drivers/usb/Config.help

CONFIG_USB
  Universal Serial Bus (USB) is a specification for a serial bus
  subsystem which offers higher speeds and more features than the
  traditional PC serial port.  The bus supplies power to peripherals
  and allows for hot swapping.  Up to 127 USB peripherals can be
  connected to a single USB port in a tree structure.  The USB port is
  the root of the tree, the peripherals are the leaves and the inner
  nodes are special USB devices called hubs.  Many newer PC's have USB
  ports and newer peripherals such as scanners, keyboards, mice,
  modems, and printers support the USB protocol and can be connected
  to the PC via those ports.

  Say Y here if your computer has a USB port and you want to use USB
  devices.  You then need to say Y to at least one of "UHCI support"
  or "OHCI support" below (the type of interface that the USB hardware
  in your computer provides to the operating system) and then choose
  from among the drivers for USB peripherals.  You may want to check
  out the information provided in <file:Documentation/usb/> and
  especially the links given in <file:Documentation/usb/usb-help.txt>.

  This code is also available as a module ( = code which can be
  inserted in and removed from the running kernel whenever you want).
  The module will be called usbcore.o.  If you want to compile it as a
  module, say M here and read <file:Documentation/modules.txt>.

CONFIG_USB_DEBUG
  Say Y here if you want the USB core & hub drivers to produce a bunch
  of debug messages to the system log. Select this if you are having a
  problem with USB support and want to see more of what is going on.

CONFIG_USB_LONG_TIMEOUT
  This option makes the standard time out a bit longer.  Basically,
  some devices are just slow to respond, so this makes usb more
  patient.  There should be no harm in selecting this, but it is
  needed for some MGE Ellipse UPSes.

  If you have an MGE Ellipse UPS, or you see timeouts in HID
  transactions, say Y; otherwise say N.

CONFIG_USB_DEVICEFS
  If you say Y here (and to "/proc file system support" in the "File
  systems section, above), you will get a file /proc/bus/usb/devices
  which lists the devices currently connected to your USB bus or
  busses, a file /proc/bus/usb/drivers which lists the USB kernel
  client drivers currently loaded, and for every connected device a
  file named  "/proc/bus/usb/xxx/yyy", where xxx is the bus number and
  yyy the device number; the latter files can be used by user space
  programs to talk directly to the device. These files are "virtual",
  meaning they are generated on the fly and not stored on the hard
  drive.

  You may need to mount the usbfs file system to see the files, use
     mount -t usbfs none /proc/bus/usb

  For the format of the various /proc/bus/usb/ files, please read
  <file:Documentation/usb/proc_usb_info.txt>.

  Please note that this code is completely unrelated to devfs, the
  "/dev file system support".

  Most users want to say Y here.

CONFIG_USB_BANDWIDTH
  If you say Y here, the USB subsystem enforces USB bandwidth
  allocation and will prevent some device opens from succeeding
  if they would cause USB bandwidth usage to go above 90% of
  the bus bandwidth.

  If you say N here, these conditions will cause warning messages
  about USB bandwidth usage to be logged and some devices or
  drivers may not work correctly.