.\" Copyright (c) 2004 Daniel Hartmeier
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.\" $OpenBSD: cdce.4,v 1.27 2022/09/10 10:10:29 jsg Exp $
.\"
.Dd $Mdocdate: September 10 2022 $
.Dt CDCE 4
.Os
.Sh NAME
.Nm cdce
.Nd USB Communication Device Class Ethernet device
.Sh SYNOPSIS
.Cd "cdce*  at uhub?"
.Sh DESCRIPTION
The
.Nm
driver provides support for USB Host-to-Host (aka USB-to-USB) bridges
based on the USB Communication Device Class (CDC) and Ethernet subclass,
including the following:
.Pp
.Bl -bullet -compact -offset indent
.It
Acer Labs USB 2.0 Data Link
.It
Dell Wireless 5530
.It
Dell Wireless 5540
.It
FRITZ!Box Fon ata 1020
.It
G.Mate YP3X00
.It
Lenovo ThinkPad USB 3.0 Ethernet adapter (FRU 03X6903)
.It
Motorola USBNET
.It
NetChip EthernetGadget
.It
Prolific PL-2501
.It
Sony Ericsson K610i
.It
Sony Ericsson F3705g
.It
Yota LU156
.It
ZTE MF831 LTE USB modem
.It
ZTE MF920V portable LTE WiFi router
.It
Zyxel P-971M
.El
.Pp
The USB bridge appears as a regular network interface on both sides,
transporting Ethernet frames.
USB 1.x bridges support speeds of up to 12Mbps, and USB 2.0 speeds of
up to 480Mbps.
Packets are
received and transmitted over separate USB bulk transfer endpoints.
.Pp
The
.Nm
driver does not support different media types or options.
For more information on configuring this device, see
.Xr ifconfig 8 .
.Sh DIAGNOSTICS
.Bl -diag
.It "cdce0: extra ethernet descriptor"
There is more than one Ethernet descriptor.
.It "cdce0: no data interface"
The data interface announced by the union descriptor cannot be found.
.It "cdce0: no descriptor for interrupt endpoint N"
.It "cdce0: interface alternate setting N failed"
.It "cdce0: no descriptor for bulk endpoint N"
.It "cdce0: could not find data bulk in/out"
For a manually added USB vendor/product, these errors indicate
that the bridge is not compatible with the driver.
.It "cdce0: watchdog timeout"
A packet was queued for transmission and a transmit command was
issued, however the device failed to acknowledge the transmission
before a timeout expired.
.It "cdce0: no memory for rx list -- packet dropped!"
Memory allocation through MGETHDR or MCLGET failed, the system
is running low on mbufs.
.It "cdce0: abort/close rx/tx/interrupt pipe failed"
.It "cdce0: rx/tx list init failed"
.It "cdce0: open rx/tx/interrupt pipe failed"
.It "cdce0: usb error on rx/tx"
.El
.Sh SEE ALSO
.Xr arp 4 ,
.Xr intro 4 ,
.Xr netintro 4 ,
.Xr usb 4 ,
.Xr hostname.if 5 ,
.Xr ifconfig 8
.Rs
.%T "Universal Serial Bus Class Definitions for Communication Devices"
.%U https://www.usb.org/document-library/class-definitions-communication-devices-12
.Re
.Rs
.%T "Data sheet Prolific PL-2501 Host-to-Host Bridge/Network Controller"
.Re
.Sh HISTORY
The
.Nm
device driver first appeared in
.Ox 3.6 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Craig Boston Aq Mt craig@tobuj.gank.org
based on the
.Xr aue 4
driver written by
.An Bill Paul Aq Mt wpaul@windriver.com
and ported to
.Ox
by
.An Daniel Hartmeier Aq Mt dhartmei@openbsd.org .
.Sh CAVEATS
Many USB devices notoriously fail to report their class and interfaces
correctly.
Undetected products might work flawlessly when their vendor and product IDs
are added to the driver manually.