Maps a paged fragment via the dma api
dma_addr_t skb_frag_dma_map(struct device * dev, const skb_frag_t * frag, size_t offset, size_t size, enum dma_data_direction dir);
dev
the device to map the fragment to
frag
the paged fragment to map
offset
the offset within the fragment (starting at the fragment's own offset)
size
the number of bytes to map
dir
the direction of the mapping (PCI_DMA_*)
Maps the page associated with frag to device.