Create multiple ramdisk KMDF - windows

Question

I have a question about the KMDF Ramdisk sample of Microsoft.
How do create more than one ramdisk device? How will the PnP manager know to call EvtDeviceAdd and can I control how many times it is called?
WdfDeviceCreate() is used to create ramdisk device in RamDiskEvtDeviceAdd(), but I can not install more than one instance of this ramdisk driver.
NTSTATUS
RamDiskEvtDeviceAdd(
IN WDFDRIVER Driver,
IN PWDFDEVICE_INIT DeviceInit
) {
WDF_OBJECT_ATTRIBUTES deviceAttributes;
NTSTATUS status;
WDFDEVICE device;
WDF_OBJECT_ATTRIBUTES queueAttributes;
WDF_IO_QUEUE_CONFIG ioQueueConfig;
PDEVICE_EXTENSION pDeviceExtension;
PQUEUE_EXTENSION pQueueContext = NULL;
WDFQUEUE queue;
DECLARE_CONST_UNICODE_STRING(ntDeviceName, NT_DEVICE_NAME);
DECLARE_CONST_UNICODE_STRING(MY_SDDL_STRING, L"D:P(A;;GA;;;SY)(A;;GA;;;BA)(A;;GA;;;WD)(A;;GA;;;RC)");
PAGED_CODE();
UNREFERENCED_PARAMETER(Driver);
// Set name
status = WdfDeviceInitAssignName(DeviceInit, &ntDeviceName);
if (!NT_SUCCESS(status)) {
return status;
}
// Set permission
status = WdfDeviceInitAssignSDDLString(DeviceInit, &MY_SDDL_STRING);
if (!NT_SUCCESS(status)) {
return status;
}
WdfDeviceInitSetDeviceType(DeviceInit, FILE_DEVICE_DISK);
WdfDeviceInitSetIoType(DeviceInit, WdfDeviceIoDirect);
WdfDeviceInitSetExclusive(DeviceInit, FALSE);
WDF_OBJECT_ATTRIBUTES_INIT_CONTEXT_TYPE(&deviceAttributes, DEVICE_EXTENSION);
deviceAttributes.EvtCleanupCallback = RamDiskEvtDeviceContextCleanup;
status = WdfDeviceCreate(&DeviceInit, &deviceAttributes, &device);
if (!NT_SUCCESS(status)) {
return status;
}
pDeviceExtension = DeviceGetExtension(device);
WDF_IO_QUEUE_CONFIG_INIT_DEFAULT_QUEUE (
&ioQueueConfig,
WdfIoQueueDispatchSequential
);
ioQueueConfig.EvtIoDeviceControl = RamDiskEvtIoDeviceControl;
ioQueueConfig.EvtIoRead = RamDiskEvtIoRead;
ioQueueConfig.EvtIoWrite = RamDiskEvtIoWrite;
WDF_OBJECT_ATTRIBUTES_INIT_CONTEXT_TYPE(&queueAttributes, QUEUE_EXTENSION);
__analysis_assume(ioQueueConfig.EvtIoStop != 0);
status = WdfIoQueueCreate( device,
&ioQueueConfig,
&queueAttributes,
&queue );
__analysis_assume(ioQueueConfig.EvtIoStop == 0);
if (!NT_SUCCESS(status)) {
return status;
}
// Context is the Queue handle
pQueueContext = QueueGetExtension(queue);
// Set the context for our default queue as our device extension.
pQueueContext->DeviceExtension = pDeviceExtension;
// Now do any RAM-Disk specific initialization
pDeviceExtension->DiskRegInfo.DriveLetter.Buffer =
(PWSTR) &pDeviceExtension->DriveLetterBuffer;
pDeviceExtension->DiskRegInfo.DriveLetter.MaximumLength =
sizeof(pDeviceExtension->DriveLetterBuffer);
// Get the disk parameters from the registry
RamDiskQueryDiskRegParameters(
WdfDriverGetRegistryPath(WdfDeviceGetDriver(device)),
&pDeviceExtension->DiskRegInfo
);
// Allocate memory for the disk image.
pDeviceExtension->DiskImage = ExAllocatePoolWithTag(
NonPagedPool,
pDeviceExtension->DiskRegInfo.DiskSize,
RAMDISK_TAG
);
if (pDeviceExtension->DiskImage) {
UNICODE_STRING deviceName;
UNICODE_STRING win32Name;
RamDiskFormatDisk(pDeviceExtension);
status = STATUS_SUCCESS;
// Now try to create a symbolic link for the drive letter.
RtlInitUnicodeString(&win32Name, DOS_DEVICE_NAME);
RtlInitUnicodeString(&deviceName, NT_DEVICE_NAME);
pDeviceExtension->SymbolicLink.Buffer = (PWSTR)
&pDeviceExtension->DosDeviceNameBuffer;
pDeviceExtension->SymbolicLink.MaximumLength =
sizeof(pDeviceExtension->DosDeviceNameBuffer);
pDeviceExtension->SymbolicLink.Length = win32Name.Length;
RtlCopyUnicodeString(&pDeviceExtension->SymbolicLink, &win32Name);
RtlAppendUnicodeStringToString(&pDeviceExtension->SymbolicLink,
&pDeviceExtension->DiskRegInfo.DriveLetter);
status = WdfDeviceCreateSymbolicLink(device,
&pDeviceExtension->SymbolicLink);
}
return status;
Please help me! Thanks

Answer 1

I understand this is an old post, but since there are no useful answers, I thought I might add my thoughts.
EvtDeviceAdd is called by the KMDF framework when a device matches a hardware ID that your INF supports. (https://msdn.microsoft.com/en-us/library/windows/hardware/ff541693%28v=vs.85%29.aspx?f=255&MSPPError=-2147217396).
According to the VirtualVolume documentation (https://code.msdn.microsoft.com/windowshardware/VirtualVolume-83334efd), the only way to create a device is to call devcon install virtvol.inf virtvol.
You can make multiple RAMDisks by calling devcon install multiple times.