ehci —
USB Enhanced Host Controller driver
ehci* at cardbus? function ?
ehci* at pci? dev ? function ?
usb* at ehci?
The ehci driver provides support for the USB Enhanced
  Host Controller Interface, which is used by USB 2.0 controllers.
EHCI controllers are peculiar in that they can only handle the USB
    2.0 protocol. This means that they normally have one or more companion
    controllers (i.e., ohci(4) or
    uhci(4)) handling USB 1.x
    devices. Consequently each USB connector is electrically connected to two
    USB controllers. The handling of this is totally automatic, but can be
    noticed since USB 1.x and USB 2.0 devices plugged in to the same connector
    appear to connect to different USB busses.
The ehci driver appeared in NetBSD
  1.6.
The support for hubs that are connected with high speed upstream and low or full
  speed downstream (i.e., for transaction translators) is limited.