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.\" $OpenBSD: ehci.4,v 1.15 2021/12/29 18:44:52 patrick Exp $
.\"
.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Lennart Augustsson.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
.\" POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: December 29 2021 $
.Dt EHCI 4
.Os
.Sh NAME
.Nm ehci
.Nd USB Enhanced Host Controller Interface
.Sh SYNOPSIS
.Cd "ehci* at acpi?"
.Cd "ehci* at cardbus?"
.Cd "ehci* at fdt?"
.Cd "ehci* at pci?"
.Cd "usb* at ehci?"
.Sh DESCRIPTION
The
.Nm
driver provides support for the USB Enhanced Host Controller Interface,
which provides an interface to
.Xr usb 4
devices.
.Pp
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.,
.Xr ohci 4
or
.Xr uhci 4 )
or an internal rate-matching hub to handle USB 1.x devices.
.Pp
If at least one companion controller is present, 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.
.Sh SEE ALSO
.Xr acpi 4 ,
.Xr cardbus 4 ,
.Xr ohci 4 ,
.Xr pci 4 ,
.Xr uhci 4 ,
.Xr usb 4
.Sh HISTORY
The
.Nm
driver has been available since
.Ox 3.6 .
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