1.\" $NetBSD: ehci.4,v 1.8 2001/11/21 17:22:56 augustss Exp $ 2.\" 3.\" Copyright (c) 2001 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Lennart Augustsson. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.\" $FreeBSD$ 31.\" 32.Dd January 15, 2017 33.Dt EHCI 4 34.Os 35.Sh NAME 36.Nm ehci 37.Nd USB Enhanced Host Controller driver 38.Sh SYNOPSIS 39.Cd "device ehci" 40.Sh DESCRIPTION 41The 42.Nm 43driver provides support for the 44.Tn USB 45Enhanced Host Controller Interface, 46which is used by 47.Tn USB 482.0 controllers. 49.Pp 50.Tn EHCI 51controllers are peculiar in that they can only handle the 52.Tn USB 532.0 protocol. 54This means that they normally have one or more companion controllers 55(i.e., 56.Xr ohci 4 57or 58.Xr uhci 4 ) 59handling USB 1.x devices. 60Consequently each 61.Tn USB 62connector is electrically connected to two 63.Tn USB 64controllers. 65The handling of this is totally automatic, 66but can be noticed since 67.Tn USB 681.x and 69.Tn USB 702.0 devices plugged in to the same 71connector appear to connect to different USB buses. 72.Sh SEE ALSO 73.Xr ohci 4 , 74.Xr uhci 4 , 75.Xr usb 4 , 76.Xr xhci 4 77.Sh HISTORY 78The 79.Nm 80device driver first appeared in 81.Fx 5.1 . 82.Sh LOADER TUNABLES 83When the kernel has been compiled with 84.Cd options USB_DEBUG , 85some tunables become available that affect the behavior of 86.Nm . 87These tunables can be set at the 88.Xr loader 8 89prompt before booting the kernel or stored in 90.Xr loader.conf 5 . 91.Bl -tag -width "xxxxxx" 92.It Va hw.usb.ehci.lostintrbug 93This tunable enables the lost interrupt quirk. 94The default value is 0 (off). 95.It Va hw.usb.ehci.iaadbug 96This tunable enables the EHCI doorbell quirk. 97The default value is 0 (off). 98.It Va hw.usb.ehci.no_hs 99This 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. 100The default value is 0 (off). 101.El 102