The IO_RESOURCE_REQUIREMENTS_LIST structure describes sets of resource configurations that can be used by a device. Each configuration represents a range of raw resources, of various types, that can be used by a device.


  ULONG            ListSize;
  INTERFACE_TYPE   InterfaceType;
  ULONG            BusNumber;
  ULONG            SlotNumber;
  ULONG            Reserved[3];
  ULONG            AlternativeLists;



The total number of bytes that constitute the IO_RESOURCE_REQUIREMENTS_LIST structure, its IO_RESOURCE_LIST array, and the latter's IO_RESOURCE_DESCRIPTOR array.


Specifies an interface type. This must be one of the types defined by INTERFACE_TYPE, in Wdm.h or Ntddk.h. (Not used by WDM drivers.)


A system-assigned, zero-based bus number. (Not used by WDM drivers.)


A system slot number. (Not used by WDM drivers.)


Not used.


The number of alternative lists (or configurations) of hardware resources that are described by this IO_RESOURCE_REQUIREMENTS_LIST structure. The List member is the header for the first alternative list.


The IO_RESOURCE_LIST structure that serves as the header for the first alternative list of hardware resources. If the IO_RESOURCE_REQUIREMENTS_LIST structure describes more than one alternative list, the second alternative list immediately follows the first alternative list in memory, and so on. The size of each alternative list depends on the length of the IO_RESOURCE_DESCRIPTOR array that it contains. For more information, see the following Remarks section.


This structure is used by the IRP_MN_FILTER_RESOURCE_REQUIREMENTS and IRP_MN_QUERY_RESOURCE_REQUIREMENTS IRPs to describe one or more alternative configurations of hardware resources.

The IO_RESOURCE_REQUIREMENTS_LIST structure is a header for a larger data structure, of variable size, that specifies one or more alternative lists of resources. All of the data in this larger structure occupies a contiguous block of memory, whose size is specified by the ListSize member. Each alternative list occupies a subblock within the larger block.

Each alternative list begins with an IO_RESOURCE_LIST structure, which serves as a header for an array of IO_RESOURCE_DESCRIPTOR structures. The length of this array determines the size of the list, which can vary from one alternative list to the next. Driver code can use pointer arithmetic to step from one alternative list to the next. For example, if a parameter named list is a pointer to the IO_RESOURCE_LIST structure at the start of one alternative list, list can be updated to point to the start of the next list as follows:

    list = (PIO_RESOURCE_LIST)(list->Descriptors + list->Count);
In this example, list->Descriptors is a pointer to the start of the IO_RESOURCE_DESCRIPTOR array, and list->Count is the number of elements in the array. For more information about the Descriptors and Count members, see IO_RESOURCE_LIST.


If a driver contains a handler for an IRP_MN_FILTER_RESOURCE_REQUIREMENTS IRP, the handler typically walks the resource list that is pointed to by the IoStatus.Information field in the IRP. The following code example contains a function—named FilterResources—that is called in the handler to walk the list. This function either verifies that a particular resource is specified in the list, or changes the resource requirements in the list without changing the size of the list. (A function that changes the size of the list would need to allocate a buffer for the updated list, write the list to this buffer, update the IoStatus.Information field in the IRP to point to the updated list, and free the buffer that contains the original list.)

The FilterResources function returns TRUE (probably from the switch statement, although the details are omitted to simplify the code example) if it finds the resource that it is looking for in the list, or if it makes a change to the list that does not change the size of the list. Otherwise, it returns FALSE.

/* Modify the resource list in place (without changing its size). */


list = reqlist->List;

for (int ix = 0; ix < reqlist->AlternativeLists; ++ix)
    /* Process resources in IO_RESOURCE_LIST block number ix. */

    for (int jx = 0; jx < list->Count; ++jx)

        desc = list->Descriptors + jx;

        switch (desc->Type)
           /* Process element jx in Descriptors array. */



    /* Advance to next IO_RESOURCE_LIST block in memory. */

    list = (PIO_RESOURCE_LIST)(list->Descriptors + list->Count);

return FALSE;



Header wdm.h (include Wdm.h, Ntddk.h, Ntifs.h, Miniport.h)

See Also