SCSI(2)SCSI(2)
NAME
openscsi, closescsi, scsiready, scsi, scsicmd, scsierror – SCSI device operations
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <disk.h>
typedef struct Scsi {
char *inquire;
int rawfd;
int nchange;
ulong changetime;
};
Scsi* openscsi(char *devdir)
void closescsi(Scsi *s)
int scsiready(Scsi *s)
int scsi(Scsi *s, uchar *cmd, int ncmd,
void *data, int ndata, int dir)
int scsicmd(Scsi *s, uchar *cmd, int ncmd,
void *data, int ndata, int dir)
char* scsierror(int asc, int ascq)
int scsiverbose;
DESCRIPTION
These routines provide an interface
to a SCSI or ATAPI device via
sd(3).
Openscsi
attempts to open the file
devdir/raw
and use it to send raw SCSI commands.
On success, it reads the device’s inquiry
string and stores it in
inquire
in the returned
Scsi
structure.
Closescsi
closes the connection and frees the
Scsi
structure.
Scsiready
sends the “unit ready” command up to three times,
returning zero if the unit responds that it is ready,
or –1 on error.
Scsierror
returns a textual description of the SCSI status
denoted by the ASC and ASCQ sense codes.
The description is found by consulting
/sys/lib/scsicodes.
The returned string will be overwritten by
the next call to
scsierror.
Scsi
and
scsicmd
execute a single SCSI command on the named device.
There should be
ncmd
bytes of
command data in
cmd;
if
dir
is
Sread,
a successful operation
will store up to
ndata
bytes into
data,
returning the number of bytes stored.
If
dir
is
Swrite,
the
ndata
bytes beginning at
data
are transmitted as the data argument to
the command, and the
number of bytes written is returned.
If
dir
is
Snone,
data
and
ndata
are ignored.
On error,
scsi
and
scsicmd
return –1.
Scsicmd
simply issues the command and
returns the result;
scsi
works a bit harder and
is the more commonly used routine.
Scsi
attempts to send the command;
if it is successful,
scsi
returns what
scsicmd
returned.
Otherwise,
scsi
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.
If the second try fails,
scsi
sends the request
sense and unit ready commands
again
and then uses
scsierror
to set
errstr
with a reason for failure.
The
nchange
and
changetime
fields
in the
Scsi
structure
record the number of times a media
change has been detected, and the
time when the current media was
inserted into the drive (really the
first time a SCSI command was issued
after it was inserted).
They are maintained by
scsi.
If
scsiverbose
is set,
these commands will produce a fair
amount of debugging output on file descriptor 2
when SCSI commands fail.
FILES
/sys/lib/scsicodes
List of textual messages corresponding to SCSI error codes;
consulted by
scsierror.
SOURCE
/sys/src/libdisk/scsi.c
SEE
sd(3),
scuzz(8)