SCSIIO(2)SCSIIO(2)NAME
ScsiIO: Scsi - SCSI device operations
SYNOPSIS
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);
DESCRIPTION
ScsiIO provides a low-level interface to a SCSI or ATAPI device via
sd(3).
Init must be called before using any other operation of the module. If
verbose is non-zero the module will produce a fair amount of debugging
output on file descriptor 2 when SCSI commands fail.
Scsi.open attempts to open the file devdir/raw on which to send raw
SCSI commands. On success, it reads the device's inquiry string and
returns a reference to a Scsi value to represent the connection. It
provides the following operations:
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.
s.rawcmd(cmd, data, io)
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 cmd. If io is
Sread, a successful operation will store the resulting bytes in
data, up to its length, returning the number of bytes stored.
If io is Swrite, the bytes in data are transmitted as the data
argument to the command, and the number of bytes written is
returned. If io is Snone, data is ignored and may be nil.
Rawcmd simply issues the command and returns the result; cmd
works a bit harder and is the more commonly used routine. It
attempts to send the commmand; if it is successful, cmd returns
the result. Otherwise, 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, cmd returns an error. On error, both functions
return -1 and set the system error string.
The nchange and changetime elements of 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 Scsi.cmd. The initial SCSI inquiry
result is kept in inquire.
Scsierror returns a textual description of the SCSI status denoted by
the ASC and ASCQ sense codes. The description is found by consulting
/lib/scsicodes.
FILES
/lib/scsicodes
List of textual messages corresponding to SCSI error codes; con‐
sulted by scsierror.
SOURCE
/appl/lib/scsiio.b
SEE ALSOdisks(2), sd(3)SCSIIO(2)
