Asynchronous Requests

This document discusses the use of asynchronous requests by device drivers.

An asynchronous request is typically used to start an operation on a device that completes at a later point of time. It returns immediately after starting the operation on the device or making a request to the driver. The user side thread is not blocked and can continue with other operations, including issuing other requests (synchronous or asynchronous).

A driver lists the available asynchronous request types in an enumeration.

• User-side Creation
  This document describes user-side creation of asynchronous requests.
• Status Query
  This document describes how the status of an asynchronous request is maintained and monitored.
• Driver-side Handling
  This document describes how device drivers handle asynchronous requests.
• Completion and Notification
  This document describes how a device driver notifies completion of an asynchronous request.