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Windows User-Mode Driver Framework (UMDF)

The Windows User-Mode Driver Framework (UMDF) enables you to develop drivers that run in user mode rather than kernel mode. This offers several advantages, including increased stability and security, easier debugging, and faster development cycles. UMDF is built on top of the Windows Driver Model (WDM) and provides an object-oriented programming model that simplifies driver development.

Key Concepts in UMDF Development

Driver Objects and Components

UMDF drivers are composed of several key objects:

• Driver Host Process: The user-mode process that hosts your driver.
• Driver Object: Represents your driver within the host process.
• Device Objects: Represent hardware devices managed by your driver.
• Framework Objects: UMDF provides various framework objects like IWDFDevice, IWDFIoRequest, and IWDFDriver to manage driver functionality.

Driver Model

UMDF follows an event-driven model. Your driver registers callbacks for various device and I/O events, and the framework invokes these callbacks when the corresponding events occur.

Getting Started with UMDF

To begin developing UMDF drivers, you'll need:

• The Windows Driver Kit (WDK)
• A supported version of Visual Studio
• Familiarity with C++ programming

The framework simplifies many aspects of driver development, including I/O handling, power management, and Plug and Play notifications.

Benefits of User-Mode Drivers

• Stability: Driver crashes in user mode do not bring down the entire operating system.
• Security: User-mode drivers operate with fewer privileges, enhancing system security.
• Simplified Debugging: Debugging user-mode code is generally easier than kernel-mode debugging.
• Faster Development: The UMDF object model and tools can accelerate the development process.

Further Resources

Explore the following sections for detailed information:

• Introduction to UMDF
• Getting Started with UMDF Drivers
• UMDF Driver Samples
• UMDF API Reference

Example: Basic Driver Structure

A minimal UMDF driver typically involves:

// DriverEntry function
NTSTATUS DriverEntry(
    _In_ PDRIVER_OBJECT  DriverObject,
    _In_ PUNICODE_STRING RegistryPath
    );

// Callback for driver initialization
HRESULT STDMETHODCALLTYPE
OnDriverInitialized(
    _In_ IWDFDriver* WdfDriver
    );
            

UMDF Versions

UMDF has evolved over different Windows versions. Ensure you are aware of the UMDF version you are targeting for compatibility and feature sets.

• UMDF 1.x: Primarily for Windows Vista and Windows 7.
• UMDF 2.x: For Windows 8 and later, offering enhanced features and modern programming practices.

Key UMDF APIs