IWDFIoQueue::Drain method (wudfddi.h)

Article
02/22/2024

[Warning: UMDF 2 is the latest version of UMDF and supersedes UMDF 1. All new UMDF drivers should be written using UMDF 2. No new features are being added to UMDF 1 and there is limited support for UMDF 1 on newer versions of Windows 10. Universal Windows drivers must use UMDF 2. For more info, see Getting Started with UMDF.]

The Drain method directs the queue to reject new incoming I/O requests and allow already-queued requests to be delivered to the driver for processing.

Syntax

void Drain(
  [in, optional] IQueueCallbackStateChange *pDrainComplete
);

Parameters

[in, optional] pDrainComplete

A pointer to the IQueueCallbackStateChange interface whose method the framework calls to deliver queue state to the driver. The framework calls the method after all requests are completed or canceled and the queue is empty. This parameter is optional and can be NULL.

Return value

None

Remarks

A driver should ensure that only one of the following methods is in progress at any given time:

IWDFIoQueue::Stop
IWDFIoQueue::Drain
IWDFIoQueue::Purge

For example, if the driver previously called Drain, it should wait for notification from the method of the interface that the pDrainComplete parameter points to before the driver calls either Stop or Purge. Violating this rule results in termination of the host process.

Requirements

Requirement	Value
End of support	Unavailable in UMDF 2.0 and later.
Target Platform	Desktop
Minimum UMDF version	1.5
Header	wudfddi.h (include Wudfddi.h)
DLL	WUDFx.dll