WDF: The Modern and Simplified Way of Developing Windows Drivers

- What is the book "Developing Drivers With The Windows Driver Foundation (Developer Reference)" and what it covers - How to download the book and the prerequisites for reading it H2: Overview of WDF - The benefits of using WDF over traditional driver models - The architecture and components of WDF - The types of drivers that can be developed with WDF: User-Mode Driver Framework (UMDF) and Kernel-Mode Driver Framework (KMDF) H3: UMDF Drivers - The advantages and limitations of UMDF drivers - The structure and features of UMDF drivers - The tools and steps for creating, building, testing, and debugging UMDF drivers H3: KMDF Drivers - The advantages and limitations of KMDF drivers - The structure and features of KMDF drivers - The tools and steps for creating, building, testing, and debugging KMDF drivers H2: WDF Concepts and Techniques - The common concepts and techniques that apply to both UMDF and KMDF drivers - How to use WDF objects, callbacks, events, requests, queues, timers, synchronization, power management, plug and play, etc. - How to handle errors and exceptions in WDF drivers H2: WDF Best Practices and Tips - The best practices and tips for writing high-quality WDF drivers that are reliable, secure, efficient, and compatible - How to use WDF verifier, static analysis, tracing, logging, testing tools, etc. - How to troubleshoot common problems and issues in WDF drivers H1: Conclusion - A summary of the main points of the article - A call to action for the readers to download the book and start developing their own WDF drivers # Article with HTML formatting Introduction

If you are a Windows driver developer or want to become one, you might have heard of Windows Driver Foundation (WDF). WDF is a set of libraries that simplify the process of writing device drivers for Windows. It provides a consistent and modern programming model that abstracts away the complexities of the underlying operating system.

Developing Drivers With The Windows Driver Foundation (Developer Reference) Download

But how do you learn WDF? Where do you start? What are the best practices and tips for developing WDF drivers? If you are looking for answers to these questions, you might want to check out the book "Developing Drivers With The Windows Driver Foundation (Developer Reference)" by Penny Orwick and Guy Smith.

This book is a comprehensive guide that covers everything you need to know about WDF. It explains the concepts, techniques, tools, and examples of developing both user-mode and kernel-mode drivers with WDF. It also provides valuable insights from the experts who designed and implemented WDF.

To download this book, you can visit this link. You will need a Microsoft account to access it. You will also need Visual Studio 2022 and Windows Driver Kit (WDK) 11 to follow along with the code samples in the book. These are free tools that you can download from Microsoft's website.

Overview of WDF

Before we dive into the details of developing drivers with WDF, let's first get an overview of what WDF is and why it is useful for driver development.

WDF is a set of libraries that provide a consistent and modern programming model for writing device drivers for Windows. It was introduced in 2006 as a replacement for the traditional driver models such as Windows Driver Model (WDM) and Windows NT Driver Model (NTDM).

The main benefits of using WDF over traditional driver models are:

• It simplifies driver development by providing high-level abstractions and common services that handle most of the driver logic.

• It improves driver quality by enforcing best practices and reducing the chances of errors and bugs.

• It enhances driver compatibility by supporting various versions of Windows and different types of devices.

• It increases driver performance by optimizing resource usage and minimizing overhead.

The architecture of WDF consists of two main components: the framework library and the framework runtime. The framework library is a set of header files and libraries that define the WDF programming interface. The framework runtime is a set of system components that implement the WDF functionality and interact with the operating system.

The types of drivers that can be developed with WDF are:

• User-Mode Driver Framework (UMDF) drivers: These are drivers that run in user mode, which is a less privileged and more secure mode than kernel mode. UMDF drivers are suitable for devices that do not require direct access to hardware or system resources, such as USB devices, Bluetooth devices, audio devices, etc.

• Kernel-Mode Driver Framework (KMDF) drivers: These are drivers that run in kernel mode, which is a more privileged and less secure mode than user mode. KMDF drivers are suitable for devices that require direct access to hardware or system resources, such as PCI devices, storage devices, network devices, etc.

UMDF Drivers

UMDF drivers are drivers that run in user mode, which is a less privileged and more secure mode than kernel mode. UMDF drivers have several advantages over kernel-mode drivers, such as:

• They are easier to develop, debug, and test, as they use the same tools and techniques as regular user-mode applications.

• They are safer to run, as they are isolated from the kernel and other drivers, and cannot cause system crashes or corruption.

• They are more portable, as they can run on different versions of Windows and different processor architectures without recompilation.

However, UMDF drivers also have some limitations, such as:

• They have higher latency and lower performance than kernel-mode drivers, as they incur additional overhead for context switching and communication with the kernel.

• They have limited access to hardware and system resources, as they rely on the kernel to perform low-level operations such as memory mapping, interrupt handling, DMA transfer, etc.

• They have stricter security requirements, as they need to comply with the user-mode security policies and permissions.

The structure of a UMDF driver consists of three main components: the driver object, the device object, and the queue object. The driver object represents the driver itself and manages its initialization and cleanup. The device object represents a single instance of the device that the driver controls and handles its configuration and events. The queue object represents a queue of I/O requests that the driver receives from the device or the application and processes them accordingly.

The features of a UMDF driver include:

• WDF objects: These are C++ objects that encapsulate various aspects of driver functionality, such as callbacks, events, requests, queues, timers, synchronization, power management, plug and play, etc. WDF objects provide a consistent and easy-to-use interface for driver development.

• COM interfaces: These are interfaces that define the communication between the driver and the framework runtime. COM interfaces allow the driver to access various services provided by the framework runtime, such as tracing, logging, testing tools, etc.

• WPP tracing: This is a mechanism that allows the driver to generate trace messages for debugging and diagnostic purposes. WPP tracing uses a preprocessor macro to insert trace statements in the driver code that can be enabled or disabled at compile time or run time.

The tools and steps for creating, building, testing, and debugging a UMDF driver are:

• Visual Studio 2022: This is an integrated development environment (IDE) that provides a graphical user interface for writing, editing, compiling, linking, debugging, and testing code. Visual Studio 2022 supports UMDF driver development with templates, wizards, project settings, code analysis, etc.

• Windows Driver Kit (WDK) 11: This is a set of tools and libraries that provide the necessary components for developing Windows drivers. WDK 11 includes the WDF headers and libraries, the WDK Test Target Setup MSI package, the WDK Test Framework, etc.

• To create a UMDF driver project in Visual Studio 2022, you need to select File > New > Project > Visual C++ > Windows Drivers > User Mode Driver (UMDF V2). You can then choose a template for your driver type (such as Empty UMDF Driver or USB UMDF Driver Template) and enter the required information for your driver project.

• To build your UMDF driver project in Visual Studio 2022, you need to select Build > Build Solution from the menu. You can see the build output in the Output window.

• To test and debug your UMDF driver project in Visual Studio 2022, you need to deploy and install your driver on a target computer that is connected to the host computer via a network or a USB cable. You also need to configure the target computer for driver deployment and testing. You can then use Visual Studio 2022 to start a debugging session and set breakpoints, watch variables, step through code, etc.

KMDF Drivers

KMDF drivers are drivers that run in kernel mode, which is a more privileged and less secure mode than user mode. KMDF drivers have several advantages over user-mode drivers, such as:

• They have lower latency and higher performance than user-mode drivers, as they have direct access to hardware and system resources.

• They have more flexibility and functionality than user-mode drivers, as they can perform low-level operations such as memory mapping, interrupt handling, DMA transfer, etc.

• They have more compatibility and stability than user-mode drivers, as they are less affected by changes in the user-mode environment.

However, KMDF drivers also have some challenges, such as:

• They are harder to develop, debug, and test, as they use different tools and techniques than regular kernel-mode applications.

• They are riskier to run, as they share the same address space with the kernel and other drivers, and can cause system crashes or corruption if they contain errors or bugs.

• They have stricter requirements and guidelines than user-mode drivers, as they need to comply with the kernel-mode security policies and conventions.

The structure of a KMDF driver consists of three main components: the driver object, the device object, and the queue object. The driver object represents the driver itself and manages its initialization and cleanup. The device object represents a single instance of the device that the driver controls and handles its configuration and events. The queue object represents a queue of I/O requests that the driver receives from the device or the application and processes them accordingly.

The features of a KMDF driver include:

• WDF objects: These are C++ objects that encapsulate various aspects of driver functionality, such as callbacks, events, requests, queues, timers, synchronization, power management, plug and play, etc. WDF objects provide a consistent and easy-to-use interface for driver development.

• WDM interfaces: These are interfaces that define the communication between the driver and the operating system. WDM interfaces allow the driver to access various services provided by the operating system, such as registry access, I/O manager, configuration manager, etc.

• WPP tracing: This is a mechanism that allows the driver to generate trace messages for debugging and diagnostic purposes. WPP tracing uses a preprocessor macro to insert trace statements in the driver code that can be enabled or disabled at compile time or run time.

The tools and steps for creating, building, testing, and debugging a KMDF driver are:

• Visual Studio 2022: This is an integrated development environment (IDE) that provides a graphical user interface for writing, editing, compiling, linking, debugging, and testing code. Visual Studio 2022 supports KMDF driver development with templates, wizards, project settings, code analysis, etc.

• Windows Driver Kit (WDK) 11: This is a set of tools and libraries that provide the necessary components for developing Windows drivers. WDK 11 includes the WDF headers and libraries, the WDK Test Target Setup MSI package, the WDK Test Framework, etc.

• To create a KMDF driver project in Visual Studio 2022, you need to select File > New > Project > Visual C++ > Windows Drivers > Kernel Mode Driver (KMDF). You can then choose a template for your driver type (such as Empty KMDF Driver or USB KMDF Driver) and enter the required information for your driver project.

• To build your KMDF driver project in Visual Studio 2022, you need to select Build > Build Solution from the menu. You can see the build output in the Output window.

• To test and debug your KMDF driver project in Visual Studio 2022, you need to deploy and install your driver on a target computer that is connected to the host computer via a network or a USB cable. You also need to configure the target computer for driver deployment and testing. You can then use Visual Studio 2022 to start a debugging session and set breakpoints, watch variables, step through code, etc.

WDF Concepts and Techniques

Now that we have an overview of UMDF and KMDF drivers, let's explore some of the common concepts and techniques that apply to both types of drivers. These concepts and techniques are based on the WDF object model, which defines how drivers interact with the framework and the operating system.

Some of the key concepts and techniques are:

• WDF objects: These are C++ objects that encapsulate various aspects of driver functionality, such as callbacks, events, requests, queues, timers, synchronization, power management, plug and play, etc. WDF objects provide a consistent and easy-to-use interface for driver development. Each WDF object has a type (such as WDFDEVICE or WDFQUEUE), an handle (such as WDFDEVICE_HANDLE or WDFQUEUE_HANDLE), and a set of properties and methods that define its behavior and state.

• Callbacks: These are functions that are implemented by the driver and invoked by the framework when certain events occur. Callbacks enable the driver to respond to device or system-related events that are reported by the framework. For example, a driver can implement a EvtDevicePrepareHardware callback to initialize the device hardware when it is powered on.

• Events: These are notifications that are sent by the framework to the driver when certain conditions are met. Events inform the driver about changes in the device or system state that may affect its operation. For example, a driver can receive a WdfDeviceD0Entry event when the device enters the working power state (D0).

• Requests: These are objects that represent I/O operations that are initiated by an application or a device. Requests contain information about the type, parameters, status, and result of an I/O operation. Requests are handled by queues, which manage their processing and completion.

• Queues: These are objects that store and manage requests that are received by the driver. Queues enable the driver to control how requests are processed and completed. For example, a driver can create multiple queues for different types of requests (such as read or write) and assign different priorities and concurrency levels to them.

• Timers: These are objects that enable the driver to perform periodic or one-time actions after a specified interval of time. Timers can be used for various purposes, such as monitoring device status, implementing timeouts, generating events, etc.

• Synchronization: This is a mechanism that enables the driver to coordinate access to shared resources among multiple threads or processors. Synchronization prevents data corruption and race conditions that may occur when concurrent operations access the same resource. For example, a driver can use locks or spinlocks to protect critical sections of code that access shared data structures.

• Power management: This is a feature that enables the driver to conserve power by adjusting the device in a low-power state when it is powered off.

• Plug and play: This is a feature that enables the driver to support dynamic device configuration and removal. Plug and play allows the driver to detect and respond to changes in the device or system state that may affect its operation. For example, a driver can implement a EvtDeviceSurpriseRemoval callback to handle the case when the device is removed unexpectedly.

• Error handling: This is a mechanism that enables the driver to report and handle errors and exceptions that may occur during driver operation. Error handling can help prevent system crashes and data corruption and improve driver reliability. For example, a driver can use WdfVerifierDbgBreakPoint to break into the debugger when an error occurs.

WDF Best Practices and Tips

Finally, let's look at some of the best practices and tips for writing high-quality WDF drivers that are reliable, secure, efficient, and compatible. These best practices and tips are based on the experience and recommendations of the WDF experts and developers.

Some of the best practices and tips are:

• Use WDF verifier: This is a tool that monitors the driver's interaction with the framework and detects any violations of WDF rules or guidelines. WDF verifier can help identify and fix common errors and bugs in WDF drivers. To enable WDF verifier, you can use the Verifier.exe command-line tool or the Driver Verifier Manager graphical user interface.

• Use static analysis: This is a feature that analyzes the driver's source code and detects any potential errors or defects. Static analysis can help improve the driver's code quality and security. To enable static analysis, you can use the /analyze compiler option or the Code Analysis window in Visual Studio 2022.

• Use tracing and logging: These are mechanisms that enable the driver to generate diagnostic messages for debugging and troubleshooting purposes. Tracing and logging can help monitor the driver's behavior and performance. To use tracing, you can use WPP tracing or Event Tracing for Windows (ETW). To use logging, you can use WDF logging or Windows Hardware Error Architecture (WHEA).

• Use testing tools: These are tools that enable the driver to verify its functionality and compatibility with various devices and systems. Testing tools can help ensure the driver's correctness and robustness. To use testing tools, you can use Windows Hardware Lab Kit (HLK), Windows Hardware Compatibility Program (HCP), Driver Test Framework (DTF), etc.

• Troubleshoot common problems: These are problems that may occur during driver development or deployment and cause errors or failures. Troubleshooting common problems can help resolve issues quickly and effectively. To troubleshoot common problems, you can use debugging tools, error codes, documentation, forums, etc.

Conclusion

In this article, we have learned how to write a Universal Windows driver using Kernel-Mode Driver Framework (KMDF) or User-Mode Driver Framework (UMDF). We have covered the following topics:

• What is Windows Driver Foundation (WDF) and why it is important for driver development.

• What is the book "Developing Drivers With The Windows Driver Foundation (Developer Reference)" and what it covers.

• How to download the book and the prerequisites for reading it.

How to create, build, test, and debug UMDF or KMDF drivers using Visual Studio 2022 and Windows Driver Kit (