acquiring-usbcamd2-features.md

title	description	keywords	ms.date
Acquiring USBCAMD2 Features	Acquiring USBCAMD2 Features	Windows 2000 Kernel Streaming Model WDK , USBCAMD2 minidriver library Streaming Model WDK Windows 2000 Kernel , USBCAMD2 minidriver library Kernel Streaming Model WDK , USBCAMD2 minidriver library USBCAMD2 features WDK Windows 2000 Kernel Streaming USB-based streaming cameras WDK USBCAMD2 cameras WDK USBCAMD2 IRP_MN_QUERY_INTERFACE	04/20/2017

Acquiring USBCAMD2 Features

You must acquire a pointer to the USBCAMD_INTERFACE structure before you can use the new USBCAMD2 features. To acquire the pointer, build and send an IRP_MN_QUERY_INTERFACE request from the camera minidriver's SRB_INITIALIZATION_COMPLETE handler in the AdapterReceivePacket callback function. The USBCAMD2 minidriver library processes this IRP and returns a direct-call interface of type USBCAMD_INTERFACE to the camera minidriver. The interface is essentially a table of function pointers.

The following code demonstrates how to build and send the IRP_MN_QUERY_INTERFACE request from the camera minidriver:

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;
}