.Cd "ehci* at cardbus?"
.Cd "ehci* at pci?"
.Cd "usb* at ehci?"
driver provides support for the USB Enhanced Host Controller Interface,
which provides an interface to
EHCI controllers are peculiar in that they can only handle the USB 2.0
This means that they normally have one or more companion controllers
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 buses.