/*
   * 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/export.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;

  		const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];

  		WARN_ON(start > offset + len);

  		end = start + skb_frag_size(frag);

  		copy = end - offset;

  		if (copy > 0) {

  			struct page *page = skb_frag_page(frag);

  
  			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;

  }