HID报告描述符主项InputReport、OutputReport,FeatureReport

HID报告描述符主项除过COLLECTION项，就是输入报告InputReport,输出报告OutputReport和特性报告FeatureReport。

ITEM_PREFIX的BIT2,BIT3为00，bit4-7的值为：

#define ITEM_TAG_MAIN_INPUT                    0x8
#define ITEM_TAG_MAIN_OUTPUT                0x9
#define ITEM_TAG_MAIN_FEATURE                0xb

InputReport、OutputReport,FeatureReport示例

 INPUT (Data,Var,Abs)                    81 02 
 OUTPUT (Data,Var,Abs)                    91 02 
 FEATURE (Data,Var,Abs)                    B1 02

这里各个后面的报告数据MainItemData为0x02,代表(Data,Var,Abs)，不过其具有多种配置，更多详见：HID主条目input item、output item和feature item详解http://www.usbzh.com/article/detail-527.html

MainItemData的结构可根据上面的定义如下结构体：

typedef struct
{
    USHORT DataConstant:1;
    USHORT ArrayVariable:1;
    USHORT Relative:1;
    USHORT Wrap:1;
    USHORT NonLinear:1;
    USHORT NoPreferred:1;
    USHORT NullState:1;
    USHORT IsVolatile:1;
    USHORT BitsBytes:1;
    UCHAR  reserved[2];
}
MAIN_ITEM_DATA, *PMAIN_ITEM_DATA;

在parser.sys中，一个报告就是一个HID_REPORT结构体，存于HID_COLLECTION的Reports指针数组中，其总数由ReportCount决定。

typedef struct _HID_REPORT
{
    UCHAR Type;
    UCHAR ReportID;
    ULONG ReportSize;   
    ULONG ItemCount;
    ULONG ItemAllocated;
    HID_REPORT_ITEM Items[1];
}HID_REPORT, *PHID_REPORT;

而HID_REPORT_ITEM是在InputReport、OutputReport,FeatureReport各个USAGE使用的size和count。

typedef struct
{
    ULONG ByteOffset;
    UCHAR Shift;
    ULONG Mask;
    UCHAR BitCount;
    UCHAR HasData;
    UCHAR Array;
    UCHAR Relative;
    ULONG Minimum;
    ULONG Maximum;
    ULONG UsageMinimum;
    ULONG UsageMaximum;
    ULONG Data;
    UCHAR Valid;
}HID_REPORT_ITEM, *PHID_REPORT_ITEM;

HID_RPORT中的HID_REPORT_ITEM成员通过HidParser_AddMainItem初始化。

  ReportType = HID_REPORT_TYPE_ANY;

                    switch (CurrentItem->Tag) {
                        case ITEM_TAG_MAIN_INPUT:
                            ReportType = HID_REPORT_TYPE_INPUT;
                            break;

                        case ITEM_TAG_MAIN_OUTPUT:
                            ReportType = HID_REPORT_TYPE_OUTPUT;
                            break;

                        case ITEM_TAG_MAIN_FEATURE:
                            ReportType = HID_REPORT_TYPE_FEATURE;
                            break;

                        default:
                            Parser->Debug("[HIDPARSE] Unknown ReportType Tag %x Type %x Size %x CurrentItemSize %x\n", CurrentItem->Tag, CurrentItem->Type, CurrentItem->Size, CurrentItemSize);
                            ASSERT(FALSE);
                            break;
                    }

                    if (ReportType == HID_REPORT_TYPE_ANY)
                        break;

                    //
                    // get report
                    //
                    Status = HidParser_GetReport(Parser, ParserContext, CurrentCollection, ReportType, ParserContext->GlobalItemState.ReportId, TRUE, &Report);
                    ASSERT(Status == HIDPARSER_STATUS_SUCCESS);

                    // fill in a sensible default if the index isn't set
                    if (!ParserContext->LocalItemState.DesignatorIndexSet) {
                        ParserContext->LocalItemState.DesignatorIndex
                            = ParserContext->LocalItemState.DesignatorMinimum;
                    }

                    if (!ParserContext->LocalItemState.StringIndexSet)
                        ParserContext->LocalItemState.StringIndex = ParserContext->LocalItemState.StringMinimum;

                    //
                    // get main item data
                    //
                    MainItemData = (PMAIN_ITEM_DATA)&Data;

                    //
                    // add states & data to the report
                    //
                    Status = HidParser_AddMainItem(Parser, ParserContext, Report, &ParserContext->GlobalItemState, &ParserContext->LocalItemState, MainItemData, CurrentCollection);
                    ASSERT(Status == HIDPARSER_STATUS_SUCCESS);
                }

                //
                // backup stack
                //
                Index = ParserContext->LocalItemState.UsageStackAllocated;
                NewUsageStack = ParserContext->LocalItemState.UsageStack;

                //
                // reset the local item state and clear the usage stack
                //
                Parser->Zero(&ParserContext->LocalItemState, sizeof(LOCAL_ITEM_STATE));

                //
                // restore stack
                //
                ParserContext->LocalItemState.UsageStack = NewUsageStack;
                ParserContext->LocalItemState.UsageStackAllocated = Index;

这里涉及到LOCAL_ITEM_STATE LocalItemState和GLOBAL_ITEM_STATE GlobalItemState的处理，后续通过LOCAL和GLOABL项来进行分析。