import re


def pci_dev_check(pci_dev):
    """Check if provided PCI address is in correct format.

    :param pci_dev: PCI address (expected format: xxxx:xx:xx.x).
    :type pci_dev: str
    :returns: True if PCI address is in correct format.
    :rtype: bool
    :raises ValueError: If PCI address is in incorrect format.
    """
    pattern = re.compile(
        r"^[0-9A-Fa-f]{4}:[0-9A-Fa-f]{2}:[0-9A-Fa-f]{2}\.[0-9A-Fa-f]$"
    )
    if not re.match(pattern, pci_dev):
        raise ValueError(
            f"PCI address {pci_dev} is not in valid format xxxx:xx:xx.x"
        )
    return True