eddaeb2095
- Mention USB 3.0 - Update links - Fix `mandoc -T lint` warnings Reviewed by: bcr, hselasky MFC after: 3 days Differential Revision: https://reviews.freebsd.org/D26349
181 lines
5.3 KiB
Groff
181 lines
5.3 KiB
Groff
.\" Copyright (c) 1997, 1998 Nick Hibma <n_hibma@FreeBSD.org>
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.\" Copyright (c) 2008 Hans Petter Selasky. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 7, 2020
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.Dt USB 4
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.Os
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.Sh NAME
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.Nm usb
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.Nd Universal Serial Bus
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device usb"
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.Ed
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.Pp
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Alternatively, to load the driver as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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usb_load="YES"
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.Ed
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.Sh USERLAND PROGRAMMING
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USB functions can be accessed from userland through the libusb library.
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See
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.Xr libusb 3
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for more information.
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.Sh DESCRIPTION
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.Fx
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provides machine-independent bus support and drivers for
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USB devices in host and device side mode.
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.Pp
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The
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.Nm
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driver has three layers:
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.Bl -tag -width 6n -offset indent
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.It USB Controller (Bus)
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.It USB Device
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.It USB Driver
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.El
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.Pp
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The controller attaches to a physical bus
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like
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.Xr pci 4 .
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The USB bus attaches to the controller, and the root hub attaches
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to the controller.
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Any devices attached to the bus will attach to the root hub
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or another hub attached to the USB bus.
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.Pp
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The
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.Nm uhub
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device will always be present as it is needed for the root hub.
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.Sh INTRODUCTION TO USB
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The USB is a system where external devices can be connected to a PC.
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The most common USB speeds are:
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.Bl -tag -width 6n -offset indent
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.It Low Speed (1.5 MBit/sec)
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.It Full Speed (12 MBit/sec)
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.It High Speed (480 MBit/sec)
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.It SuperSpeed (5 GBit/sec)
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.El
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.Pp
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Each USB has a USB controller that is the master of the bus.
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The physical communication is simplex which means the host controller only
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communicates with one USB device at a time.
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.Pp
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There can be up to 127 devices connected to an USB HUB tree.
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The addresses are assigned dynamically by the host when each device is
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attached to the bus.
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.Pp
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Within each device there can be up to 16 endpoints.
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Each endpoint is individually addressed and the addresses are static.
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Each of these endpoints will communicate in one of four different modes:
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.Em control , isochronous , bulk ,
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or
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.Em interrupt .
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A device always has at least one endpoint.
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This endpoint has address 0 and is a control endpoint and is used to give
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commands to and extract basic data, such as descriptors, from the device.
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Each endpoint, except the control endpoint, is unidirectional.
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.Pp
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The endpoints in a device are grouped into interfaces.
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An interface is a logical unit within a device, e.g., a compound device with
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both a keyboard and a trackball, would present one interface for each.
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An interface can sometimes be set into different modes, called alternate
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settings, which affects how it operates.
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Different alternate settings can have different endpoints within it.
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.Pp
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A device may operate in different configurations.
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Depending on the configuration, the device may present different sets of
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endpoints and interfaces.
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.Pp
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The bus enumeration of the USB bus proceeds in several steps:
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.Bl -enum
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.It
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Any interface specific driver can attach to the device.
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.It
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If none is found, generic interface class drivers can attach.
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.El
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.Sh SYSCTL VARIABLES
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The following variables are available as both
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.Xr sysctl 8
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variables and
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.Xr loader 8
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tunables:
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.Bl -tag -width indent
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.It Va hw.usb.debug
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Debug output level, where 0 is debugging disabled and larger values increase
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debug message verbosity.
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Default is 0.
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.El
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.Sh SEE ALSO
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The USB specifications can be found at:
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.Pp
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.D1 Pa https://www.usb.org/documents
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.Pp
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.Xr libusb 3 ,
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.Xr aue 4 ,
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.Xr axe 4 ,
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.Xr axge 4 ,
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.Xr cue 4 ,
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.Xr ehci 4 ,
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.Xr kue 4 ,
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.Xr mos 4 ,
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.Xr ohci 4 ,
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.Xr pci 4 ,
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.Xr rue 4 ,
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.Xr ucom 4 ,
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.Xr udav 4 ,
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.Xr uhci 4 ,
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.Xr uhid 4 ,
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.Xr ukbd 4 ,
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.Xr ulpt 4 ,
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.Xr umass 4 ,
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.Xr ums 4 ,
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.Xr uplcom 4 ,
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.Xr urio 4 ,
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.Xr uvscom 4 ,
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.Xr xhci 4
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.Xr usbconfig 8 ,
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.Xr usbdi 9
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.Sh STANDARDS
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The
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.Nm
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module complies with the USB 3.0 standard.
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.Sh HISTORY
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The
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.Nm
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module has been inspired by the
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.Nx
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USB stack initially written by
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.An Lennart Augustsson .
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The
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.Nm
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module was written by
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.An Hans Petter Selasky Aq Mt hselasky@FreeBSD.org .
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