ssize_t vfio_pci_vga_rw()

in pci/vfio_pci_rdwr.c [291:357]

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

ssize_t vfio_pci_vga_rw(struct vfio_pci_core_device *vdev, char __user *buf,
			       size_t count, loff_t *ppos, bool iswrite)
{
	int ret;
	loff_t off, pos = *ppos & VFIO_PCI_OFFSET_MASK;
	void __iomem *iomem = NULL;
	unsigned int rsrc;
	bool is_ioport;
	ssize_t done;

	if (!vdev->has_vga)
		return -EINVAL;

	if (pos > 0xbfffful)
		return -EINVAL;

	switch ((u32)pos) {
	case 0xa0000 ... 0xbffff:
		count = min(count, (size_t)(0xc0000 - pos));
		iomem = ioremap(0xa0000, 0xbffff - 0xa0000 + 1);
		off = pos - 0xa0000;
		rsrc = VGA_RSRC_LEGACY_MEM;
		is_ioport = false;
		break;
	case 0x3b0 ... 0x3bb:
		count = min(count, (size_t)(0x3bc - pos));
		iomem = ioport_map(0x3b0, 0x3bb - 0x3b0 + 1);
		off = pos - 0x3b0;
		rsrc = VGA_RSRC_LEGACY_IO;
		is_ioport = true;
		break;
	case 0x3c0 ... 0x3df:
		count = min(count, (size_t)(0x3e0 - pos));
		iomem = ioport_map(0x3c0, 0x3df - 0x3c0 + 1);
		off = pos - 0x3c0;
		rsrc = VGA_RSRC_LEGACY_IO;
		is_ioport = true;
		break;
	default:
		return -EINVAL;
	}

	if (!iomem)
		return -ENOMEM;

	ret = vga_get_interruptible(vdev->pdev, rsrc);
	if (ret) {
		is_ioport ? ioport_unmap(iomem) : iounmap(iomem);
		return ret;
	}

	/*
	 * VGA MMIO is a legacy, non-BAR resource that hopefully allows
	 * probing, so we don't currently worry about access in relation
	 * to the memory enable bit in the command register.
	 */
	done = do_io_rw(vdev, false, iomem, buf, off, count, 0, 0, iswrite);

	vga_put(vdev->pdev, rsrc);

	is_ioport ? ioport_unmap(iomem) : iounmap(iomem);

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

	return done;
}