From 000841f6e85427abc4972b3f80a45df4d33c067a Mon Sep 17 00:00:00 2001
From: Robert Fisk <robert_fisk@fastmail.fm>
Date: Mon, 24 Oct 2016 11:45:41 +1300
Subject: [PATCH] Refactor and improve HID report item parsing

---
 Downstream/Inc/downstream_hid.h |  2 +-
 Downstream/Src/downstream_hid.c | 12 +++++++++---
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/Downstream/Inc/downstream_hid.h b/Downstream/Inc/downstream_hid.h
index cc36c5b..b011aa8 100644
--- a/Downstream/Inc/downstream_hid.h
+++ b/Downstream/Inc/downstream_hid.h
@@ -32,7 +32,7 @@
 
 
 //Stuff for parsing HID descriptors:
-#define HID_ITEM_LONG               0xFE
+#define HID_ITEM_LONG               0xFC
 #define HID_ITEM_MASK               0xFC
 #define HID_ITEM_LENGTH_MASK        0x03
 
diff --git a/Downstream/Src/downstream_hid.c b/Downstream/Src/downstream_hid.c
index 236a314..effcf72 100644
--- a/Downstream/Src/downstream_hid.c
+++ b/Downstream/Src/downstream_hid.c
@@ -93,7 +93,7 @@ static HAL_StatusTypeDef Downstream_HID_Mouse_ParseReportDescriptor(void)
                                                               (ReportYBitLength == 0)      ||
                                                               (ReportWheelBitLength == 0)))
     {
-        switch (ItemHeader & HID_ITEM_MASK)
+        switch (ItemHeader)
         {
         case HID_ITEM_USAGE_PAGE:
             currentUsagePage = ItemData;
@@ -239,8 +239,14 @@ static HAL_StatusTypeDef Downstream_HID_GetNextReportItem(void)
         return HAL_ERROR;
     }
 
-    ItemHeader = *ReportDataPointer++;
-    itemLength = ItemHeader & HID_ITEM_LENGTH_MASK;
+    ItemHeader = *ReportDataPointer & HID_ITEM_MASK;
+    itemLength = *ReportDataPointer & HID_ITEM_LENGTH_MASK;
+    ReportDataPointer++;
+
+    if (itemLength == 3)
+    {
+        itemLength = 4;                         //Length = 3 actually means 4 bytes
+    }
 
     if (ItemHeader == HID_ITEM_LONG)
     {