= PCI Express root port
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A <PCI Express root port> is a port in a root complex that starts a <PCI Express> link leading toward downstream devices or a switch. The <PCI Express root port> is represented as a logical bridge in the hierarchy. It is distinct from the <PCI Express endpoint> that provides a device function.<The PCI Express Port Bus Driver Guide HOWTO>[§2.2, root ports, switch ports and logical bridge structure]{ref}
For example, a storage <PCI Express endpoint> can attach directly to one <PCI Express root port>, while another root port connects to a switch serving several devices. Port services such as error reporting, hot plugging or power management concern that hierarchy and its links. Requiring a root-port service driver is therefore a different task from writing the <device driver> for the storage endpoint.
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