Re: [pyusb-users] Input/Output error

Diego Jacobi Wed, 23 Jun 2010 21:26:52 -0700

Thanks, but i am sadly confirming that this is not the error this time.

I have correctly detached it with:


interface = dev.get_interface_altsetting()
dev.detach_kernel_driver(interface.bInterfaceNumber)

which works, because "dmesg" logs it and the /dev/ttyUSB0 is released.

but in the error stage it says exactly the same:

Traceback (most recent call last):
  File "./pyusb.py", line 160, in <module>
    xdata_set_register(dev,UART1_MCR, MCR_DTR | MCR_RTS, 0xFF)
  File "./pyusb.py", line 136, in xdata_set_register
    print dev.ctrl_transfer(requesttype,command, value, moduleid, msg)
  File "/usr/local/lib/python2.6/site-packages/usb/core.py", line 668,
in ctrl_transfer
    self.__get_timeout(timeout)
  File "/usr/local/lib/python2.6/site-packages/usb/_debug.py", line
53, in do_trace
    return f(*args, **named_args)
  File "/usr/local/lib/python2.6/site-packages/usb/backend/libusb10.py",
line 541, in ctrl_transfer
    timeout))
  File "/usr/local/lib/python2.6/site-packages/usb/backend/libusb10.py",
line 356, in _check
    raise USBError(_str_error[retval.value])
usb.core.USBError: Input/output error



In libusb10.py, this is the function raising the error:

# check a libusb function call
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
           raise USBError(_str_error[retval.value])
    return retval



That means, that the return value is less than cero, which means error
in the lbusb call.
Maybe because of my parameters.
But the call is:
   dev.ctrl_transfer(requesttype,command, value, moduleid, msg)
where all of them are integers excepting the msg parameter, which is
an ordered list of integers between 0 and 255.

Also the list of errors:
# map return codes to strings
_str_error = {
    _LIBUSB_SUCCESS:'Success (no error)',
    _LIBUSB_ERROR_IO:'Input/output error',
    _LIBUSB_ERROR_INVALID_PARAM:'Invalid parameter',
    _LIBUSB_ERROR_ACCESS:'Access denied (insufficient permissions)',
    _LIBUSB_ERROR_NO_DEVICE:'No such device (it may have been disconnected)',
    _LIBUSB_ERROR_NOT_FOUND:'Entity not found',
    _LIBUSB_ERROR_BUSY:'Resource busy',
    _LIBUSB_ERROR_TIMEOUT:'Operation timed out',
    _LIBUSB_ERROR_OVERFLOW:'Overflow',
    _LIBUSB_ERROR_PIPE:'Pipe error',
    _LIBUSB_ERROR_INTERRUPTED:'System call interrupted (perhaps due to signal)',
    _LIBUSB_ERROR_NO_MEM:'Insufficient memory',
    _LIBUSB_ERROR_NOT_SUPPORTED:'Operation not supported or
unimplemented on this platform',
    _LIBUSB_ERROR_OTHER:'Unknown error'
}

discard other posibilities like timeout..

Can somebody give a better example on how to call ctrl_transfer with a
data payload ?

Thanks
Diego




NOTE:
It is possible to call the detach function like this:
   dev.detach_kernel_driver(interface)
if in the class definition of Interface we add
    self._as_parameter_ = self.bInterfaceNumber
so ctypes automatically reads the interface number instead of giving a
ctype error.

ALSO the reattach doesnt work:
/usr/lib/libusb-1.0.so.0: undefined symbol: libusb_attach_kernel_driver




2010/6/23 Xiaofan Chen <xiaof...@gmail.com>:
> On Thu, Jun 24, 2010 at 9:08 AM, Diego Jacobi <jacobidi...@gmail.com> wrote:
>
>> There is a driver in the kernel for sure.
>> Could you please expand your answer on this?
>> How do i detach a driver from the kernel in user space?
>
> For libusb-0.1
> http://libusb.sourceforge.net/doc/function.usbdetachkerneldrivernp.html
> For libusb-1.0
> http://libusb.sourceforge.net/api-1.0/group__dev.html#ga0bc7a17090debf6d2b2711c505ad9725
>
> To run the above as a normal user, you have to have the proper
> permission to do that (no need to being root), again the proper
> way is to use udev rules.
>
>> Also the problem would be, that it is the driver the one that loads
>> the firmware and initialices it.
>
> That is not a problem. After you attach the device, a driver
> loads the firmware to the device. Then maybe the same driver
> or a different driver is bound to the device with the firmware.
>
> To use libusb/pyusb, you detach the last driver bound to the
> device.
>
>> I have had experiences where an HID device can receive usb
>> transactions from a normal application.
>
> Even for HID device, you have to detach the kernel driver
> if you want to use libusb/pyusb to communicate with the
> device.
>
>
> --
> Xiaofan http://mcuee.blogspot.com
>
> ------------------------------------------------------------------------------
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Re: [pyusb-users] Input/Output error

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