linux/net/core/skb_dma_map.c
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   1/* skb_dma_map.c: DMA mapping helpers for socket buffers.
   2 *
   3 * Copyright (C) David S. Miller <davem@davemloft.net>
   4 */
   5
   6#include <linux/kernel.h>
   7#include <linux/module.h>
   8#include <linux/dma-mapping.h>
   9#include <linux/skbuff.h>
  10
  11int skb_dma_map(struct device *dev, struct sk_buff *skb,
  12                enum dma_data_direction dir)
  13{
  14        struct skb_shared_info *sp = skb_shinfo(skb);
  15        dma_addr_t map;
  16        int i;
  17
  18        map = dma_map_single(dev, skb->data,
  19                             skb_headlen(skb), dir);
  20        if (dma_mapping_error(dev, map))
  21                goto out_err;
  22
  23        sp->dma_maps[0] = map;
  24        for (i = 0; i < sp->nr_frags; i++) {
  25                skb_frag_t *fp = &sp->frags[i];
  26
  27                map = dma_map_page(dev, fp->page, fp->page_offset,
  28                                   fp->size, dir);
  29                if (dma_mapping_error(dev, map))
  30                        goto unwind;
  31                sp->dma_maps[i + 1] = map;
  32        }
  33        sp->num_dma_maps = i + 1;
  34
  35        return 0;
  36
  37unwind:
  38        while (--i >= 0) {
  39                skb_frag_t *fp = &sp->frags[i];
  40
  41                dma_unmap_page(dev, sp->dma_maps[i + 1],
  42                               fp->size, dir);
  43        }
  44        dma_unmap_single(dev, sp->dma_maps[0],
  45                         skb_headlen(skb), dir);
  46out_err:
  47        return -ENOMEM;
  48}
  49EXPORT_SYMBOL(skb_dma_map);
  50
  51void skb_dma_unmap(struct device *dev, struct sk_buff *skb,
  52                   enum dma_data_direction dir)
  53{
  54        struct skb_shared_info *sp = skb_shinfo(skb);
  55        int i;
  56
  57        dma_unmap_single(dev, sp->dma_maps[0],
  58                         skb_headlen(skb), dir);
  59        for (i = 0; i < sp->nr_frags; i++) {
  60                skb_frag_t *fp = &sp->frags[i];
  61
  62                dma_unmap_page(dev, sp->dma_maps[i + 1],
  63                               fp->size, dir);
  64        }
  65}
  66EXPORT_SYMBOL(skb_dma_unmap);
  67