[linux.git] / Documentation / usb / proc_usb_info.txt

/proc/bus/usb filesystem output
===============================
(version 2010.09.13)


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.

In many modern systems the usbfs filesystem isn't used at all.  Instead
USB device nodes are created under /dev/usb/ or someplace similar.  The
"devices" file is available in debugfs, typically as
/sys/kernel/debug/usb/devices.


**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.  Multi-byte fields in the device descriptor
are converted to host endianness by the kernel.  The configuration
descriptors are in bus endian format! The configuration descriptor
are wTotalLength bytes apart. If a device returns less configuration
descriptor data than indicated by wTotalLength there will be a hole in
the file for the missing bytes.  This 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/core/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=dddd 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);
		  also used for Wireless USB, which has no fixed speed
	5000	Mbit/s for SuperSpeed USB (added for USB 3.0)

    For reasons lost in the mists of time, the Port number is always
    too low by 1.  For example, a device plugged into port 4 will
    show up with "Port=03".

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
| |__ "*" indicates the active altsetting (others are " ")
|__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, and which altsetting it activated.

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
1da177e4 LT	2	===============================
834e2312	3	(version 2010.09.13)
1da177e4 LT	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
67748df8	10	In many modern systems the usbfs filesystem isn't used at all. Instead
834e2312 AS	11	USB device nodes are created under /dev/usb/ or someplace similar. The
	12	"devices" file is available in debugfs, typically as
	13	/sys/kernel/debug/usb/devices.
	14
1da177e4 LT	15
	16	NOTE: If /proc/bus/usb appears empty, and a host controller
	17	driver has been linked, then you need to mount the
	18	filesystem. Issue the command (as root):
	19
	20	mount -t usbfs none /proc/bus/usb
	21
	22	An alternative and more permanent method would be to add
	23
	24	none /proc/bus/usb usbfs defaults 0 0
	25
	26	to /etc/fstab. This will mount usbfs at each reboot.
	27	You can then issue `cat /proc/bus/usb/devices` to extract
5f980948	28	USB device information, and user mode drivers can use usbfs
1da177e4 LT	29	to interact with USB devices.
	30
	31	There are a number of mount options supported by usbfs.
	32	Consult the source code (linux/drivers/usb/core/inode.c) for
	33	information about those options.
	34
	35	NOTE: The filesystem has been renamed from "usbdevfs" to
	36	"usbfs", to reduce confusion with "devfs". You may
	37	still see references to the older "usbdevfs" name.
	38
	39	For more information on mounting the usbfs file system, see the
5f980948	40	"USB Device Filesystem" section of the USB Guide. The latest copy
1da177e4 LT	41	of the USB Guide can be found at http://www.linux-usb.org/
	42
	43
	44	THE /proc/bus/usb/BBB/DDD FILES:
	45	--------------------------------
	46	Each connected USB device has one file. The BBB indicates the bus
	47	number. The DDD indicates the device address on that bus. Both
	48	of these numbers are assigned sequentially, and can be reused, so
	49	you can't rely on them for stable access to devices. For example,
	50	it's relatively common for devices to re-enumerate while they are
	51	still connected (perhaps someone jostled their power supply, hub,
	52	or USB cable), so a device might be 002/027 when you first connect
	53	it and 002/048 sometime later.
	54
	55	These files can be read as binary data. The binary data consists
	56	of first the device descriptor, then the descriptors for each
21a96315 HG	57	configuration of the device. Multi-byte fields in the device descriptor
	58	are converted to host endianness by the kernel. The configuration
	59	descriptors are in bus endian format! The configuration descriptor
	60	are wTotalLength bytes apart. If a device returns less configuration
	61	descriptor data than indicated by wTotalLength there will be a hole in
	62	the file for the missing bytes. This information is also shown
9a9fafb8	63	in text form by the /proc/bus/usb/devices file, described later.
1da177e4 LT	64
	65	These files may also be used to write user-level drivers for the USB
	66	devices. You would open the /proc/bus/usb/BBB/DDD file read/write,
	67	read its descriptors to make sure it's the device you expect, and then
	68	bind to an interface (or perhaps several) using an ioctl call. You
	69	would issue more ioctls to the device to communicate to it using
	70	control, bulk, or other kinds of USB transfers. The IOCTLs are
	71	listed in the <linux/usbdevice_fs.h> file, and at this writing the
064e875a	72	source code (linux/drivers/usb/core/devio.c) is the primary reference
1da177e4 LT	73	for how to access devices through those files.
	74
	75	Note that since by default these BBB/DDD files are writable only by
	76	root, only root can write such user mode drivers. You can selectively
	77	grant read/write permissions to other users by using "chmod". Also,
	78	usbfs mount options such as "devmode=0666" may be helpful.
	79
	80
	81
	82	THE /proc/bus/usb/devices FILE:
	83	-------------------------------
	84	In /proc/bus/usb/devices, each device's output has multiple
	85	lines of ASCII output.
	86	I made it ASCII instead of binary on purpose, so that someone
	87	can obtain some useful data from it without the use of an
	88	auxiliary program. However, with an auxiliary program, the numbers
	89	in the first 4 columns of each "T:" line (topology info:
	90	Lev, Prnt, Port, Cnt) can be used to build a USB topology diagram.
	91
	92	Each line is tagged with a one-character ID for that line:
	93
	94	T = Topology (etc.)
	95	B = Bandwidth (applies only to USB host controllers, which are
	96	virtualized as root hubs)
	97	D = Device descriptor info.
	98	P = Product ID info. (from Device descriptor, but they won't fit
	99	together on one line)
	100	S = String descriptors.
	101	C = Configuration descriptor info. (* = active configuration)
	102	I = Interface descriptor info.
	103	E = Endpoint descriptor info.
	104
	105	=======================================================================
	106
	107	/proc/bus/usb/devices output format:
	108
	109	Legend:
	110	d = decimal number (may have leading spaces or 0's)
	111	x = hexadecimal number (may have leading spaces or 0's)
	112	s = string
	113
	114
	115	Topology info:
	116
834e2312 AS	117	T: Bus=dd Lev=dd Prnt=dd Port=dd Cnt=dd Dev#=ddd Spd=dddd MxCh=dd
834e2312 AS	118	\| \| \| \| \| \| \| \| \|__MaxChildren
1da177e4 LT	119	\| \| \| \| \| \| \| \|__Device Speed in Mbps
	120	\| \| \| \| \| \| \|__DeviceNumber
	121	\| \| \| \| \| \|__Count of devices at this level
	122	\| \| \| \| \|__Connector/Port on Parent for this device
	123	\| \| \| \|__Parent DeviceNumber
	124	\| \| \|__Level in topology for this bus
	125	\| \|__Bus number
	126	\|__Topology info tag
	127
	128	Speed may be:
	129	1.5 Mbit/s for low speed USB
	130	12 Mbit/s for full speed USB
834e2312 AS	131	480 Mbit/s for high speed USB (added for USB 2.0);
	132	also used for Wireless USB, which has no fixed speed
	133	5000 Mbit/s for SuperSpeed USB (added for USB 3.0)
1da177e4	134
834e2312 AS	135	For reasons lost in the mists of time, the Port number is always
	136	too low by 1. For example, a device plugged into port 4 will
	137	show up with "Port=03".
1da177e4 LT	138
	139	Bandwidth info:
	140	B: Alloc=ddd/ddd us (xx%), #Int=ddd, #Iso=ddd
	141	\| \| \| \|__Number of isochronous requests
	142	\| \| \|__Number of interrupt requests
	143	\| \|__Total Bandwidth allocated to this bus
	144	\|__Bandwidth info tag
	145
	146	Bandwidth allocation is an approximation of how much of one frame
	147	(millisecond) is in use. It reflects only periodic transfers, which
	148	are the only transfers that reserve bandwidth. Control and bulk
	149	transfers use all other bandwidth, including reserved bandwidth that
	150	is not used for transfers (such as for short packets).
5f980948	151
1da177e4 LT	152	The percentage is how much of the "reserved" bandwidth is scheduled by
	153	those transfers. For a low or full speed bus (loosely, "USB 1.1"),
	154	90% of the bus bandwidth is reserved. For a high speed bus (loosely,
	155	"USB 2.0") 80% is reserved.
	156
	157
	158	Device descriptor info & Product ID info:
	159
	160	D: Ver=x.xx Cls=xx(s) Sub=xx Prot=xx MxPS=dd #Cfgs=dd
	161	P: Vendor=xxxx ProdID=xxxx Rev=xx.xx
	162
	163	where
	164	D: Ver=x.xx Cls=xx(sssss) Sub=xx Prot=xx MxPS=dd #Cfgs=dd
	165	\| \| \| \| \| \| \|__NumberConfigurations
	166	\| \| \| \| \| \|__MaxPacketSize of Default Endpoint
	167	\| \| \| \| \|__DeviceProtocol
	168	\| \| \| \|__DeviceSubClass
	169	\| \| \|__DeviceClass
	170	\| \|__Device USB version
	171	\|__Device info tag #1
	172
	173	where
	174	P: Vendor=xxxx ProdID=xxxx Rev=xx.xx
	175	\| \| \| \|__Product revision number
	176	\| \| \|__Product ID code
	177	\| \|__Vendor ID code
	178	\|__Device info tag #2
	179
	180
	181	String descriptor info:
	182
	183	S: Manufacturer=ssss
	184	\| \|__Manufacturer of this device as read from the device.
	185	\| For USB host controller drivers (virtual root hubs) this may
	186	\| be omitted, or (for newer drivers) will identify the kernel
	187	\| version and the driver which provides this hub emulation.
	188	\|__String info tag
	189
	190	S: Product=ssss
	191	\| \|__Product description of this device as read from the device.
	192	\| For older USB host controller drivers (virtual root hubs) this
	193	\| indicates the driver; for newer ones, it's a product (and vendor)
	194	\| description that often comes from the kernel's PCI ID database.
	195	\|__String info tag
	196
	197	S: SerialNumber=ssss
	198	\| \|__Serial Number of this device as read from the device.
	199	\| For USB host controller drivers (virtual root hubs) this is
	200	\| some unique ID, normally a bus ID (address or slot name) that
	201	\| can't be shared with any other device.
	202	\|__String info tag
	203
	204
	205
	206	Configuration descriptor info:
	207
	208	C:* #Ifs=dd Cfg#=dd Atr=xx MPwr=dddmA
	209	\| \| \| \| \| \|__MaxPower in mA
	210	\| \| \| \| \|__Attributes
	211	\| \| \| \|__ConfiguratioNumber
	212	\| \| \|__NumberOfInterfaces
	213	\| \|__ "*" indicates the active configuration (others are " ")
	214	\|__Config info tag
5f980948	215
1da177e4 LT	216	USB devices may have multiple configurations, each of which act
	217	rather differently. For example, a bus-powered configuration
	218	might be much less capable than one that is self-powered. Only
	219	one device configuration can be active at a time; most devices
	220	have only one configuration.
	221
	222	Each configuration consists of one or more interfaces. Each
	223	interface serves a distinct "function", which is typically bound
	224	to a different USB device driver. One common example is a USB
	225	speaker with an audio interface for playback, and a HID interface
	226	for use with software volume control.
	227
	228
	229	Interface descriptor info (can be multiple per Config):
	230
2360e4aa DB	231	I:* If#=dd Alt=dd #EPs=dd Cls=xx(sssss) Sub=xx Prot=xx Driver=ssss
	232	\| \| \| \| \| \| \| \| \|__Driver name
	233	\| \| \| \| \| \| \| \| or "(none)"
	234	\| \| \| \| \| \| \| \|__InterfaceProtocol
	235	\| \| \| \| \| \| \|__InterfaceSubClass
	236	\| \| \| \| \| \|__InterfaceClass
	237	\| \| \| \| \|__NumberOfEndpoints
	238	\| \| \| \|__AlternateSettingNumber
	239	\| \| \|__InterfaceNumber
	240	\| \|__ "*" indicates the active altsetting (others are " ")
1da177e4 LT	241	\|__Interface info tag
	242
	243	A given interface may have one or more "alternate" settings.
	244	For example, default settings may not use more than a small
	245	amount of periodic bandwidth. To use significant fractions
	246	of bus bandwidth, drivers must select a non-default altsetting.
5f980948	247
1da177e4 LT	248	Only one setting for an interface may be active at a time, and
	249	only one driver may bind to an interface at a time. Most devices
	250	have only one alternate setting per interface.
	251
	252
	253	Endpoint descriptor info (can be multiple per Interface):
	254
	255	E: Ad=xx(s) Atr=xx(ssss) MxPS=dddd Ivl=dddss
	256	\| \| \| \| \|__Interval (max) between transfers
	257	\| \| \| \|__EndpointMaxPacketSize
	258	\| \| \|__Attributes(EndpointType)
	259	\| \|__EndpointAddress(I=In,O=Out)
	260	\|__Endpoint info tag
	261
	262	The interval is nonzero for all periodic (interrupt or isochronous)
	263	endpoints. For high speed endpoints the transfer interval may be
	264	measured in microseconds rather than milliseconds.
	265
	266	For high speed periodic endpoints, the "MaxPacketSize" reflects
	267	the per-microframe data transfer size. For "high bandwidth"
	268	endpoints, that can reflect two or three packets (for up to
	269	3KBytes every 125 usec) per endpoint.
	270
	271	With the Linux-USB stack, periodic bandwidth reservations use the
	272	transfer intervals and sizes provided by URBs, which can be less
	273	than those found in endpoint descriptor.
	274
	275
	276	=======================================================================
	277
	278
	279	If a user or script is interested only in Topology info, for
	280	example, use something like "grep ^T: /proc/bus/usb/devices"
	281	for only the Topology lines. A command like
	282	"grep -i ^[tdp]: /proc/bus/usb/devices" can be used to list
	283	only the lines that begin with the characters in square brackets,
	284	where the valid characters are TDPCIE. With a slightly more able
	285	script, it can display any selected lines (for example, only T, D,
	286	and P lines) and change their output format. (The "procusb"
	287	Perl script is the beginning of this idea. It will list only
	288	selected lines [selected from TBDPSCIE] or "All" lines from
	289	/proc/bus/usb/devices.)
	290
	291	The Topology lines can be used to generate a graphic/pictorial
	292	of the USB devices on a system's root hub. (See more below
	293	on how to do this.)
	294
	295	The Interface lines can be used to determine what driver is
2360e4aa	296	being used for each device, and which altsetting it activated.
1da177e4 LT	297
	298	The Configuration lines could be used to list maximum power
	299	(in milliamps) that a system's USB devices are using.
	300	For example, "grep ^C: /proc/bus/usb/devices".
	301
	302
	303	Here's an example, from a system which has a UHCI root hub,
	304	an external hub connected to the root hub, and a mouse and
	305	a serial converter connected to the external hub.
	306
834e2312	307	T: Bus=00 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=12 MxCh= 2
1da177e4 LT	308	B: Alloc= 28/900 us ( 3%), #Int= 2, #Iso= 0
	309	D: Ver= 1.00 Cls=09(hub ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
	310	P: Vendor=0000 ProdID=0000 Rev= 0.00
	311	S: Product=USB UHCI Root Hub
	312	S: SerialNumber=dce0
	313	C:* #Ifs= 1 Cfg#= 1 Atr=40 MxPwr= 0mA
	314	I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
	315	E: Ad=81(I) Atr=03(Int.) MxPS= 8 Ivl=255ms
5f980948	316
834e2312	317	T: Bus=00 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 2 Spd=12 MxCh= 4
1da177e4 LT	318	D: Ver= 1.00 Cls=09(hub ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
	319	P: Vendor=0451 ProdID=1446 Rev= 1.00
	320	C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=100mA
	321	I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
	322	E: Ad=81(I) Atr=03(Int.) MxPS= 1 Ivl=255ms
5f980948	323
834e2312	324	T: Bus=00 Lev=02 Prnt=02 Port=00 Cnt=01 Dev#= 3 Spd=1.5 MxCh= 0
1da177e4 LT	325	D: Ver= 1.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
	326	P: Vendor=04b4 ProdID=0001 Rev= 0.00
	327	C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=100mA
	328	I: If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=02 Driver=mouse
	329	E: Ad=81(I) Atr=03(Int.) MxPS= 3 Ivl= 10ms
5f980948	330
834e2312	331	T: Bus=00 Lev=02 Prnt=02 Port=02 Cnt=02 Dev#= 4 Spd=12 MxCh= 0
1da177e4 LT	332	D: Ver= 1.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
	333	P: Vendor=0565 ProdID=0001 Rev= 1.08
	334	S: Manufacturer=Peracom Networks, Inc.
	335	S: Product=Peracom USB to Serial Converter
	336	C:* #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr=100mA
	337	I: If#= 0 Alt= 0 #EPs= 3 Cls=00(>ifc ) Sub=00 Prot=00 Driver=serial
	338	E: Ad=81(I) Atr=02(Bulk) MxPS= 64 Ivl= 16ms
	339	E: Ad=01(O) Atr=02(Bulk) MxPS= 16 Ivl= 16ms
	340	E: Ad=82(I) Atr=03(Int.) MxPS= 8 Ivl= 8ms
	341
	342
	343	Selecting only the "T:" and "I:" lines from this (for example, by using
	344	"procusb ti"), we have:
	345
834e2312 AS	346	T: Bus=00 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=12 MxCh= 2
834e2312 AS	347	T: Bus=00 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 2 Spd=12 MxCh= 4
1da177e4	348	I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
834e2312	349	T: Bus=00 Lev=02 Prnt=02 Port=00 Cnt=01 Dev#= 3 Spd=1.5 MxCh= 0
1da177e4	350	I: If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=02 Driver=mouse
834e2312	351	T: Bus=00 Lev=02 Prnt=02 Port=02 Cnt=02 Dev#= 4 Spd=12 MxCh= 0
1da177e4 LT	352	I: If#= 0 Alt= 0 #EPs= 3 Cls=00(>ifc ) Sub=00 Prot=00 Driver=serial
	353
	354
	355	Physically this looks like (or could be converted to):
	356
	357	+------------------+
	358	\| PC/root_hub (12)\| Dev# = 1
	359	+------------------+ (nn) is Mbps.
	360	Level 0 \| CN.0 \| CN.1 \| [CN = connector/port #]
	361	+------------------+
	362	/
	363	/
	364	+-----------------------+
	365	Level 1 \| Dev#2: 4-port hub (12)\|
	366	+-----------------------+
	367	\|CN.0 \|CN.1 \|CN.2 \|CN.3 \|
	368	+-----------------------+
	369	\ \____________________
	370	\_____ \
	371	\ \
	372	+--------------------+ +--------------------+
	373	Level 2 \| Dev# 3: mouse (1.5)\| \| Dev# 4: serial (12)\|
	374	+--------------------+ +--------------------+
	375
	376
	377
	378	Or, in a more tree-like structure (ports [Connectors] without
	379	connections could be omitted):
	380
	381	PC: Dev# 1, root hub, 2 ports, 12 Mbps
	382	\|_ CN.0: Dev# 2, hub, 4 ports, 12 Mbps
	383	\|_ CN.0: Dev #3, mouse, 1.5 Mbps
	384	\|_ CN.1:
	385	\|_ CN.2: Dev #4, serial, 12 Mbps
	386	\|_ CN.3:
	387	\|_ CN.1:
	388
	389
	390	### END ###