A Critical Analysis of the Windows mLAN Driver Supervisor: Prof. Foss By: Shaun Miles

Overview mLAN system WDM DriverStudio Framework Object model IEEE 1394 IEC 61883 WDM DriverStudio Framework Object model IOCTL analysis Conclusion and Questions

mLAN

mLAN cont. Bus manages itself – no server PC is useful tool – connection management Application suit Driver makes PC look like mLAN device

FireWire – IEEE 1394 Flexible serial bus Fast – good for real time multimedia Control and Status Register architecture Standardises offset locations Node – addressable entity

Asynchronous or Isochronous Asynchronous – control packets Data integrity Any time arrival Isochronous – streaming packets Continuous stream CIP – IEC 61883 Ideal for real-time systems

IEC 61883.6 High level streaming standard Audio and music data transmission Based on mLAN specification Common isochronous packet – CIP AM824 8 bit label 24 bit audio/music data

Why study the driver? To understand the driver Platform to investigate mLAN potential Model driver for future extensions Audio/video extension?

Windows Driver Model Kernel-mode vs user-mode drivers All kernel-mode drivers – WDM drivers Supports PnP – device management Driver – communication pathway – I/O Layered architecture – driver stack

IO request packet Further specifies the type of request within the major category All IRPs have a major function code Categorises type of request Target device object of the I/O request Specifies IOCTL code if has major function code of IRP_MJ_DEVICE_ CONTROL

I/O Control code Means for driver responding to IO request Custom codes for special drivers – mLAN Definable codes with handler routine Communication pathway Contained in IRP – IO request packet Use DeviceIoControl IOCTL code Handle to device - GUID Input/output buffer

DriverEntry AddDevice IRP Handler User-mode space Application Ah, a new device This is the driver to load WIN32 API I/O Manger The kernel PnP Manger System Registry Object Manger – system addressable memory Driver object IRP Device Object DriverEntry AddDevice IRP Handler New Device!!

DriverStudio Driver development tool C++ class library framework Utility classes Forms skeleton, backbone of driver Encapsulates essential driver features Used by mLAN

mLAN driver object model

Kernel Streaming Minidriver Stream Minidriver Filter driver Controls adapter Stream Adapter Controls stream Controls hardware Stream Data processing of media stream

IOCTL code handling

mLAN IOCTL codes Grouped by underlying functionality IEEE 1394 asynchronous requests IEEE 1394 isochronous streaming IEC 61883 ASIO – Audio Streaming Input Output WDM Streaming (KS)

WDM Streaming (KS) Inter-driver communication KS Minidriver to mLAN

ASIO Implements ASIO driver functionality Overrides ASIO classes Used by applications for audio record and playback

Asynchronous IEEE 1394 Asynchronous communication with bus via Firewire bus driver Allocate/deallocate bus resources Channel Bandwidth Address range Driver state information

Isochronous IEEE 1394 Allocate/deallocate stream resource Start stream creates WDM minidriver to control stream Make several requests to Firewire driver to service initial request

61883 Uses 61883 protocol driver Formatting of stream data Used for plug modelling and connectivity Plug – input/output Start/end point of stream

Conclusion Driver is clearly structured Modules based on functionality Compilation problems due to incompatability issues Analysis done manually, time consuming and messy Missed out on powerful debugging tool

Questions? Thank you