Basics

Courtesy: http://en.wikipedia.org/wiki/Device_driver

Device Driver
- an extension of OS
- a "bridge" between hardware and applications (and Operating Systems)
- abstracted into logical and physical layers (and hence can be categorized as Logical Device Drivers (LDD) and Physical Device Drivers (PDD))
- LDD written by OS vendors where as PDD written by device vendors

An attempt by Microsoft to reduce system instability due to poorly written device drivers by creating a new framework for driver development called "WINDOWS DRIVER FOUNDATION (WDF)".

WDF - includes UMDF (User Mode Driver Framework) and KMDF (Kernel Mode driver Framework)

1. UMDF - implements a message-based protocol for communicating with their devices - as user mode drivers.
- any malfunction on these drivers does not cause any system instability

2. KMDF - allows development of kernel-mode device drivers, but attempts 2 provide std implementations functions that are well known to cause probs, including cancellation of IO operations, power management, and PnP device support

Device Drivers on Windows, can run on *both Ring 0 and Ring 3*