static int alpha_pci_map_sg()

in kernel/pci_iommu.c [631:707]

• 57 lines of code
• 15 McCabe index (conditional complexity)

static int alpha_pci_map_sg(struct device *dev, struct scatterlist *sg,
			    int nents, enum dma_data_direction dir,
			    unsigned long attrs)
{
	struct pci_dev *pdev = alpha_gendev_to_pci(dev);
	struct scatterlist *start, *end, *out;
	struct pci_controller *hose;
	struct pci_iommu_arena *arena;
	dma_addr_t max_dma;
	int dac_allowed;

	BUG_ON(dir == PCI_DMA_NONE);

	dac_allowed = dev ? pci_dac_dma_supported(pdev, pdev->dma_mask) : 0;

	/* Fast path single entry scatterlists.  */
	if (nents == 1) {
		sg->dma_length = sg->length;
		sg->dma_address
		  = pci_map_single_1(pdev, SG_ENT_VIRT_ADDRESS(sg),
				     sg->length, dac_allowed);
		if (sg->dma_address == DMA_MAPPING_ERROR)
			return -EIO;
		return 1;
	}

	start = sg;
	end = sg + nents;

	/* First, prepare information about the entries.  */
	sg_classify(dev, sg, end, alpha_mv.mv_pci_tbi != 0);

	/* Second, figure out where we're going to map things.  */
	if (alpha_mv.mv_pci_tbi) {
		hose = pdev ? pdev->sysdata : pci_isa_hose;
		max_dma = pdev ? pdev->dma_mask : ISA_DMA_MASK;
		arena = hose->sg_pci;
		if (!arena || arena->dma_base + arena->size - 1 > max_dma)
			arena = hose->sg_isa;
	} else {
		max_dma = -1;
		arena = NULL;
		hose = NULL;
	}

	/* Third, iterate over the scatterlist leaders and allocate
	   dma space as needed.  */
	for (out = sg; sg < end; ++sg) {
		if ((int) sg->dma_address < 0)
			continue;
		if (sg_fill(dev, sg, end, out, arena, max_dma, dac_allowed) < 0)
			goto error;
		out++;
	}

	/* Mark the end of the list for pci_unmap_sg.  */
	if (out < end)
		out->dma_length = 0;

	if (out - start == 0) {
		printk(KERN_WARNING "pci_map_sg failed: no entries?\n");
		return -ENOMEM;
	}
	DBGA("pci_map_sg: %ld entries\n", out - start);

	return out - start;

 error:
	printk(KERN_WARNING "pci_map_sg failed: "
	       "could not allocate dma page tables\n");

	/* Some allocation failed while mapping the scatterlist
	   entries.  Unmap them now.  */
	if (out > start)
		pci_unmap_sg(pdev, start, out - start, dir);
	return -ENOMEM;
}