EvtChildListAddressDescriptionDuplicate function

[Applies to KMDF only]

A driver's EvtChildListAddressDescriptionDuplicate event callback function duplicates a child address description.

Syntax


EVT_WDF_CHILD_LIST_ADDRESS_DESCRIPTION_DUPLICATE EvtChildListAddressDescriptionDuplicate;

NTSTATUS EvtChildListAddressDescriptionDuplicate(
  _In_   WDFCHILDLIST ChildList,
  _In_   PWDF_CHILD_ADDRESS_DESCRIPTION_HEADER SourceAddressDescription,
  _Out_  PWDF_CHILD_ADDRESS_DESCRIPTION_HEADER DestinationAddressDescription
)
{ ... }

Parameters

ChildList [in]

A handle to a framework child-list object.

SourceAddressDescription [in]

A pointer to a WDF_CHILD_ADDRESS_DESCRIPTION_HEADER structure that identifies the source location of the child address description.

DestinationAddressDescription [out]

A pointer to a WDF_CHILD_ADDRESS_DESCRIPTION_HEADER structure that identifies the destination location of the child address description.

Return value

The EvtChildListAddressDescriptionDuplicate callback function must return STATUS_SUCCESS, or another status value for which NT_SUCCESS(status) equals TRUE, if the operation succeeds. Otherwise, this function must return a status value for which NT_SUCCESS(status) equals FALSE.

Remarks

If a bus driver is using dynamic enumeration, it can register an EvtChildListAddressDescriptionDuplicate callback function by calling WdfFdoInitSetDefaultChildListConfig or WdfChildListCreate.

The framework duplicates driver-supplied address descriptions so that it can have internal copies of the descriptions.

The EvtChildListAddressDescriptionDuplicate callback function must create a duplicate copy of an address description. A driver must supply this callback function if its child devices require an address description, and if the framework cannot call RtlCopyMemory to duplicate the address description. (The framework cannot call RtlCopyMemory if the description contains pointers to additional memory.)

If your driver provides address descriptions but does not provide a EvtChildListAddressDescriptionDuplicate callback function, the framework duplicates address descriptions by calling RtlCopyMemory.

The following steps describe a typical scenario:

  1. The driver determines that a child device exists.

  2. The driver creates an address description by filling in a driver-defined structure that contains a WDF_CHILD_ADDRESS_DESCRIPTION_HEADER structure and possibly by dynamically allocating additional memory to store address information that has a device-specific size.

  3. The driver calls WdfChildListAddOrUpdateChildDescriptionAsPresent to report a child device, supplying a pointer to the address description.

  4. The framework calls the EvtChildListAddressDescriptionDuplicate callback function (if it exists) or RtlCopyMemory to duplicate the address description so that it can have an internal copy of the description.

The framework can use RtlCopyMemory to duplicate an address description, if the description consists of a single structure with a predetermined size that is specified by the AddressDescriptionSize member of the WDF_CHILD_ADDRESS_DESCRIPTION_HEADER structure. However, sometimes the description must also contain additional information that is stored in dynamically allocated memory. In this case, you will typically define a description structure so that a member points to the dynamically allocated memory, and your driver must provide an EvtChildListAddressDescriptionDuplicate callback function. The callback function must do the following:

  1. Allocate additional memory, typically by calling ExAllocatePool.

  2. Store the allocated memory's address in the driver-defined address description structure (that is, the callback function's DestinationAddressDescription structure).

  3. Copy other structure members from the callback function's SourceAddressDescription structure to the callback function's DestinationAddressDescription structure.

The only framework child-list object method that a driver's EvtChildListAddressDescriptionDuplicate callback function can call is WdfChildListGetDevice.

The framework acquires an internal child-list object lock before calling the EvtChildListAddressDescriptionDuplicate callback function. The callback function must only perform operations that are related to the described duplication operation, such as calling framework memory object methods and accessing object context space. It must not call methods that access other drivers.

If your driver supplies an EvtChildListAddressDescriptionDuplicate callback function, it might also need EvtChildListAddressDescriptionCopy and EvtChildListAddressDescriptionCleanup callback functions.

For more information about dynamic enumeration, see Enumerating the Devices on a Bus.

Examples

To define an EvtChildListAddressDescriptionDuplicate callback function, you must first provide a function declaration that identifies the type of callback function you’re defining. Windows provides a set of callback function types for drivers. Declaring a function using the callback function types helps Code Analysis for Drivers, Static Driver Verifier (SDV), and other verification tools find errors, and it’s a requirement for writing drivers for the Windows operating system.

For example, to define an EvtChildListAddressDescriptionDuplicate callback function that is named MyChildListAddressDescriptionDuplicate, use the EVT_WDF_CHILD_LIST_ADDRESS_DESCRIPTION_DUPLICATE type as shown in this code example:


EVT_WDF_CHILD_LIST_ADDRESS_DESCRIPTION_DUPLICATE MyChildListAddressDescriptionDuplicate;

Then, implement your callback function as follows:



_Use_decl_annotations_
NTSTATUS
 MyChildListAddressDescriptionDuplicate (
 WDFCHILDLIST  ChildList,
    PWDF_CHILD_ADDRESS_DESCRIPTION_HEADER  SourceAddressDescription,
    PWDF_CHILD_ADDRESS_DESCRIPTION_HEADER  DestinationAddressDescription
    )
  {...}

The EVT_WDF_CHILD_LIST_ADDRESS_DESCRIPTION_DUPLICATE function type is defined in the WdfChildlist.h header file. To more accurately identify errors when you run the code analysis tools, be sure to add the _Use_decl_annotations_ annotation to your function definition. The_Use_decl_annotations_ annotation ensures that the annotations that are applied to the EVT_WDF_CHILD_LIST_ADDRESS_DESCRIPTION_DUPLICATE function type in the header file are used. For more information about the requirements for function declarations, see Declaring Functions by Using Function Role Types for KMDF Drivers. For information about _Use_decl_annotations_, see Annotating Function Behavior.

Requirements

Minimum KMDF version

1.0

Header

WdfChildlist.h (include Wdf.h)

IRQL

<= DISPATCH_LEVEL

See also

ExAllocatePool
EvtChildListAddressDescriptionCleanup
RtlCopyMemory
WDF_CHILD_ADDRESS_DESCRIPTION_HEADER
WdfChildListAddOrUpdateChildDescriptionAsPresent
WdfChildListCreate
WdfChildListGetDevice
WdfFdoInitSetDefaultChildListConfig

 

 

Send comments about this topic to Microsoft

Afficher:
© 2014 Microsoft