USB Device enumeration / order question

NTDEV
1

Running Win2K, are devices on the USB bus enumerated in a predictable way? If I have two or more devices of the same VID/PID how does an application know which device handle maps to a physical device? Can the devices serial number be used?

Larry

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2

> Running Win2K, are devices on the USB bus enumerated

in a predictable way?

There is no guarantee.

If I have two or more devices of the same VID/PID how
does an application know which device handle maps to
a physical device? Can the devices serial number be used?

Yes, the serial number can be used for that purpose.

Marc Reinig
System Solutions

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3

Larry,

IIRC, the SetupDiXxxx provided name maps to device based on the device’s
serial number descriptor if it provides one, or the location in the hub tree
if it does not. This is assuming your device driver uses a device interface
and the system-provided symbolic link, rather than a driver-provided
symbolic link.

-Tim

Timothy A. Johns — xxxxx@driverdev.com
Driver Development Corporation — 800.841.0092
Bring Up Your Hardware — Fast. www.driverdev.com

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Harmon, Larry CT
Sent: Thursday, July 19, 2001 9:11 AM
To: NT Developers Interest List
Subject: [ntdev] USB Device enumeration / order question

Running Win2K, are devices on the USB bus enumerated in a
predictable way? If I have two or more devices of the same
VID/PID how does an application know which device handle maps to
a physical device? Can the devices serial number be used?

Larry

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