-------- Original-Nachricht --------
> Datum: Mon, 12 Nov 2012 08:43:33 -0200
> Von: Wander Lairson Costa <wander.lair...@gmail.com>
> An: pyusb-users@lists.sourceforge.net
> Betreff: Re: [pyusb-users] Devices disconnects after several request
> 2012/11/12 Stefano Di Martino <stefan...@gmx.net>:
> > Hi,
> > I tested it under Linux, but there was no problem. But I tested it on an
> another Computer with Python 2.7 instead of 2.5.
> > The other thing is, I can't reproduce this problem, with C.
> >
> > I made a simple stress test with python:
> >
> > This works:
> >
> > for i in range(100):
> > usb.core.find(find_all=True)
> >
> > This don't work!
> >
> > for i in range(100):
> > device_list = usb.core.find(find_all=True)
> >
> > Two lines of code (besides the import), nothing more...
> > The error message:
> >
> > "usb.core.USBError: [Errno 19] No such device (it may have been
> disconnected)"
> >
> > Where it happens:
> >
> > class _DevIterator(object):
> > def __init__(self):
> > self.dev_list = POINTER(c_void_p)()
> > self.num_devs = _check(_lib.libusb_get_device_list(
> > None,
> > byref(self.dev_list))
> > ).value # Here!
> >
> >
> > def _check(retval):
> > if isinstance(retval, int):
> > retval = c_int(retval)
> > if isinstance(retval, c_int):
> > if retval.value < 0:
> > from usb.core import USBError
> > ret = retval.value
> > raise USBError(_str_error[ret], ret, _libusb_errno[ret]) #
> Here the Exception rises.
> > return retval
> >
> >
> > My simple C code:
> >
> > for(i = 0; i < 100; i++) {
> > cnt = libusb_get_device_list(NULL, &devs);
> > if (cnt < 0)
> > return (int) cnt;
> > if (i < 99)
> > libusb_free_device_list(devs, 1);
> > }
> >
>
> What happens if you don't call libusb_free_device_list?
It crashes. Enable debug won't help, because it crashes before it can print
debug messages.
By the way: I've found out, that it only crashes, when a Cherry keyboard is
attached:
Device Descriptor:
bcdUSB: 0x0200
bDeviceClass: 0x00
bDeviceSubClass: 0x00
bDeviceProtocol: 0x00
bMaxPacketSize0: 0x08 (8)
idVendor: 0x046A (Cherry GMBH)
idProduct: 0x0011
bcdDevice: 0x0100
iManufacturer: 0x00
iProduct: 0x00
iSerialNumber: 0x00
bNumConfigurations: 0x01
ConnectionStatus: DeviceConnected
Current Config Value: 0x01
Device Bus Speed: Low
Device Address: 0x01
Open Pipes: 1
Endpoint Descriptor:
bEndpointAddress: 0x81
Transfer Type: Interrupt
wMaxPacketSize: 0x0008 (8)
bInterval: 0x0A
Best regards
Stefano
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