Re: [libusb] Windows composite device fix

[Sameeh J. <sa...@da...>]

Extending UsbDk - one of libusb's backend on Windows - to support composite
devices would be a good option I believe.

Checkout the source code here:
https://github.com/daynix/UsbDk

On Fri, 27 Apr 2018, 11:18 Paul Qureshi, <pa...@wo...> wrote:

> Hi.
>
> I've been trying to get dfu-util to work properly on Windows. After
> submitting a patch to fix the control transfer interface selection (
> https://github.com/libusb/libusb/pull/398) it can now write firmware in
> DFU
> mode. Unfortunately, it still can't work with runtime mode because libusb
> does not support composite devices on Windows.
>
> The only fix at the moment is to replace the composite parent driver with
> Zadig, but this is unsatisfactory as it means composite devices can't "just
> work" on Windows.
>
> Pete Batard provides great insight into this issue here:
> https://sourceforge.net/p/libusb/mailman/message/33176212/
>
> The short version is that Windows treats composite devices as multiple
> different devices from a driver point of view, where as Linux treats them
> as one device. As a result, libusb is unable to open the parent device as
> it does not have a supported driver.
>
> I now have to choose between writing a new, Windows only DFU tool or fixing
> libusb. So I thought fixing libusb would be the better option. When
> researching this issue it seems to be affecting a lot of people.
>
> What is the best way to sort this out once and for all?
>
> Is adding support for the Windows composite driver likely to work?
> Unfortunately, as Pete Batard notes, the Windows back-end is a bit of a
> jungle because it tries to fit the libusb model. The goal would be to allow
> libusb to seamlessly open any interface on the composite device,
> automatically selecting the correct child device.
>
> What other options exist?
>
> To be clear I'm willing to do the work here, I'm just looking for some
> discussion of the best way to implement this.
>
> Regards,
> Paul
>
>
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