root/arch/x86/kernel/pci-nommu.c

DEFINITIONS

1. check_addr
2. nommu_map_single
3. nommu_map_sg
4. nommu_free_coherent
5. no_iommu_init

/* 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/iommu.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 && !is_buffer_dma_capable(*hwdev->dma_mask, bus, size)) {
                if (*hwdev->dma_mask >= DMA_32BIT_MASK)
                        printk(KERN_ERR
                            "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, phys_addr_t paddr, size_t size,
               int direction)
{
        dma_addr_t bus = paddr;
        WARN_ON(size == 0);
        if (!check_addr("map_single", hwdev, bus, size))
                                return bad_dma_address;
        flush_write_buffers();
        return bus;
}


/* 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;

        WARN_ON(nents == 0 || sg[0].length == 0);

        for_each_sg(sg, s, nents, i) {
                BUG_ON(!sg_page(s));
                s->dma_address = sg_phys(s);
                if (!check_addr("map_sg", hwdev, s->dma_address, s->length))
                        return 0;
                s->dma_length = s->length;
        }
        flush_write_buffers();
        return nents;
}

static void nommu_free_coherent(struct device *dev, size_t size, void *vaddr,
                                dma_addr_t dma_addr)
{
        free_pages((unsigned long)vaddr, get_order(size));
}

struct dma_mapping_ops nommu_dma_ops = {
        .alloc_coherent = dma_generic_alloc_coherent,
        .free_coherent = nommu_free_coherent,
        .map_single = nommu_map_single,
        .map_sg = nommu_map_sg,
        .is_phys = 1,
};

void __init no_iommu_init(void)
{
        if (dma_ops)
                return;

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