iommu sg merging: add accessors for segment_boundary_mask in device_dma_parameters()

This adds new accessors for segment_boundary_mask in device_dma_parameters
structure in the same way I did for max_segment_size.  So we can easily change
where to place struct device_dma_parameters in the future.

dma_get_segment boundary returns 0xffffffff if dma_parms in struct device
isn't set up properly.  0xffffffff is the default value used in the block
layer and the scsi mid layer.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Greg KH <greg@kroah.com>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/dma-mapping.h

@@ -75,6 +75,21 @@ static inline unsigned int dma_set_max_seg_size(struct device *dev,
 		return -EIO;
 }
 
+static inline unsigned long dma_get_seg_boundary(struct device *dev)
+{
+	return dev->dma_parms ?
+		dev->dma_parms->segment_boundary_mask : 0xffffffff;
+}
+
+static inline int dma_set_seg_boundary(struct device *dev, unsigned long mask)
+{
+	if (dev->dma_parms) {
+		dev->dma_parms->segment_boundary_mask = mask;
+		return 0;
+	} else
+		return -EIO;
+}
+
 /* flags for the coherent memory api */
 #define	DMA_MEMORY_MAP			0x01
 #define DMA_MEMORY_IO			0x02