.\" $NetBSD: ehci.4,v 1.8 2001/11/21 17:22:56 augustss Exp $
.\"
.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Lennart Augustsson.
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.\" $FreeBSD: src/share/man/man4/ehci.4,v 1.2.22.1.6.1 2010/12/21 17:09:25 kensmith Exp $
.\"
.Dd March 20, 2005
.Dt EHCI 4
.Os
.Sh NAME
.Nm ehci
.Nd USB Enhanced Host Controller driver
.Sh SYNOPSIS
.Cd "device ehci"
.Sh DESCRIPTION
The
.Nm
driver provides support for the
.Tn USB
Enhanced Host Controller Interface,
which is used by
.Tn USB
2.0 controllers.
.Pp
.Tn EHCI
controllers are peculiar in that they can only handle the
.Tn USB
2.0 protocol.
This means that they normally have one or more companion controllers
(i.e.,
.Xr ohci 4
or
.Xr uhci 4 )
handling USB 1.x devices.
Consequently each
.Tn USB
connector is electrically connected to two
.Tn USB
controllers.
The handling of this is totally automatic,
but can be noticed since
.Tn USB
1.x and
.Tn USB
2.0 devices plugged in to the same
connector appear to connect to different USB busses.
.Sh SEE ALSO
.Xr ohci 4 ,
.Xr uhci 4 ,
.Xr usb 4
.Sh HISTORY
The
.Nm
device driver first appeared in
.Fx 5.1 .
.Sh BUGS
The driver is not finished and is quite buggy.
.Pp
There is currently no support for isochronous transfers.