[Libusb-win32-devel] Read/write and release/claim_interface

[<and...@nt...>]

Hi

I don't understand the behavior of subsequent read/write operations when =
using usb_release_interface() and usb_claim_interface() between the =
read/writes.
My test device is a AT90SUB1287 and loops the data from an OUT bulk =
endpoint to an IN bulk endpoint.
I'm using the latest CVS source, but I had the same problem with the =
official libusb-win32-snapshot 20060827.

This scenario works fine:
****************************
- usb_open()
- usb_set_configuration()
- usb_claim_interface()
- usb_set_altinterface()
	- usb_bulk_write()	(multiple read/writes work fine)
	- usb_bulk_read()
- usb_release_interface()
- usb_close()

This scenario gives me a timeout error, but read/write work after some =
timeout errors again:
****************************
- usb_open()
- usb_set_configuration()
- usb_claim_interface()
- usb_set_altinterface()
	- usb_bulk_write()	(works fine, I get the data on the device)
- usb_release_interface()
**
- usb_claim_interface()
- usb_set_altinterface()
	- usb_bulk_read()		(works fine, I get the data from the device)
- usb_release_interface()
**
- usb_claim_interface()
- usb_set_altinterface()
	- usb_bulk_write()	(no failure (libusb), but I don't get any data on =
the device)
- usb_release_interface()
**
- usb_claim_interface()
- usb_set_altinterface()
	- usb_bulk_write()	(no failure (libusb), but I don't get any data on =
the device)
	- usb_bulk_read()		(fails, timeout error)
	- usb_bulk_write()	(works fine, I get the data on the device)
	- usb_bulk_read()		(fails, timeout error)
	- from now on all read/write are successful again
- usb_release_interface()
- usb_close()

****************************

Is it not allowed to claim the interface again after release?
I'm wondering why writing to the device succeeds, although I don't get =
any data on the device? I can write as many times as I want without =
getting an error from libusb. The device can buffer only one transfer.
Strange is, that it starts working again after some subsequent =
write/reads.

Any hints are appreciated!
Thanks, Andreas