portable/GCC/ARM_CM3/portmacro.h
add the following define for 

#define portBYTE_HEAP_ALIGNMENT     4 // this value is used to allocate heap




- portable/MemMang/heap_1.c
following there is the modification done in this revision against the base heap_1.c
The modifications add a currentTOTAL_HEAP_SIZE variable that hold the current heap size,
used instead of the configTOTAL_HEAP_SIZE macro that can be changed by the added
xPortIncreaseHeapSize function.
Also it allows for configurable aligments for Heap and Stack allocations.

--- ../op_evo/FreeRTOSV7.4.0/FreeRTOS/Source/portable/MemMang/heap_1.c	2013-04-06 15:04:22.760048534 +0200
+++ ./flight/PiOS/Common/libraries/FreeRTOS/Source/portable/MemMang/heap_1.c	2013-04-08 02:23:01.649194752 +0200
@@ -92,26 +92,30 @@
 
 #undef MPU_WRAPPERS_INCLUDED_FROM_API_FILE
 
-/* A few bytes might be lost to byte aligning the heap start address. */
-#define configADJUSTED_HEAP_SIZE	( configTOTAL_HEAP_SIZE - portBYTE_ALIGNMENT )
 
 /* Allocate the memory for the heap. */
-static unsigned char ucHeap[ configTOTAL_HEAP_SIZE ];
+static unsigned char ucHeap[ configTOTAL_HEAP_SIZE ]  __attribute__ ((section (".heap")));
 static size_t xNextFreeByte = ( size_t ) 0;
 
+static size_t currentTOTAL_HEAP_SIZE = configTOTAL_HEAP_SIZE;
+void *pvPortMallocGeneric( size_t xWantedSize, size_t alignment);
+
+/* A few bytes might be lost to byte aligning the heap start address. */
+#define configADJUSTED_HEAP_SIZE    (currentTOTAL_HEAP_SIZE - portBYTE_ALIGNMENT)
+
 /*-----------------------------------------------------------*/
 
-void *pvPortMalloc( size_t xWantedSize )
+void *pvPortMallocGeneric( size_t xWantedSize, size_t alignment)
 {
 void *pvReturn = NULL;
 static unsigned char *pucAlignedHeap = NULL;
-
+size_t mask = alignment-1;
 	/* Ensure that blocks are always aligned to the required number of bytes. */
 	#if portBYTE_ALIGNMENT != 1
-		if( xWantedSize & portBYTE_ALIGNMENT_MASK )
+		if( xWantedSize & mask )
 		{
-			/* Byte alignment required. */
-			xWantedSize += ( portBYTE_ALIGNMENT - ( xWantedSize & portBYTE_ALIGNMENT_MASK ) );
+		    			/* Byte alignment required. */
+			xWantedSize += ( alignment - ( xWantedSize & mask ) );
 		}
 	#endif
 
@@ -120,7 +124,7 @@
 		if( pucAlignedHeap == NULL )
 		{
 			/* Ensure the heap starts on a correctly aligned boundary. */
-			pucAlignedHeap = ( unsigned char * ) ( ( ( portPOINTER_SIZE_TYPE ) &ucHeap[ portBYTE_ALIGNMENT ] ) & ( ( portPOINTER_SIZE_TYPE ) ~portBYTE_ALIGNMENT_MASK ) );
+			pucAlignedHeap = ( unsigned char * ) ( ( ( portPOINTER_SIZE_TYPE ) &ucHeap[ alignment ] ) & ( ( portPOINTER_SIZE_TYPE ) ~ mask ) );
 		}
 
 		/* Check there is enough room left for the allocation. */
@@ -147,6 +151,11 @@
 
 	return pvReturn;
 }
+
+void *pvPortMalloc( size_t xWantedSize){
+    return pvPortMallocGeneric(xWantedSize, portBYTE_HEAP_ALIGNMENT);
+}
+
 /*-----------------------------------------------------------*/
 
 void vPortFree( void *pv )
@@ -172,6 +181,12 @@
 {
 	return ( configADJUSTED_HEAP_SIZE - xNextFreeByte );
 }
+/*-----------------------------------------------------------*/
 
-
-
+void xPortIncreaseHeapSize( size_t bytes )
+{
+    vTaskSuspendAll();
+    currentTOTAL_HEAP_SIZE = configTOTAL_HEAP_SIZE + bytes;
+    xTaskResumeAll();
+}
+/*-----------------------------------------------------------*/