Portable Device Drivers
This section provides information and guidance on developing drivers for portable devices on the Windows platform. Portable devices encompass a wide range of peripherals that can be connected and disconnected from a host system, including but not limited to:
- USB flash drives and external hard drives
- Digital cameras and media players
- Smartphones and tablets
- Bluetooth devices
- Printers and scanners
Developing drivers for these devices often involves understanding specific Windows driver models and frameworks. The primary frameworks and models relevant to portable device drivers include:
Windows Driver Frameworks (WDF)
The Windows Driver Frameworks (WDF) provide a more streamlined and object-oriented approach to driver development compared to the older Windows Driver Model (WDM). WDF offers two frameworks:
- Kernel-Mode Driver Framework (KMDF): For developing kernel-mode drivers. It simplifies common driver tasks and reduces the amount of boilerplate code required.
- User-Mode Driver Framework (UMDF): For developing user-mode drivers. This is particularly useful for devices where stability and security are paramount, or for devices that are simpler to implement in user mode.
WDF is the recommended approach for most new driver development. It provides built-in handling for many common driver operations, allowing developers to focus on device-specific functionality.
Windows Driver Model (WDM)
While WDF is preferred, understanding WDM is still valuable, especially when working with legacy drivers or in specific scenarios. WDM is the foundational driver model in Windows. It uses a set of callback functions and I/O Request Packets (IRPs) to manage communication between the operating system and hardware.
Key concepts in WDM include:
- Device Objects: Represent hardware devices.
- Driver Objects: Represent the driver itself.
- I/O Request Packets (IRPs): Structures that carry I/O requests and their parameters.
- I/O Stack Locations: Each driver in a device stack has an I/O stack location within an IRP.
For portable devices, specific WDM models might be used, such as the USB device driver model or the Mass Storage Device Class driver.
Common Device Classes and Protocols
When developing portable device drivers, you will often interact with standard device classes and protocols. Some common ones include:
- USB (Universal Serial Bus): A widely used interface for connecting peripherals. Drivers will need to conform to USB specifications and use the Windows USB driver stack.
- MTP (Media Transfer Protocol) / PTP (Picture Transfer Protocol): Protocols used for transferring media files, common for cameras and media players.
- Mass Storage Class: For devices that emulate storage, like USB drives and external HDDs.
- HID (Human Interface Device): For input devices like keyboards, mice, and game controllers.
Key Resources
Here are some essential resources for developing portable device drivers:
Note on UMDF 2.0 and KMDF
UMDF 2.0 is designed to be very similar to KMDF, sharing much of the same API design. This makes it easier for developers to switch between developing kernel-mode and user-mode drivers. For new development, it is generally recommended to use WDF (either KMDF or UMDF) over direct WDM programming.
Important Considerations
When developing drivers for portable devices, always consider:
- Device Power Management: Ensure your driver correctly handles device power states to conserve energy.
- Plug and Play: Implement proper handling for devices being connected and disconnected.
- Security: For user-mode drivers, adhere to security best practices to protect the system.
- Error Handling: Robust error handling is crucial for stable operation.