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 <linux/rtnetlink.h> /* for BUG_TRAP */
31#include <net/tcp.h>
32#include <net/netdma.h>
33
34#define NET_DMA_DEFAULT_COPYBREAK 4096
35
36int sysctl_tcp_dma_copybreak = NET_DMA_DEFAULT_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	dma_cookie_t cookie = 0;
55
56	/* Copy header. */
57	if (copy > 0) {
58		if (copy > len)
59			copy = len;
60		cookie = dma_memcpy_to_iovec(chan, to, pinned_list,
61					    skb->data + offset, copy);
62		if (cookie < 0)
63			goto fault;
64		len -= copy;
65		if (len == 0)
66			goto end;
67		offset += copy;
68	}
69
70	/* Copy paged appendix. Hmm... why does this look so complicated? */
71	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
72		int end;
73
74		BUG_TRAP(start <= offset + len);
75
76		end = start + skb_shinfo(skb)->frags[i].size;
77		copy = end - offset;
78		if ((copy = end - offset) > 0) {
79			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
80			struct page *page = frag->page;
81
82			if (copy > len)
83				copy = len;
84
85			cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list, page,
86					frag->page_offset + offset - start, copy);
87			if (cookie < 0)
88				goto fault;
89			len -= copy;
90			if (len == 0)
91				goto end;
92			offset += copy;
93		}
94		start = end;
95	}
96
97	if (skb_shinfo(skb)->frag_list) {
98		struct sk_buff *list = skb_shinfo(skb)->frag_list;
99
100		for (; list; list = list->next) {
101			int end;
102
103			BUG_TRAP(start <= offset + len);
104
105			end = start + list->len;
106			copy = end - offset;
107			if (copy > 0) {
108				if (copy > len)
109					copy = len;
110				cookie = dma_skb_copy_datagram_iovec(chan, list,
111						offset - start, to, copy,
112						pinned_list);
113				if (cookie < 0)
114					goto fault;
115				len -= copy;
116				if (len == 0)
117					goto end;
118				offset += copy;
119			}
120			start = end;
121		}
122	}
123
124end:
125	if (!len) {
126		skb->dma_cookie = cookie;
127		return cookie;
128	}
129
130fault:
131	return -EFAULT;
132}
133