dmf.4

早期freebsd实现

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.\"     @(#)dmf.4	8.1 (Berkeley) 6/5/93
.\"
.Dd June 5, 1993
.Dt DMF 4 vax
.Os BSD 4.2
.Sh NAME
.Nm dmf
.Nd
.Tn DMF-32
terminal multiplexor
.Sh SYNOPSIS
.Cd "device dmf0 at uba? csr 0160340 vector dmfsrint dmfsxint dmfdaint dmfdbint dmfrint dmfxint dmflint"
.Sh DESCRIPTION
The
.Nm dmf
device provides 8 lines of asynchronous serial line support.
The first two of these have full modem control.
The device also provides a line printer port
similar to the
.Tn LP-11 .
Other features of the
.Tn DMF-32
are not supported.
During autoconfiguration, the driver examines the configuration of each
.Tn DMF-32
and adjusts the interrupt vectors so that fewer vector locations are used
if possible.
.Pp
An optional argument
.Ar flags
may be supplied with the device specification
in the config file indicating
that the line corresponding to
bit number
.Ar i
is not properly
connected, and should be treated as hard-wired with carrier
always present.  Thus specifying
.Ql flags 0x04
for
.Li dmf0
would cause line
.Pa ttyA2
to be treated in this way.
Flags should be set for all lines without hardware support for modem control.
.Pp
Normal
.Tn I/O
control parameters for individual lines are managed by
.Xr ioctl 2
calls.
Line speeds may be initiated via
.Xr getty 8
and
.Xr stty 1
or may be communicated by other programs which
utilize
.Xr ioctl
such as
.Xr ifcongif 8 ,
see
.Xr tty 4  .
.Pp
The serial line part of the
.Nm dmf
driver normally enables the input silos with a short timeout
(30 milliseconds); this allows multiple characters to be received
per interrupt during periods of high-speed input.
.Pp
A line printer port on a
.Nm dmf
is designated by
a minor device number of the form
.Pf 128+ Ns Ar n .
See
.Xr MAKEDEV 8 .
Column and lines per page may be changed from the default
132 columns and 66 lines by encoding the number of columns
in bits 8-15 of flags and the number of lines in bits 16-23.
This device does not provide the fancy output canonicalization
features of the
.Xr lp 4
driver.
.Sh FILES
.Bl -tag -width "/dev/tty[A-CE-I][0-7]" -compact
.It Pa /dev/tty[A-CE-I][0-7]
.It Pa /dev/ttyd[0-7]
.It Pa /dev/lp
.El
.Sh DIAGNOSTICS
.Bl -diag
.It dmf%d: NXM line %d.
No response from
.Tn UNIBUS
on a DMA transfer
within a timeout period.  This is often followed by a
.Tn UNIBUS
adapter
error.  This occurs most frequently when the
.Tn UNIBUS
is heavily loaded
and when devices which hog the bus (such as
.Tn RK07 Ns s )
are present.
It is not serious.
.Pp
.It dmf%d: silo overflow.
The character input silo overflowed
before it could be serviced.  This can happen if a hard error occurs
when the
.Tn CPU
is running with elevated priority, as the system will
then print a message on the console with interrupts disabled.
It is not serious.
.Pp
.It dmfsrint, dmfsxint, dmfdaint, dmfdbint.
One of the unsupported parts of the dmf interrupted; something
is amiss, check your interrupt vectors for a conflict with another
device.
.El
.Sh SEE ALSO
.Xr tty 4
.Sh HISTORY
The
.Nm
driver appeared in
.Bx 4.2 .
.Sh BUGS
It should be possible to set the silo timeout with a configuration file option,
as the value is a trade-off between efficiency and response time for flow
control and character echo.