kernels/linux-2.4.0/include/asm-i386/pci.h
/* Map a set of buffers described by scatterlist in streaming
 * mode for DMA.  This is the scather-gather version of the
 * above pci_map_single interface.  Here the scatter gather list
 * elements are each tagged with the appropriate dma address
 * and length.  They are obtained via sg_dma_{address,length}(SG).
 *
 * NOTE: An implementation may be able to use a smaller number of
 *       DMA address/length pairs than there are SG table elements.
 *       (for example via virtual mapping capabilities)
 *       The routine returns the number of addr/length pairs actually
 *       used, at most nents.
 *
 * Device ownership issues as mentioned above for pci_map_single are
 * the same here.
 */
Map a set of buffers described by scatterlist in streaming
mode for DMA.  This is the scather-gather version of the
above pci_map_single interface.  Here the scatter gather list
elements are each tagged with the appropriate dma address
and length.  They are obtained via sg_dma_{address,length}(SG).

An implementation may be able to use a smaller number of
DMA address/length pairs than there are SG table elements.
(for example via virtual mapping capabilities)
The routine returns the number of addr/length pairs actually
used, at most nents.

Device ownership issues as mentioned above for pci_map_single are
the same here.
Map a set of buffers described by scatterlist in streaming mode for DMA . This is the scather - gather version of the above pci_map_single interface . Here the scatter gather list elements are each tagged with the appropriate dma address and length . They are obtained via sg_dma_ { address length } ( SG ) . An implementation may be able to use a smaller number of DMA address / length pairs than there are SG table elements . ( for example via virtual mapping capabilities ) The routine returns the number of addr / length pairs actually used at most nents . Device ownership issues as mentioned above for pci_map_single are the same here .
extern inline int pci_map_sg(struct pci_dev *hwdev, struct scatterlist *sg,
			     int nents, int direction)
{
	if (direction == PCI_DMA_NONE)
		BUG();
	return nents;
}
extern inline int pci_map_sg ( struct pci_dev * hwdev , struct scatterlist * sg , int nents , int direction ) { if ( direction == PCI_DMA_NONE ) BUG ( ) ; return nents ; }
Map a set of buffers described by scatterlist in streaming
 mode for DMA.
Map a set of buffers described by scatterlist in streaming mode for DMA .