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.TH SCSIIO 2
.SH NAME
ScsiIO: Scsi \- SCSI device operations
.SH SYNOPSIS
.EX
include "scsi.m";
scsiio := load ScsiIO ScsiIO->PATH;
Scsi: adt {
inquire: string;
rawfd: ref Sys->FD;
nchange: int;
changetime: int;
open: fn(devdir: string): ref Scsi;
rawcmd: fn(s: self ref Scsi, cmd: array of byte,
data: array of byte, io: int): int;
cmd: fn(s: self ref Scsi, cmd: array of byte,
data: array of byte, io: int): int;
ready: fn(s: self ref Scsi): int;
};
Sread, Swrite, Snone: con iota;
scsierror: fn(asc: int, ascq: int): string;
init: fn(verbose: int);
.EE
.SH DESCRIPTION
.B ScsiIO
provides a low-level interface to a SCSI or ATAPI device via
.IR sd (3).
.PP
.B Init
must be called before using any other operation of the module.
If
.I verbose
is non-zero
the module will produce a fair
amount of debugging output on file descriptor 2
when SCSI commands fail.
.PP
.B Scsi.open
attempts to open the file
.IB devdir /raw
on which to send raw SCSI commands.
On success, it reads the device's inquiry
string and returns a reference to a
.B Scsi
value to represent the connection.
It provides the following operations:
.TP
.IB s .ready()
Sends the ``unit ready'' command up to three times,
returning zero once the unit responds that it is ready,
or \-1 on error.
.TP
.IB s .rawcmd( "cmd, data, io" )
.PD 0
.TP
.IB s .cmd( "cmd, data, io" )
Both these functions execute a single SCSI command on the named device.
The command data is in the byte array
.IR cmd .
If
.I io
is
.BR Sread ,
a successful operation will store the resulting bytes in
.IR data ,
up to its length,
returning the number of bytes stored.
If
.I io
is
.BR Swrite ,
the bytes in
.I data
are transmitted as the data argument to
the command, and the
number of bytes written is returned.
If
.I io
is
.BR Snone ,
.I data
is ignored and may be nil.
.B Rawcmd
simply issues the command and
returns the result;
.B cmd
works a bit harder and
is the more commonly used routine.
It attempts to send the commmand;
if it is successful,
.B cmd
returns the result.
Otherwise,
.B cmd
sends a request sense command to
obtain the reason for the failure,
sends a unit ready command in
an attempt to bring the unit out of any
inconsistent states, and tries again.
It also accounts for media change.
If the second try fails,
.B cmd
returns an error.
On error, both functions return \-1 and set the system error string.
.PD
.PP
The
.B nchange
and
.B changetime
elements of
.B Scsi
the number of times a media
change has been detected, and the
first time the current media was detected (the
first time a SCSI command was issued
after it was inserted).
They are maintained by
.BR Scsi.cmd .
The initial SCSI inquiry result is kept in
.BR inquire .
.PP
.I Scsierror
returns a textual description of the SCSI status
denoted by the ASC and ASCQ sense codes.
The description is found by consulting
.BR /lib/scsicodes .
.SH FILES
.TF
.TP
.B /lib/scsicodes
List of textual messages corresponding to SCSI error codes;
consulted by
.BR scsierror .
.SH SOURCE
.B /appl/lib/scsiio.b
.SH SEE ALSO
.IR disks (2),
.IR sd (3)
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