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/* Fallback functions when the main IOMMU code is not compiled in. This
   code is roughly equivalent to i386. */
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <linux/string.h>
#include <linux/dma-mapping.h>
#include <linux/scatterlist.h>

#include <asm/gart.h>
#include <asm/processor.h>
#include <asm/dma.h>

static int
check_addr(char *name, struct device *hwdev, dma_addr_t bus, size_t size)
        if (hwdev && bus + size > *hwdev->dma_mask) {
            if (*hwdev->dma_mask >= DMA_32BIT_MASK)
                      "nommu_%s: overflow %Lx+%zu of device mask %Lx\n",
                        name, (long long)bus, size,
                        (long long)*hwdev->dma_mask);
            return 0;
      return 1;

static dma_addr_t
nommu_map_single(struct device *hwdev, void *ptr, size_t size,
             int direction)
      dma_addr_t bus = virt_to_bus(ptr);
      if (!check_addr("map_single", hwdev, bus, size))
                        return bad_dma_address;
      return bus;

static void nommu_unmap_single(struct device *dev, dma_addr_t addr,size_t size,
                  int direction)

/* Map a set of buffers described by scatterlist in streaming
 * mode for DMA.  This is the scatter-gather version of the
 * above pci_map_single interface.  Here the scatter gather list
 * elements are each tagged with the appropriate dma address
 * and length.  They are obtained via sg_dma_{address,length}(SG).
 * NOTE: An implementation may be able to use a smaller number of
 *       DMA address/length pairs than there are SG table elements.
 *       (for example via virtual mapping capabilities)
 *       The routine returns the number of addr/length pairs actually
 *       used, at most nents.
 * Device ownership issues as mentioned above for pci_map_single are
 * the same here.
static int nommu_map_sg(struct device *hwdev, struct scatterlist *sg,
             int nents, int direction)
      struct scatterlist *s;
      int i;

      for_each_sg(sg, s, nents, i) {
            s->dma_address = virt_to_bus(sg_virt(s));
            if (!check_addr("map_sg", hwdev, s->dma_address, s->length))
                  return 0;
            s->dma_length = s->length;
      return nents;

/* Unmap a set of streaming mode DMA translations.
 * Again, cpu read rules concerning calls here are the same as for
 * pci_unmap_single() above.
static void nommu_unmap_sg(struct device *dev, struct scatterlist *sg,
              int nents, int dir)

const struct dma_mapping_ops nommu_dma_ops = {
      .map_single = nommu_map_single,
      .unmap_single = nommu_unmap_single,
      .map_sg = nommu_map_sg,
      .unmap_sg = nommu_unmap_sg,
      .is_phys = 1,

void __init no_iommu_init(void)
      if (dma_ops)

      force_iommu = 0; /* no HW IOMMU */
      dma_ops = &nommu_dma_ops;

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