Re: [libusb] Correct use of libusb with composite device

[RisingEdgeIndustries <su...@ri...>]

All,

Thank you for the replies!  This is very helpful. I have already changed my
code over to try to use the WINUSB only approach for the entire composite
device.  Now that I'm stuck I'm hoping I can figure out/understand what I'm
messing up as I'd like to continue to use MS OS 2.0 descriptors to do more
advanced stuff.

I will be working this week on testing changes and reading more about your
feedback here.  I think I have to be missing something obvious because I
see the traffic and enumeration happens, but WINUSB never replaces
usbccgp.sys.  It just enumerates with usbccgp.sys, then interface 0 is my
HID interface which comes up fine then interface 1 (bulk) fails which makes
sense because I'm no longer using the descriptors to associate WINUSB with
interface 1 like I was before.  This is due to me attempting to change to
WINUSB being assigned to the entire composite device.

David - quick question about your example.  Even testing that example
exactly with my composite device, it doesn't seem to work.  Would that mean
there is a difference between how you apply that compatible ID descriptor
to a composite vs non-composite device?  I assumed that structure would
work for composite, but I'm wondering if you need a configuration
descriptor etc...  Said differently, in the image I posted with the red
box, you can't just use the descriptors in the red box?  you need more like
the configuration subset header and the following information for that?

Als, in Windows 10, is there a way to see the MS OS 2.0 descriptor
information from the operating systems point of view during enumeration?
Maybe I could see what windows is getting vs what I think it is getting
from the device side?  I've tried to use event viewer but can't track down
any MS OS 2.0 descriptor info.

Thank you for your time!



On Sun, Jul 23, 2023 at 3:18 AM Xiaofan Chen <xia...@gm...> wrote:

> On Sun, Jul 23, 2023 at 11:38 AM RisingEdgeIndustries
> <su...@ri...> wrote:
> >
> > Hi David,
> >
> > Thank you for the help.  I actually went that route first, but libusb1.0
> doesn't
> > support multiple interfaces with the usbccgp.sys driver.  I have to
> change to
> > using WINUSB for the entire composite device.
>
> As mentioned before, this is incorrect and should not happen. libusb works
> fine with multiple interfaces with the USB composite parent driver with a
> few
> exceptions. It should work with your case since you are not using USB IAD
> and CDC-ACM.
>
> You should really post your libusb code and the debug log (with
> LIBUSB_DEBUG=4).
>
> libusb git main will also work with USB devices with IAD
> but still has some exceptions.
>
> Reference:
> https://github.com/libusb/libusb/pull/965 (merged)
> https://github.com/libusb/libusb/pull/1181 (not merged)
> https://github.com/libusb/libusb/issues/1238 (no PR yet)
>
> --
> Xiaofan
>