WDDM 子设备关状态

WDDM中使用来DxgkDdiQueryChildStatus查询子设备的状态

     InitialData.DxgkDdiQueryChildStatus             = BddDdiQueryChildStatus;

和其它的回调函数一样，最终的处理函数其实是BASIC_DISPLAY_DRIVER的成员函数QueryChildStatus。

子设备的状态一般有连接状态、旋转状态和无线投屏三种，所以其分别对应不同的数据结构体。
在BddDdiQueryChildStatus的参数INOUT_PDXGK_CHILD_STATUS 结构体中，包含一个三个状态的公用体。

typedef struct _DXGK_CHILD_STATUS {
  DXGK_CHILD_STATUS_TYPE Type;
  ULONG                  ChildUid;
  union {
    struct {
      BOOLEAN Connected;
    } HotPlug;
    struct {
      UCHAR Angle;
    } Rotation;
    struct {
      BOOLEAN                         Connected;
      D3DKMDT_VIDEO_OUTPUT_TECHNOLOGY MiracastMonitorType;
    } Miracast;
  };
} DXGK_CHILD_STATUS, *PDXGK_CHILD_STATUS;

• ChildUid:ChildUid用于标识是获取那个设备。
• DXGK_CHILD_STATUS_TYPE：用于标识是查询什么类型的状态，这是一个枚举量，包含 三种类型：

  typedef enum _DXGK_CHILD_STATUS_TYPE {
  StatusUninitialized,
  StatusConnection,
  StatusRotation,
  StatusMiracastConnection
  } DXGK_CHILD_STATUS_TYPE, *PDXGK_CHILD_STATUS_TYPE;
  

由于我们的子设备是TypeVideoOutput类型，并且不支持旋转，所以只支持设备插拔的状态。

无线投屏是WDDM1.3所支持的，这里我们不考虑。

最终代码如下：

 NTSTATUS BASIC_DISPLAY_DRIVER::QueryChildStatus(_Inout_ DXGK_CHILD_STATUS* pChildStatus,
                                                _In_    BOOLEAN            NonDestructiveOnly)
{
    PAGED_CODE();

    UNREFERENCED_PARAMETER(NonDestructiveOnly);
    BDD_ASSERT(pChildStatus != NULL);
    BDD_ASSERT(pChildStatus->ChildUid < MAX_CHILDREN);

    switch (pChildStatus->Type)
    {
        case StatusConnection:
        {
            // HpdAwarenessInterruptible was reported since HpdAwarenessNone is deprecated.
            // However, BDD has no knowledge of HotPlug events, so just always return connected.
            pChildStatus->HotPlug.Connected = IsDriverActive();
            return STATUS_SUCCESS;
        }

        case StatusRotation:
        {
            // D3DKMDT_MOA_NONE was reported, so this should never be called
            BDD_LOG_ERROR0("Child status being queried for StatusRotation even though D3DKMDT_MOA_NONE was reported");
            return STATUS_INVALID_PARAMETER;
        }

        default:
        {
            BDD_LOG_WARNING1("Unknown pChildStatus->Type (0x%I64x) requested.", pChildStatus->Type);
            return STATUS_NOT_SUPPORTED;
        }
    }
}