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-/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 ###
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