1/*
  2 * Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
  3 * Portions based on net/core/datagram.c and copyrighted by their authors.
  4 *
  5 * This program is free software; you can redistribute it and/or modify it
  6 * under the terms of the GNU General Public License as published by the Free
  7 * Software Foundation; either version 2 of the License, or (at your option)
  8 * any later version.
  9 *
 10 * This program is distributed in the hope that it will be useful, but WITHOUT
 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 12 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 13 * more details.
 14 *
 15 * You should have received a copy of the GNU General Public License along with
 16 * this program; if not, write to the Free Software Foundation, Inc., 59
 17 * Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 18 *
 19 * The full GNU General Public License is included in this distribution in the
 20 * file called COPYING.
 21 */
 22
 23/*
 24 * This code allows the net stack to make use of a DMA engine for
 25 * skb to iovec copies.
 26 */
 27
 28#include <linux/dmaengine.h>
 29#include <linux/socket.h>
 30#include <net/tcp.h>
 31#include <net/netdma.h>
 32
 33#define NET_DMA_DEFAULT_COPYBREAK 4096
 34
 35int sysctl_tcp_dma_copybreak = NET_DMA_DEFAULT_COPYBREAK;
 36EXPORT_SYMBOL(sysctl_tcp_dma_copybreak);
 37
 38/**
 39 *	dma_skb_copy_datagram_iovec - Copy a datagram to an iovec.
 40 *	@skb - buffer to copy
 41 *	@offset - offset in the buffer to start copying from
 42 *	@iovec - io vector to copy to
 43 *	@len - amount of data to copy from buffer to iovec
 44 *	@pinned_list - locked iovec buffer data
 45 *
 46 *	Note: the iovec is modified during the copy.
 47 */
 48int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
 49			struct sk_buff *skb, int offset, struct iovec *to,
 50			size_t len, struct dma_pinned_list *pinned_list)
 51{
 52	int start = skb_headlen(skb);
 53	int i, copy = start - offset;
 54	struct sk_buff *frag_iter;
 55	dma_cookie_t cookie = 0;
 56
 57	/* Copy header. */
 58	if (copy > 0) {
 59		if (copy > len)
 60			copy = len;
 61		cookie = dma_memcpy_to_iovec(chan, to, pinned_list,
 62					    skb->data + offset, copy);
 63		if (cookie < 0)
 64			goto fault;
 65		len -= copy;
 66		if (len == 0)
 67			goto end;
 68		offset += copy;
 69	}
 70
 71	/* Copy paged appendix. Hmm... why does this look so complicated? */
 72	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 73		int end;
 74
 75		WARN_ON(start > offset + len);
 76
 77		end = start + skb_shinfo(skb)->frags[i].size;
 78		copy = end - offset;
 79		if (copy > 0) {
 80			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 81			struct page *page = frag->page;
 82
 83			if (copy > len)
 84				copy = len;
 85
 86			cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list, page,
 87					frag->page_offset + offset - start, copy);
 88			if (cookie < 0)
 89				goto fault;
 90			len -= copy;
 91			if (len == 0)
 92				goto end;
 93			offset += copy;
 94		}
 95		start = end;
 96	}
 97
 98	skb_walk_frags(skb, frag_iter) {
 99		int end;
100
101		WARN_ON(start > offset + len);
102
103		end = start + frag_iter->len;
104		copy = end - offset;
105		if (copy > 0) {
106			if (copy > len)
107				copy = len;
108			cookie = dma_skb_copy_datagram_iovec(chan, frag_iter,
109							     offset - start,
110							     to, copy,
111							     pinned_list);
112			if (cookie < 0)
113				goto fault;
114			len -= copy;
115			if (len == 0)
116				goto end;
117			offset += copy;
118		}
119		start = end;
120	}
121
122end:
123	if (!len) {
124		skb->dma_cookie = cookie;
125		return cookie;
126	}
127
128fault:
129	return -EFAULT;
130}