.\" $NetBSD: ehci.4,v 1.8 2001/11/21 17:22:56 augustss 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
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" $FreeBSD: releng/10.1/share/man/man4/ehci.4 232507 2012-03-04 16:59:45Z eadler $
.\"
.Dd March 4, 2012
.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 xhci 4 ,
.Xr ohci 4 ,
.Xr uhci 4 ,
.Xr usb 4
.Sh HISTORY
The
.Nm
device driver first appeared in
.Fx 5.1 .
.Sh LOADER TUNABLES
When the kernel has been compiled with
.Cd options USB_DEBUG ,
some tunables become available that affect the behavior of
.Nm .
These tunables can be set at the
.Xr loader 8
prompt before booting the kernel or stored in
.Xr loader.conf 5 .
.Bl -tag -width "xxxxxx"
.It Va hw.usb.ehci.lostintrbug
This tunable enables the lost interrupt quirk.
The default value is 0 (off).
.It Va hw.usb.ehci.iaadbug
This tunable enables the EHCI doorbell quirk.
The default value is 0 (off).
.It Va hw.usb.ehci.no_hs
This tunable disables USB devices to attach like HIGH-speed ones and will force all attached devices to attach to the FULL- or LOW-speed companion controller.
The default value is 0 (off).
.El