ssize_t vfio_pci_bar_rw()

in pci/vfio_pci_rdwr.c [227:289]

• 49 lines of code
• 11 McCabe index (conditional complexity)

ssize_t vfio_pci_bar_rw(struct vfio_pci_core_device *vdev, char __user *buf,
			size_t count, loff_t *ppos, bool iswrite)
{
	struct pci_dev *pdev = vdev->pdev;
	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
	int bar = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
	size_t x_start = 0, x_end = 0;
	resource_size_t end;
	void __iomem *io;
	struct resource *res = &vdev->pdev->resource[bar];
	ssize_t done;

	if (pci_resource_start(pdev, bar))
		end = pci_resource_len(pdev, bar);
	else if (bar == PCI_ROM_RESOURCE &&
		 pdev->resource[bar].flags & IORESOURCE_ROM_SHADOW)
		end = 0x20000;
	else
		return -EINVAL;

	if (pos >= end)
		return -EINVAL;

	count = min(count, (size_t)(end - pos));

	if (bar == PCI_ROM_RESOURCE) {
		/*
		 * The ROM can fill less space than the BAR, so we start the
		 * excluded range at the end of the actual ROM.  This makes
		 * filling large ROM BARs much faster.
		 */
		io = pci_map_rom(pdev, &x_start);
		if (!io) {
			done = -ENOMEM;
			goto out;
		}
		x_end = end;
	} else {
		int ret = vfio_pci_setup_barmap(vdev, bar);
		if (ret) {
			done = ret;
			goto out;
		}

		io = vdev->barmap[bar];
	}

	if (bar == vdev->msix_bar) {
		x_start = vdev->msix_offset;
		x_end = vdev->msix_offset + vdev->msix_size;
	}

	done = do_io_rw(vdev, res->flags & IORESOURCE_MEM, io, buf, pos,
			count, x_start, x_end, iswrite);

	if (done >= 0)
		*ppos += done;

	if (bar == PCI_ROM_RESOURCE)
		pci_unmap_rom(pdev, io);
out:
	return done;
}