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Using I/O Targets in UMDF

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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.

The archived UMDF 1 samples can be found in the Windows 11, version 22H2 - May 2022 Driver Samples Update.

For more info, see Getting Started with UMDF.

When a driver receives an I/O request, the driver might be able to process the request by itself, or it might require the assistance of other drivers. If the driver requires assistance, it can forward the request to another driver, or it can create one or more new requests and send them to another driver.

UMDF-based drivers use I/O targets to send I/O requests to another driver. Each I/O target is represented by an I/O target object. Each I/O target object is primarily a queue. When a driver sends a request to an I/O target, the framework stores the request in the queue until it can deliver the request to the I/O target.

The framework supports both general I/O targets and specialized I/O targets:

  • General I/O targets can be used by all UMDF drivers, but they do not support any special, device-specific data formats.

  • Specialized I/O targets enable UMDF drivers to send I/O requests that require special, target-specific data formatting. Currently, the framework provides support for USB I/O targets.

If the framework provides specialized I/O targets that support your device's data format, your driver should use the specialized I/O targets. Otherwise, the driver should use general I/O targets.