Writing Windows WDM Device Drivers

NTSTATUS ClaimResources(IN PDEVICE_OBJECT phddo) {
 PPHDIO_DEVICE_EXTENSION dx = (PPHDIO_DEVICE_EXTENSION)phddo->DeviceExtension;
 // Get resource count: either 1 (IOport) or 2 (IOport&IRQ)
 ULONG PartialResourceCount = 1;
 if (dx->GotInterrupt) PartialResourceCount++;
 // Get size of required CM_RESOURCE_LIST
 ULONG ListSize = FIELD_OFFSET(CM_RESOURCE_LIST, List[0]);
 ListSize += sizeof(CM_FULL_RESOURCE_DESCRIPTOR) + ((PartialResourceCount-1) * sizeof(CM_PARTIAL_RESOURCE_DESCRIPTOR));
 // Allocate CM_RESOURCE_LIST
 PCM_RESOURCE_LIST ResourceList = (PCM_RESOURCE_LIST)ExAllocatePool(PagedPool, ListSize);
 if (ResourceList==NULL) {
  DebugPrintMsg('Cannot allocate memory for ResourceList');
  return STATUS_INSUFFICIENT_RESOURCES;
 }
 RtlZeroMemory(ResourceList, ListSize);
 // Only one Full Resource Descriptor needed, for ISA
 ResourceList->Count = 1;
 // Initialise Full Resource Descriptor
 PCM_FULL_RESOURCE_DESCRIPTOR FullRD = &ResourceList->List[0];
 FullRD->InterfaceType = Isa;
 FullRD->BusNumber = 0;
 FullRD->PartialResourceList.Count = PartialResourceCount;
 // Initialise Partial Resource Descriptor for IO port
 PCM_PARTIAL_RESOURCE_DESCRIPTOR resource = &FullRD->PartialResourceList.PartialDescriptors[0];
 resource->Type = CmResourceTypePort;
 resource->ShareDisposition = CmResourceShareDriverExciusive;
 resource->Flags = CM_RESOURCE_PORT_IO;
 resource->u.Port.Start = dx->PortStartAddress;
 resource->u.Port.Length = dx->PortLength;
 // Initialise Partial Resource Descriptor for Interrupt
 if (dx->GotInterrupt) {
  resource++;
  resource->Type = CmResourceTypeInterrupt;
  resource->ShareDisposition = CmResourceShareDriverExclusive;
  if (dx->Mode==Latched) resource->Flags = CM_RESOURCE_INTERRUPT_LATCHED;
  else resource->F1ags = CM_RESOURCE_INTERRUPT_LEVEL_SENSITIVE;
  resource->u.Interrupt.Level = dx->Irql;
  resource->u.Interrupt.Vector = dx->Irql;
  resource->u.Interrupt.Affinity = 1;
 }
 // Ask for resources for the driver
 DebugPrint('Allocating %d resources', PartialResourceCount);
 DebugPrint('phddo->DriverObject %x', phddo->DriverObject);
 if (dx->ResourceOverride) DebugPrintMsg('Resource override conflict');
 BOOLEAN ConflictDetected;
 NTSTATUS status = IoReportResourceUsage(NULL,
  phddo->DriverObject, ResourceList, ListSize, // Driver resources
  NULL, NULL, 0, // Device resources
  dx->ResourceOverride, &ConflictDetected);
 // Cope (or override) if resource conflict found
 if (ConflictDetected) {
  DebugPrintMsg('ConflictDetected');
  if (dx->ResourceOverride) {
   DebugPrintMsg('Conflict detected and overridden');
   status = STATUS_SUCCESS;
  }
 }
 // Free allocated memory
 ExFreePool(ResourceList);
 return status;
}

Table 18.1 shows the parameters for IoReportResourceUsage. If you are allocating resources for the whole driver, use the DriverObject, DriverList, and DriverListSize parameters; otherwise, set these to NULL. Do the same for the per-device parameters, DeviceObject, DeviceList, and DeviceListSize.

In the NT and Windows 2000 platforms, the resource assignments end up in the registry in the HKLMHARDWARERESOURCEMAP key[45]. If you specify a DriverClassName parameter, this string is used as a subkey to hold the resource assignments. Otherwise, in NT 4 and NT 3.51, the resource assignments end up in the 'OtherDrivers' subkey. In W2000, the resource assignments are in the 'PnP Manager' subkey. You can use RegEdt32 to inspect the raw and translated resource assignments. In NT 3.51 and NT 4 this is the only way to view the resources used by the system. In Windows 2000 and Windows 98, the Device Manager properties for a device shows its resource usage; in W2000, the PHDIo device can be found if you opt to show hidden devices.

IoReportResourceUsage checks for resource conflicts and, if none, assigns the new resources. The OverrideConflict parameter can be used to force the storage of the new resource list, even if there were conflicts. The output ConflictDetected BOOLEAN says whether a conflict was detected. If its ResourceOverride field is true, PHDIo ignores a resource conflict and forces a STATUS_SUCCESS return.

Table 18.1 IoReportResourceUsage function

NTSTATUS IoReportResourceUsage	(IRQL==PASSIVE_LEVEL)
Parameter	Description
IN PUNICODE_STRING DriverClassName	Optional resource class name
IN PDRIVER_OBJECT DriverObject	Driver object pointer