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28 .\" $FreeBSD: src/share/man/man4/usb.4,v 1.9.2.10 2002/12/19 20:48:25 trhodes Exp $
35 .Nd Universal Serial Bus
43 provides machine-independent bus support and drivers for
49 driver has three layers: the controller, the bus, and the
51 The controller attaches to a physical bus
56 bus attaches to the controller, and the root hub attaches
58 Any devices attached to the bus will attach to the root hub
59 or another hub attached to the
65 device will always be present as it is needed for the
67 .Sh INTRODUCTION TO USB
70 is a 12 Mb/s serial bus (1.5 Mb/s for low speed devices).
73 has a host controller that is the master of the bus;
74 all other devices on the bus only speak when spoken to.
76 There can be up to 127 devices (apart from the host controller)
77 on a bus, each with its own address.
78 The addresses are assigned
79 dynamically by the host when each device is attached to the bus.
81 Within each device there can be up to 16 endpoints.
83 is individually addressed and the addresses are static.
84 Each of these endpoints will communicate in one of four different modes:
85 .Em control , isochronous , bulk ,
88 A device always has at least one endpoint.
89 This endpoint has address 0 and is a control
90 endpoint and is used to give commands to and extract basic data,
91 such as descriptors, from the device.
92 Each endpoint, except the control endpoint, is unidirectional.
94 The endpoints in a device are grouped into interfaces.
95 An interface is a logical unit within a device; e.g.\&
96 a compound device with both a keyboard and a trackball would present
97 one interface for each.
98 An interface can sometimes be set into different modes,
99 called alternate settings, which affects how it operates.
100 Different alternate settings can have different endpoints
103 A device may operate in different configurations.
105 configuration, the device may present different sets of endpoints
108 Each device located on a hub has several
111 .Bl -tag -compact -width xxxxxx
113 this is the number of the port on the closest upstream hub.
115 this is the configuration the device must be in for this driver to attach.
116 This locator does not set the configuration; it is iterated by the bus
119 this is the interface number within a device that an interface driver
122 this is the 16 bit vendor id of the device.
124 this is the 16 bit product id of the device.
126 this is the 16 bit release (revision) number of the device.
128 The first locator can be used to pin down a particular device
129 according to its physical position in the device tree.
130 The last three locators can be used to pin down a particular
131 device according to what device it actually is.
133 The bus enumeration of the
135 bus proceeds in several steps:
138 Any device specific driver can attach to the device.
140 If none is found, any device class specific driver can attach.
142 If none is found, all configurations are iterated over.
143 For each configuration, all the interfaces are iterated over, and interface
145 If any interface driver attached in a certain
146 configuration, the iteration over configurations is stopped.
148 If still no drivers have been found, the generic
152 .Sh USB CONTROLLER INTERFACE
153 Use the following to get access to the
155 specific structures and defines.
161 can be opened and a few operations can be performed on it.
164 system call will say that I/O is possible on the controller device when a
166 device has been connected or disconnected to the bus.
170 commands are supported on the controller device:
171 .Bl -tag -width xxxxxx
173 This command will cause a complete bus discovery to be initiated.
174 If any devices attached or detached from the bus they will be
175 processed during this command.
176 This is the only way that new devices are found on the bus.
177 .It Dv USB_DEVICEINFO Vt "struct usb_device_info"
178 This command can be used to retrieve some information about a device
182 field should be filled before the call and the other fields will
183 be filled by information about the device on that address.
184 Should no such device exist, an error is reported.
186 struct usb_device_info {
189 usb_event_cookie_t cookie;
190 char product[USB_MAX_STRING_LEN];
191 char vendor[USB_MAX_STRING_LEN];
203 char devnames[USB_MAX_DEVNAMES][USB_MAX_DEVNAMELEN];
205 #define USB_PORT_ENABLED 0xff
206 #define USB_PORT_SUSPENDED 0xfe
207 #define USB_PORT_POWERED 0xfd
208 #define USB_PORT_DISABLED 0xfc
215 contain the topological information for the device.
217 contains the device names of the connected drivers.
221 Zip drive connected will be
227 fields contain self-explanatory descriptions of the device.
228 .Va productNo , vendorNo , releaseNo , class , subclass
231 contain the corresponding values from the device descriptors.
234 field shows the current configuration of the device.
237 indicates whether the device is a full speed (0) or low speed (1)
241 field shows the power consumption in milli-amps drawn at 5 volts,
242 or zero if the device is self powered.
244 If the device is a hub, the
246 field is non-zero, and the
248 field contains the addresses of the connected devices.
249 If no device is connected to a port, one of the
251 values indicates its status.
252 .It Dv USB_DEVICESTATS Vt "struct usb_device_stats"
253 This command retrieves statistics about the controller.
255 struct usb_device_stats {
262 field is indexed by the transfer kind, i.e.\&
264 and indicates how many transfers of each kind that has been completed
266 .It Dv USB_REQUEST Vt "struct usb_ctl_request"
267 This command can be used to execute arbitrary requests on the control pipe.
270 and should be used with great care since it
271 can destroy the bus integrity.
276 contains definitions for the types used by the various
279 The naming convention of the fields for the various
281 descriptors exactly follows the naming in the
284 Byte sized fields can be accessed directly, but word (16 bit)
285 sized fields must be access by the
288 .Fn USETW field value
289 macros to handle byte order and alignment properly.
292 .Aq Pa dev/usb/usbhid.h
293 similarly contains the definitions for
294 Human Interface Devices
296 .Sh USB EVENT INTERFACE
299 events are reported via the
302 This devices can be opened for reading and each
304 will yield an event record (if something has happened).
307 system call can be used to determine if an event record is available
310 The event record has the following definition:
314 #define USB_EVENT_CTRLR_ATTACH 1
315 #define USB_EVENT_CTRLR_DETACH 2
316 #define USB_EVENT_DEVICE_ATTACH 3
317 #define USB_EVENT_DEVICE_DETACH 4
318 #define USB_EVENT_DRIVER_ATTACH 5
319 #define USB_EVENT_DRIVER_DETACH 6
320 struct timespec ue_time;
325 struct usb_device_info ue_device;
327 usb_event_cookie_t ue_cookie;
335 field identifies the type of event that is described.
336 The possible events are attach/detach of a host controller,
337 a device, or a device driver.
338 The union contains information
339 pertinent to the different types of events.
343 contains the number of the
345 bus for host controller events.
349 record contains information about the device in a device event event.
353 is an opaque value that uniquely determines which which
354 device a device driver has been attached to (i.e., it equals
355 the cookie value in the device that the driver attached to).
359 contains the name of the device (driver) as seen in, e.g.,
362 Note that there is a separation between device and device
364 A device event is generated when a physical
366 device is attached or detached.
370 have zero, one, or many device drivers associated with it.
374 specifications can be found at:
376 .D1 Pa http://www.usb.org/developers/docs.html
398 driver first appeared in
403 driver was written by
404 .An Lennart Augustsson Aq augustss@carlstedt.se