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[from http://www.charmed.com/txt/proc_usb_info.txt]
/proc/bus/usb filesystem output
===============================
(version 2000.08.15)


The /proc filesystem for USB devices generates
/proc/bus/usb/drivers and /proc/bus/usb/devices.

/proc/bus/usb/drivers lists the registered drivers,
one per line, with each driver's USB minor dev node
number range if applicable.

**NOTE**: If /proc/bus/usb appears empty, you need
          to mount the filesystem, issue the command (as root):

      mount -t usbdevfs none /proc/bus/usb

	  An alternative and more permanent method would be to add

      none  /proc/bus/usb  usbdevfs  defaults  0  0

	  to /etc/fstab.  This will mount usbdevfs at each reboot.
	  You can then issue `cat /proc/bus/usb/devices` to extract
	  USB device information.

For more information on mounting the usbdevfs 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/

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.
(I think.  I haven't proved this, but I have tested it with 3
different topo/connections and it looked possible.)

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


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


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.
|__String info tag

S:  Product=ssss
|   |__Product description of this device as read from the device,
|      except that it is a generated string for USB host controllers
|      (virtual root hubs), in the form "USB *HCI Root Hub".
|__String info tag

S:  SerialNumber=ssss
|   |__Serial Number of this device as read from the device,
|      except that it is a generated string for USB host controllers
|      (virtual root hubs), and represents the host controller's
|      unique identification in the system (currently I/O or
|      memory-mapped base address).
|__String info tag


Configuration descriptor info:

C:  #Ifs=dd Cfg#=dd Atr=xx MPwr=dddmA
|   |       |       |      |__MaxPower in mA
|   |       |       |__Attributes
|   |       |__ConfiguratioNumber
|   |__NumberOfInterfaces
|__Config info tag


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
|   |      |      |       |             |      |__InterfaceProtocol
|   |      |      |       |             |__InterfaceSubClass
|   |      |      |       |__InterfaceClass
|   |      |      |__NumberOfEndpoints
|   |      |__AlternateSettingNumber
|   |__InterfaceNumber
|__Interface info tag


Endpoint descriptor info (can be multiple per Interface):

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

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


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 ###