static ssize_t vfio_pci_igd_cfg_rw()

in pci/vfio_pci_igd.c [281:372]

• 68 lines of code
• 20 McCabe index (conditional complexity)

static ssize_t vfio_pci_igd_cfg_rw(struct vfio_pci_core_device *vdev,
				   char __user *buf, size_t count, loff_t *ppos,
				   bool iswrite)
{
	unsigned int i = VFIO_PCI_OFFSET_TO_INDEX(*ppos) - VFIO_PCI_NUM_REGIONS;
	struct pci_dev *pdev = vdev->region[i].data;
	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
	size_t size;
	int ret;

	if (pos >= vdev->region[i].size || iswrite)
		return -EINVAL;

	size = count = min(count, (size_t)(vdev->region[i].size - pos));

	if ((pos & 1) && size) {
		u8 val;

		ret = pci_user_read_config_byte(pdev, pos, &val);
		if (ret)
			return ret;

		if (copy_to_user(buf + count - size, &val, 1))
			return -EFAULT;

		pos++;
		size--;
	}

	if ((pos & 3) && size > 2) {
		u16 val;

		ret = pci_user_read_config_word(pdev, pos, &val);
		if (ret)
			return ret;

		val = cpu_to_le16(val);
		if (copy_to_user(buf + count - size, &val, 2))
			return -EFAULT;

		pos += 2;
		size -= 2;
	}

	while (size > 3) {
		u32 val;

		ret = pci_user_read_config_dword(pdev, pos, &val);
		if (ret)
			return ret;

		val = cpu_to_le32(val);
		if (copy_to_user(buf + count - size, &val, 4))
			return -EFAULT;

		pos += 4;
		size -= 4;
	}

	while (size >= 2) {
		u16 val;

		ret = pci_user_read_config_word(pdev, pos, &val);
		if (ret)
			return ret;

		val = cpu_to_le16(val);
		if (copy_to_user(buf + count - size, &val, 2))
			return -EFAULT;

		pos += 2;
		size -= 2;
	}

	while (size) {
		u8 val;

		ret = pci_user_read_config_byte(pdev, pos, &val);
		if (ret)
			return ret;

		if (copy_to_user(buf + count - size, &val, 1))
			return -EFAULT;

		pos++;
		size--;
	}

	*ppos += count;

	return count;
}