sio(4)

NAME

sio - fast interrupt driven asynchronous serial communica

tions interface

SYNOPSIS

For standard ISA ports:
      device sio
      In /boot/device.hints:
      hint.sio.0.at="isa"
      hint.sio.0.port="0x3f8"
      hint.sio.0.flags="0x10"
      hint.sio.0.irq="4"
      hint.sio.1.at="isa"
      hint.sio.1.port="0x2f8"
      hint.sio.1.flags="0x0"
      hint.sio.1.irq="3"
For AST compatible multiport cards with 4 ports:
      options COM_MULTIPORT
      device sio
      In /boot/device.hints:
      hint.sio.4.at="isa"
      hint.sio.4.port="0x2a0"
      hint.sio.4.flags="0x701"
      hint.sio.5.at="isa"
      hint.sio.5.port="0x2a8"
      hint.sio.5.flags="0x701"
      hint.sio.6.at="isa"
      hint.sio.6.port="0x2b0"
      hint.sio.6.flags="0x701"
      hint.sio.7.at="isa"
      hint.sio.7.port="0x2b8"
      hint.sio.7.flags="0x701"
      hint.sio.7.irq="12"
For Boca Board compatible multiport cards with 8 ports:
      options COM_MULTIPORT
      device sio
      In /boot/device.hints:
      hint.sio.4.at="isa"
      hint.sio.4.port="0x100"
      hint.sio.4.flags="0xb05"
      ...
      hint.sio.11.at="isa"
      hint.sio.11.port="0x138"
      hint.sio.11.flags="0xb05"
      hint.sio.11.irq="12"
For Netmos Nm9845 multiport cards with 6 ports:
      options COM_MULTIPORT
      device sio
      In /boot/device.hints:
      hint.sio.4.at="isa"
      hint.sio.4.port="0xb000"
      hint.sio.4.flags="0x901"
      hint.sio.5.at="isa"
      hint.sio.5.port="0xb400"
      hint.sio.5.flags="0x901"
      hint.sio.6.at="isa"
      hint.sio.6.port="0xb800"
      hint.sio.6.flags="0x901"
      hint.sio.7.at="isa"
      hint.sio.7.port="0xbc00"
      hint.sio.7.flags="0x901"
      hint.sio.8.at="isa"
      hint.sio.8.port="0xc000"
      hint.sio.8.flags="0x901"
      hint.sio.9.at="isa"
      hint.sio.9.port="0xac00"
      hint.sio.9.flags="0x901"
      hint.sio.9.irq="12"
For Hayes ESP cards:
      options COM_ESP
      device sio
      ...
For single port PCI and PCCARD cards:
      device sio
      No  lines are required in /boot/device.hints for these
cards.
For dual port PCI cards that share an interrupt:
      device sio
      options COM_MULTIPORT
      In /boot/device.hints:
      hint.sio.2.flags="0x201"
      hint.sio.3.flags="0x201"
Meaning of flags:
      0x00001   shared IRQs
      0x00002   disable FIFO
      0x00004   no AST/4 compatible IRQ control register
      0x00008   recover sooner from lost output interrupts
      0x00010   device is potential system console
      0x00020   device is forced to become system console
      0x00040   device is reserved for  low-level  IO  (e.g.
for remote ker                nel debugging)
      0x00080   use this port for remote kernel debugging
      0x0??00   minor number of master port
      0x10000   PPS timestamping on CTS instead of DCD
      0x20000     device is assumed to use a 16650A-type (ex
tended FIFO)
                chip
Minor numbering:
      0bOLIMMMMM
        callOut
         Lock
          Initial
           MMMMMinor

DESCRIPTION

The sio driver provides support for NS8250-, NS16450-,

NS16550 and
NS16550A-based EIA RS-232C (CCITT V.24) communications in

terfaces. The
NS8250 and NS16450 have single character buffers, the

NS16550A has 16
character FIFO input and output buffers.

Input and output for each line may set to one of following

baud rates;
50, 75, 110, 134.5, 150, 300, 600, 1200, 1800, 2400, 4800,

9600, 19200,
28800, 38400, 57600, or 115200. Your hardware may limit

your baud rate
choices.

The driver supports `multiport' cards. Multiport cards are

those that
have one or more groups of ports that share an Interrupt Re

quest (IRQ)
line per group. Shared IRQs on different cards are not sup

ported. Frequently 4 ports share 1 IRQ; some 8 port cards have 2 groups

of 4 ports,
thus using 2 IRQs. Some cards allow the first 2 serial

ports to have
separate IRQs per port (as per DOS PC standard).

Some cards have an IRQ control register for each group.

Some cards
require special initialization related to such registers.

Only AST/4
compatible IRQ control registers are supported. Some cards

have an IRQ
status register for each group. The driver does not require

or use such
registers yet. To work, the control and status registers

for a group, if
any, must be mapped to the scratch register (register 7) of

a port in the
group. Such a port is called a master port.

The driver supports controller based PCI modems. The 3Com

FaxModem PCI
and the Advantec 56k Voice Messaging PCI FaxModem are the

only cards supported. WinModems, softmodems, hfc modems and any other

modems that are
not controller based are not supported.

The flags keyword may be used on each device sio line in the

kernel configuration file to disable the FIFO on 16550A UARTs (see the

synopsis).
Disabling the FIFO should rarely be necessary.

The flags keyword must be used for all ports that are part

of an IRQ
sharing group. One bit specifies IRQ sharing; another bit

specifies
whether the port does not require AST/4 compatible initial

ization. The
minor number of the device corresponding a master port for

the group is
encoded as a bitfield in the high byte. The same master

port must be
specified for all ports in a group.

The irq specification must be given for master ports and for

ports that
are not part of an IRQ sharing group, and not for other

ports.

In the synopsis, flags 0x701 means that the 8th port (sio7)

is the master
port, and that the port is on a multiport card with shared

IRQs and an
AST/4 compatible IRQ control register.

flags 0xb05 means that the 12th port (sio11) is the master

port, and that
the port is on a multiport card with shared IRQs and no spe

cial IRQ control register.

Which port is the master port depends on the card type.

Consult the
hardware documentation of your card. Since IRQ status reg

isters are
never used, and IRQ control registers are only used for

AST/4 compatible
cards, and some cards map the control/status registers to

all ports in a
group, any port in a group will sometimes do for the master

port. Choose
a port containing an IRQ status register for forwards com

patibility, and
the highest possible port for consistency.

Serial ports controlled by the sio driver can be used for

both `callin'
and `callout'. For each port there is a callin device and a

callout
device. The minor number of the callout device is 128 high

er than that
of the corresponding callin port. The callin device is gen

eral purpose.
Processes opening it normally wait for carrier and for the

callout device
to become inactive. The callout device is used to steal the

port from
processes waiting for carrier on the callin device. Pro

cesses opening it
do not wait for carrier and put any processes waiting for

carrier on the
callin device into a deeper sleep so that they do not con

flict with the
callout session. The callout device is abused for handling

programs that
are supposed to work on general ports and need to open the

port without
waiting but are too stupid to do so.

The sio driver also supports an initial-state and a lock

state control
device for each of the callin and the callout "data" de

vices. The minor
number of the initial-state device is 32 higher than that of

the corresponding data device. The minor number of the lock-state

device is 64
higher than that of the corresponding data device. The

termios settings
of a data device are copied from those of the corresponding

initial-state
device on first opens and are not inherited from previous

opens. Use
stty(1) in the normal way on the initial-state devices to

program initial
termios states suitable for your setup.

The lock termios state acts as flags to disable changing the

termios
state. E.g., to lock a flag variable such as CRTSCTS, use

stty crtscts
on the lock-state device. Speeds and special characters may

be locked by
setting the corresponding value in the lock-state device to

any nonzero
value.

Correct programs talking to correctly wired external devices

work with
almost arbitrary initial states and almost no locking, but

other setups
may benefit from changing some of the default initial state

and locking
the state. In particular, the initial states for non

(POSIX) standard
flags should be set to suit the devices attached and may

need to be
locked to prevent buggy programs from changing them. E.g.,

CRTSCTS
should be locked on for devices that support RTS/CTS hand

shaking at all
times and off for devices that do not support it at all.

CLOCAL should
be locked on for devices that do not support carrier. HUPCL

may be
locked off if you do not want to hang up for some reason.

In general,
very bad things happen if something is locked to the wrong

state, and
things should not be locked for devices that support more

than one setting. The CLOCAL flag on callin ports should be locked off

for logins to
avoid certain security holes, but this needs to be done by

getty if the
callin port is used for anything else.

FILES

/dev/ttyd? for callin ports
/dev/ttyd?.init
/dev/ttyd?.lock corresponding callin initial-state and

lock-state

devices

/dev/cuad? for callout ports
/dev/cuad?.init
/dev/cuad?.lock corresponding callout initial-state and

lock-state

devices

/etc/rc.d/serial examples of setting the initial-state and

lock-state

devices

The device numbers are made from the set [0-9a-v] so that

more than 10
ports can be supported.

DIAGNOSTICS

sio%d: silo overflow. Problem in the interrupt handler.

sio%d: interrupt-level buffer overflow. Problem in the bot

tom half of
the driver.

sio%d: tty-level buffer overflow. Problem in the applica

tion. Input has
arrived faster than the given module could process it and

some has been
lost.

SEE ALSO

stty(1), termios(4), tty(4), comcontrol(8)

HISTORY

The sio driver is derived from the HP9000/300 dca(4) driver

and is currently under development.

BUGS

Data loss may occur at very high baud rates on slow systems,

or with too
many ports on any system, or on heavily loaded systems when

crtscts cannot be used. The use of NS16550A's reduces system load and

helps to
avoid data loss.

Stay away from plain NS16550's. These are early implementa

tions of the
chip with non-functional FIFO hardware.

The constants which define the locations of the various se

rial ports are
holdovers from DOS. As shown, hex addresses can be and for

clarity probably should be used instead.

Note that on the AST/4 the card's dipswitches should not be

set to use
interrupt sharing. AST/4-like interrupt sharing is only

used when
multiple AST/4 cards are installed in the same system. The

sio driver
does not support more than 1 AST/4 on one IRQ.

The examples in the synopsis are too vendor-specific.

BSD October 17, 2004

BSD