USB_FILL_BULK_URB(9) Host-Side Data Types and Macro USB_FILL_BULK_URB(9)NAME
usb_fill_bulk_urb - macro to help initialize a bulk urb
SYNOPSIS
void usb_fill_bulk_urb(struct urb * urb, struct usb_device * dev, unsigned int pipe, void * transfer_buffer, int buffer_length,
usb_complete_t complete_fn, void * context);
ARGUMENTS
urb
pointer to the urb to initialize.
dev
pointer to the struct usb_device for this urb.
pipe
the endpoint pipe
transfer_buffer
pointer to the transfer buffer
buffer_length
length of the transfer buffer
complete_fn
pointer to the usb_complete_t function
context
what to set the urb context to.
DESCRIPTION
Initializes a bulk urb with the proper information needed to submit it to a device.
COPYRIGHT Kernel Hackers Manual 2.6. July 2010 USB_FILL_BULK_URB(9)
Check Out this Related Man Page
USB_UNLINK_URB(9) USB Core APIs USB_UNLINK_URB(9)NAME
usb_unlink_urb - abort/cancel a transfer request for an endpoint
SYNOPSIS
int usb_unlink_urb(struct urb * urb);
ARGUMENTS
urb
pointer to urb describing a previously submitted request, may be NULL
DESCRIPTION
This routine cancels an in-progress request. URBs complete only once per submission, and may be canceled only once per submission.
Successful cancellation means termination of urb will be expedited and the completion handler will be called with a status code indicating
that the request has been canceled (rather than any other code).
Drivers should not call this routine or related routines, such as usb_kill_urb or usb_unlink_anchored_urbs, after their disconnect method
has returned. The disconnect function should synchronize with a driver's I/O routines to insure that all URB-related activity has completed
before it returns.
This request is always asynchronous. Success is indicated by returning -EINPROGRESS, at which time the URB will probably not yet have been
given back to the device driver. When it is eventually called, the completion function will see urb->status == -ECONNRESET. Failure is
indicated by usb_unlink_urb returning any other value. Unlinking will fail when urb is not currently "linked" (i.e., it was never
submitted, or it was unlinked before, or the hardware is already finished with it), even if the completion handler has not yet run.
UNLINKING AND ENDPOINT QUEUES
[The behaviors and guarantees described below do not apply to virtual root hubs but only to endpoint queues for physical USB devices.]
Host Controller Drivers (HCDs) place all the URBs for a particular endpoint in a queue. Normally the queue advances as the controller
hardware processes each request. But when an URB terminates with an error its queue generally stops (see below), at least until that URB's
completion routine returns. It is guaranteed that a stopped queue will not restart until all its unlinked URBs have been fully retired,
with their completion routines run, even if that's not until some time after the original completion handler returns. The same behavior and
guarantee apply when an URB terminates because it was unlinked.
Bulk and interrupt endpoint queues are guaranteed to stop whenever an URB terminates with any sort of error, including -ECONNRESET,
-ENOENT, and -EREMOTEIO. Control endpoint queues behave the same way except that they are not guaranteed to stop for -EREMOTEIO errors.
Queues for isochronous endpoints are treated differently, because they must advance at fixed rates. Such queues do not stop when an URB
encounters an error or is unlinked. An unlinked isochronous URB may leave a gap in the stream of packets; it is undefined whether such gaps
can be filled in.
Note that early termination of an URB because a short packet was received will generate a -EREMOTEIO error if and only if the
URB_SHORT_NOT_OK flag is set. By setting this flag, USB device drivers can build deep queues for large or complex bulk transfers and clean
them up reliably after any sort of aborted transfer by unlinking all pending URBs at the first fault.
When a control URB terminates with an error other than -EREMOTEIO, it is quite likely that the status stage of the transfer will not take
place.
COPYRIGHT Kernel Hackers Manual 2.6. July 2010 USB_UNLINK_URB(9)