centos man page for usb_alloc_urb

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 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.

RETURN
       A pointer to the new urb, or NULL if no memory is available.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014							  USB_ALLOC_URB(9)