FTDI serial device remains busy after closing

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Hiya,

I'm having a really strange issue with a particular device that uses
the FTDI serial chipset. After connection, I'm able to initially open
and communicate with the device no problem. Issues occur when trying
to close the device connection. Some applications are able to close
the device without any issue. In other cases the device seems to
remain open, and attempting to open the device again will result in a
"Device or resource busy" error message. The only way to resolve this
is to physically reconnect the device. From a development standpoint,
issuing a close() on the device fd returns successfully and there
doesn't seem to be any indication that the device should remain in a
'busy' state. This problem does not occur with another device that
uses a serial chipset by Prolific... in that case, all applications
are able to successfully close the device and re-open it.

I ran an strace on one application which did close the device
successfully, and one application which did not. I tried to isolate
the relevant information from each trace:
[http://pastebin.com/riJKvCS4]. I'm not too sure what else I can do to
help figure out what's going on and would appreciate any advice. I'm
running Arch Linux, kernel v 3.1.5-1.


Regards,

Pris
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