Re: [libusb] libusb Asynchronous Bulk Transfer Timeout On Linux Ubuntu

[Ian M. <ian...@gm...>]

David,

Yes.  I have tried it both ways: reattaching the kernel driver and leaving
it detached.  Neither approach changes the outcome unfortunately.

Ian

On Tue, Sep 12, 2017 at 3:36 PM, Ian Murtaugh <ian...@gm...>
wrote:

> I am using libusb on Ubuntu and am attempting to send 4 bytes of data via
> an asynchronous bulk transfer. I am able to successfully perform the
> following steps:
>
> Allocate the transfer via libusb_alloc_transfer.
> Fill the bulk transfer via libusb_fill_bulk_transfer.
> Detach the kernel driver via libusb_detach_kernel_driver.
> Claim the interface via libusb_claim_interface.
> Submit the transfer via libusb_submit_transfer.
> Lastly, reattach the kernal driver via libusb_attach_kernel_driver.
> The code will then run until the transfer times out and the callback
> function is called. Enabling libusb debug provides the following messages:
>
> [10.033374] [000026fe] libusb: debug [handle_events] timerfd triggered
> [10.033375] [000026fe] libusb: debug [libusb_cancel_transfer] transfer
> 0x55555576de80
> [10.036908] [000026fe] libusb: debug [disarm_timerfd]
> [10.036919] [000026fe] libusb: debug [handle_events] poll() 3 fds with
> timeout in 0ms
> [10.036921] [000026fe] libusb: debug [handle_events] poll() returned 1
> [10.036924] [000026fe] libusb: debug [reap_for_handle] urb type=3
> status=-2 transferred=0
> [10.036926] [000026fe] libusb: debug [handle_bulk_completion] handling
> completion status -2 of bulk urb 1/1
> [10.036927] [000026fe] libusb: debug [handle_bulk_completion] abnormal
> reap: urb status -2
> [10.036928] [000026fe] libusb: debug [handle_bulk_completion] abnormal
> reap: last URB handled, reporting
> [10.036930] [000026fe] libusb: debug [usbi_handle_transfer_cancellation]
> detected timeout cancellation
> [10.036931] [000026fe] libusb: debug [disarm_timerfd]
> [10.036932] [000026fe] libusb: debug [usbi_handle_transfer_completion]
> transfer 0x55555576de80 has callback 0x7ffff7bd4c78
> Questions:
>
> What does a URB status of -2 mean?
> Based on your knowledge or experience, what could possibly prevent the
> transfer from actually taking place?
>