allow HID submodules to create runtime descriptors

with this PR you can add

\#include Keyboard.h
\#include Mouse.h
\#include HID.h

in the top of the sketch and you will expose a Mouse+Keyboard

From the library pow, simply add

static HID_Descriptor cb = {
	.length = sizeof(_hidReportDescriptor),
	.descriptor = _hidReportDescriptor,
};
static HIDDescriptorListNode node(&cb);
HID.AppendDescriptor(&node);

in the class' constructor and you are done!

libraries/HID/HID.cpp

@@ -44,6 +44,9 @@ static u8 HID_INTERFACE;
 
 HIDDescriptor _hidInterface;
 
+static HIDDescriptorListNode* rootNode = NULL;
+static uint8_t sizeof_hidReportDescriptor = 0;
+static uint8_t modules_count = 0;
 //================================================================================
 //================================================================================
 //	Driver
@@ -54,18 +57,45 @@ u8 _hid_idle = 1;
 int HID_GetInterface(u8* interfaceNum)
 {
 	interfaceNum[0] += 1;	// uses 1
+	_hidInterface =
+	{
+		D_INTERFACE(HID_INTERFACE,1,3,0,0),
+		D_HIDREPORT(sizeof_hidReportDescriptor),
+		D_ENDPOINT(USB_ENDPOINT_IN (HID_ENDPOINT_INT),USB_ENDPOINT_TYPE_INTERRUPT,0x40,0x01)
+	};
 	return USB_SendControl(0,&_hidInterface,sizeof(_hidInterface));
 }
 
 int HID_GetDescriptor(int8_t t)
 {
 	if (HID_REPORT_DESCRIPTOR_TYPE == t) {
-		return USB_SendControl(TRANSFER_PGM,_hidReportDescriptor,getsizeof_hidReportDescriptor());
+		HIDDescriptorListNode* current = rootNode;
+		int total = 0;
+		while(current != NULL) {
+			total += USB_SendControl(TRANSFER_PGM,current->cb->descriptor,current->cb->length);
+			current = current->next;
+		}
+		return total;
 	} else {
 		return 0;
 	}
 }
 
+void HID_::AppendDescriptor(HIDDescriptorListNode *node)
+{
+	if (modules_count == 0) {
+		rootNode = node;
+	} else {
+		HIDDescriptorListNode *current = rootNode;
+		while(current->next != NULL) {
+			current = current->next;
+		}
+		current->next = node;
+	}
+	modules_count++;
+	sizeof_hidReportDescriptor += node->cb->length;
+}
+
 void HID_::SendReport(u8 id, const void* data, int len)
 {
 	USB_Send(HID_TX, &id, 1);
@@ -129,13 +159,6 @@ HID_::HID_(void)
 	static PUSBListNode node(&cb);
 
 	HID_ENDPOINT_INT = PUSB_AddFunction(&node, &HID_INTERFACE);
-
-	_hidInterface =
-	{
-		D_INTERFACE(HID_INTERFACE,1,3,0,0),
-		D_HIDREPORT(getsizeof_hidReportDescriptor()),
-		D_ENDPOINT(USB_ENDPOINT_IN (HID_ENDPOINT_INT),USB_ENDPOINT_TYPE_INTERRUPT,0x40,0x01)
-	};
 }
 
 int HID_::begin(void)

libraries/HID/HID.h

@@ -42,16 +42,27 @@
 #define HID_REPORT_DESCRIPTOR_TYPE      0x22
 #define HID_PHYSICAL_DESCRIPTOR_TYPE    0x23
 
+typedef struct __attribute__((packed)) {
+  u8 length;
+  const void* descriptor;
+} HID_Descriptor;
+
+class HIDDescriptorListNode {
+public:
+  HIDDescriptorListNode *next = NULL;
+  const HID_Descriptor * cb;
+  HIDDescriptorListNode(const HID_Descriptor *ncb) {cb = ncb;}
+};
+
 class HID_
 {
 public:
   HID_(void);
   int begin(void);
   void SendReport(uint8_t id, const void* data, int len);
+  void AppendDescriptor(HIDDescriptorListNode* node);
 };
 
-extern HID_ HID;
-
 typedef struct
 {
   u8 len;     // 9
@@ -77,11 +88,6 @@ typedef struct
 #define D_HIDREPORT(_descriptorLength) \
   { 9, 0x21, 0x1, 0x1, 0, 1, 0x22, _descriptorLength, 0 }
 
-extern const u8 _hidReportDescriptor[] PROGMEM;
-
-// MUST be declared by the module
-size_t getsizeof_hidReportDescriptor();
-
 #define WEAK __attribute__ ((weak))
 
 #endif