Re: [pyusb-users] [Libusbx-devel] [Released] PyUSB 1.0.0 beta 1

[Wander L. C. <wan...@gm...>]

2013/10/30 Johannes Stezenbach <js...@si...>:

>> >> >> > [2249737.372143] usb 1-1.1: usbfs: process 32478 (python) did not claim interface 0 before use
>> >> >> >
>> >> >>
>> >> >> Interface claiming, in another hand, is handled internally by PyUSB,
>> >> >> this might be a bug.
>> >> >
>> >> > usb.control.get_interface() does not claim the interface.
>> >> >
>> >>
>> >> Ah, no because control requests against endpoint 0 does not need
>> >> interface claiming.
>> >
>> > So I wonder what cause the kernel to complain.
>> >
>>
>> Maybe it is just a debug info without real meaning...
>
> I tried again and the
>     alternate_setting = usb.control.get_interface(dev, interface_number)
> line in the tutorial causes the Linux kernel warning (Linux 3.10.14).
>
> So it seems the Linux kernel disagrees with your assumption?
> If the control request is for USB_RECIP_INTERFACE it checks if
> the interface has been claimed:
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/usb/core/devio.c#n765
>
>

I don't have time right now, but I need to look further into this, as
it might be a problem with PyUSB. Thanks to pointing this out.
For now, what if you explicitly claim the interface (with
usb.util.claim_interface function) before calling get_interface?


-- 
Best Regards,
Wander Lairson Costa