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

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

Hi Matthias,
Please see below for replies.

At 10:28 AM 9/22/2021 +0000, lib...@li... wrote:
>Date: Wed, 22 Sep 2021 11:18:38 +0200
>From: Matthias Bolte <mat...@go...>
>To: Xiaofan Chen <xia...@gm...>
>Cc: Robert Ritchey <R.R...@qu...>,  libusb-devel
>         <lib...@li...>
>Subject: Re: [libusb] libusb_open returns -12
>         (LIBUSB_ERROR_NOT_SUPPORTED)
>Message-ID:
>         <CABBroziihYB-fguK0Zqr1kNLh+tCbvLYXmnUfNBtu3uRLmZ3=g...@ma...>
>Content-Type: text/plain; charset="UTF-8"
>
>Am Mi., 22. Sept. 2021 um 03:38 Uhr schrieb Xiaofan Chen <xia...@gm...>:
> >
> > 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
>
>That is not true. I've successfully run libusb on Windows with the
>same Windows device change notifications as used here for years now.
>
>A few things to check:
>
>- Why are you only checking the vendor ID before opening the device?
>You should check the product ID too to avoid trying to open the wrong
>device.

I do check the product ID before I try to open the device to check the
serial number.  I only open my devices, both in the attach and detach.

>- Are you sure that Windows has loaded the correct device driver for
>your device. Preferably WinUSB, assuming we're talking about a vendor
>specific device and not a class device.

I do use WinUSB, I support the Microsoft extended descriptors to load
the WinUSB driver.  I have actually been running this code for 8 years
now but my old version of attach and detach only looked for one
device.  I now need to support 2 devices.

>- Currently your code assumes that no errors will ever occur and dies
>with an assert on the first error it sees. Make your code more robust
>and actually deal with errors correctly. Do not give up everything on
>the first error, but only give up the specific device you're currently
>checking. There was a bug in libusb that resulted in libusb
>enumerating the same device multiple times, but only one of the
>multiple instances of the same device could be opened successfully.
>This bug has since been fixed in libusb, but maybe you're using an old
>libusb version or there is a different version of this bug still
>present.

I receive no errors before I get the LIBUSB_ERROR_NOT_SUPPORTED
error.  As I mentioned, when I was checking for only 1 device I never
had an error in 8 years.  I never ran into the bug you described before.

>- What libusb version are you using? There were several critical
>improvements in the USB enumeration logic of libusb on Windows lately.
>If you're not using the latest release 1.0.24 then you should start
>there. If the problem persists, try the current git version to see if
>this is due to a libusb bug that has been fixed, but not released yet.
>If that doesn't help, test backwards through the libusb releases to
>check if this is a bug in libusb that has been introduced in a recent
>release.

I am running a release I downloaded in 2014 and have never had an issue
in all this time until I re-worked my code for multiple devices.  That is why
I thought I must have missed something in reworking my code that I have
not been able to find over the last 3 days of debugging.

>You can take a look at my project using libusb, but the code is not so
>easy to follow, as it started with libusb 1.0.6 and went through to
>libusb 1.0.24 and deals with 5 different operating systems:
>
>https://github.com/Tinkerforge/brickd

Thank you.  I am sure this will be helpful for me to see how you deal
with errors returned.

-Bob
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Robert Ritchey
Quest Engineering & Development, Inc.
Suite B-8
6125 South Ash Avenue
Tempe, AZ 85283
Tel: (480) 460-2652
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