1.\" $OpenBSD: ehci.4,v 1.15 2021/12/29 18:44:52 patrick 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.Dd $Mdocdate: December 29 2021 $ 31.Dt EHCI 4 32.Os 33.Sh NAME 34.Nm ehci 35.Nd USB Enhanced Host Controller Interface 36.Sh SYNOPSIS 37.Cd "ehci* at acpi?" 38.Cd "ehci* at cardbus?" 39.Cd "ehci* at fdt?" 40.Cd "ehci* at pci?" 41.Cd "usb* at ehci?" 42.Sh DESCRIPTION 43The 44.Nm 45driver provides support for the USB Enhanced Host Controller Interface, 46which provides an interface to 47.Xr usb 4 48devices. 49.Pp 50EHCI controllers are peculiar in that they can only handle the USB 2.0 51protocol. 52This means that they normally have one or more companion controllers 53(i.e., 54.Xr ohci 4 55or 56.Xr uhci 4 ) 57or an internal rate-matching hub to handle USB 1.x devices. 58.Pp 59If at least one companion controller is present, each USB connector is 60electrically connected to two USB controllers. 61The handling of this is totally automatic, 62but can be noticed since USB 1.x and USB 2.0 devices plugged in to the same 63connector appear to connect to different USB buses. 64.Sh SEE ALSO 65.Xr acpi 4 , 66.Xr cardbus 4 , 67.Xr ohci 4 , 68.Xr pci 4 , 69.Xr uhci 4 , 70.Xr usb 4 71.Sh HISTORY 72The 73.Nm 74driver has been available since 75.Ox 3.6 . 76