Add user-filtering to the HID report parser, so that the user code can decide which items are to be stored into the HID_ReportInfo_t structure and which should be discarded to save on RAM usage.

Demos/Host/LowLevel/KeyboardHostWithParser/HIDReport.c

@@ -70,3 +70,25 @@ uint8_t GetHIDReportData(void)
 	return ParseSuccessful;
 }
 
+/** Callback for the HID Report Parser. This function is called each time the HID report parser is about to store
+ *  an IN, OUT or FEATURE item into the HIDReportInfo structure. To save on RAM, we are able to filter out items
+ *  we aren't interested in (preventing us from being able to extract them later on, but saving on the RAM they would
+ *  have occupied).
+ *
+ *  \param CurrentItemAttributes  Pointer to the attrbutes of the item the HID report parser is currently working with
+ *
+ *  \return Boolean true if the item should be stored into the HID report structure, false if it should be discarded
+ */
+bool CALLBACK_HIDParser_FilterHIDReportItem(HID_ReportItem_Attributes_t* CurrentItemAttributes)
+{
+	/* Check the attributes of the current item - see if we are interested in it or not */
+	if (CurrentItemAttributes->Usage.Page == USAGE_PAGE_KEYBOARD)
+	{
+		/* Only store KEYBOARD usage page items into the Processed HID Report structure to save RAM */
+		return true;
+	}
+	else
+	{
+		return false;
+	}
+}

Demos/Host/LowLevel/KeyboardHostWithParser/HIDReport.h

@@ -77,4 +77,6 @@
 	/* Function Prototypes: */
 		uint8_t GetHIDReportData(void);
 
+		bool CALLBACK_HIDParser_FilterHIDReportItem(HID_ReportItem_Attributes_t* CurrentItemAttributes);
+		
 #endif

Demos/Host/LowLevel/MouseHostWithParser/HIDReport.c

@@ -69,3 +69,27 @@ uint8_t GetHIDReportData(void)
 	
 	return ParseSuccessful;
 }
+
+/** Callback for the HID Report Parser. This function is called each time the HID report parser is about to store
+ *  an IN, OUT or FEATURE item into the HIDReportInfo structure. To save on RAM, we are able to filter out items
+ *  we aren't interested in (preventing us from being able to extract them later on, but saving on the RAM they would
+ *  have occupied).
+ *
+ *  \param CurrentItemAttributes  Pointer to the attrbutes of the item the HID report parser is currently working with
+ *
+ *  \return Boolean true if the item should be stored into the HID report structure, false if it should be discarded
+ */
+bool CALLBACK_HIDParser_FilterHIDReportItem(HID_ReportItem_Attributes_t* CurrentItemAttributes)
+{
+	/* Check the attributes of the current item - see if we are interested in it or not */
+	if ((CurrentItemAttributes->Usage.Page == USAGE_PAGE_BUTTON) ||
+	    (CurrentItemAttributes->Usage.Page == USAGE_PAGE_GENERIC_DCTRL))
+	{
+		/* Only store BUTTON and GENERIC_DESKTOP_CONTROL items into the Processed HID Report structure to save RAM */
+		return true;
+	}
+	else
+	{
+		return false;
+	}
+}

Demos/Host/LowLevel/MouseHostWithParser/HIDReport.h

@@ -86,4 +86,6 @@
 	/* Function Prototypes: */
 		uint8_t GetHIDReportData(void);
 		
+		bool CALLBACK_HIDParser_FilterHIDReportItem(HID_ReportItem_Attributes_t* CurrentItemAttributes);
+		
 #endif

LUFA/Drivers/USB/Class/Host/HIDParser.c

@@ -35,16 +35,14 @@
 
 uint8_t USB_ProcessHIDReport(const uint8_t* ReportData, uint16_t ReportSize, HID_ReportInfo_t* const ParserData)
 {
-	HID_StateTable_t  StateTable[HID_STATETABLE_STACK_DEPTH];
+	HID_StateTable_t      StateTable[HID_STATETABLE_STACK_DEPTH];
-	HID_StateTable_t* CurrStateTable          = &StateTable[0];
+	HID_StateTable_t*     CurrStateTable          = &StateTable[0];
-	uint16_t          UsageStack[HID_USAGE_STACK_DEPTH];
-	uint8_t           UsageStackSize          = 0;
-	uint16_t          BitOffsetIn             = 0;
-	uint16_t          BitOffsetOut            = 0;
-#if defined(HID_ENABLE_FEATURE_PROCESSING)
-	uint16_t          BitOffsetFeature        = 0;
-#endif
 	HID_CollectionPath_t* CurrCollectionPath  = NULL;
+	uint16_t              UsageStack[HID_USAGE_STACK_DEPTH];
+	uint8_t               UsageStackSize          = 0;
+	uint16_t              BitOffsetIn             = 0;
+	uint16_t              BitOffsetOut            = 0;
+	uint16_t              BitOffsetFeature        = 0;
 
 	ParserData->TotalReportItems     = 0;
 	ParserData->UsingMultipleReports = false;
@@ -131,10 +129,7 @@ uint8_t USB_ProcessHIDReport(const uint8_t* ReportData, uint16_t ReportSize, HID
 				ParserData->UsingMultipleReports = true;
 				BitOffsetIn      = 0;
 				BitOffsetOut     = 0;
-
-				#if defined(HID_ENABLE_FEATURE_PROCESSING)
 				BitOffsetFeature = 0;
-				#endif
 				break;
 			case (TYPE_LOCAL | TAG_LOCAL_USAGE):
 				if (UsageStackSize == HID_USAGE_STACK_DEPTH)
@@ -197,27 +192,22 @@ uint8_t USB_ProcessHIDReport(const uint8_t* ReportData, uint16_t ReportSize, HID
 				break;
 			case (TYPE_MAIN | TAG_MAIN_INPUT):
 			case (TYPE_MAIN | TAG_MAIN_OUTPUT):
-#if defined(HID_ENABLE_FEATURE_PROCESSING)
 			case (TYPE_MAIN | TAG_MAIN_FEATURE):
-#endif
 				for (uint8_t ReportItemNum = 0; ReportItemNum < CurrStateTable->ReportCount; ReportItemNum++)
 				{
-					HID_ReportItem_t* CurrReportItem = &ParserData->ReportItems[ParserData->TotalReportItems];
+					HID_ReportItem_t NewReportItem;
-				
-					if (ParserData->TotalReportItems == HID_MAX_REPORTITEMS)
-					  return HID_PARSE_InsufficientReportItems;
 				  
-					memcpy(&CurrReportItem->Attributes,
+					memcpy(&NewReportItem.Attributes,
 					       &CurrStateTable->Attributes,
 					       sizeof(HID_ReportItem_Attributes_t));
 
-					CurrReportItem->ItemFlags      = ReportItemData;
+					NewReportItem.ItemFlags      = ReportItemData;
-					CurrReportItem->CollectionPath = CurrCollectionPath;
+					NewReportItem.CollectionPath = CurrCollectionPath;
-					CurrReportItem->ReportID       = CurrStateTable->ReportID;
+					NewReportItem.ReportID       = CurrStateTable->ReportID;
 
 					if (UsageStackSize)
 					{
-						CurrReportItem->Attributes.Usage.Usage = UsageStack[0];
+						NewReportItem.Attributes.Usage.Usage = UsageStack[0];
 
 						for (uint8_t i = 0; i < UsageStackSize; i++)
 						  UsageStack[i] = UsageStack[i + 1];
@@ -226,42 +216,41 @@ uint8_t USB_ProcessHIDReport(const uint8_t* ReportData, uint16_t ReportSize, HID
 					}
 					else
 					{
-						CurrReportItem->Attributes.Usage.Usage = 0;
+						NewReportItem.Attributes.Usage.Usage = 0;
 					}
 											
 					switch (HIDReportItem & TAG_MASK)
 					{
 						case TAG_MAIN_INPUT:
-							CurrReportItem->ItemType  = REPORT_ITEM_TYPE_In;
+							NewReportItem.ItemType  = REPORT_ITEM_TYPE_In;
-							CurrReportItem->BitOffset = BitOffsetIn;
+							NewReportItem.BitOffset = BitOffsetIn;
 								
 							BitOffsetIn += CurrStateTable->Attributes.BitSize;
-							
 							break;
 						case TAG_MAIN_OUTPUT:
-							CurrReportItem->ItemType  = REPORT_ITEM_TYPE_Out;
+							NewReportItem.ItemType  = REPORT_ITEM_TYPE_Out;
-							CurrReportItem->BitOffset = BitOffsetOut;
+							NewReportItem.BitOffset = BitOffsetOut;
 								
 							BitOffsetOut += CurrStateTable->Attributes.BitSize;
-							
 							break;
-#if defined(HID_ENABLE_FEATURE_PROCESSING)
 						case TAG_MAIN_FEATURE:
-							CurrReportItem->ItemType  = REPORT_ITEM_TYPE_Feature;						
+							NewReportItem.ItemType  = REPORT_ITEM_TYPE_Feature;						
-							CurrReportItem->BitOffset = BitOffsetFeature;
+							NewReportItem.BitOffset = BitOffsetFeature;
 								
 							BitOffsetFeature += CurrStateTable->Attributes.BitSize;
-
 							break;
-#endif
 					}
 
-#if defined(HID_INCLUDE_CONSTANT_DATA_ITEMS)
+					if (!(ReportItemData & IOF_CONSTANT) && CALLBACK_HIDParser_FilterHIDReportItem(&CurrStateTable->Attributes))
-					ParserData->TotalReportItems++;
+					{					
-#else
+						if (ParserData->TotalReportItems == HID_MAX_REPORTITEMS)
-					if (!(ReportItemData & IOF_CONSTANT))
+						  return HID_PARSE_InsufficientReportItems;
-					  ParserData->TotalReportItems++;
+					
-#endif
+						memcpy(&ParserData->ReportItems[ParserData->TotalReportItems],
+						       &NewReportItem, sizeof(HID_ReportItem_t));
+					
+						ParserData->TotalReportItems++;
+					}
 				}
 				
 				UsageStackSize = 0;

LUFA/Drivers/USB/Class/Host/HIDParser.h

@@ -46,16 +46,11 @@
  *  Functions, macros, variables, enums and types related to the parsing of HID class device report descriptors.
  *
  *  The processed HID report is presented back to the user application as a flat structure containing each report
- *  item's IN, OUT and FEATURE (if desired) items along with each item's attributes.
+ *  item's IN, OUT and FEATURE items along with each item's attributes.
  *
  *  This library portion also allows for easy setting and retrieval of data from a HID report, including devices
  *  with multiple reports on the one HID interface.
  *
- *  By default, FEATURE reports and IN/OUT reports with constant data are ignored in the HID report when processed
- *  to save on memory. This can be overridden by defining the HID_ENABLE_FEATURE_PROCESSING or
- *  HID_INCLUDE_CONSTANT_DATA_ITEMS tokens in the user project makefile, passing them to the compiler via the -D
- *  switch.
- *
  *  @{
  */
 
@@ -108,13 +103,13 @@
 		#endif
 		
 		#if !defined(HID_MAX_REPORTITEMS) || defined(__DOXYGEN__)
-			/** Constant indicating the maximum number of report items (IN, OUT or FEATURE if enabled) that can be
+			/** Constant indicating the maximum number of report items (IN, OUT or FEATURE) that can be processed 
-			 *  processed in the report item descriptor. A large value allows for more report items to be
+			 *  in the report item descriptor and stored in the user HID Report Info structure. A large value allows
-			 *  processed, but consumes more memory. By default this is set to 30 items, but this can be
+			 *  for more report items to be stored, but consumes more memory. By default this is set to 20 items, 
-			 *  overridden by defining HID_MAX_REPORTITEMS to another value in the user project makefile, passing
+			 *  but this can be overridden by defining HID_MAX_REPORTITEMS to another value in the user project
-			 *  the define to the compiler using the -D compiler switch.
+			 *  makefile, passing the define to the compiler using the -D compiler switch.
 			 */
-			#define HID_MAX_REPORTITEMS           30
+			#define HID_MAX_REPORTITEMS           20
 		#endif
 
 	/* Public Interface - May be used in end-application: */
@@ -251,6 +246,17 @@
 			void USB_SetHIDReportItemInfo(uint8_t* ReportData, const HID_ReportItem_t* ReportItem)
 			                              ATTR_NON_NULL_PTR_ARG(1, 2);
 										  
+			/** Callback routine for the HID Report Parser. This callback <b>must</b> be implemented by the user code when
+			 *  the parser is used, to determine what report IN, OUT and FEATURE item's information is stored into the user
+			 *  HID_ReportInfo_t structure. This can be used to filter only those items the application will be using, so that
+			 *  no RAM is wasted storing the attributes for report items which will never be referenced by the application.
+			 *
+			 *  \param CurrentItemAttributes  Pointer to the current report item attributes for user checking
+			 *
+			 *  \return Boolean true if the item should be stored into the HID_ReportInfo_t structure, false if it should be ignored
+			 */
+			bool CALLBACK_HIDParser_FilterHIDReportItem(HID_ReportItem_Attributes_t* CurrentItemAttributes);
+
 	/* Private Interface - For use in library only: */
 	#if !defined(__DOXYGEN__)
 		/* Type Defines: */

LUFA/ManPages/ChangeLog.txt

@@ -18,6 +18,8 @@
   *  - Added ShutDown() functions for all hardware peripheral drivers, so that peripherals can be turned off after use
   *  - Added new CDC_Device_Flush() command to the device mode CDC Class driver to flush Device->Host data
   *  - Added extra masks to the SPI driver, changed SPI_Init() so that the clock polarity and sample modes can be set
+  *  - Added new callback to the HID report parser, so that the user application can filter only the items it is interested
+  *    in to be stored into the HIDReportInfo structure to save RAM
   *  
   *  <b>Changed:</b>
   *  - SetIdle requests to the HID device driver with a 0 idle period (send changes only) now only affect the requested
@@ -32,6 +34,8 @@
   *  - Changed the parameters and behaviour of the USB_GetDeviceConfigDescriptor() function so that it now performs size checks
   *    and data validations internally, to simplify user code
   *  - Changed HIDParser to only zero out important values in the Parsed HID Report Item Information structure to save cycles
+  *  - The HID report parser now always processed FEATURE items - HID_ENABLE_FEATURE_PROCESSING token now has no effect
+  *  - The HID report parser now always ignores constant-data items, HID_INCLUDE_CONSTANT_DATA_ITEMS token now has no effect
   *
   *  <b>Fixed:</b>
   *  - Fixed possible lockup in the CDC device class driver, when the host sends data that is a multiple of the

LUFA/ManPages/CompileTimeTokens.txt

@@ -23,17 +23,6 @@
  *  \section Sec_SummaryUSBClassTokens USB Class Driver Related Tokens
  *  This section describes compile tokens which affect USB class-specific drivers in the LUFA library.
  *
- *  <b>HID_ENABLE_FEATURE_PROCESSING</b> - ( \ref Group_HIDParser ) \n
- *  Define this token to enable the processing of FEATURE HID report items, if any, into the processed HID structure.
- *  By default FEATURE items (which are device features settable by the host but not directly visible by the user) are
- *  skipped when processing a device HID report.
- *
- *  <b>HID_INCLUDE_CONSTANT_DATA_ITEMS</b> - ( \ref Group_HIDParser ) \n
- *  By default, constant data items (usually used as spacers to align separate report items to a byte or word boundary)
- *  in the HID report are skipped during report processing. It is highly unusual for an application to make any use of
- *  constant data items (as they do not carry any useful data and only occupy limited RAM) however if required defining
- *  this switch will put constant data items into the processed HID report structure.
- *
  *  <b>HID_STATETABLE_STACK_DEPTH</b> - ( \ref Group_HIDParser ) \n
  *  HID reports may contain PUSH and POP elements, to store and retrieve the current HID state table onto a stack. This
  *  allows for reports to save the state table before modifying it slightly for a data item, and then restore the previous

LUFA/ManPages/MigrationInformation.txt

@@ -24,6 +24,10 @@
  *      preallocate the largest allowable buffer, and pass the size of the buffer to the function. This allows for a single
  *      call to the function to retrieve, size check and validate the Configuration Descriptor rather than having the user
  *      application perform these intermediatary steps.
+ *    - The HID report parser now requires a mandatory callback in the user code, to filter only the items the application
+ *      is interested in into the processed HID report item structure to save RAM. See \ref CALLBACK_HIDParser_FilterHIDReportItem().
+ *    - The HID report parser now always parses FEATURE and always ignores constant-data items - the HID_ENABLE_FEATURE_PROCESSING
+ *      and HID_INCLUDE_CONSTANT_DATA_ITEMS compile time tokens now have no effect.
  *
  * \section Sec_Migration090810 Migrating from 090605 to 090810
  *