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

[David G. <dav...@gm...>]

The example file I linked to can be compiled two different ways: as a
composite device with WinUSB on one interface or a non-composite device
with WinUSB taking over the whole device.  There are different descriptors
for each case.  Both of them worked the last time I checked.  Maybe Windows
has cached some old descriptors for your device or you made an error.

--David Grayson

On Sun, Jul 23, 2023, 9:16 PM RisingEdgeIndustries <
su...@ri...> wrote:

> 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
>>
>