User-Mode Driver Framework: Introduction And Overview Jeffrey Copeland

User-Mode Driver Framework: Introduction And Overview Jeffrey Copeland Program Manager Windows Device Experience Group Microsoft Corporation

Introduction What this talk covers Overview Future directions Intended audience Other sessions of interest Following talk on UMDF architecture Tomorrow’s UMDF lab session and Q&A

Why User Mode? High-quality drivers are difficult to write Crash statistics prove this User mode drivers are “safer” Some Windows driver models already live in user space Printers, audio, imaging UMDF is the general purpose user space model

A Quick Word About WDF Windows Driver Foundation is the successor to WDM WDM is deprecated New Kernel Mode and User Mode driver frameworks – KMDF and UMDF These fit into the driver life cycle Driver kit Test tools Installation tools

How To Expose A Device You can use a stand-alone application with a DLL to directly access the device Non-shared device You can write a service to share the device You can write a driver to use normal I/O Not WDM – Old technology UMDF? KMDF?

UMDF versus KMDF When to use UMDF Protocol buses – USB, 1394, IP Software-only drivers – Filters, virtual ports You must use KMDF if you need More stringent timing requirements Hardware access – DMA, interrupts Kernel-mode clients or access to kernel data Hybrid-model drivers

Where Can You Use UMDF?

Where Can You Use UMDF? Today Device classes: Cell phones, media players, cameras, other portable devices RFID, NFC Biometric and other security devices Devices which currently are accessed directly through applications or services Buses: USB – through WinUSB I/O Target IP – sockets through WinSock Bluetooth – RFCOMM or WinSock Any bus that provides user-mode access

Where Can You Use UMDF? Factors to consider today Can the device use a UMDF class driver? Can the driver access device over that bus? Does the kernel need to access the device? Future Working with device teams to drive availability Need Feedback to help set priorities

UMDF Developers Existing driver developers Who want to move drivers to user space Who already have the “driver mindset” New driver developers Coming from application development Who need to provide device support Who are learning new skills Anyone who wants to Build a driver without a lot of development overhead Reduce the risks associated with traditional drivers Stop causing blue screens

UMDF Developers UMDF developers come from two directions Application Programmers Kernel Programmers The application programmer still needs to understand something about low-level system facilities

UMDF Structure UMDF driver Framework loads driver Driver then creates structure and specifies callbacks and event handlers C and “COM-lite” For more details stay for the UMDF technical talk

UMDF Structure Driver Manager User Kernel UM UM driver driver Framework Framework Host Process Reflector Kernel Driver . Kernel Driver Device Stack CoInstaller

Performance Test system: hyper-threaded 3.2Ghz P4, 1GB Performance sample available Null driver Raw throughput up to 4 gigabits/sec Buffer size “sweet spot” 64-128 Kb Win32 I/O target – USB hard drive Throughput 170 megabits/sec CPU usage 11% UMDF can easily saturate a USB 2.0 bus’s maximum speed of 480 megabits/sec No adverse performance impact in existing UMDF drivers

Why To Use UMDF Single WDF model – Both KM and UM Quicker development time PnP/Power boilerplate is encapsulated Debugging in user mode is easier! Crashes in testing don’t force a reboot Access to user-mode services Shallow learning curve for application developers

Why To Use UMDF Improved stability UM drivers are isolated from each other Kernel is isolated from UM drivers A step toward general driver isolation Increased security Compromised driver can’t crash the system But may still compromise device data Recoverability Driver can recover or be restarted after a crash without a blue screen

Why To Use UMDF “Writing a UMDF driver is relatively easy once you get your hands around using COM-lite. Perhaps best of all, when your driver crashes while you're debugging it, the system stays running.” – Mark Cariddi, OSR – The NT Insider “Plug-and-play and power management are easier to use. Queues and I/O targets are straight-forward, and they have what I needed already.” – Janet Schneider, Microsoft Storage Team

Why To Use UMDF “UMDF allows me to focus on the functional implementation, rather than the intricacies of driver development. The best part about UMDF drivers is that a crash doesn't cause a blue screen.” – Dan Polivy, Microsoft SideShow developer

Smart Card As A Case Study Rewrite of an existing WDM driver Developer had driver knowledge, but not WDM or WDF experience 2 months to come up to speed on WDF and the existing driver 1½ months to re-implement the driver in UMDF

Smart Card As A Case Study 35% code reduction – measured in source bytes 4000 lines of PnP code removed Functionally identical driver with less code, higher robustness, more maintainability Code now “feels simpler” Results are similar to experience porting WDM network and modem drivers to KMDF

Smart Card Janet Schneider Storage Driver developer Microsoft

SideShow Dan Polivy Mobile PC developer Microsoft

UMDF Availability Beta UMDF available For Windows Vista now For Windows XP next week As update to the Beta 2 Windows Driver Kit Available for Windows Server 2003 at same time as release for Windows Server codenamed "Longhorn"

UMDF In The Future New driver models will move to WDF New features in UMDF We’re in post-Windows Vista planning now We need your feedback Help us decide Possible convergence on OS platforms Windows Mobile

Resources Join the WDF Beta Program https://connect.microsoft.com/availableprograms.aspx Sign in with your Microsoft Passport, and join the WDK/WDF beta Participate in the UMDF newsgroup microsoft.beta.windows.driverfoundation.umdf at betanews.microsoft.com WHDC web site DevCon 2005 presentations http://www.microsoft.com/whdc/driver/wdf/UMDF.mspx Join us for the UMDF lab and Q&A Wednesday Lab requires a Design Preview Agreement Ask the Experts Tuesday evening

Call To Action Install the Windows Driver Kit Try UMDF for your driver projects Send us feedback! We want to know how to make the framework better We want to know what features are still missing Respond to our survey UMDFFDBK @ microsoft.com

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