cm(4)

NAME

cm - SMC Arcnet Ethernet device driver

SYNOPSIS

To compile this driver into the kernel, place the  following
lines in your
kernel configuration file:
      device isa
      device cm
Alternatively,  to load the driver as a module at boot time,
place the
following line in loader.conf(5):
      if_cm_load="YES"

DESCRIPTION

The cm driver provides support for the Arcnet ISA network

adapters.

This driver also has quirks preset in the device.hints(5)

file for card
detection.

HARDWARE

The cm driver supports the following card models:

+o SMC90c26
+o SMC90c56
+o SMC90c66 in '56 compatibility mode.

IMPLEMENTATION NOTES

When the NOARP flag is set on the cm interface, it does not

employ the
address resolution protocol described in arp(4) to dynami

cally map
between Internet and Ethernet addresses on the local net

work. Instead it
uses the least significant 8 bits of the IP address as the

hardware
address like described in RFC 1051 and RFC 1201.

With the IFF_LINK0 flag cleared IP/ARP/RARP encoding is done

according to
RFC 1201 that is, with Packet Header Definition Standard

header and
packet type 212 / 213. The MTU is normally 1500. The

IFF_LINK0 flag is
cleared by default.

With the IFF_LINK0 flag set, IP and ARP encoding is done ac

cording to the
deprecated RFC 1051 encoding, that is with simple header,

packet type 240
/ 241, and the MTU is 507.

When switching between the two modes, use

ifconfig interfacename down up

to switch the MTU.

DIAGNOSTICS

The following driver specific error messages may be report

ed:

reset: card reset, link addr = 0x%02x (cm%d) The card is

being reset and
a new link address assigned.

srint: restarted rx on buf cm%d The rx buffer has been emp

tied and will
be reset.

SEE ALSO

netintro(4), watchdog(4), device.hints(5), ifconfig(8),

watchdog(8)

HISTORY

The cm device was ported from NetBSD by Max Khon

<fjoe@FreeBSD.org> and
first appeared in FreeBSD 4.6. This manual page first ap

peared in
FreeBSD 5.3.

AUTHORS

This manual page was written by Tom Rhodes <trhodes@FreeB

SD.org>. The
IMPLEMENTATION NOTES section was submitted by Max Khon <fjoe@FreeBSD.org> and originated from NetBSD.

BUGS

The cm driver code could do with a bit of improvement, it

would be nice
if some one could come along and take care of this.

The IMPLEMENTATION NOTES section is specific to all Arcnet

devices (see
sys/net/if_arcsubr.c) and should be moved to a more generic

location.

BSD July 16, 2005

BSD