/* * Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved. * Portions based on net/core/datagram.c and copyrighted by their authors. * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by the Free * Software Foundation; either version 2 of the License, or (at your option) * any later version. * * This program is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for * more details. * * You should have received a copy of the GNU General Public License along with * this program; if not, write to the Free Software Foundation, Inc., 59 * Temple Place - Suite 330, Boston, MA  02111-1307, USA. * * The full GNU General Public License is included in this distribution in the * file called COPYING. */ /* * This code allows the net stack to make use of a DMA engine for * skb to iovec copies. */ #include <linux/dmaengine.h>#include <linux/socket.h>#include <linux/rtnetlink.h> /* for BUG_TRAP */#include <net/tcp.h> #define NET_DMA_DEFAULT_COPYBREAK 4096 int sysctl_tcp_dma_copybreak = NET_DMA_DEFAULT_COPYBREAK; /** *	dma_skb_copy_datagram_iovec - Copy a datagram to an iovec. *	@skb - buffer to copy *	@offset - offset in the buffer to start copying from *	@iovec - io vector to copy to *	@len - amount of data to copy from buffer to iovec *	@pinned_list - locked iovec buffer data * *	Note: the iovec is modified during the copy. */int dma_skb_copy_datagram_iovec(struct dma_chan *chan,			struct sk_buff *skb, int offset, struct iovec *to,			size_t len, struct dma_pinned_list *pinned_list){	int start = skb_headlen(skb);	int i, copy = start - offset;	dma_cookie_t cookie = 0; 	/* Copy header. */	if (copy > 0) {		if (copy > len)			copy = len;		cookie = dma_memcpy_to_iovec(chan, to, pinned_list,		                            skb->data + offset, copy);		if (cookie < 0)			goto fault;		len -= copy;		if (len == 0)			goto end;		offset += copy;	} 	/* Copy paged appendix. Hmm... why does this look so complicated? */	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {		int end; 		BUG_TRAP(start <= offset + len); 		end = start + skb_shinfo(skb)->frags[i].size;		copy = end - offset;		if ((copy = end - offset) > 0) {			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];			struct page *page = frag->page; 			if (copy > len)				copy = len; 			cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list, page,					frag->page_offset + offset - start, copy);			if (cookie < 0)				goto fault;			len -= copy;			if (len == 0)				goto end;			offset += copy;		}		start = end;	} 	if (skb_shinfo(skb)->frag_list) {		struct sk_buff *list = skb_shinfo(skb)->frag_list; 		for (; list; list = list->next) {			int end; 			BUG_TRAP(start <= offset + len); 			end = start + list->len;			copy = end - offset;			if (copy > 0) {				if (copy > len)					copy = len;				cookie = dma_skb_copy_datagram_iovec(chan, list,				                offset - start, to, copy,				                pinned_list);				if (cookie < 0)					goto fault;				len -= copy;				if (len == 0)					goto end;				offset += copy;			}			start = end;		}	} end:	if (!len) {		skb->dma_cookie = cookie;		return cookie;	} fault: 	return -EFAULT;}