Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

3 files changed, 879 insertions, 0 deletions

diff --git a/Documentation/networking/device_drivers/hamradio/baycom.rst b/Documentation/networking/device_drivers/hamradio/baycom.rst
new file mode 100644
index 000000000..fe2d010f0
--- /dev/null
+++ b/Documentation/networking/device_drivers/hamradio/baycom.rst
@@ -0,0 +1,174 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============================
+Linux Drivers for Baycom Modems
+===============================
+
+Thomas M. Sailer, HB9JNX/AE4WA, <sailer@ife.ee.ethz.ch>
+
+The drivers for the baycom modems have been split into
+separate drivers as they did not share any code, and the driver
+and device names have changed.
+
+This document describes the Linux Kernel Drivers for simple Baycom style
+amateur radio modems.
+
+The following drivers are available:
+====================================
+
+baycom_ser_fdx:
+  This driver supports the SER12 modems either full or half duplex.
+  Its baud rate may be changed via the ``baud`` module parameter,
+  therefore it supports just about every bit bang modem on a
+  serial port. Its devices are called bcsf0 through bcsf3.
+  This is the recommended driver for SER12 type modems,
+  however if you have a broken UART clone that does not have working
+  delta status bits, you may try baycom_ser_hdx.
+
+baycom_ser_hdx:
+  This is an alternative driver for SER12 type modems.
+  It only supports half duplex, and only 1200 baud. Its devices
+  are called bcsh0 through bcsh3. Use this driver only if baycom_ser_fdx
+  does not work with your UART.
+
+baycom_par:
+  This driver supports the par96 and picpar modems.
+  Its devices are called bcp0 through bcp3.
+
+baycom_epp:
+  This driver supports the EPP modem.
+  Its devices are called bce0 through bce3.
+  This driver is work-in-progress.
+
+The following modems are supported:
+
+======= ========================================================================
+ser12   This is a very simple 1200 baud AFSK modem. The modem consists only
+	of a modulator/demodulator chip, usually a TI TCM3105. The computer
+	is responsible for regenerating the receiver bit clock, as well as
+	for handling the HDLC protocol. The modem connects to a serial port,
+	hence the name. Since the serial port is not used as an async serial
+	port, the kernel driver for serial ports cannot be used, and this
+	driver only supports standard serial hardware (8250, 16450, 16550)
+
+par96   This is a modem for 9600 baud FSK compatible to the G3RUH standard.
+	The modem does all the filtering and regenerates the receiver clock.
+	Data is transferred from and to the PC via a shift register.
+	The shift register is filled with 16 bits and an interrupt is signalled.
+	The PC then empties the shift register in a burst. This modem connects
+	to the parallel port, hence the name. The modem leaves the
+	implementation of the HDLC protocol and the scrambler polynomial to
+	the PC.
+
+picpar  This is a redesign of the par96 modem by Henning Rech, DF9IC. The modem
+	is protocol compatible to par96, but uses only three low power ICs
+	and can therefore be fed from the parallel port and does not require
+	an additional power supply. Furthermore, it incorporates a carrier
+	detect circuitry.
+
+EPP     This is a high-speed modem adaptor that connects to an enhanced parallel
+	port.
+
+	Its target audience is users working over a high speed hub (76.8kbit/s).
+
+eppfpga This is a redesign of the EPP adaptor.
+======= ========================================================================
+
+All of the above modems only support half duplex communications. However,
+the driver supports the KISS (see below) fullduplex command. It then simply
+starts to send as soon as there's a packet to transmit and does not care
+about DCD, i.e. it starts to send even if there's someone else on the channel.
+This command is required by some implementations of the DAMA channel
+access protocol.
+
+
+The Interface of the drivers
+============================
+
+Unlike previous drivers, these drivers are no longer character devices,
+but they are now true kernel network interfaces. Installation is therefore
+simple. Once installed, four interfaces named bc{sf,sh,p,e}[0-3] are available.
+sethdlc from the ax25 utilities may be used to set driver states etc.
+Users of userland AX.25 stacks may use the net2kiss utility (also available
+in the ax25 utilities package) to convert packets of a network interface
+to a KISS stream on a pseudo tty. There's also a patch available from
+me for WAMPES which allows attaching a kernel network interface directly.
+
+
+Configuring the driver
+======================
+
+Every time a driver is inserted into the kernel, it has to know which
+modems it should access at which ports. This can be done with the setbaycom
+utility. If you are only using one modem, you can also configure the
+driver from the insmod command line (or by means of an option line in
+``/etc/modprobe.d/*.conf``).
+
+Examples::
+
+  modprobe baycom_ser_fdx mode="ser12*" iobase=0x3f8 irq=4
+  sethdlc -i bcsf0 -p mode "ser12*" io 0x3f8 irq 4
+
+Both lines configure the first port to drive a ser12 modem at the first
+serial port (COM1 under DOS). The * in the mode parameter instructs the driver
+to use the software DCD algorithm (see below)::
+
+  insmod baycom_par mode="picpar" iobase=0x378
+  sethdlc -i bcp0 -p mode "picpar" io 0x378
+
+Both lines configure the first port to drive a picpar modem at the
+first parallel port (LPT1 under DOS). (Note: picpar implies
+hardware DCD, par96 implies software DCD).
+
+The channel access parameters can be set with sethdlc -a or kissparms.
+Note that both utilities interpret the values slightly differently.
+
+
+Hardware DCD versus Software DCD
+================================
+
+To avoid collisions on the air, the driver must know when the channel is
+busy. This is the task of the DCD circuitry/software. The driver may either
+utilise a software DCD algorithm (options=1) or use a DCD signal from
+the hardware (options=0).
+
+======= =================================================================
+ser12   if software DCD is utilised, the radio's squelch should always be
+	open. It is highly recommended to use the software DCD algorithm,
+	as it is much faster than most hardware squelch circuitry. The
+	disadvantage is a slightly higher load on the system.
+
+par96   the software DCD algorithm for this type of modem is rather poor.
+	The modem simply does not provide enough information to implement
+	a reasonable DCD algorithm in software. Therefore, if your radio
+	feeds the DCD input of the PAR96 modem, the use of the hardware
+	DCD circuitry is recommended.
+
+picpar  the picpar modem features a builtin DCD hardware, which is highly
+	recommended.
+======= =================================================================
+
+
+
+Compatibility with the rest of the Linux kernel
+===============================================
+
+The serial driver and the baycom serial drivers compete
+for the same hardware resources. Of course only one driver can access a given
+interface at a time. The serial driver grabs all interfaces it can find at
+startup time. Therefore the baycom drivers subsequently won't be able to
+access a serial port. You might therefore find it necessary to release
+a port owned by the serial driver with 'setserial /dev/ttyS# uart none', where
+# is the number of the interface. The baycom drivers do not reserve any
+ports at startup, unless one is specified on the 'insmod' command line. Another
+method to solve the problem is to compile all drivers as modules and
+leave it to kmod to load the correct driver depending on the application.
+
+The parallel port drivers (baycom_par, baycom_epp) now use the parport subsystem
+to arbitrate the ports between different client drivers.
+
+vy 73s de
+
+Tom Sailer, sailer@ife.ee.ethz.ch
+
+hb9jnx @ hb9w.ampr.org
diff --git a/Documentation/networking/device_drivers/hamradio/index.rst b/Documentation/networking/device_drivers/hamradio/index.rst
new file mode 100644
index 000000000..7e7317320
--- /dev/null
+++ b/Documentation/networking/device_drivers/hamradio/index.rst
@@ -0,0 +1,19 @@
+.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+
+Amateur Radio Device Drivers
+============================
+
+Contents:
+
+.. toctree::
+   :maxdepth: 2
+
+   baycom
+   z8530drv
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`
diff --git a/Documentation/networking/device_drivers/hamradio/z8530drv.rst b/Documentation/networking/device_drivers/hamradio/z8530drv.rst
new file mode 100644
index 000000000..d2942760f
--- /dev/null
+++ b/Documentation/networking/device_drivers/hamradio/z8530drv.rst
@@ -0,0 +1,686 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+=========================================================
+SCC.C - Linux driver for Z8530 based HDLC cards for AX.25
+=========================================================
+
+
+This is a subset of the documentation. To use this driver you MUST have the
+full package from:
+
+Internet:
+
+    1. ftp://ftp.ccac.rwth-aachen.de/pub/jr/z8530drv-utils_3.0-3.tar.gz
+
+    2. ftp://ftp.pspt.fi/pub/ham/linux/ax25/z8530drv-utils_3.0-3.tar.gz
+
+Please note that the information in this document may be hopelessly outdated.
+A new version of the documentation, along with links to other important
+Linux Kernel AX.25 documentation and programs, is available on
+http://yaina.de/jreuter
+
+Copyright |copy| 1993,2000 by Joerg Reuter DL1BKE <jreuter@yaina.de>
+
+portions Copyright |copy| 1993 Guido ten Dolle PE1NNZ
+
+for the complete copyright notice see >> Copying.Z8530DRV <<
+
+1. Initialization of the driver
+===============================
+
+To use the driver, 3 steps must be performed:
+
+     1. if compiled as module: loading the module
+     2. Setup of hardware, MODEM and KISS parameters with sccinit
+     3. Attach each channel to the Linux kernel AX.25 with "ifconfig"
+
+Unlike the versions below 2.4 this driver is a real network device
+driver. If you want to run xNOS instead of our fine kernel AX.25
+use a 2.x version (available from above sites) or read the
+AX.25-HOWTO on how to emulate a KISS TNC on network device drivers.
+
+
+1.1 Loading the module
+======================
+
+(If you're going to compile the driver as a part of the kernel image,
+ skip this chapter and continue with 1.2)
+
+Before you can use a module, you'll have to load it with::
+
+	insmod scc.o
+
+please read 'man insmod' that comes with module-init-tools.
+
+You should include the insmod in one of the /etc/rc.d/rc.* files,
+and don't forget to insert a call of sccinit after that. It
+will read your /etc/z8530drv.conf.
+
+1.2. /etc/z8530drv.conf
+=======================
+
+To setup all parameters you must run /sbin/sccinit from one
+of your rc.*-files. This has to be done BEFORE you can
+"ifconfig" an interface. Sccinit reads the file /etc/z8530drv.conf
+and sets the hardware, MODEM and KISS parameters. A sample file is
+delivered with this package. Change it to your needs.
+
+The file itself consists of two main sections.
+
+1.2.1 configuration of hardware parameters
+==========================================
+
+The hardware setup section defines the following parameters for each
+Z8530::
+
+    chip    1
+    data_a  0x300                   # data port A
+    ctrl_a  0x304                   # control port A
+    data_b  0x301                   # data port B
+    ctrl_b  0x305                   # control port B
+    irq     5                       # IRQ No. 5
+    pclock  4915200                 # clock
+    board   BAYCOM                  # hardware type
+    escc    no                      # enhanced SCC chip? (8580/85180/85280)
+    vector  0                       # latch for interrupt vector
+    special no                      # address of special function register
+    option  0                       # option to set via sfr
+
+
+chip
+	- this is just a delimiter to make sccinit a bit simpler to
+	  program. A parameter has no effect.
+
+data_a
+	- the address of the data port A of this Z8530 (needed)
+ctrl_a
+	- the address of the control port A (needed)
+data_b
+	- the address of the data port B (needed)
+ctrl_b
+	- the address of the control port B (needed)
+
+irq
+	- the used IRQ for this chip. Different chips can use different
+	  IRQs or the same. If they share an interrupt, it needs to be
+	  specified within one chip-definition only.
+
+pclock  - the clock at the PCLK pin of the Z8530 (option, 4915200 is
+	  default), measured in Hertz
+
+board
+	- the "type" of the board:
+
+	   =======================  ========
+	   SCC type                 value
+	   =======================  ========
+	   PA0HZP SCC card          PA0HZP
+	   EAGLE card               EAGLE
+	   PC100 card               PC100
+	   PRIMUS-PC (DG9BL) card   PRIMUS
+	   BayCom (U)SCC card       BAYCOM
+	   =======================  ========
+
+escc
+	- if you want support for ESCC chips (8580, 85180, 85280), set
+	  this to "yes" (option, defaults to "no")
+
+vector
+	- address of the vector latch (aka "intack port") for PA0HZP
+	  cards. There can be only one vector latch for all chips!
+	  (option, defaults to 0)
+
+special
+	- address of the special function register on several cards.
+	  (option, defaults to 0)
+
+option  - The value you write into that register (option, default is 0)
+
+You can specify up to four chips (8 channels). If this is not enough,
+just change::
+
+	#define MAXSCC 4
+
+to a higher value.
+
+Example for the BAYCOM USCC:
+----------------------------
+
+::
+
+	chip    1
+	data_a  0x300                   # data port A
+	ctrl_a  0x304                   # control port A
+	data_b  0x301                   # data port B
+	ctrl_b  0x305                   # control port B
+	irq     5                       # IRQ No. 5 (#)
+	board   BAYCOM                  # hardware type (*)
+	#
+	# SCC chip 2
+	#
+	chip    2
+	data_a  0x302
+	ctrl_a  0x306
+	data_b  0x303
+	ctrl_b  0x307
+	board   BAYCOM
+
+An example for a PA0HZP card:
+-----------------------------
+
+::
+
+	chip 1
+	data_a 0x153
+	data_b 0x151
+	ctrl_a 0x152
+	ctrl_b 0x150
+	irq 9
+	pclock 4915200
+	board PA0HZP
+	vector 0x168
+	escc no
+	#
+	#
+	#
+	chip 2
+	data_a 0x157
+	data_b 0x155
+	ctrl_a 0x156
+	ctrl_b 0x154
+	irq 9
+	pclock 4915200
+	board PA0HZP
+	vector 0x168
+	escc no
+
+A DRSI would should probably work with this:
+--------------------------------------------
+(actually: two DRSI cards...)
+
+::
+
+	chip 1
+	data_a 0x303
+	data_b 0x301
+	ctrl_a 0x302
+	ctrl_b 0x300
+	irq 7
+	pclock 4915200
+	board DRSI
+	escc no
+	#
+	#
+	#
+	chip 2
+	data_a 0x313
+	data_b 0x311
+	ctrl_a 0x312
+	ctrl_b 0x310
+	irq 7
+	pclock 4915200
+	board DRSI
+	escc no
+
+Note that you cannot use the on-board baudrate generator off DRSI
+cards. Use "mode dpll" for clock source (see below).
+
+This is based on information provided by Mike Bilow (and verified
+by Paul Helay)
+
+The utility "gencfg"
+--------------------
+
+If you only know the parameters for the PE1CHL driver for DOS,
+run gencfg. It will generate the correct port addresses (I hope).
+Its parameters are exactly the same as the ones you use with
+the "attach scc" command in net, except that the string "init" must
+not appear. Example::
+
+	gencfg 2 0x150 4 2 0 1 0x168 9 4915200
+
+will print a skeleton z8530drv.conf for the OptoSCC to stdout.
+
+::
+
+	gencfg 2 0x300 2 4 5 -4 0 7 4915200 0x10
+
+does the same for the BAYCOM USCC card. In my opinion it is much easier
+to edit scc_config.h...
+
+
+1.2.2 channel configuration
+===========================
+
+The channel definition is divided into three sub sections for each
+channel:
+
+An example for scc0::
+
+	# DEVICE
+
+	device scc0	# the device for the following params
+
+	# MODEM / BUFFERS
+
+	speed 1200		# the default baudrate
+	clock dpll		# clock source:
+				# 	dpll     = normal half duplex operation
+				# 	external = MODEM provides own Rx/Tx clock
+				#	divider  = use full duplex divider if
+				#		   installed (1)
+	mode nrzi		# HDLC encoding mode
+				#	nrzi = 1k2 MODEM, G3RUH 9k6 MODEM
+				#	nrz  = DF9IC 9k6 MODEM
+				#
+	bufsize	384		# size of buffers. Note that this must include
+				# the AX.25 header, not only the data field!
+				# (optional, defaults to 384)
+
+	# KISS (Layer 1)
+
+	txdelay 36              # (see chapter 1.4)
+	persist 64
+	slot    8
+	tail    8
+	fulldup 0
+	wait    12
+	min     3
+	maxkey  7
+	idle    3
+	maxdef  120
+	group   0
+	txoff   off
+	softdcd on
+	slip    off
+
+The order WITHIN these sections is unimportant. The order OF these
+sections IS important. The MODEM parameters are set with the first
+recognized KISS parameter...
+
+Please note that you can initialize the board only once after boot
+(or insmod). You can change all parameters but "mode" and "clock"
+later with the Sccparam program or through KISS. Just to avoid
+security holes...
+
+(1) this divider is usually mounted on the SCC-PBC (PA0HZP) or not
+    present at all (BayCom). It feeds back the output of the DPLL
+    (digital pll) as transmit clock. Using this mode without a divider
+    installed will normally result in keying the transceiver until
+    maxkey expires --- of course without sending anything (useful).
+
+2. Attachment of a channel by your AX.25 software
+=================================================
+
+2.1 Kernel AX.25
+================
+
+To set up an AX.25 device you can simply type::
+
+	ifconfig scc0 44.128.1.1 hw ax25 dl0tha-7
+
+This will create a network interface with the IP number 44.128.20.107
+and the callsign "dl0tha". If you do not have any IP number (yet) you
+can use any of the 44.128.0.0 network. Note that you do not need
+axattach. The purpose of axattach (like slattach) is to create a KISS
+network device linked to a TTY. Please read the documentation of the
+ax25-utils and the AX.25-HOWTO to learn how to set the parameters of
+the kernel AX.25.
+
+2.2 NOS, NET and TFKISS
+=======================
+
+Since the TTY driver (aka KISS TNC emulation) is gone you need
+to emulate the old behaviour. The cost of using these programs is
+that you probably need to compile the kernel AX.25, regardless of whether
+you actually use it or not. First setup your /etc/ax25/axports,
+for example::
+
+	9k6	dl0tha-9  9600  255 4 9600 baud port (scc3)
+	axlink	dl0tha-15 38400 255 4 Link to NOS
+
+Now "ifconfig" the scc device::
+
+	ifconfig scc3 44.128.1.1 hw ax25 dl0tha-9
+
+You can now axattach a pseudo-TTY::
+
+	axattach /dev/ptys0 axlink
+
+and start your NOS and attach /dev/ptys0 there. The problem is that
+NOS is reachable only via digipeating through the kernel AX.25
+(disastrous on a DAMA controlled channel). To solve this problem,
+configure "rxecho" to echo the incoming frames from "9k6" to "axlink"
+and outgoing frames from "axlink" to "9k6" and start::
+
+	rxecho
+
+Or simply use "kissbridge" coming with z8530drv-utils::
+
+	ifconfig scc3 hw ax25 dl0tha-9
+	kissbridge scc3 /dev/ptys0
+
+
+3. Adjustment and Display of parameters
+=======================================
+
+3.1 Displaying SCC Parameters:
+==============================
+
+Once a SCC channel has been attached, the parameter settings and
+some statistic information can be shown using the param program::
+
+	dl1bke-u:~$ sccstat scc0
+
+	Parameters:
+
+	speed       : 1200 baud
+	txdelay     : 36
+	persist     : 255
+	slottime    : 0
+	txtail      : 8
+	fulldup     : 1
+	waittime    : 12
+	mintime     : 3 sec
+	maxkeyup    : 7 sec
+	idletime    : 3 sec
+	maxdefer    : 120 sec
+	group       : 0x00
+	txoff       : off
+	softdcd     : on
+	SLIP        : off
+
+	Status:
+
+	HDLC                  Z8530           Interrupts         Buffers
+	-----------------------------------------------------------------------
+	Sent       :     273  RxOver :     0  RxInts :   125074  Size    :  384
+	Received   :    1095  TxUnder:     0  TxInts :     4684  NoSpace :    0
+	RxErrors   :    1591                  ExInts :    11776
+	TxErrors   :       0                  SpInts :     1503
+	Tx State   :    idle
+
+
+The status info shown is:
+
+==============	==============================================================
+Sent		number of frames transmitted
+Received	number of frames received
+RxErrors	number of receive errors (CRC, ABORT)
+TxErrors	number of discarded Tx frames (due to various reasons)
+Tx State	status of the Tx interrupt handler: idle/busy/active/tail (2)
+RxOver		number of receiver overruns
+TxUnder		number of transmitter underruns
+RxInts		number of receiver interrupts
+TxInts		number of transmitter interrupts
+EpInts		number of receiver special condition interrupts
+SpInts		number of external/status interrupts
+Size		maximum size of an AX.25 frame (*with* AX.25 headers!)
+NoSpace		number of times a buffer could not get allocated
+==============	==============================================================
+
+An overrun is abnormal. If lots of these occur, the product of
+baudrate and number of interfaces is too high for the processing
+power of your computer. NoSpace errors are unlikely to be caused by the
+driver or the kernel AX.25.
+
+
+3.2 Setting Parameters
+======================
+
+
+The setting of parameters of the emulated KISS TNC is done in the
+same way in the SCC driver. You can change parameters by using
+the kissparms program from the ax25-utils package or use the program
+"sccparam"::
+
+     sccparam <device> <paramname> <decimal-|hexadecimal value>
+
+You can change the following parameters:
+
+===========   =====
+param	      value
+===========   =====
+speed         1200
+txdelay       36
+persist       255
+slottime      0
+txtail        8
+fulldup       1
+waittime      12
+mintime       3
+maxkeyup      7
+idletime      3
+maxdefer      120
+group         0x00
+txoff         off
+softdcd       on
+SLIP          off
+===========   =====
+
+
+The parameters have the following meaning:
+
+speed:
+     The baudrate on this channel in bits/sec
+
+     Example: sccparam /dev/scc3 speed 9600
+
+txdelay:
+     The delay (in units of 10 ms) after keying of the
+     transmitter, until the first byte is sent. This is usually
+     called "TXDELAY" in a TNC.  When 0 is specified, the driver
+     will just wait until the CTS signal is asserted. This
+     assumes the presence of a timer or other circuitry in the
+     MODEM and/or transmitter, that asserts CTS when the
+     transmitter is ready for data.
+     A normal value of this parameter is 30-36.
+
+     Example: sccparam /dev/scc0 txd 20
+
+persist:
+     This is the probability that the transmitter will be keyed
+     when the channel is found to be free.  It is a value from 0
+     to 255, and the probability is (value+1)/256.  The value
+     should be somewhere near 50-60, and should be lowered when
+     the channel is used more heavily.
+
+     Example: sccparam /dev/scc2 persist 20
+
+slottime:
+     This is the time between samples of the channel. It is
+     expressed in units of 10 ms.  About 200-300 ms (value 20-30)
+     seems to be a good value.
+
+     Example: sccparam /dev/scc0 slot 20
+
+tail:
+     The time the transmitter will remain keyed after the last
+     byte of a packet has been transferred to the SCC. This is
+     necessary because the CRC and a flag still have to leave the
+     SCC before the transmitter is keyed down. The value depends
+     on the baudrate selected.  A few character times should be
+     sufficient, e.g. 40ms at 1200 baud. (value 4)
+     The value of this parameter is in 10 ms units.
+
+     Example: sccparam /dev/scc2 4
+
+full:
+     The full-duplex mode switch. This can be one of the following
+     values:
+
+     0:   The interface will operate in CSMA mode (the normal
+	  half-duplex packet radio operation)
+     1:   Fullduplex mode, i.e. the transmitter will be keyed at
+	  any time, without checking the received carrier.  It
+	  will be unkeyed when there are no packets to be sent.
+     2:   Like 1, but the transmitter will remain keyed, also
+	  when there are no packets to be sent.  Flags will be
+	  sent in that case, until a timeout (parameter 10)
+	  occurs.
+
+     Example: sccparam /dev/scc0 fulldup off
+
+wait:
+     The initial waittime before any transmit attempt, after the
+     frame has been queue for transmit.  This is the length of
+     the first slot in CSMA mode.  In full duplex modes it is
+     set to 0 for maximum performance.
+     The value of this parameter is in 10 ms units.
+
+     Example: sccparam /dev/scc1 wait 4
+
+maxkey:
+     The maximal time the transmitter will be keyed to send
+     packets, in seconds.  This can be useful on busy CSMA
+     channels, to avoid "getting a bad reputation" when you are
+     generating a lot of traffic.  After the specified time has
+     elapsed, no new frame will be started. Instead, the trans-
+     mitter will be switched off for a specified time (parameter
+     min), and then the selected algorithm for keyup will be
+     started again.
+     The value 0 as well as "off" will disable this feature,
+     and allow infinite transmission time.
+
+     Example: sccparam /dev/scc0 maxk 20
+
+min:
+     This is the time the transmitter will be switched off when
+     the maximum transmission time is exceeded.
+
+     Example: sccparam /dev/scc3 min 10
+
+idle:
+     This parameter specifies the maximum idle time in full duplex
+     2 mode, in seconds.  When no frames have been sent for this
+     time, the transmitter will be keyed down.  A value of 0 is
+     has same result as the fullduplex mode 1. This parameter
+     can be disabled.
+
+     Example: sccparam /dev/scc2 idle off	# transmit forever
+
+maxdefer
+     This is the maximum time (in seconds) to wait for a free channel
+     to send. When this timer expires the transmitter will be keyed
+     IMMEDIATELY. If you love to get trouble with other users you
+     should set this to a very low value ;-)
+
+     Example: sccparam /dev/scc0 maxdefer 240	# 2 minutes
+
+
+txoff:
+     When this parameter has the value 0, the transmission of packets
+     is enable. Otherwise it is disabled.
+
+     Example: sccparam /dev/scc2 txoff on
+
+group:
+     It is possible to build special radio equipment to use more than
+     one frequency on the same band, e.g. using several receivers and
+     only one transmitter that can be switched between frequencies.
+     Also, you can connect several radios that are active on the same
+     band.  In these cases, it is not possible, or not a good idea, to
+     transmit on more than one frequency.  The SCC driver provides a
+     method to lock transmitters on different interfaces, using the
+     "param <interface> group <x>" command.  This will only work when
+     you are using CSMA mode (parameter full = 0).
+
+     The number <x> must be 0 if you want no group restrictions, and
+     can be computed as follows to create restricted groups:
+     <x> is the sum of some OCTAL numbers:
+
+
+     ===  =======================================================
+     200  This transmitter will only be keyed when all other
+	  transmitters in the group are off.
+     100  This transmitter will only be keyed when the carrier
+	  detect of all other interfaces in the group is off.
+     0xx  A byte that can be used to define different groups.
+	  Interfaces are in the same group, when the logical AND
+	  between their xx values is nonzero.
+     ===  =======================================================
+
+     Examples:
+
+     When 2 interfaces use group 201, their transmitters will never be
+     keyed at the same time.
+
+     When 2 interfaces use group 101, the transmitters will only key
+     when both channels are clear at the same time.  When group 301,
+     the transmitters will not be keyed at the same time.
+
+     Don't forget to convert the octal numbers into decimal before
+     you set the parameter.
+
+     Example: (to be written)
+
+softdcd:
+     use a software dcd instead of the real one... Useful for a very
+     slow squelch.
+
+     Example: sccparam /dev/scc0 soft on
+
+
+4. Problems
+===========
+
+If you have tx-problems with your BayCom USCC card please check
+the manufacturer of the 8530. SGS chips have a slightly
+different timing. Try Zilog...  A solution is to write to register 8
+instead to the data port, but this won't work with the ESCC chips.
+*SIGH!*
+
+A very common problem is that the PTT locks until the maxkeyup timer
+expires, although interrupts and clock source are correct. In most
+cases compiling the driver with CONFIG_SCC_DELAY (set with
+make config) solves the problems. For more hints read the (pseudo) FAQ
+and the documentation coming with z8530drv-utils.
+
+I got reports that the driver has problems on some 386-based systems.
+(i.e. Amstrad) Those systems have a bogus AT bus timing which will
+lead to delayed answers on interrupts. You can recognize these
+problems by looking at the output of Sccstat for the suspected
+port. If it shows under- and overruns you own such a system.
+
+Delayed processing of received data: This depends on
+
+- the kernel version
+
+- kernel profiling compiled or not
+
+- a high interrupt load
+
+- a high load of the machine --- running X, Xmorph, XV and Povray,
+  while compiling the kernel... hmm ... even with 32 MB RAM ...  ;-)
+  Or running a named for the whole .ampr.org domain on an 8 MB
+  box...
+
+- using information from rxecho or kissbridge.
+
+Kernel panics: please read /linux/README and find out if it
+really occurred within the scc driver.
+
+If you cannot solve a problem, send me
+
+- a description of the problem,
+- information on your hardware (computer system, scc board, modem)
+- your kernel version
+- the output of cat /proc/net/z8530
+
+4. Thor RLC100
+==============
+
+Mysteriously this board seems not to work with the driver. Anyone
+got it up-and-running?
+
+
+Many thanks to Linus Torvalds and Alan Cox for including the driver
+in the Linux standard distribution and their support.
+
+::
+
+	Joerg Reuter	ampr-net: dl1bke@db0pra.ampr.org
+			AX-25   : DL1BKE @ DB0ABH.#BAY.DEU.EU
+			Internet: jreuter@yaina.de
+			WWW     : http://yaina.de/jreuter