On Tue, Oct 29, 2013 at 06:06:43PM -0200, Wander Lairson Costa wrote:
> 2013/10/29 Johannes Stezenbach <j...@sig21.net>:
> > On Tue, Oct 29, 2013 at 02:58:45PM -0200, Wander Lairson Costa wrote:
> >
> > I was testing with a Linux based device and gadget g_zero, and
> > the EPIPE error stuck unless I added either intf.set_altsetting()
> > or explicit CLEAR_FEATURE(ENDPOINT_STALL). I remember having read
> > both SET_INTERFACE and SET_CONFIGURATION should reset the endpoint state
> > including data toggles and any device FIFOs, but I'm not sure
> > where I read it. Might have been Cypress FX2 documentation.
> >
>
> This probably is device specific, that's the reason is real hard to
> have generic sample code that will work for you, and that's because I
> chose to post minimum code snippets in the tutorial.
OK, it looks like a bug in the PCD (peripheral controller driver)
which does not clear STALL in usb_ep_enable(). Thus I was
confused and the intf.set_altsetting() is not needed,
dev.set_configuration() is sufficient.
> >> >> > [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
Thanks,
Johannes
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