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 opera-
tions:
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
SCSIIO(2) SCSIIO(2)
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 com-
mand 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; consulted by scsierror.
SOURCE
/appl/lib/scsiio.b
SEE ALSO
disks(2), sd(3)