usb_alloc_urb(9) [suse man page]

USB_ALLOC_URB(9)						   USB Core APIs						  USB_ALLOC_URB(9)

NAME

       usb_alloc_urb - creates a new urb for a USB driver to use

SYNOPSIS

       struct urb * usb_alloc_urb(int iso_packets, gfp_t mem_flags);

ARGUMENTS

       iso_packets
	   number of iso packets for this urb

       mem_flags
	   the type of memory to allocate, see kmalloc for a list of valid options for this.

DESCRIPTION

       Creates an urb for the USB driver to use, initializes a few internal structures, incrementes the usage counter, and returns a pointer to
       it.

       If no memory is available, NULL is returned.

       If the driver want to use this urb for interrupt, control, or bulk endpoints, pass '0' as the number of iso packets.

       The driver must call usb_free_urb when it is finished with the urb.

COPYRIGHT

Kernel Hackers Manual 2.6.					     July 2010							  USB_ALLOC_URB(9)

USB_POISON_URB(9)						   USB Core APIs						 USB_POISON_URB(9)

NAME

       usb_poison_urb - reliably kill a transfer and prevent further use of an URB

SYNOPSIS

       void usb_poison_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. It is guaranteed that upon return all completion handlers will have finished and the URB will
       be totally idle and cannot be reused. These features make this an ideal way to stop I/O in a disconnect callback. If the request has not
       already finished or been unlinked the completion handler will see urb->status == -ENOENT.

       After and while the routine runs, attempts to resubmit the URB will fail with error -EPERM. Thus even if the URB's completion handler
       always tries to resubmit, it will not succeed and the URB will become idle.

       The URB must not be deallocated while this routine is running. In particular, when a driver calls this routine, it must insure that the
       completion handler cannot deallocate the URB.

       This routine may not be used in an interrupt context (such as a bottom half or a completion handler), or when holding a spinlock, or in
       other situations where the caller can't schedule.

       This routine should not be called by a driver after its disconnect method has returned.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014							 USB_POISON_URB(9)