arch/x86_64/kernel/pci-dma.c

   1 /*
   2  * Dynamic DMA mapping support.
   3  */
   4
   5 #include <linux/types.h>
   6 #include <linux/mm.h>
   7 #include <linux/string.h>
   8 #include <linux/pci.h>
   9 #include <linux/module.h>
  10 #include <asm/io.h>
  11
  12 /* Map a set of buffers described by scatterlist in streaming
  13  * mode for DMA.  This is the scatter-gather version of the
  14  * above pci_map_single interface.  Here the scatter gather list
  15  * elements are each tagged with the appropriate dma address
  16  * and length.  They are obtained via sg_dma_{address,length}(SG).
  17  *
  18  * NOTE: An implementation may be able to use a smaller number of
  19  *       DMA address/length pairs than there are SG table elements.
  20  *       (for example via virtual mapping capabilities)
  21  *       The routine returns the number of addr/length pairs actually
  22  *       used, at most nents.
  23  *
  24  * Device ownership issues as mentioned above for pci_map_single are
  25  * the same here.
  26  */
  27 int dma_map_sg(struct device *hwdev, struct scatterlist *sg,
  28                int nents, int direction)
  29 {
  30         int i;
  31
  32         BUG_ON(direction == DMA_NONE);
  33         for (i = 0; i < nents; i++ ) {
  34                 struct scatterlist *s = &sg[i];
  35                 BUG_ON(!s->page);
  36                 s->dma_address = virt_to_bus(page_address(s->page) +s->offset);
  37                 s->dma_length = s->length;
  38         }
  39         return nents;
  40 }
  41
  42 EXPORT_SYMBOL(dma_map_sg);
  43
  44 /* Unmap a set of streaming mode DMA translations.
  45  * Again, cpu read rules concerning calls here are the same as for
  46  * pci_unmap_single() above.
  47  */
  48 void dma_unmap_sg(struct device *dev, struct scatterlist *sg,
  49                   int nents, int dir)
  50 {
  51         int i;
  52         for (i = 0; i < nents; i++) {
  53                 struct scatterlist *s = &sg[i];
  54                 BUG_ON(s->page == NULL);
  55                 BUG_ON(s->dma_address == 0);
  56                 dma_unmap_single(dev, s->dma_address, s->dma_length, dir);
  57         }
  58 }
  59
  60 EXPORT_SYMBOL(dma_unmap_sg);