Re: [libusb] libusb_open returns -12 (LIBUSB_ERROR_NOT_SUPPORTED)

[Robert R. <R.R...@Qu...>]

Hi,
I had this working when I did not try to detect multiple devices.  I could
reboot my device multiple times, disconnecting and reconnecting.  I now
need to detect 2 devices of mine connected and when I reworked the
code for this is when I started getting the error -12.

Are you saying that there is something in the lib that normally prevents
this and my previous success was a fluke?

Thank you for the quick reply.

At 09:35 AM 9/22/2021 +0800, Xiaofan Chen wrote:
>On Wed, Sep 22, 2021 at 7:37 AM Robert Ritchey
><R.R...@qu...> wrote:
> >
> > I am running under Windows and check for my device when I get a
> > DBT_DEVICEARRIVAL event and check to see if it is gone when I get a
> > DBT_DEVICEREMOVECOMPLETE event.
> >
> > The scenario is that I can open the device, do some transfers (actually
> > download firmware), then tell the device to boot.  It disconnects, and I
> > release the interface and close it successfully.
> >
> > When the firmware boots I get DBT_DEVICEARRIVAL event and look for
> > my device. I can get the device list and descriptors but when I find my
> > device and try to open I get this error.
> >
> > LIBUSB_ERROR_NOT_SUPPORTED seems like a strange error code to
> > get for libusb_open.  I have single stepped through it many times and it
> > seems right but I must be missing something.
>
>I could be wrong but I believe there is no solution for now until hotplug
>is supported by the Windows backend.
>Ref: https://github.com/libusb/libusb/issues/86
>
>Right now no developers are actively working on this feature so it will
>take some time. In fact, since Chris seems to be busy after his last commit in
>February 2021, there is no libusb developer on the Windows side as of now.
>
>--
>Xiaofan

Robert Ritchey
Quest Engineering
Tempe, AZ
(480) 460-2652