[linux-2.6-block.git] / Documentation / usb / proc_usb_info.txt

/proc/bus/usb filesystem output
===============================
(version 2003.05.30)


The usbfs filesystem for USB devices is traditionally mounted at
/proc/bus/usb.  It provides the /proc/bus/usb/devices file, as well as
the /proc/bus/usb/BBB/DDD files.


**NOTE**: If /proc/bus/usb appears empty, and a host controller
	  driver has been linked, then you need to mount the
	  filesystem.  Issue the command (as root):

      mount -t usbfs none /proc/bus/usb

	  An alternative and more permanent method would be to add

      none  /proc/bus/usb  usbfs  defaults  0  0

	  to /etc/fstab.  This will mount usbfs at each reboot.
	  You can then issue `cat /proc/bus/usb/devices` to extract
	  USB device information, and user mode drivers can use usbfs 
	  to interact with USB devices.

	  There are a number of mount options supported by usbfs.
	  Consult the source code (linux/drivers/usb/core/inode.c) for
	  information about those options.

**NOTE**: The filesystem has been renamed from "usbdevfs" to
	  "usbfs", to reduce confusion with "devfs".  You may
	  still see references to the older "usbdevfs" name.

For more information on mounting the usbfs file system, see the
"USB Device Filesystem" section of the USB Guide. The latest copy 
of the USB Guide can be found at http://www.linux-usb.org/


THE /proc/bus/usb/BBB/DDD FILES:
--------------------------------
Each connected USB device has one file.  The BBB indicates the bus
number.  The DDD indicates the device address on that bus.  Both
of these numbers are assigned sequentially, and can be reused, so
you can't rely on them for stable access to devices.  For example,
it's relatively common for devices to re-enumerate while they are
still connected (perhaps someone jostled their power supply, hub,
or USB cable), so a device might be 002/027 when you first connect
it and 002/048 sometime later.

These files can be read as binary data.  The binary data consists
of first the device descriptor, then the descriptors for each
configuration of the device.  That information is also shown in
text form by the /proc/bus/usb/devices file, described later.

These files may also be used to write user-level drivers for the USB
devices.  You would open the /proc/bus/usb/BBB/DDD file read/write,
read its descriptors to make sure it's the device you expect, and then
bind to an interface (or perhaps several) using an ioctl call.  You
would issue more ioctls to the device to communicate to it using
control, bulk, or other kinds of USB transfers.  The IOCTLs are
listed in the <linux/usbdevice_fs.h> file, and at this writing the
source code (linux/drivers/usb/devio.c) is the primary reference
for how to access devices through those files.

Note that since by default these BBB/DDD files are writable only by
root, only root can write such user mode drivers.  You can selectively
grant read/write permissions to other users by using "chmod".  Also,
usbfs mount options such as "devmode=0666" may be helpful.


THE /proc/bus/usb/devices FILE:
-------------------------------
In /proc/bus/usb/devices, each device's output has multiple
lines of ASCII output.
I made it ASCII instead of binary on purpose, so that someone
can obtain some useful data from it without the use of an
auxiliary program.  However, with an auxiliary program, the numbers
in the first 4 columns of each "T:" line (topology info:
Lev, Prnt, Port, Cnt) can be used to build a USB topology diagram.

Each line is tagged with a one-character ID for that line:

T = Topology (etc.)
B = Bandwidth (applies only to USB host controllers, which are
    virtualized as root hubs)
D = Device descriptor info.
P = Product ID info. (from Device descriptor, but they won't fit
    together on one line)
S = String descriptors.
C = Configuration descriptor info. (* = active configuration)
I = Interface descriptor info.
E = Endpoint descriptor info.

=======================================================================

/proc/bus/usb/devices output format:

Legend:
  d = decimal number (may have leading spaces or 0's)
  x = hexadecimal number (may have leading spaces or 0's)
  s = string


Topology info:

T:  Bus=dd Lev=dd Prnt=dd Port=dd Cnt=dd Dev#=ddd Spd=ddd MxCh=dd
|   |      |      |       |       |      |        |       |__MaxChildren
|   |      |      |       |       |      |        |__Device Speed in Mbps
|   |      |      |       |       |      |__DeviceNumber
|   |      |      |       |       |__Count of devices at this level
|   |      |      |       |__Connector/Port on Parent for this device
|   |      |      |__Parent DeviceNumber
|   |      |__Level in topology for this bus
|   |__Bus number
|__Topology info tag

    Speed may be:
    	1.5	Mbit/s for low speed USB
	12	Mbit/s for full speed USB
	480	Mbit/s for high speed USB (added for USB 2.0)


Bandwidth info:
B:  Alloc=ddd/ddd us (xx%), #Int=ddd, #Iso=ddd
|   |                       |         |__Number of isochronous requests
|   |                       |__Number of interrupt requests
|   |__Total Bandwidth allocated to this bus
|__Bandwidth info tag

    Bandwidth allocation is an approximation of how much of one frame
    (millisecond) is in use.  It reflects only periodic transfers, which
    are the only transfers that reserve bandwidth.  Control and bulk
    transfers use all other bandwidth, including reserved bandwidth that
    is not used for transfers (such as for short packets).
    
    The percentage is how much of the "reserved" bandwidth is scheduled by
    those transfers.  For a low or full speed bus (loosely, "USB 1.1"),
    90% of the bus bandwidth is reserved.  For a high speed bus (loosely,
    "USB 2.0") 80% is reserved.


Device descriptor info & Product ID info:

D:  Ver=x.xx Cls=xx(s) Sub=xx Prot=xx MxPS=dd #Cfgs=dd
P:  Vendor=xxxx ProdID=xxxx Rev=xx.xx

where
D:  Ver=x.xx Cls=xx(sssss) Sub=xx Prot=xx MxPS=dd #Cfgs=dd
|   |        |             |      |       |       |__NumberConfigurations
|   |        |             |      |       |__MaxPacketSize of Default Endpoint
|   |        |             |      |__DeviceProtocol
|   |        |             |__DeviceSubClass
|   |        |__DeviceClass
|   |__Device USB version
|__Device info tag #1

where
P:  Vendor=xxxx ProdID=xxxx Rev=xx.xx
|   |           |           |__Product revision number
|   |           |__Product ID code
|   |__Vendor ID code
|__Device info tag #2


String descriptor info:

S:  Manufacturer=ssss
|   |__Manufacturer of this device as read from the device.
|      For USB host controller drivers (virtual root hubs) this may
|      be omitted, or (for newer drivers) will identify the kernel
|      version and the driver which provides this hub emulation.
|__String info tag

S:  Product=ssss
|   |__Product description of this device as read from the device.
|      For older USB host controller drivers (virtual root hubs) this
|      indicates the driver; for newer ones, it's a product (and vendor)
|      description that often comes from the kernel's PCI ID database.
|__String info tag

S:  SerialNumber=ssss
|   |__Serial Number of this device as read from the device.
|      For USB host controller drivers (virtual root hubs) this is
|      some unique ID, normally a bus ID (address or slot name) that
|      can't be shared with any other device.
|__String info tag


Configuration descriptor info:

C:* #Ifs=dd Cfg#=dd Atr=xx MPwr=dddmA
| | |       |       |      |__MaxPower in mA
| | |       |       |__Attributes
| | |       |__ConfiguratioNumber
| | |__NumberOfInterfaces
| |__ "*" indicates the active configuration (others are " ")
|__Config info tag
    
    USB devices may have multiple configurations, each of which act
    rather differently.  For example, a bus-powered configuration
    might be much less capable than one that is self-powered.  Only
    one device configuration can be active at a time; most devices
    have only one configuration.

    Each configuration consists of one or more interfaces.  Each
    interface serves a distinct "function", which is typically bound
    to a different USB device driver.  One common example is a USB
    speaker with an audio interface for playback, and a HID interface
    for use with software volume control.


Interface descriptor info (can be multiple per Config):

I:  If#=dd Alt=dd #EPs=dd Cls=xx(sssss) Sub=xx Prot=xx Driver=ssss
|   |      |      |       |             |      |       |__Driver name
|   |      |      |       |             |      |          or "(none)"
|   |      |      |       |             |      |__InterfaceProtocol
|   |      |      |       |             |__InterfaceSubClass
|   |      |      |       |__InterfaceClass
|   |      |      |__NumberOfEndpoints
|   |      |__AlternateSettingNumber
|   |__InterfaceNumber
|__Interface info tag

    A given interface may have one or more "alternate" settings.
    For example, default settings may not use more than a small
    amount of periodic bandwidth.  To use significant fractions
    of bus bandwidth, drivers must select a non-default altsetting.
    
    Only one setting for an interface may be active at a time, and
    only one driver may bind to an interface at a time.  Most devices
    have only one alternate setting per interface.


Endpoint descriptor info (can be multiple per Interface):

E:  Ad=xx(s) Atr=xx(ssss) MxPS=dddd Ivl=dddss
|   |        |            |         |__Interval (max) between transfers
|   |        |            |__EndpointMaxPacketSize
|   |        |__Attributes(EndpointType)
|   |__EndpointAddress(I=In,O=Out)
|__Endpoint info tag

    The interval is nonzero for all periodic (interrupt or isochronous)
    endpoints.  For high speed endpoints the transfer interval may be
    measured in microseconds rather than milliseconds.

    For high speed periodic endpoints, the "MaxPacketSize" reflects
    the per-microframe data transfer size.  For "high bandwidth"
    endpoints, that can reflect two or three packets (for up to
    3KBytes every 125 usec) per endpoint.

    With the Linux-USB stack, periodic bandwidth reservations use the
    transfer intervals and sizes provided by URBs, which can be less
    than those found in endpoint descriptor.


=======================================================================


If a user or script is interested only in Topology info, for
example, use something like "grep ^T: /proc/bus/usb/devices"
for only the Topology lines.  A command like
"grep -i ^[tdp]: /proc/bus/usb/devices" can be used to list
only the lines that begin with the characters in square brackets,
where the valid characters are TDPCIE.  With a slightly more able
script, it can display any selected lines (for example, only T, D,
and P lines) and change their output format.  (The "procusb"
Perl script is the beginning of this idea.  It will list only
selected lines [selected from TBDPSCIE] or "All" lines from
/proc/bus/usb/devices.)

The Topology lines can be used to generate a graphic/pictorial
of the USB devices on a system's root hub.  (See more below
on how to do this.)

The Interface lines can be used to determine what driver is
being used for each device.

The Configuration lines could be used to list maximum power
(in milliamps) that a system's USB devices are using.
For example, "grep ^C: /proc/bus/usb/devices".


Here's an example, from a system which has a UHCI root hub,
an external hub connected to the root hub, and a mouse and
a serial converter connected to the external hub.

T:  Bus=00 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12  MxCh= 2
B:  Alloc= 28/900 us ( 3%), #Int=  2, #Iso=  0
D:  Ver= 1.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=0000 ProdID=0000 Rev= 0.00
S:  Product=USB UHCI Root Hub
S:  SerialNumber=dce0
C:* #Ifs= 1 Cfg#= 1 Atr=40 MxPwr=  0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   8 Ivl=255ms
T:  Bus=00 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  2 Spd=12  MxCh= 4
D:  Ver= 1.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=0451 ProdID=1446 Rev= 1.00
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=255ms
T:  Bus=00 Lev=02 Prnt=02 Port=00 Cnt=01 Dev#=  3 Spd=1.5 MxCh= 0
D:  Ver= 1.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=04b4 ProdID=0001 Rev= 0.00
C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=01 Prot=02 Driver=mouse
E:  Ad=81(I) Atr=03(Int.) MxPS=   3 Ivl= 10ms
T:  Bus=00 Lev=02 Prnt=02 Port=02 Cnt=02 Dev#=  4 Spd=12  MxCh= 0
D:  Ver= 1.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=0565 ProdID=0001 Rev= 1.08
S:  Manufacturer=Peracom Networks, Inc.
S:  Product=Peracom USB to Serial Converter
C:* #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 3 Cls=00(>ifc ) Sub=00 Prot=00 Driver=serial
E:  Ad=81(I) Atr=02(Bulk) MxPS=  64 Ivl= 16ms
E:  Ad=01(O) Atr=02(Bulk) MxPS=  16 Ivl= 16ms
E:  Ad=82(I) Atr=03(Int.) MxPS=   8 Ivl=  8ms


Selecting only the "T:" and "I:" lines from this (for example, by using
"procusb ti"), we have:

T:  Bus=00 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12  MxCh= 2
T:  Bus=00 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  2 Spd=12  MxCh= 4
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
T:  Bus=00 Lev=02 Prnt=02 Port=00 Cnt=01 Dev#=  3 Spd=1.5 MxCh= 0
I:  If#= 0 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=01 Prot=02 Driver=mouse
T:  Bus=00 Lev=02 Prnt=02 Port=02 Cnt=02 Dev#=  4 Spd=12  MxCh= 0
I:  If#= 0 Alt= 0 #EPs= 3 Cls=00(>ifc ) Sub=00 Prot=00 Driver=serial


Physically this looks like (or could be converted to):

                      +------------------+
                      |  PC/root_hub (12)|   Dev# = 1
                      +------------------+   (nn) is Mbps.
    Level 0           |  CN.0   |  CN.1  |   [CN = connector/port #]
                      +------------------+
                          /
                         /
            +-----------------------+
  Level 1   | Dev#2: 4-port hub (12)|
            +-----------------------+
            |CN.0 |CN.1 |CN.2 |CN.3 |
            +-----------------------+
                \           \____________________
                 \_____                          \
                       \                          \
               +--------------------+      +--------------------+
  Level 2      | Dev# 3: mouse (1.5)|      | Dev# 4: serial (12)|
               +--------------------+      +--------------------+


Or, in a more tree-like structure (ports [Connectors] without
connections could be omitted):

PC:  Dev# 1, root hub, 2 ports, 12 Mbps
|_ CN.0:  Dev# 2, hub, 4 ports, 12 Mbps
     |_ CN.0:  Dev #3, mouse, 1.5 Mbps
     |_ CN.1:
     |_ CN.2:  Dev #4, serial, 12 Mbps
     |_ CN.3:
|_ CN.1:


                         ### END ###
Commit	Line	Data
1da177e4 LT	1	/proc/bus/usb filesystem output
	2	===============================
	3	(version 2003.05.30)
	4
	5
	6	The usbfs filesystem for USB devices is traditionally mounted at
	7	/proc/bus/usb. It provides the /proc/bus/usb/devices file, as well as
	8	the /proc/bus/usb/BBB/DDD files.
	9
	10
	11	NOTE: If /proc/bus/usb appears empty, and a host controller
	12	driver has been linked, then you need to mount the
	13	filesystem. Issue the command (as root):
	14
	15	mount -t usbfs none /proc/bus/usb
	16
	17	An alternative and more permanent method would be to add
	18
	19	none /proc/bus/usb usbfs defaults 0 0
	20
	21	to /etc/fstab. This will mount usbfs at each reboot.
	22	You can then issue `cat /proc/bus/usb/devices` to extract
	23	USB device information, and user mode drivers can use usbfs
	24	to interact with USB devices.
	25
	26	There are a number of mount options supported by usbfs.
	27	Consult the source code (linux/drivers/usb/core/inode.c) for
	28	information about those options.
	29
	30	NOTE: The filesystem has been renamed from "usbdevfs" to
	31	"usbfs", to reduce confusion with "devfs". You may
	32	still see references to the older "usbdevfs" name.
	33
	34	For more information on mounting the usbfs file system, see the
	35	"USB Device Filesystem" section of the USB Guide. The latest copy
	36	of the USB Guide can be found at http://www.linux-usb.org/
	37
	38
	39	THE /proc/bus/usb/BBB/DDD FILES:
	40	--------------------------------
	41	Each connected USB device has one file. The BBB indicates the bus
	42	number. The DDD indicates the device address on that bus. Both
	43	of these numbers are assigned sequentially, and can be reused, so
	44	you can't rely on them for stable access to devices. For example,
	45	it's relatively common for devices to re-enumerate while they are
	46	still connected (perhaps someone jostled their power supply, hub,
	47	or USB cable), so a device might be 002/027 when you first connect
	48	it and 002/048 sometime later.
	49
	50	These files can be read as binary data. The binary data consists
	51	of first the device descriptor, then the descriptors for each
	52	configuration of the device. That information is also shown in
	53	text form by the /proc/bus/usb/devices file, described later.
	54
	55	These files may also be used to write user-level drivers for the USB
	56	devices. You would open the /proc/bus/usb/BBB/DDD file read/write,
	57	read its descriptors to make sure it's the device you expect, and then
	58	bind to an interface (or perhaps several) using an ioctl call. You
	59	would issue more ioctls to the device to communicate to it using
	60	control, bulk, or other kinds of USB transfers. The IOCTLs are
	61	listed in the <linux/usbdevice_fs.h> file, and at this writing the
	62	source code (linux/drivers/usb/devio.c) is the primary reference
	63	for how to access devices through those files.
	64
65	Note that since by default these BBB/DDD files are writable only by
66	root, only root can write such user mode drivers. You can selectively
67	grant read/write permissions to other users by using "chmod". Also,
68	usbfs mount options such as "devmode=0666" may be helpful.
69
70
71
72	THE /proc/bus/usb/devices FILE:
73	-------------------------------
74	In /proc/bus/usb/devices, each device's output has multiple
75	lines of ASCII output.
76	I made it ASCII instead of binary on purpose, so that someone
77	can obtain some useful data from it without the use of an
78	auxiliary program. However, with an auxiliary program, the numbers
79	in the first 4 columns of each "T:" line (topology info:
80	Lev, Prnt, Port, Cnt) can be used to build a USB topology diagram.
81
82	Each line is tagged with a one-character ID for that line:
83
84	T = Topology (etc.)
85	B = Bandwidth (applies only to USB host controllers, which are
86	virtualized as root hubs)
87	D = Device descriptor info.
88	P = Product ID info. (from Device descriptor, but they won't fit
89	together on one line)
90	S = String descriptors.
91	C = Configuration descriptor info. (* = active configuration)
92	I = Interface descriptor info.
93	E = Endpoint descriptor info.
94
95	=======================================================================
96
97	/proc/bus/usb/devices output format:
98
99	Legend:
100	d = decimal number (may have leading spaces or 0's)
101	x = hexadecimal number (may have leading spaces or 0's)
102	s = string
103
104
105	Topology info:
106
107	T: Bus=dd Lev=dd Prnt=dd Port=dd Cnt=dd Dev#=ddd Spd=ddd MxCh=dd
108	\| \| \| \| \| \| \| \| \|__MaxChildren
109	\| \| \| \| \| \| \| \|__Device Speed in Mbps
110	\| \| \| \| \| \| \|__DeviceNumber
111	\| \| \| \| \| \|__Count of devices at this level
112	\| \| \| \| \|__Connector/Port on Parent for this device
113	\| \| \| \|__Parent DeviceNumber
114	\| \| \|__Level in topology for this bus
115	\| \|__Bus number
116	\|__Topology info tag
117
118	Speed may be:
119	1.5 Mbit/s for low speed USB
120	12 Mbit/s for full speed USB
121	480 Mbit/s for high speed USB (added for USB 2.0)
122
123
124	Bandwidth info:
125	B: Alloc=ddd/ddd us (xx%), #Int=ddd, #Iso=ddd
126	\| \| \| \|__Number of isochronous requests
127	\| \| \|__Number of interrupt requests
128	\| \|__Total Bandwidth allocated to this bus
129	\|__Bandwidth info tag
130
131	Bandwidth allocation is an approximation of how much of one frame
132	(millisecond) is in use. It reflects only periodic transfers, which
133	are the only transfers that reserve bandwidth. Control and bulk
134	transfers use all other bandwidth, including reserved bandwidth that
135	is not used for transfers (such as for short packets).
136
137	The percentage is how much of the "reserved" bandwidth is scheduled by
138	those transfers. For a low or full speed bus (loosely, "USB 1.1"),
139	90% of the bus bandwidth is reserved. For a high speed bus (loosely,
140	"USB 2.0") 80% is reserved.
141
142
143	Device descriptor info & Product ID info:
144
145	D: Ver=x.xx Cls=xx(s) Sub=xx Prot=xx MxPS=dd #Cfgs=dd
146	P: Vendor=xxxx ProdID=xxxx Rev=xx.xx
147
148	where
149	D: Ver=x.xx Cls=xx(sssss) Sub=xx Prot=xx MxPS=dd #Cfgs=dd
150	\| \| \| \| \| \| \|__NumberConfigurations
151	\| \| \| \| \| \|__MaxPacketSize of Default Endpoint
152	\| \| \| \| \|__DeviceProtocol
153	\| \| \| \|__DeviceSubClass
154	\| \| \|__DeviceClass
155	\| \|__Device USB version
156	\|__Device info tag #1
157
158	where
159	P: Vendor=xxxx ProdID=xxxx Rev=xx.xx
160	\| \| \| \|__Product revision number
161	\| \| \|__Product ID code
162	\| \|__Vendor ID code
163	\|__Device info tag #2
164
165
166	String descriptor info:
167
168	S: Manufacturer=ssss
169	\| \|__Manufacturer of this device as read from the device.
170	\| For USB host controller drivers (virtual root hubs) this may
171	\| be omitted, or (for newer drivers) will identify the kernel
172	\| version and the driver which provides this hub emulation.
173	\|__String info tag
174
175	S: Product=ssss
176	\| \|__Product description of this device as read from the device.
177	\| For older USB host controller drivers (virtual root hubs) this
178	\| indicates the driver; for newer ones, it's a product (and vendor)
179	\| description that often comes from the kernel's PCI ID database.
180	\|__String info tag
181
182	S: SerialNumber=ssss
183	\| \|__Serial Number of this device as read from the device.
184	\| For USB host controller drivers (virtual root hubs) this is
185	\| some unique ID, normally a bus ID (address or slot name) that
186	\| can't be shared with any other device.
187	\|__String info tag
188
189
190
191	Configuration descriptor info:
192
193	C:* #Ifs=dd Cfg#=dd Atr=xx MPwr=dddmA
194	\| \| \| \| \| \|__MaxPower in mA
195	\| \| \| \| \|__Attributes
196	\| \| \| \|__ConfiguratioNumber
197	\| \| \|__NumberOfInterfaces
198	\| \|__ "*" indicates the active configuration (others are " ")
199	\|__Config info tag
200
201	USB devices may have multiple configurations, each of which act
202	rather differently. For example, a bus-powered configuration
203	might be much less capable than one that is self-powered. Only
204	one device configuration can be active at a time; most devices
205	have only one configuration.
206
207	Each configuration consists of one or more interfaces. Each
208	interface serves a distinct "function", which is typically bound
209	to a different USB device driver. One common example is a USB
210	speaker with an audio interface for playback, and a HID interface
211	for use with software volume control.
212
213
214	Interface descriptor info (can be multiple per Config):
215
216	I: If#=dd Alt=dd #EPs=dd Cls=xx(sssss) Sub=xx Prot=xx Driver=ssss
217	\| \| \| \| \| \| \| \|__Driver name
218	\| \| \| \| \| \| \| or "(none)"
219	\| \| \| \| \| \| \|__InterfaceProtocol
220	\| \| \| \| \| \|__InterfaceSubClass
221	\| \| \| \| \|__InterfaceClass
222	\| \| \| \|__NumberOfEndpoints
223	\| \| \|__AlternateSettingNumber
224	\| \|__InterfaceNumber
225	\|__Interface info tag
226
227	A given interface may have one or more "alternate" settings.
228	For example, default settings may not use more than a small
229	amount of periodic bandwidth. To use significant fractions
230	of bus bandwidth, drivers must select a non-default altsetting.
231
232	Only one setting for an interface may be active at a time, and
233	only one driver may bind to an interface at a time. Most devices
234	have only one alternate setting per interface.
235
236
237	Endpoint descriptor info (can be multiple per Interface):
238
239	E: Ad=xx(s) Atr=xx(ssss) MxPS=dddd Ivl=dddss
240	\| \| \| \| \|__Interval (max) between transfers
241	\| \| \| \|__EndpointMaxPacketSize
242	\| \| \|__Attributes(EndpointType)
243	\| \|__EndpointAddress(I=In,O=Out)
244	\|__Endpoint info tag
245
246	The interval is nonzero for all periodic (interrupt or isochronous)
247	endpoints. For high speed endpoints the transfer interval may be
248	measured in microseconds rather than milliseconds.
249
250	For high speed periodic endpoints, the "MaxPacketSize" reflects
251	the per-microframe data transfer size. For "high bandwidth"
252	endpoints, that can reflect two or three packets (for up to
253	3KBytes every 125 usec) per endpoint.
254
255	With the Linux-USB stack, periodic bandwidth reservations use the
256	transfer intervals and sizes provided by URBs, which can be less
257	than those found in endpoint descriptor.
258
259
260	=======================================================================
261
262
263	If a user or script is interested only in Topology info, for
264	example, use something like "grep ^T: /proc/bus/usb/devices"
265	for only the Topology lines. A command like
266	"grep -i ^[tdp]: /proc/bus/usb/devices" can be used to list
267	only the lines that begin with the characters in square brackets,
268	where the valid characters are TDPCIE. With a slightly more able
269	script, it can display any selected lines (for example, only T, D,
270	and P lines) and change their output format. (The "procusb"
271	Perl script is the beginning of this idea. It will list only
272	selected lines [selected from TBDPSCIE] or "All" lines from
273	/proc/bus/usb/devices.)
274
275	The Topology lines can be used to generate a graphic/pictorial
276	of the USB devices on a system's root hub. (See more below
277	on how to do this.)
278
279	The Interface lines can be used to determine what driver is
280	being used for each device.
281
282	The Configuration lines could be used to list maximum power
283	(in milliamps) that a system's USB devices are using.
284	For example, "grep ^C: /proc/bus/usb/devices".
285
286
287	Here's an example, from a system which has a UHCI root hub,
288	an external hub connected to the root hub, and a mouse and
289	a serial converter connected to the external hub.
290
291	T: Bus=00 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=12 MxCh= 2
292	B: Alloc= 28/900 us ( 3%), #Int= 2, #Iso= 0
293	D: Ver= 1.00 Cls=09(hub ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
294	P: Vendor=0000 ProdID=0000 Rev= 0.00
295	S: Product=USB UHCI Root Hub
296	S: SerialNumber=dce0
297	C:* #Ifs= 1 Cfg#= 1 Atr=40 MxPwr= 0mA
298	I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
299	E: Ad=81(I) Atr=03(Int.) MxPS= 8 Ivl=255ms
300	T: Bus=00 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 2 Spd=12 MxCh= 4
301	D: Ver= 1.00 Cls=09(hub ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
302	P: Vendor=0451 ProdID=1446 Rev= 1.00
303	C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=100mA
304	I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
305	E: Ad=81(I) Atr=03(Int.) MxPS= 1 Ivl=255ms
306	T: Bus=00 Lev=02 Prnt=02 Port=00 Cnt=01 Dev#= 3 Spd=1.5 MxCh= 0
307	D: Ver= 1.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
308	P: Vendor=04b4 ProdID=0001 Rev= 0.00
309	C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=100mA
310	I: If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=02 Driver=mouse
311	E: Ad=81(I) Atr=03(Int.) MxPS= 3 Ivl= 10ms
312	T: Bus=00 Lev=02 Prnt=02 Port=02 Cnt=02 Dev#= 4 Spd=12 MxCh= 0
313	D: Ver= 1.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
314	P: Vendor=0565 ProdID=0001 Rev= 1.08
315	S: Manufacturer=Peracom Networks, Inc.
316	S: Product=Peracom USB to Serial Converter
317	C:* #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr=100mA
318	I: If#= 0 Alt= 0 #EPs= 3 Cls=00(>ifc ) Sub=00 Prot=00 Driver=serial
319	E: Ad=81(I) Atr=02(Bulk) MxPS= 64 Ivl= 16ms
320	E: Ad=01(O) Atr=02(Bulk) MxPS= 16 Ivl= 16ms
321	E: Ad=82(I) Atr=03(Int.) MxPS= 8 Ivl= 8ms
322
323
324	Selecting only the "T:" and "I:" lines from this (for example, by using
325	"procusb ti"), we have:
326
327	T: Bus=00 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=12 MxCh= 2
328	T: Bus=00 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 2 Spd=12 MxCh= 4
329	I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
330	T: Bus=00 Lev=02 Prnt=02 Port=00 Cnt=01 Dev#= 3 Spd=1.5 MxCh= 0
331	I: If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=02 Driver=mouse
332	T: Bus=00 Lev=02 Prnt=02 Port=02 Cnt=02 Dev#= 4 Spd=12 MxCh= 0
333	I: If#= 0 Alt= 0 #EPs= 3 Cls=00(>ifc ) Sub=00 Prot=00 Driver=serial
334
335
336	Physically this looks like (or could be converted to):
337
338	+------------------+
339	\| PC/root_hub (12)\| Dev# = 1
340	+------------------+ (nn) is Mbps.
341	Level 0 \| CN.0 \| CN.1 \| [CN = connector/port #]
342	+------------------+
343	/
344	/
345	+-----------------------+
346	Level 1 \| Dev#2: 4-port hub (12)\|
347	+-----------------------+
348	\|CN.0 \|CN.1 \|CN.2 \|CN.3 \|
349	+-----------------------+
350	\ \____________________
351	\_____ \
352	\ \
353	+--------------------+ +--------------------+
354	Level 2 \| Dev# 3: mouse (1.5)\| \| Dev# 4: serial (12)\|
355	+--------------------+ +--------------------+
356
357
358
359	Or, in a more tree-like structure (ports [Connectors] without
360	connections could be omitted):
361
362	PC: Dev# 1, root hub, 2 ports, 12 Mbps
363	\|_ CN.0: Dev# 2, hub, 4 ports, 12 Mbps
364	\|_ CN.0: Dev #3, mouse, 1.5 Mbps
365	\|_ CN.1:
366	\|_ CN.2: Dev #4, serial, 12 Mbps
367	\|_ CN.3:
368	\|_ CN.1:
369
370
371	### END ###