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Technical Q&A USB03
USBGetNextDeviceByClass Requires deviceRef
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Q When I make the USBGetNextDeviceByClass
call, error -43 (file not found) error is returned. My device is
attached, and is displayed by USB Prober. The call used to work, but
no longer. Why?
A If you make the USBGetNextDeviceByClass
call, you must set the input deviceRef parameter to a valid device
ref or to the predefined constant kNoDeviceRef . If the deviceRef
parameter is a different value, then error -43 results. If you set
the input deviceRef value to a valid deviceRef , then
USBGetNextDeviceByClass returns the next device that is found in the
"USB device list", which matches the specified criteria. The key
point here is that the input deviceRef value must be valid or -1.
Note that error -43 might still be returned, if there are no more
devices in the device list.
[Sep 28 1998]
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