NDIS_PD_FLUSH_QUEUE callback function (ndis.h)

Article
10/21/2021

The PacketDirect (PD) platform calls a PD-capable miniport driver's PDFlushQueue function to flush a specified queue, ensuring that any items that are not yet in a complete state in the queue will be completed imminently.

Note You must declare the function by using the NDIS_PD_FLUSH_QUEUE type. For more information, see the following Examples section.

Syntax

NDIS_PD_FLUSH_QUEUE NdisPdFlushQueue;

VOID() NdisPdFlushQueue(
  [in, out] NDIS_PD_QUEUE *Queue
)
{...}

Parameters

[in, out] Queue

The queue to flush. For more information, see the NDIS_PD_QUEUE structure.

Return value

This callback function does not return a value.

Remarks

The caller is responsible for waiting for and draining all previously posted requests before closing the queue. The caller must not post any further PD_BUFFER structures to the queue after this call. The primary use case for this routine is flushing the receive queues--if there's no incoming traffic, posted buffers will sit in the receive queue indefinitely, and these need to be drained by being flushed before the queue can be closed. The same issue does not exist for transmit queues in practice because transmit requests will not pend indefinitely. However, providers must honor the flush call for transmit queues (this may be a no-operation if the provider knows that the pending transmit request will complete very soon, which is the typical case except for L2 flow control).

Examples

To define a PDFlushQueue function, you must first provide a function declaration that identifies the type of function you're defining. Windows provides a set of function types for drivers. Declaring a function using the 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 a PDFlushQueue function that is named "MyPDFlushQueue", use the NDIS_PD_FLUSH_QUEUE type as shown in this code example:

NDIS_PD_FLUSH_QUEUE MyPDFlushQueue;

Then, implement your function as follows:

_Use_decl_annotations_
VOID
 MyPDFlushQueue(
    NDIS_PD_QUEUE*  NdisPDQueue
    )
  {...}

The NDIS_PD_FLUSH_QUEUE function type is defined in the Ntddndis.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 NDIS_PD_FLUSH_QUEUE 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 NDIS Drivers.

For information about Use_decl_annotations, see Annotating Function Behavior.

Requirements

Requirement	Value
Minimum supported client	Windows 10
Minimum supported server	Windows Server 2016
Target Platform	Windows
Header	ndis.h
IRQL	<= DISPATCH_LEVEL

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