cdceem(4)

cdceem4

Usb communication device class ethernet emulation model driver

Usage

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

device uhci device ohci device usb device miibus device uether device cdceem

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

if_cdceem_load="YES"

Overview

The cdceem driver provides support for USB devices based on the USB Communication Device Class Ethernet Emulation Model (CDC EEM) specification.

The driver works on both host, and device-side; see usb_template(4) for details.

The USB device appears as a regular network interface on both sides, transporting Ethernet frames.

For more information on configuring this device, see ifconfig(8).

The cdceem driver does not support different media types or options.

Sysctl variables

The following variables are available as both sysctl(8) variables and loader(8) tunables:

hw.usb.cdceem.debug

Verbosity level for log messages from the cdceem driver. Set to 0 to disable logging or 1 to warn about potential problems. Larger values enable debugging output. Defaults to 1.

hw.usb.cdceem.send_echoes

If set to 1, the driver will send an Echo EEM packet when the interface is brought up. While responding to Echo is mandatory, some devices cannot handle it. Only use for debugging. Defaults to 0.

hw.usb.cdceem.send_fake_crc

If set to 1, the driver will use 0xdeadbeef as the CRC value for outgoing Data EEM packets. Only use for debugging. Defaults to 0.

Releases

19 releases since FreeBSD 12.1-RELEASE; the text changed 6 times.

  1. 12.1
  2. 12.2
  3. 12.3
  4. 12.4
  5. 13.0–13.2
  6. 13.3–14.4
  7. 14.5–16.0

History

The cdceem device driver first appeared in FreeBSD 12.1.

Authors

The cdceem driver was written by Edward Tomasz Napierala ⟨[email protected]⟩ under sponsorship from Hewlett Packard Enterprise.

From base 16.0-CURRENT-20261027-61c70dc16a79 in FreeBSD 16.0-CURRENT (2026-10-27). Parsed by carta from the page's mdoc source.