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COMX drivers for the 2.2 kernel
Originally written by: Tivadar Szemethy, <>
Currently maintained by: Gergely Madarasz <>
Last change: 21/06/1999.
This document describes the software drivers and their use for the
COMX line of synchronous serial adapters for Linux version 2.2.0 and
The cards are produced and sold by ITC-Pro Ltd. Budapest, Hungary
For further info contact <>
or (mostly in Hungarian).
The firmware files and software are available from
Currently, the drivers support the following cards and protocols:
COMX (2x64 kbps intelligent board)
CMX (1x256 + 1x128 kbps intelligent board)
HiCOMX (2x2Mbps intelligent board)
LoCOMX (1x512 kbps passive board)
MixCOM (1x512 or 2x512kbps passive board with a hardware watchdog an
optional BRI interface and optional flashROM (1-32M))
SliceCOM (1x2Mbps channelized E1 board)
PciCOM (X21)
At the moment of writing this document, the (Cisco)-HDLC, LAPB, SyncPPP and
Frame Relay (DTE, rfc1294 IP encapsulation with partially implemented Q933a
LMI) protocols are available as link-level protocol.
X.25 support is being worked on.
Load the comx.o module and the hardware-specific and protocol-specific
modules you'll need into the running kernel using the insmod utility.
This creates the /proc/comx directory.
See the example scripts in the 'etc' directory.
The COMX driver set has a new type of user interface based on the /proc
filesystem which eliminates the need for external user-land software doing
IOCTL calls.
Each network interface or device (i.e. those ones you configure with 'ifconfig'
and 'route' etc.) has a corresponding directory under /proc/comx. You can
dynamically create a new interface by saying 'mkdir /proc/comx/comx0' (or you
can name it whatever you want up to 8 characters long, comx[n] is just a
Generally the files contained in these directories are text files, which can
be viewed by 'cat filename' and you can write a string to such a file by
saying 'echo _string_ >filename'. This is very similar to the sysctl interface.
Don't use a text editor to edit these files, always use 'echo' (or 'cat'
where appropriate).
When you've created the comx[n] directory, two files are created automagically
in it: 'boardtype' and 'protocol'. You have to fill in these files correctly
for your board and protocol you intend to use (see the board and protocol
descriptions in this file below or the example scripts in the 'etc' directory).
After filling in these files, other files will appear in the directory for
setting the various hardware- and protocol-related informations (for example
irq and io addresses, keepalive values etc.) These files are set to default
values upon creation, so you don't necessarily have to change all of them.
When you're ready with filling in the files in the comx[n] directory, you can
configure the corresponding network interface with the standard network
configuration utilities. If you're unable to bring the interfaces up, look up
the various kernel log files on your system, and consult the messages for
a probable reason.
To create the interface 'comx0' which is the first channel of a COMX card:
insmod comx
# insmod comx-hw-comx ; insmod comx-proto-ppp (these are usually
autoloaded if you use the kernel module loader)
mkdir /proc/comx/comx0
echo comx >/proc/comx/comx0/boardtype
echo 0x360 >/proc/comx/comx0/io <- jumper-selectable I/O port
echo 0x0a >/proc/comx/comx0/irq <- jumper-selectable IRQ line
echo 0xd000 >/proc/comx/comx0/memaddr <- software-configurable memory
address. COMX uses 64 KB, and this
can be: 0xa000, 0xb000, 0xc000,
0xd000, 0xe000. Avoid conflicts
with other hardware.
cat </etc/siol1.rom >/proc/comx/comx0/firmware <- the firmware for the card
echo HDLC >/proc/comx/comx0/protocol <- the data-link protocol
echo 10 >/proc/comx/comx0/keepalive <- the keepalive for the protocol
ifconfig comx0 pointopoint netmask <-
finally configure it with ifconfig
Check its status:
cat /proc/comx/comx0/status
If you want to use the second channel of this board:
mkdir /proc/comx/comx1
echo comx >/proc/comx/comx1/boardtype
echo 0x360 >/proc/comx/comx1/io
echo 10 >/proc/comx/comx1/irq
echo 0xd000 >/proc/comx/comx1/memaddr
echo 1 >/proc/comx/comx1/channel <- channels are numbered
as 0 (default) and 1
Now, check if the driver recognized that you're going to use the other
channel of the same adapter:
cat /proc/comx/comx0/twin
cat /proc/comx/comx1/twin
You don't have to load the firmware twice, if you use both channels of
an adapter, just write it into the channel 0's /proc firmware file.
Default values: io 0x360 for COMX, 0x320 (HICOMX), irq 10, memaddr 0xd0000
The LoCOMX driver doesn't require firmware, and it doesn't use memory either,
but it uses DMA channels 1 and 3. You can set the clock rate (if enabled by
jumpers on the board) by writing the kbps value into the file named 'clock'.
Set it to 'external' (it is the default) if you have external clock source.
(Note: currently the LoCOMX driver does not support the internal clock)
On the HICOMX, COMX and CMX, you have to load the firmware (it is different for
the three cards!). All these adapters can share the same memory
address (we usually use 0xd0000). On the CMX you can set the internal
clock rate (if enabled by jumpers on the small adapter boards) by writing
the kbps value into the 'clock' file. You have to do this before initializing
the card. If you use both HICOMX and CMX/COMX cards, initialize the HICOMX
first. The I/O address of the HICOMX board is not configurable by any
method available to the user: it is hardwired to 0x320, and if you have to
change it, consult ITC-Pro Ltd.
The MixCOM board doesn't require firmware, the driver communicates with
it through I/O ports. You can have three of these cards in one machine.
The SliceCOM board doesn't require firmware. You can have 4 of these cards
in one machine. The driver doesn't (yet) support shared interrupts, so
you will need a separate IRQ line for every board.
Read Documentation/networking/slicecom.txt for help on configuring
this adapter.
The HDLC/SyncPPP line protocol driver uses the kernel's built-in syncppp
driver (syncppp.o). You don't have to manually select syncppp.o when building
the kernel, the dependencies compile it in automatically.
(setting up hw parameters, see above)
# using HDLC:
echo hdlc >/proc/comx/comx0/protocol
echo 10 >/proc/comx/comx0/keepalive <- not necessary, 10 is the default
ifconfig comx0 pointopoint netmask
(setting up hw parameters, see above)
# using PPP:
echo ppp >/proc/comx/comx0/protocol
ifconfig comx0 up
ifconfig comx0 pointopoint netmask
For this, you'll need to configure LAPB support (See 'LAPB Data Link Driver' in
'Network options' section) into your kernel (thanks to Jonathan Naylor for his
excellent implementation).
comx-proto-lapb.o provides the following files in the appropriate directory
(the default values in parens): t1 (5), t2 (1), n2 (20), mode (DTE, STD) and
window (7). Agree with the administrator of your peer router on these
settings (most people use defaults, but you have to know if you are DTE or
(setting up hw parameters, see above)
echo lapb >/proc/comx/comx0/protocol
echo dce >/proc/comx/comx0/mode <- DCE interface in this example
ifconfig comx0 pointopoint netmask
You DON'T need any other frame relay related modules from the kernel to use
COMX-Frame Relay. This protocol is a bit more complicated than the others,
because it allows to use 'subinterfaces' or DLCIs within one physical device.
First you have to create the 'master' device (the actual physical interface)
as you would do for other protocols. Specify 'frad' as protocol type.
Now you can bring this interface up by saying 'ifconfig comx0 up' (or whatever
you've named the interface). Do not assign any IP address to this interface
and do not set any routes through it.
Then, set up your DLCIs the following way: create a comx interface for each
DLCI you intend to use (with mkdir), and write 'dlci' to the 'boardtype' file,
and 'ietf-ip' to the 'protocol' file. Currently, the only supported
encapsulation type is this (also called as RFC1294/1490 IP encapsulation).
Write the DLCI number to the 'dlci' file, and write the name of the physical
COMX device to the file called 'master'.
Now you can assign an IP address to this interface and set routes using it.
See the example file for further info and example config script.
Notes: this driver implements a DTE interface with partially implemented
Q933a LMI.
You can find an extensively commented example in the 'etc' directory.
Type of the hardware. Valid values are:
'comx', 'hicomx', 'locomx', 'cmx', 'slicecom'.
Data-link protocol on this channel. Can be: HDLC, LAPB, PPP, FRAD
You can read the channel's actual status from the 'status' file, for example
'cat /proc/comx/comx3/status'.
Interpreted in seconds (default is 1). Used to avoid line jitter: the system
will consider the line status 'UP' only if it is up for at least this number
of seconds.
You can set various debug options through this file. Valid options are:
'comx_events', 'comx_tx', 'comx_rx', 'hw_events', 'hw_tx', 'hw_rx'.
You can enable a debug options by writing its name prepended by a '+' into
the debug file, for example 'echo +comx_rx >comx0/debug'.
Disabling an option happens similarly, use the '-' prefix
(e.g. 'echo -hw_rx >debug').
Debug results can be read from the debug file, for example:
tail -f /proc/comx/comx2/debug