获取 USBCAMD2 功能
必须先获取指向 USBCAMD_INTERFACE 结构的指针,然后才能使用新的 USBCAMD2 功能。 若要获取指针,请在 AdapterReceivePacket 回调函数中从相机微型驱动程序的SRB_INITIALIZATION_COMPLETE处理程序生成并发送IRP_MN_QUERY_INTERFACE请求。 USBCAMD2 微型驱动程序库处理此 IRP,并将USBCAMD_INTERFACE类型的直接调用接口返回到相机微型驱动程序。 接口实质上是一个函数指针表。
以下代码演示如何从相机微型驱动程序生成和发送IRP_MN_QUERY_INTERFACE请求:
KeInitializeEvent(&Event, NotificationEvent, FALSE);
Irp = IoBuildSynchronousFsdRequest(
IRP_MJ_PNP,
pDeviceObject,
NULL,
0,
NULL,
&Event,
&IoStatusBlock);
if (NULL != Irp)
{
Irp->RequestorMode = KernelMode;
IrpStackNext = IoGetNextIrpStackLocation(Irp);
//
// Create an interface query out of the Irp.
//
IrpStackNext->MinorFunction = IRP_MN_QUERY_INTERFACE;
IrpStackNext->Parameters.QueryInterface.InterfaceType = (GUID*)&GUID_USBCAMD_INTERFACE;
IrpStackNext->Parameters.QueryInterface.Size = sizeof(*pUsbcamdInterface);
IrpStackNext->Parameters.QueryInterface.Version = USBCAMD_VERSION_200;
IrpStackNext->Parameters.QueryInterface.Interface = (PINTERFACE)pUsbcamdInterface;
IrpStackNext->Parameters.QueryInterface.InterfaceSpecificData = NULL;
Status = IoCallDriver(pDeviceObject, Irp);
if (STATUS_PENDING == Status)
{
//
// This waits using KernelMode so that the stack, and therefore the
// event on that stack, is not paged out.
//
KeWaitForSingleObject(&Event, Executive, KernelMode, FALSE, NULL);
Status = IoStatusBlock.Status;
}
}
else
{
Status = STATUS_INSUFFICIENT_RESOURCES;
}