user_dma.c
3.26 KB
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/*
* 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 <net/tcp.h>
#include <net/netdma.h>
#define NET_DMA_DEFAULT_COPYBREAK 4096
int sysctl_tcp_dma_copybreak = NET_DMA_DEFAULT_COPYBREAK;
EXPORT_SYMBOL(sysctl_tcp_dma_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;
struct sk_buff *frag_iter;
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;
WARN_ON(start > offset + len);
end = start + skb_shinfo(skb)->frags[i].size;
copy = end - offset;
if (copy > 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;
}
skb_walk_frags(skb, frag_iter) {
int end;
WARN_ON(start > offset + len);
end = start + frag_iter->len;
copy = end - offset;
if (copy > 0) {
if (copy > len)
copy = len;
cookie = dma_skb_copy_datagram_iovec(chan, frag_iter,
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;
}