Transcript Windows Driver Foundation: Introduction Murtuza Naguthanawala Program Manager Networking And Devices Murtuzan @ microsoft.com Microsoft Corporation.

Windows Driver Foundation:
Introduction
Murtuza Naguthanawala
Program Manager
Networking And Devices
Murtuzan @ microsoft.com
Microsoft Corporation
Session Goals
Attendees should leave this session with
the following:
A better understanding of Windows Driver
Foundation (WDF)
Know how to use WDF
Session Outline
Overview
Limitations of the current driver models
Windows Driver Foundation
Model
Kernel mode framework
User mode framework
Static verification tools
Windows Driver Model (WDM): Overview
Generic Model – WDM
Specific driver models – Miniports for popular
device classes
WDM Features
Asynchronous and packet-based IO
Layering of drivers
Dynamic loading and unloading of drivers
Plug and Play
Power management
Large device coverage
Flexible
Low-level high-performance interfaces
Current Windows Driver Models
Device/Driver Classes
Current Model
Display Adapters
Video port
Storage Adapters (SCSI & ATA)
Scsiport, Storport, ATAport,
Network Adapters
NDIS
Video Capture
AvStream
Audio Adapters
AVStream, PortCls
File System filters
FS Mini filter
Printers
UniDrv
Scanners,Cameras
WIA
PCI, PC Card, generic filter drivers
WDM
Modems, Cable Modem
WDM & NDIS WDM
Biometric Devices
WDM
Smart Card Devices
WDM
Keyboard/Mouse Filters
WDM
Legacy Devices (Serial, Parallel)
WDM
Portable Media Players
WMDM
UPnP & Network Connected Devices,
Cell Phones
No support
USB, 1394, Bluetooth, SD devices
WDM (kernel), no support (user)
Others
WDM
Limitations With Current Driver Models
Generic driver model is too complex
Poor DDI design
Inconsistent miniport models
The current approach requires many drivers to
use kernel mode
User Mode could be an option
Does not allow extension and future growth
Limitations: Generic Driver Model
Lots of hard-to-understand boiler plate code
Plug and Play and Power Management (PnP/PM)
have complicated state machines
Never coherently described and cannot be well
expressed in documentation
Not easily testable
Asynchronous I/O & Cancellation
Synchronization
Documentation is not adequate
End user experience
Drivers are the #1 cause of blue screens in the system
Limitations: DDI Design
DDIs directly exposed by kernel
Key OS data structures exposed to drivers
Hard to version
Even the OS Version Query DDI is OS
version dependent!
Subtle changes in kernel break drivers
e.g., Changing the default pool size
Cannot make improvements to the kernel easily
Only C is supported
Limitations: Inconsistent Driver Models
Inconsistent interfaces
Hard to transfer expertise from one device class
to another
Not flexible enough to keep up with
HW innovation
Device classes appear on multiple buses
Duplication of testing and documentation efforts
Tools/technologies cannot be leveraged across
all models
e.g., Driver Verifier, PREfast
Limitations: Kernel mode required
Not every device needs interrupts, DMA, register
access, has strict timing requirements etc.
Many USB device drivers could be written in
user mode
Lower reliability
Kernel-mode drivers can crash the system
Driver Model Design Goals
Consistent set of DDIs
DDIs not tied to core OS components
Language agnostic
Supports verification by static analysis tools
Diagnosability
Supports driver isolation
Bugs in a driver do not bring down system or other driversDDIs
classified into two categories
Base model: Supports base functionality across all device classes,
including
PnP, PM, Async I/O, Queues, DMA, hardware access
Synchronization, Communication with drivers
Device class extension
Derives from base model; only adds device specific functionality
e.g., Device I/O Control processing
Driver Model for Device Class Support
Base Model
(PnP/PM/IO/Synch)
Device Specific
Extension (Packet,
Device I/O Control,
CDB processing)
Driver
How To Get to Driver Model?
Our plan is to get to the driver model
goals incrementally
Keep supporting existing driver models
WDM will continue to be supported
Existing mini-port models will continue to be supported
Define the basic model
Define a consistent way to extend the
basic model
Ensure that newer device classes use the
new approach
Windows Driver Foundation
Driver Model and Windows Drivers
Foundation
WDF becomes the base model
WDF
(PnP/PM/IO/Synch)
Device Specific
Extension (Packet,
Device I/O Control,
CDB processing)
Driver
Windows Driver Foundation- Experience
Windows Driver Foundation
WDF is the steppingstone to the ideal
driver model
WDF Contains
A Model
Multiple frameworks
Kernel Mode Framework
User Mode Framework
Static
Driver
Verifier
PREfast
WDF
Model
Verification Tools
Static Driver Verifier
PREfast for Drivers
Kernel
Mode
Framework
User Mode
Framework
Windows Driver Foundation - Goals
Simplicity: No harder than it needs to be to
accomplish a task
Fast time to market for drivers
Reduce crashes and blue screens generated by
drivers in the system
Provide complete driver development experience
Driver model
UMDF, KMDF
Develop,test and qualify
Built-in diagnosibility, tracing, verification tools
Logo programs for drivers
Deployment, Install and Maintain
Support versioning
Windows Driver Foundation: Model
One conceptual model to learn for all (both kernel and
user-mode) drivers
Model implies
Object model, object hierarchies, state machines
Does not refer to DDIs, data structures etc.
Note that a framework may only implement a subset of the
model
e.g., User mode framework will not implement support
for Interrupts
Supports rich and deep functionality (unlike WDM)
Intelligent defaulting
Allows implementation in many languages (C, C++)
Allows verification by static tools
Enables driver isolation using user mode driver framework
WDF Value Proposition
A quicker, cheaper and easier way of developing and
deploying your driver to market
Reduced chances that device driver is a cause of
system crash
Reduced support costs
Better diagnosability and debugging and logging support
Improved system stability and reliability
Higher quality drivers
Automated discovery of driver bugs via static tools
System robustness
Better system security
User mode tools like Visual Studio can be used for
development
Better power management
Consistent experience across pluggable devices
WDF Device Support Scope: Longhorn
Device Class / Driver Model
KMDF
UMDF
SDV
PFD
Modem, CD ROM devices,
Keyboard, Mouse
Yes
No
Yes
Yes
SCSI – StorPort
No
No
No
Yes
Display cards
No
No
No
Yes
Ethernet devices
No
No
No
Yes
DSL/Cable Modems
Yes
No
No
Yes
Video Capture devices (Webcams)
No
No
No
Yes
Anti-virus filters
No
No
Yes
Yes
Digital cameras/portable media
players/cell phones/PDAs etc
No
Yes
No
Yes
Printers
No
No
No
Yes
Scanners
No
No
No
Yes
Kernel Mode Driver Framework
Kernel Mode Driver Framework
Previously referred to as “Windows Driver Framework”
Implements the model in kernel mode
Built as a library on top of WDM
Supported from Windows 2000 and forward
Beta/Pre-release bits are available today
Object based
‘C’ only
Supports
PNP and Power
WMI
DMA
Requests and Queue
IO targets
Kernel Mode Driver Framework Status
Feature complete
e.g. Object Model, PnP/PM, I/O queues etc.
Beta bits are available through beta program
22 samples in the kit
Installs with Windows Server SP1 DDK
Current Windows codenamed “Longhorn” drivers
using KMDF
Universal audio bus driver
WinUSB
Monitor function driver
Internal MSFT test drivers
DDIs are open to refinement based on feedback
from the WDF beta program
Kernel Mode Driver Framework
Proof Points
Case Study: PCIDRV Sample
Metric
WDM
WDF
Comments
Line Count
13147
7271
Explicit registration of
granular event callbacks
add to the line count
LOC devoted to
PnP/PM
7991
1795
Almost 6000 lines of
code is eliminated
Locks
8
3
This is the most
important stat. This
explains the complexity
State variables
devoted to
PnP/PM
30
0
This explains that there
are fewer paths in the
driver and thus less
testing and complexity
This sample is written for the Intel E100B NIC Card. This is a WDM version
of a network driver. Both samples are in the DDK and are functionally
equivalent.
Case Study: Serial Sample
Metric
WDM
WDF
Comments
Line Count
24000
17000
Explicit registration
of granular event
callbacks add to the
line count
LOC devoted to PnP/PM
5000
2500
Locks & Synchronization Primitives
10
0
This is the most
important stat. This
explains the
complexity
State variables devoted to PnP/PM
53
0
There are fewer
paths in the driver
and hence less
complexity
WDF sample does not support multi-port serial (WDM sample supports it).
WDM stats exclude multi-port support serial code
Case Study: OSRUSBFX2 Sample
Metric
WDM
WDF
Comments
Line Count
16350
2300
Explicit registration
of granular event
callbacks add to the
line count
LOC devoted to PnP/PM
6700
742
742 includes code to
initialize the USB
Locks (6 Events, 3 SpinLocks)
9
0
This is the most
important stat. This
explains the
complexity
State variables devoted to PnP/PM
21
0
There are fewer
paths in the driver
and hence less
complexity
The WDM version of OSRUSBFx2 sample available on osronline.com and
the WDF version provided in the DDK are functionally equivalent.
User Mode Driver Framework
User Mode Driver Framework
Implements the model in user mode
Support for:
PnP/PM, Asynchronous I/O, layering
No support for:
Interrupts, DMA, access to hardware registers, client
address space etc.
Languages
C++
Fits within the Windows I/O model
Naming, security, discovery APIs remain the same
Applications write to Win32 APIs
Supports recovery from driver crashes increase system robustness
Kernel mode drivers CANNOT be stacked on top of user mode
drivers
Supported in Longhorn only
Down level support to Windows XP being evaluated
Kernel Mode/User Mode Feature
Comparison
When KMDF
DMA, Interrupt, requires use of non paged pool, strict timing requirements
Access to hardware
When UMDF
Software drivers, drivers that just need PNP and IO support
Devices on protocol bus (USB-based “Hello Kitty device”)
Feature
PnP/PM
Async I/O
Filter support
Recovery from failure
Languages
Interrupts, DMA etc
Driver Installation
KMDF
UMDF
Yes
Yes
Yes
No
C
Yes
Yes
Yes
Yes
Yes
Yes
C++
No
Yes
User Mode Driver Framework Status
WinHEC
Development platform is Windows Driver Kit (WDK)
Current Windows Team Clients
ActiveSync (Windows Mobile devices)
MTP (media players, cameras)
Aux display
Potential device classes
Cellular phones
Portable media players, Scanners, Cameras
Network connected devices
Any protocol bus (USB) based devices not related to input,
display, storage or networking
Devices that need PNP and IO support
Verification Tools
Verify that drivers follow interface specifications
Dynamic
Driver Verifier already built in to Windows
Static
PREfast
Verifies rules within the scope of a function
Many WDM specific rules (IRQL checking) have been added
Static Driver Verifier
Uses formal checking technology
Examines the entire code path in the driver
Currently focused on verifying WDM rules
WDF interfaces designed to be easily verified by
these tools
Works on both Kernel and User mode driver frameworks
Summary
WDF is the new driver model for driver
development
It addresses key IHV/OEM concerns
Fast time to market, technical support costs, learning curve etc
KMDF backward compatible up to Windows 2000
It intends to reduce customer pain points
WDF intends to provides a complete driver
development experience
Aims to reduce OS crashes due to poorlywritten drivers
WDF targets production of high quality of drivers
for Windows
Call to Action
Work together with us to make WDF successful
Consider WDF for any Windows driver development project
Join WDF beta program
Use the guest account (Guest ID: Guest4WDF) on
http://beta.microsoft.com to sign up for beta
Contact info
Email
Kmdffdbk @ microsoft.com
Umdffdbk @ microsoft.com
Pfdfdbk @ microsoft.com
Sdvfdbk @ microsoft.com
-
Kernel Mode Driver Framework
User Mode Driver Framework
PREfast for Drivers
Static Driver Verifier
Newsgroups
microsoft.beta.windows.driverfoundation
microsoft.beta.windows.driverfoundation.announcements
Web Resources
http://www.microsoft.com/whdc/driver/wdf/default.mspx
http://www.microsoft.com/whdc/DevTools/ddk/default.mspx
Community Resources
Windows Hardware & Driver Central (WHDC)
www.microsoft.com/whdc/default.mspx
Technical Communities
www.microsoft.com/communities/products/default.mspx
Non-Microsoft Community Sites
www.microsoft.com/communities/related/default.mspx
Microsoft Public Newsgroups
www.microsoft.com/communities/newsgroups
Technical Chats and Webcasts
www.microsoft.com/communities/chats/default.mspx
www.microsoft.com/webcasts
Microsoft Blogs
www.microsoft.com/communities/blogs
© 2005 Microsoft Corporation. All rights reserved.
This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.