Using chained MDLs can boost performance during data transfers because it avoids double buffering. This allows the transfer buffer to be segmented in physical memory hence removing restrictions on the number, size, and alignment of buffers. For more information, see How to Open and Close Static Streams in a USB Bulk Endpoint.Ī client driver can specify the payload in a chain of MDLs instead of a contiguous buffer. After streams have been opened, the client driver can perform data transfers to and from specific streams. The Windows Driver Kit (WDK) for Windows 8 provides new device driver interfaces (DDIs) that allow a client driver to can open up to 255 streams in a bulk endpoint. Streams provide the client driver with the ability to perform multiple data transfers to a single bulk endpoint. Some of features are configurable by the client driver. The USB driver stack for USB 3.0 devices supports many new features. To see an architectural block diagram of the USB driver stack and a brief description of the new drivers, see USB 3.0 Driver Stack Architecture. The new driver stack maintains compatibility with the existing client drivers that were built and tested on earlier versions of the Windows operating system. The new drivers are based on Kernel Mode Driver Framework (KMDF) and implement features defined in the USB 3.0 specification. The new stack includes drivers that are loaded by Windows when a USB 3.0 device is attached to an xHCI host controller. Windows 8 provides a new USB driver stack to support USB 3.0 devices. New USB-specific failure messages in Device Managerįor information about new features in USB in general, see New for USB Drivers.
Enhanced debugging and diagnostic capabilities.New Visual Studio templates for USB client drivers (*New for Beta).New User Mode I/O Control Requests for USB 3.0 Hubs.New Routines for Allocating and Building URBs.Client contract version for USB client drivers.This topic summarizes the new features and improvements for Universal Serial Bus (USB) client drivers in Windows 8.
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