NAME

udbp —

USB Double Bulk Pipe driver

SYNOPSIS

To compile this driver into the kernel, place the following line in your kernel configuration file:

device udbp

Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

udbp_load="YES"

DESCRIPTION

The udbp driver provides support for host-to-host cables that contain at least two bulk pipes (one for each direction). This typically includes cables branded for use with Windows USB Easy Transfer, and many cables based on the Prolific PL2xx1 series of USB bridge chips. A useful (but non-comprehensive) list of compatible USB host cables is listed in the SEE ALSO section below.

It requires netgraph(4) to be available. This can be done either by adding options NETGRAPH to your kernel configuration file, or alternatively loading netgraph(4) as a module, either from /boot/loader.conf or from the command line, before the udbp module.

EXAMPLES

options NETGRAPH

device udbp

Add the udbp driver to the kernel.

kldload netgraph

kldload udbp

Load the netgraph(4) module and then the udbp driver.

ngctl mkpeer udbp0: eiface data
  ether

ifconfig ngeth0 ether
  aa:dd:xx:xx:xx

ifconfig ngeth0 inet
  169.254.x.x/16

Create a new Ethernet network interface node and connect its ether hook to the data hook of the udbp driver.

This enables FreeBSD to communicate with a Linux peer (e.g. using the plusb driver). The Linux node should be configured to prefer link-local IPv4 addresses (e.g. using Network Manager in Debian and Red Hat derived distributions).

Whilst both FreeBSD and Linux are able to interoperate by loosely following CDC EEM 1.0 in their behaviour, neither implementation has been expressly designed to follow its specification.

CAVEATS

The point-to-point nature and additional latency of USB host-host links makes them unsuitable as a "drop-in" replacement for an Ethernet LAN; for a USB 3.0 SuperSpeed cable, latency is comparable to 100BaseTX Ethernet (but often worse), with throughput comparable to 2.5GBASE-T.

However, their energy efficiency makes them attractive for embedded applications. A Plugable PL27A1 cable claims 24mA of USB3 bus power, as compared to 150mA for a typical USB 3.0 to Gigabit Ethernet interface.

HISTORY

The udbp driver first appeared in FreeBSD 5.0.

BUGS

The udbp driver does not support the special packets described in section 5.1 of the CDC EEM specification.

AUTHORS

The udbp driver was written by Doug Ambrisko <ambrisko@whistle.com>, Julian Elischer <julian@FreeBSD.org> and Nick Hibma <n_hibma@FreeBSD.org>.

This manual page was written by Nick Hibma <n_hibma@FreeBSD.org> and updated by Bruce Simpson <bms@FreeBSD.org>.