Re: [Libusb-devel] usbfs: usb_submit_urb returned -121

[Alan S. <st...@ro...>]

On Fri, 25 Jun 2010, Peter Stuge wrote:

> Ludovic Rousseau wrote:
> > libusb returns -99 (LIBUSB_ERROR_OTHER)
> ..
> > libusb:warning [do_sync_bulk_transfer] unrecognised status code 1
> 
> Alan's description is helpful. libusb does handle when transfer >=2
> in a multi-URB transfer submitted to Linux fails. libusb discards the
> previous transfers

Do you mean it discards the as-yet-unsubmitted URBs and cancels the 
outstanding URBs?

>  and sets reap_action=SUBMIT_FAILED. As libusb is
> reaping the URBs, it notices that one could not be submitted, and
> returns an error.

I gather that the difficulty is how to tell whether or not a submission
failure represents an error.  The criterion is simple: If the errno
value from the failed submission ioctl is EREMOTEIO then it's not an
error (it's merely a rejection because the transer has already
completed), otherwise it is.

> Ludovic, please try the attached patch. It checks if any data was
> already transferred by this multi-URB transfer, and if so returns
> without error - and although I think this might work I'm not positive
> that it's correct to require any data to have been transferred -
> could there have been a 0 byte transfer instead of the 28 here?

That does not sound right.

Alan Stern