centos man page for usb_sg_init

USB_SG_INIT(9)							   USB Core APIs						    USB_SG_INIT(9)

NAME
       usb_sg_init - initializes scatterlist-based bulk/interrupt I/O request

SYNOPSIS
       int usb_sg_init(struct usb_sg_request * io, struct usb_device * dev, unsigned pipe, unsigned period, struct scatterlist * sg, int nents,
		       size_t length, gfp_t mem_flags);

ARGUMENTS
       io
	   request block being initialized. until usb_sg_wait returns, treat this as a pointer to an opaque block of memory,

       dev
	   the usb device that will send or receive the data

       pipe
	   endpoint "pipe" used to transfer the data

       period
	   polling rate for interrupt endpoints, in frames or (for high speed endpoints) microframes; ignored for bulk

       sg
	   scatterlist entries

       nents
	   how many entries in the scatterlist

       length
	   how many bytes to send from the scatterlist, or zero to send every byte identified in the list.

       mem_flags
	   SLAB_* flags affecting memory allocations in this call

DESCRIPTION
       This initializes a scatter/gather request, allocating resources such as I/O mappings and urb memory (except maybe memory used by USB
       controller drivers).

       The request must be issued using usb_sg_wait, which waits for the I/O to complete (or to be canceled) and then cleans up all resources
       allocated by usb_sg_init.

       The request may be canceled with usb_sg_cancel, either before or after usb_sg_wait is called.

RETURN
       Zero for success, else a negative errno value.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014							    USB_SG_INIT(9)