[libusb] Read timeout after first write/read

[Sumant O. <soe...@xs...>]

Hi guys,

I'm trying to communicate synchronously using libusb to a PICKit 3
(04d8:900a).

The device has one configuration, with one interface and
alt-interface. This interface has two interrupt endpoints (one in,
one out) that I need to use.

I notice the following behavior.

After opening the device and detaching the dummy kernel driver, I
set the configuration, claim the interface, and set the
alt-interface. I can write to and then read from the endpoints, but when repeating a write
followed by a read, I very frequently get a read timeout. I need
to (essentially) close the device, unplug, and replug, to be able
to read again (after writing). Note that I do check the current
configuration first, to see if I need to set it.

Clearing halt conditions doesn't help at all.

However, when I on purpose don't set the configuration, don't
claim the interface and don't set the alt-interface, I can write
and read without any timeout issues, as often as I want.

What's going on here? I've tried both libusb-compat and libusb-1.0
with the synchronous interface only, on linux. I'm mostly used to
the old libusb (thus mostly using libusb-compat for now) since it
worked for all my previous projects, and am only now looking a bit
into libusb-1.0 to see if it would remedy the situation, without
luck.

Thanks,
Sumant


--
Sumant Oemrawsingh