TH SCSI 2
SH NAME
openscsi, closescsi, scsiready, scsi, scsicmd, scsierror \- SCSI device operations
SH SYNOPSIS
nf
ft L
#include <u.h>
#include <libc.h>
#include <disk.h>
ft
PP
ft L
typedef struct Scsi {
       char  *inquire;
       int   rawfd;
       int   nchange;
       ulong changetime;
};
ft
PP
B
Scsi* openscsi(char *devdir)
PP
B
void  closescsi(Scsi *s)
PP
B
int   scsiready(Scsi *s)
PP
ft L
int   scsi(Scsi *s, uchar *cmd, int ncmd,
br
                   void *data, int ndata, int dir)
PP
ft L
int   scsicmd(Scsi *s, uchar *cmd, int ncmd,
br
                   void *data, int ndata, int dir)
PP
B
char* scsierror(int asc, int ascq)
PP
B
int   scsiverbose;
SH DESCRIPTION
These routines provide an interface
to a SCSI or ATAPI device via
IR sd (3).
PP
I Openscsi
attempts to open the file
IB devdir /raw
and use it to send raw SCSI commands.
On success, it reads the device's inquiry
string and stores it in
I inquire
in the returned
B Scsi
structure.
I Closescsi
closes the connection and frees the
B Scsi
structure.
PP
I Scsiready
sends the ``unit ready'' command up to three times,
returning zero if the unit responds that it is ready,
or \-1 on error.
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 /sys/lib/scsicodes .
The returned string will be overwritten by
the next call to
IR scsierror .
PP
I Scsi
and
I scsicmd
execute a single SCSI command on the named device.
There should be
I ncmd
bytes of
command data in
IR cmd ;
if
I dir
is
BR Sread ,
a successful operation
will store up to
I ndata
bytes into
IR data ,
returning the number of bytes stored.
If
I dir
is
BR Swrite ,
the
I ndata
bytes beginning at
I data
are transmitted as the data argument to
the command, and the
number of bytes written is returned.
If
I dir
is
BR Snone ,
I data
and
I ndata
are ignored.
On error,
I scsi
and
I scsicmd
return \-1.
I Scsicmd
simply issues the command and
returns the result;
I scsi
works a bit harder and
is the more commonly used routine.
I Scsi
attempts to send the command;
if it is successful,
I scsi
returns what
I scsicmd
returned.
Otherwise,
I 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,
I scsi
sends the request
sense and unit ready commands
again
and then uses
I scsierror
to set
I errstr
with a reason for failure.
PP
The
B nchange
and
B changetime
fields
in the
B 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
IR scsi .
PP
If
I scsiverbose
is set,
these commands will produce a fair
amount of debugging output on file descriptor 2
when SCSI commands fail.
SH FILES
TP
B /sys/lib/scsicodes
List of textual messages corresponding to SCSI error codes;
consulted by
BR scsierror .
SH SOURCE
B /sys/src/libdisk/scsi.c
SH SEE ALSO
IR sd (3),
IR scuzz (8)

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