Problem with USB driver using two devices

[Wolfgang Wilhelm]

Dear Sir,

we are a small company FAST ComTec GmbH 
(www.fastcomtec.com) and produce multichannel analyzers 
with Windows software. I am the software developer and 
would like to get our software working also under Linux 
with the help of WINE.

I was already successfull with our USB devices and most
of our PCI cards, but now we have found that our USB
driver does not work with the second device if more than
one USB device is connected. The "read" function does 
not work with the second device, all other functions work.
(tested with Debian v 8, kernel 3.16.0)

The driver is based on a skeleton source provided by you. 
The driver source can be downloaded here:

https://www.fastcomtec.com/ftp/usb1mcs6.zip

Please could you have a look on it if you can see an error?
Or do you think it could be an error in the Linux kernel?

With best regards,
Wolfgang Wilhelm
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Dr. Wolfgang Wilhelm, FAST ComTec GmbH
Gruenwalder Weg 28a, 82041 Oberhaching, Germany
Phone +49 89 665180 28, Fax +49 89 665180 40
mailto:wilhelm@xxxxxxxxxxxxxx http://www.fastcomtec.com
Handelsregister Muenchen HRB 73004
General Manager: Dr. Wolfgang Wagner