qmi_wwan 1-1.3:1.8: nonzero urb status received: -71 (-71 == EPROTO)

Bjørn Mork bjorn at mork.no
Tue Oct 28 00:58:50 PDT 2014

Gopakumar Choorakkot Edakkunni <gopakumar.c.e at gmail.com> writes:

> Hi QMI experts,
> I have an AC 340U modem for which I periodically monitor the signal
> strength using the qmicli below. At times when my signal strength drop
> badly down to zero, I see that qmicli spits out the below errors
> continuosly. I did a google and saw some discussions around the EPIPE
> error, but none around EPROTO. Any thoughts/comments/suggestions would be
> very helpful !
> qmicli -d </dev/...> --nas-get-signal-info
> <logs>
> qmi_wwan 1-1.3:1.8: nonzero urb status received: -71 (-71 == EPROTO)
> qmi_wwan 1-1.3:1.8: wdm_int_callback - 0 bytes
> qmi_wwan 1-1.3:1.8: nonzero urb status received: -71
> qmi_wwan 1-1.3:1.8: wdm_int_callback - 0 bytes

The meanings of URB callback error codes are documented in
Documentation/usb/error-codes.txt available in the kernel source or
here: https://www.kernel.org/doc/Documentation/usb/error-codes.txt

Which says:

 -EPROTO (*, **)	a) bitstuff error
 			b) no response packet received within the
  			   prescribed bus turn-around time
  			c) unknown USB error 

with the following additional notes:

 (*) Error codes like -EPROTO, -EILSEQ and -EOVERFLOW normally indicate
 hardware problems such as bad devices (including firmware) or cables.

 (**) This is also one of several codes that different kinds of host
 controller use to indicate a transfer has failed because of device
 disconnect.  In the interval before the hub driver starts disconnect
 processing, devices may receive such fault reports for every request.

I don't know why you get those errors.  I can only say that they are
completely unexpected at that point, and that I cannot think of anything
the driver could possibly do with it.  This is a symptom of a modem
hardware and/or firmware bug. The driver can only do what it does now:
Log the error and attempt to continue.

Did I understand you correctly that the modem actually still works after
these errors, without having to be reset?  If so, then you are lucky and
can just ignore the errors :-)


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