Recommendations for Continua USB PHDC Device Driver ...

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Recommendations for Continua USB PHDC
Device Driver Interoperability
March 2012
Executive Summary
This paper defines the Continua Health Alliance ® position on USB PHDC driver interoperability as it pertains
to Continua Design Guidelines 1.5. Potential problems with interoperability related to Windows * USB PHDC
device drivers are evaluated and recommendations that developers of PAN Managers for USB transport can
implement. Based on the analysis of these problems, recommendations for a Continua strategy is
discussed and the handling of generic Windows drivers based on WinUSB and LibUSB are provided.
This paper does not cover application level interoperability beyond the development of USB drivers.
Recommendations for Continua USB PHDC Device Driver Interoperability
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Contents
Executive Summary ..................................................................... 1
Introduction ................................................................................ 2
Background and Description of USB PHDC Drivers Issues .................. 3
Presentation of Continua USB Devices to User ............................. 4
Figure 1 Windows Device Manager ................................................. 4
Interoperability of USB PHDC Managers ...................................... 5
Generic USB Drivers ................................................................. 6
Figure 2 USB PHDC Driver from Generic USB Driver ......................... 6
Figure 3 Interface GUID ................................................................ 6
Native OS Driver...................................................................... 7
Integration of New Continua Devices with Existing Managers ........ 8
Conclusions and Recommendations ................................................ 9
Step I: Initial Approach ............................................................ 9
Step II: OS Vendor Certified Device INF File................................ 9
Step III: OS Vendor Certified Universal INF File ........................... 9
The Best: Native OS Driver ....................................................... 9
Continua Recommendation for Use of Generic USB Drivers .............. 10
Glossary ............................................................................... 11
References ............................................................................ 11
Legal .................................................................................... 11
Introduction
Continua Health Alliance strives to ensure interoperability for all Continua certified devices. USB devices
are prevalent in the healthcare realm and must adhere to these interoperability requirements. This paper
provides the background and description of issues in regard to the development of Continua USB PHDC
drivers. This includes how a Continua USB device is presented to the user, interoperability of generic or
native USB drivers, and the integration of new Continua devices with existing managers. This paper
concludes with recommendations for the implementation of these device drivers (Native and Generic).
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Background and Description of USB PHDC Drivers Issues
A Continua USB PHDC Manager is interchangeable with the Continua Application Hosting Device (AHD).
Continua USB PHDC Managers operating on major consumer operating systems (OS) require a USB PHDC
class driver to enable wired connectivity with Continua PAN USB devices.
Currently there are no native USB PHDC drivers provided with any major OS on the market (e.g., MS
Windows, Mac OS or Linux). A Continua AHD must deploy its own USB PHDC driver which can result in
interoperability issues.
It is in the interest of Continua Health Alliance to provide guidance in following areas, until a native USB
PHDC driver is available in each OS:
Seamless presentation of Continua USB devices to the end user
Interoperability of multiple USB PHDC Managers deployed on the same end user system
Integration of new Continua certified devices with existing USB PHDC Managers
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Presentation of Continua USB Devices to User
The end user experience with USB-based devices starts with the device manager on the operating system.
For troubleshooting and usability reasons, the Continua devices should have a consistent appearance in
the operating system.
For example, the Windows OS provides a device manager view of all connected devices (see Figure 1).
Figure 1 - Windows Device Manager
The device driver (USB PHDC driver) is responsible for providing the OS with information necessary to
display the connected device details. The information consists of:
Setup GUID 1
Device Class Name
Device Name
Recommendation:
All Continua USB PHDC Driver solutions should be consistent in use of the Setup GUID
and Device Class Name
Continua should facilitate consistent use of the Device Name provided by the device
manufacturer
1 The Setup GUID responsible for the device appearance in the OS is different from Interface GUID related to the device
API mentioned later in this document.
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Interoperability of USB PHDC Managers
As mentioned earlier, there currently is no native Continua USB PHDC driver available for Windows or any
other OS.
In theory, the Continua USB PHDC device vendors should provide a way for applications, such as Continua
Managers, to access the device. Historically, this has meant to implement a function driver for the device
and installing the driver in the operating system.
Currently, this responsibility was de facto moved to the USB Manager side, because the Continua
certification process does not require device manufacturers to provide a driver with a standard API for the
device. In this situation, there is potential for multiple drivers to be installed for the same USB PHDC device
on the same system. Each of these drivers could have a different API.
Depending on the driver the OS selects for the connected device, some managers may not have access to
the device if they are designed for a driver with a different API.
Recommendation:
The problem of Manager interoperability is difficult to solve. A single USB PHDC driver native to
an OS for all PHDC class devices is the only way to ensure real interoperability with multiple
connecting Managers [1].
In most situations the generic USB drivers available for major operating systems can be
used and Continua can, at a minimum, provide guidelines to improve interoperability
between managers using the same generic driver
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Generic USB Drivers
Device drivers require significant development effort and some devices are simple enough that they do not
require the full support of a custom function driver. The generic USB driver is a software library that uses
external information to make any USB device available to the operating system. The external information
is usually provided in a text file with a .INF extension (INF File). See Figure 2.
Figure 2 - USB PHDC Driver from Generic USB Driver
USB PHDC Driver
Generic USB Driver
INF file A
INF file B
Device A
Device B
Currently there are two major generic USB drivers available:
1. LibUSB: Open source for Windows, LINUX,and etc.
2. WinUSB: Part of the Windows OS starting with XP SP3
The advantage of using the generic USB drivers is that the API defined by the driver can be utilized by
Continua Managers for any new devices of the same class as long as the INF file is constructed correctly:
This means consistent use of the same industry-wide Interface GUID value within the device class
for a particular generic USB driver
Figure 3 - Interface GUID
Driver API
(Uses Interface GUID to discover and communicate with the device)
Generic USB Driver
INF File
Interface GUID
← mapping
Info from USB Device
• Vendor ID
• Product ID
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Figure 3 illustrates the use of the Interface GUID. The device manufacturer supplies the Vendor ID and
Product ID. This is mapped to a GUID representing the interface for the class of devices, for this paper, the
USB PHDC class. A Manager application uses the generic driver API with the Interface GUID to
communicate with the device.
NOTE:
The API is different between LibUSB and WinUSB. Thus, the manufacturer should provide
separate INF files, each with a distinct Interface GUID, for each generic driver.
Recommendation:
To allow Continua USB PHDC Managers to discover and communicate with agents, Continua
should provide guidelines for use of generic USB drivers on major operating systems:
Continua USB PHDC Driver based on generic USB drivers should use consistent
industry-wide Interface GUIDs in the INF files.
The Interface GUID shall be specific to a particular driver API (e.g. LibUSB or WinUSB)
Native OS Driver
There are some limitations with use of generic OS drivers. The MSDN document, “How to Use WinUSB to
Communicate with a USB Device” [1] provides a comparison of WinUSB drivers with drivers developed
using the Windows Driver Foundation (WDF) framework.
The best solution for interoperability is the native OS driver which supports concurrent access to the device
and is supplied as part of the operating system.
This results in:
A seamless use experience with the device class
A solution for Multiple Manager / Concurrency Issues
A Standard API for all Managers
The elimination of driver signing
Recommendation:
To allow Continua USB PHDC Managers to discover and communicate with any USB PHDC agent
seamlessly, Continua should strive to provide OS native USB PHDC drivers for all major operating
systems on the market.
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Integration of New Continua Devices with Existing Managers
To improve the use experience there is benefit to driver signing. This eliminates the security risk warning
on most major operating systems.
To accomplish this for non-native Windows OS drivers and generic drivers with INF files, Microsoft must
certify the INF file (through the WHQL 2 process). This is either provided per device (Product ID, Vendor ID)
or with one INF file covering multiple devices.
An INF file is based on the driver’s Interface Global Unique ID (GUID). As mentioned previously, if the INF
file is not certified by Microsoft, a security warning is displayed to the end-user during driver installation.
Each agent device manufacturer must provide its USB Product ID and Vendor ID to the driver manufacturer
(for generation of the driver’s INF file) before the manager can interface to it.
Recommendation:
Continua should facilitate the Product ID and Vendor ID information for certified Continua
Devices
Continua should provide a path for OS vendor certification and signing of generic USB
driver INF files
Continua should drive the adoption of OS native USB PHDC drivers
2 Indications are that the security message is completely avoided with WHQL certification because certification will result
in the release of the driver with the next Service Pack. Thus, driver installation is not required..
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Conclusions and Recommendations
Step I: Initial Approach
Publish INF file creation recommendation on Setup GUID, Interface GUID, and string values for
each driver API (see Continua Recommendation for Use of Generic USB Drivers)
Host a database of PID and VID and unsigned INF files for certified devices
NOTE:
The Unsigned INF file results in a warning message to the user.
Step II: OS Vendor Certified Device INF File
Publish INF file creation recommendation on Setup GUID, Interface GUID, and string values for
each driver API (see Continua Recommendation for Use of Generic USB Drivers)
Host a database of OS Vendor certified and signed INF files for individual certified devices
NOTE:
INF files for Windows OS need certification through the Microsoft WHQL process for all Continua
certified devices.
Step III: OS Vendor Certified Universal INF File
Publish INF file creation recommendation on Setup GUID, Interface GUID, and string values for
each driver API (see Continua Recommendation for Use of Generic USB Drivers)
Provide OS Vendor certified and signed single universal INF file for all current and future Continua
devices that are used with major generic USB Drivers
NOTE:
INF files for Windows OS need certification through the Microsoft WHQL process for all Continua
certified devices.
The Best: Native OS Driver
OS Vendors (e.g., Microsoft) provide a native PHDC driver (does not need an INF file)
NOTE: This solution is not available in MS Windows OS as of Win 7.
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Continua Recommendation for Use of Generic USB Drivers
Continua Health Alliance recommends that Managers for USB PHDC that provide a USB PHDC driver based
on a generic USB driver use the following values in the INF file:
Attribute INF File Element WinUSB Value LibUSB Value
Device Class GUID [Version]/ ClassGUID {182A3B42-D570-4066-8D13-
C72202B40D78}
{EB781AAF-9C70-4523-A5DF-
642A87ECA567}
Device Class Text [Version]/Class PHDC
libusb-win32 devices
[Strings]/ClassName
Interface GUID [Dev_AddReg] {B8B610DE-FB41-40A1-A4D6- N/A
AB28E87C5F08}
Device GUID [Strings]/DeviceGUID N/A D0C36FAA-CE6D-4887-A3AA-
6FC42D3037E5}
NOTE: Continua should negotiate the API, Setup, Interface GUID, and the class name with OS vendors
that create native drivers.
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Glossary
Term
AHD
GUID
PAN
API
USB PHDC
Description
Application Hosting Device
Global Unique Identifier
Personal Area Network
An application programming interface
USB device class that represents Personal Healthcare Devices
References
[1] How to Use WinUSB to Communicate with a USB Device
http://msdn.microsoft.com/en-us/windows/hardware/gg487341
Legal
Continua is a trademark of Continua Health Alliance and CONTINUA HEALTH ALLIANCE and the
CONTINUA HEALTH ALLIANCE logo are registered service marks of Continua Health Alliance.
*Other names and brands may be claimed as the property of others.
Copyright © 2012 Continua Health Alliance. All rights reserved.
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