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:

       •   SMC90c26
       •   SMC90c56
       •   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 dynamically map between Internet and Ethernet  addresses  on  the  local  network.
       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 according 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 reported:

       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 emptied 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 appeared in FreeBSD 5.3.

AUTHORS

       This manual page was written by Tom Rhodes <trhodes@FreeBSD.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.

Debian                                            July 16, 2005                                            CM(4)