Multiple device driver? (KMDF/WDF)

Question

I've just written a KMDF USB driver. Now I want to connect several (up to at least four) devices to the PC. Where do I start? I've noted that when I connect the second device to the PC it use the very same instance of the driver as for the first connected device. EvtDeviceAdd(...) runs one time per device and since I don't have any handling for several devices things get weird... Right now my EvtDeviceAdd looks like this:

NTSTATUS EvtDeviceAdd(IN WDFDRIVER Driver, IN PWDFDEVICE_INIT DeviceInit) {
    WDF_PNPPOWER_EVENT_CALLBACKS        pnpPowerCallbacks;
    WDF_OBJECT_ATTRIBUTES               attributes;
    NTSTATUS                            status;
    WDFDEVICE                           device;
    WDF_DEVICE_PNP_CAPABILITIES         pnpCaps;
    WDF_IO_QUEUE_CONFIG                 ioQueueConfig;
    PDEVICE_CONTEXT                     pDevContext;
    WDFQUEUE                            queue;
    PWSTR                               driverRegistryPath;

    UNREFERENCED_PARAMETER(Driver);
    PAGED_CODE();

    DbgPrint("New device was added\n");

    WDF_PNPPOWER_EVENT_CALLBACKS_INIT(&pnpPowerCallbacks);
    pnpPowerCallbacks.EvtDevicePrepareHardware = EvtDevicePrepareHardware;
    WdfDeviceInitSetPnpPowerEventCallbacks(DeviceInit, &pnpPowerCallbacks);

    WdfDeviceInitSetIoType(DeviceInit, WdfDeviceIoBuffered);

    WDF_OBJECT_ATTRIBUTES_INIT_CONTEXT_TYPE(&attributes, DEVICE_CONTEXT);

    status = WdfDeviceCreate(&DeviceInit, &attributes, &device);
    if (!NT_SUCCESS(status)) {
        DbgPrint("WdfDeviceCreate failed with Status code %!STATUS!\n", status);
        return status;
    }

    pDevContext = GetDeviceContext(device);

    WDF_DEVICE_PNP_CAPABILITIES_INIT(&pnpCaps);
    pnpCaps.SurpriseRemovalOK = WdfTrue;

    WdfDeviceSetPnpCapabilities(device, &pnpCaps);

    WDF_IO_QUEUE_CONFIG_INIT_DEFAULT_QUEUE(&ioQueueConfig, WdfIoQueueDispatchParallel);

    ioQueueConfig.EvtIoRead = EvtIoRead;
    ioQueueConfig.EvtIoWrite = EvtIoWrite;
    ioQueueConfig.EvtIoDeviceControl = EvtIoDeviceControl;
    ioQueueConfig.PowerManaged = WdfTrue;

    status = WdfIoQueueCreate(device, &ioQueueConfig, WDF_NO_OBJECT_ATTRIBUTES, &queue);
    if (!NT_SUCCESS(status)) {
        DbgPrint("WdfIoQueueCreate failed  %!STATUS!\n", status);
        return status;
    }
    pDevContext->DeviceIOControlQueue = queue;

    status = WdfDeviceCreateDeviceInterface(device, (LPGUID) &GUID_DEVINTERFACE_MYDEVICE, NULL);

    if (!NT_SUCCESS(status)) {
        DbgPrint("WdfDeviceCreateDeviceInterface failed  %!STATUS!\n", status);
        return status;
    }
}

Where do I start? Is there any good examples?

score 0 · Answer 1 · answered Oct 22 '12 at 21:20

There is only one instance of the driver in memory for all the connected devices (it's a singleton). The OS calls to the driver are accompanied with the relevant device context and from that point the devices shouldn't interfere with each other operation. The problems begin if non-constant global/static variables are being used. Since the Kernel space is shared, such variables will be actually shared and accessible from all attached devices. For this reason global/static data shouldn't be device-specific and should be guarded since it's shared resource. There are some samples in the WDK demonstrating multi-device drivers.

Multiple device driver? (KMDF/WDF)

1 Answers1