1 .\" Copyright (c) 1997, 1998 Nick Hibma <n_hibma@FreeBSD.org>
2 .\" Copyright (c) 2008 Hans Petter Selasky. All rights reserved.
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32 .Nd Universal Serial Bus
34 To compile this driver into the kernel,
35 place the following line in your
36 kernel configuration file:
37 .Bd -ragged -offset indent
41 Alternatively, to load the driver as a
42 module at boot time, place the following line in
44 .Bd -literal -offset indent
47 .Sh USERLAND PROGRAMMING
48 USB functions can be accessed from userland through the libusb library.
54 provides machine-independent bus support and drivers for
56 devices in host and device side mode.
60 driver has three layers:
61 .Bl -tag -width 6n -offset indent
62 .It USB Controller (Bus)
67 The controller attaches to a physical bus
72 bus attaches to the controller, and the root hub attaches
74 Any devices attached to the bus will attach to the root hub
75 or another hub attached to the
81 device will always be present as it is needed for the root hub.
82 .Sh INTRODUCTION TO USB
85 is a system where external devices can be connected to a PC.
86 The most common USB speeds are:
87 .Bl -tag -width 6n -offset indent
88 .It Low Speed (1.5MBit/sec)
89 .It Full Speed (12MBit/sec)
90 .It High Speed (480MBit/sec)
95 has a USB controller that is the master of the bus.
96 The physical communication is simplex which means the host controller only
97 communicates with one USB device at a time.
99 There can be up to 127 devices connected to an USB HUB tree.
100 The addresses are assigned dynamically by the host when each device is
103 Within each device there can be up to 16 endpoints.
104 Each endpoint is individually addressed and the addresses are static.
105 Each of these endpoints will communicate in one of four different modes:
106 .Em control , isochronous , bulk ,
109 A device always has at least one endpoint.
110 This endpoint has address 0 and is a control endpoint and is used to give
111 commands to and extract basic data, such as descriptors, from the device.
112 Each endpoint, except the control endpoint, is unidirectional.
114 The endpoints in a device are grouped into interfaces.
115 An interface is a logical unit within a device, e.g., a compound device with
116 both a keyboard and a trackball, would present one interface for each.
117 An interface can sometimes be set into different modes, called alternate
118 settings, which affects how it operates.
119 Different alternate settings can have different endpoints within it.
121 A device may operate in different configurations.
122 Depending on the configuration, the device may present different sets of
123 endpoints and interfaces.
125 The bus enumeration of the
127 bus proceeds in several steps:
130 Any interface specific driver can attach to the device.
132 If none is found, generic interface class drivers can attach.
137 driver exposes the following variables in the
142 .Bl -tag -width ".Va debug"
144 Debug output level, where 0 is debugging disabled and larger values increase
145 debug message verbosity.
150 specifications can be found at:
152 .D1 Pa http://www.usb.org/developers/docs/
182 module complies with the USB 2.0 standard.
186 module has been inspired by the
188 USB stack initially written by
189 .An Lennart Augustsson .
192 module was written by
193 .An Hans Petter Selasky Aq Mt hselasky@FreeBSD.org .