Re: [pyusb-users] 回覆: help on win7: Entity not found

[Jonas M. <jo...@pr...>]

On Wed, Apr 28, 2021 at 01:49:30AM +0000, CM-Wu  Ben - 吳文鐘 wrote:
> 寄件者: Jonas Malaco via pyusb-users <pyu...@li...>
> 寄件日期: 2021年4月27日 下午 05:16
> 收件者: pyu...@li... <pyu...@li...>
> 副本: Jonas Malaco <jo...@pr...>
> 主旨: Re: [pyusb-users] help on win7: Entity not found
> 
> On Tue, Apr 27, 2021 at 08:18:09AM +0000, CM-Wu  Ben - 吳文鐘 wrote:
> > Hi,
> > I got a problem when dealing with control transfer on win7.
> >
> > After set backend(libusb1), find usb device, I can send standard/class USB request via dev.ctrl_transfer() successfully, but failed when sending vendor request.
> >
> > the reason is 'Entity not found'
> > Is there any restrictions when sending vendor request?
> 
> Not generally, no.
> 
> But the OS driver may not support it (e.g. Windows Generic HID).
> 
> Try running with LIBUSB_DEBUG=4, that may give you some useful
> information.
> ------------------
> 
> Thanks for your information.
> I tried to run with LIBUSB_DEBUG=4, and found that it is windows HID driver that handle the request, which does not support it.
> 
> The device I'm testing is a composite device, which has audio interface within it.
> Do windows audio driver support the handling of control transfer ?

I don't know.  And even if it does, it and/or the device may only accept
control transfers through it that are related to that particular
interface.

My suggestion is for you to install WinUSB with Zadig.  See:

https://github.com/libusb/libusb/wiki/FAQ#How_to_use_libusb_under_Windows

> If yes, is it possible to send control transfer via audio driver? how to do it using libusb backend?

Try to ask in the libusb mailling list.

Thanks,
Jonas


> Thanks
> 
> 
> 
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