freebsd-dev/lib/libscsi/scsi.3

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.Dd November 20, 1994
.Dt SCSI 3
.Os
.Sh NAME
.Nm scsireq_buff_decode ,
.Nm scsireq_build ,
.Nm scsireq_decode ,
.Nm scsireq_encode
.Nm scsireq_enter
.Nm scsireq_new ,
.Nm scsireq_reset ,
.Nm SCSIREQ_ERROR ,
.Nm scsi_open
.Nm scsi_debug
.Nm scsi_debug_output
.Nd SCSI User library
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/scsiio.h>
.Fd #include <libscsi.h>
.Ft int
.Fn scsireq_buff_decode "u_char *ptr, size_t len, char *fmt, ..."
.Ft struct scsireq *
.Fn scsireq_build "struct scsireq *s, u_long len, caddr_t buf, u_long flags, char *fmt, ..."
.Ft int
.Fn scsireq_decode "struct scsireq *, char *fmt, ..."
.Ft int
.Fn scsireq_encode "struct scsireq *, char *fmt, ..."
.Ft int
.Fn scsireq_enter "int fid, struct scsireq *s"
.Ft struct scsireq *
.Fn scsireq_new void
.Ft struct scsireq *
.Fn scsireq_reset "struct scsireq *"
.Ft int
.Fn SCSIREQ_ERROR "struct scsireq *"
.Ft int
.Fn scsi_open "const char *path, int flags"
.Ft void
.Fn scsi_debug "FILE *f, int ret, struct scsireq *s"
.Ft FILE *
.Fn scsi_debug_output "char *s"
.Sh DESCRIPTION
These functions
use the SCIOCCOMMAND
.Xr ioctl 2
of the FreeBSD SCSI subsystem
to provide user level access to SCSI commands.
The programmer must know the SCSI CDB (Command Descriptor
Block) to perform the desired command.  These functions assist in
building up the CDB, submitting it to the SCSI subsystem, and decoding
the result.
.Pp
Look at the
.Xr scsi 8
command before using the library directly - simple programs are
best implemented as scripts using that facility.
.Pp
To provide for security,
not all devices accept the SCIOCCOMAND ioctl.  It is accepted by the
control device for tape drives, partition D for disk drives, partition C
for CD ROM drives, and any "unknown" device.
The "super scsi"
.Xr ssc 4
device also accepts the ioctl.
.Pp
Most of the SCSI library functions build up and manipulate the
.Ar scsireq
structure found in the include file
.Aq Pa sys/scsiio.h :
.Bd -literal -offset indent
#define	SENSEBUFLEN 48
.Pp
typedef struct	scsireq {
	u_long	flags;		/* info about the request status and type */
	u_long	timeout;
	u_char	cmd[16];	/* 12 is actually the max */
	u_char	cmdlen;
	caddr_t	databuf;	/* address in user space of buffer */
	u_long	datalen;	/* size of user buffer (request) */
	u_long	datalen_used;	/* size of user buffer (used)*/
	u_char	sense[SENSEBUFLEN]; /* returned sense will be in here */
	u_char	senselen;	/* sensedata request size (MAX of SENSEBUFLEN)*/
	u_char	senselen_used;	/* return value only */
	u_char	status;		/* what the scsi status was from the adapter */
	u_char	retsts;		/* the return status for the command */
	int	error;		/* error bits */
} scsireq_t;
.Ed
.Pp
.Fn scsireq_new
allocates a new
.Ar scsireq
structure and returns a pointer to it or NULL if it can't allocate
memory.
.Pp
.Fn scsireq_reset
resets the structure to reasonable values and returns the same pointer passed
in to it.
It gracefully handles the NULL pointer passed in to it so that you can
unconditionally use
.Ar scsireq_new .
.Pp
.Fn scsireq_build
builds up a scsireq structure based on the information provided in
the variable argument list.
It gracefully handles a NULL pointer passed to it.
.Pp
.Fr len
is the length of the data phase; the data transfer direction is
determined by the
.Ar flags
argument.
.Pp
.Fr buf
is the data buffer used during the SCSI data phase.  If it is NULL it
is allocated via malloc and
.Ar scsireq->databuf
is set to point to the newly allocated memory.
.Pp
.Fr flags
are the flags defined in
.Aq Pa sys/scsiio.h :
.Bd -literal -offset indent
/* bit defintions for flags */
#define SCCMD_READ		0x00000001
#define SCCMD_WRITE		0x00000002
#define SCCMD_IOV		0x00000004
#define SCCMD_ESCAPE		0x00000010
#define SCCMD_TARGET		0x00000020
.Ed
Only two of these flags are supported in this release of the software:
.Fr SCCMD_READ
indicates a data in phase (a transfer into the user buffer at
.Ar scsireg->databuf
), and
.Fr SCCMD_WRITE
indicates a data out phase (a transfer out of the user buffer).
.Pp
.Fr fmt
is a CDB format specifier used to build up the SCSI CDB.
This text string is made up of a list of field specifiers.  Field
specifiers specify the value for each CDB field (including indicating
that the value be taken from the next argument in the
variable argument list), the width
of the field in bits or bytes, and an optional name.  White space is
ignored, and the pound sign ('#') introduces a comment that ends at the
end of the current line.
.Pp
The optional name is the first part of a field specifier and
is in curly braces.  The text in curly braces in this example are
the names:
.Bd -literal -offset indent
.Fr "{PS} v:b1 {Reserved} 0:b1 {Page Code} v:b6 # Mode select page"
.Ed
.Pp
This field specifier has two one bit fields and one six bit field.
The second one bit field is the constant value 0 and the first
one bit field and the six bit field are taken from the variable
argument list.
Multi byte fields are swapped into the SCSI byte order in the
CDB and white space is ignored.
.Pp
When the field is a hex value or the letter v, (e.g.,
.Fr "1A"
or
.Fr "v" )
then a single byte value
is copied to the next unused byte of the CDB.
When the letter
.Fr v
is used the next integer argument is taken from the variable argument list
and that value used.
.Pp
A constant hex value followed by a field width specifier or the letter
.Fr v
followed by a field width specifier (e.g.,
.Fr 3:4 ,
.Fr 3:b4 ,
.Fr 3:i3 ,
.FR v:i3 )
specifies a field of a given bit or byte width.
Either the constant value or (for the V specifier) the next integer value from
the variable argument list is copied to the next unused
bits or bytes of the CDB.
.Pp
A decimal number or the letter
.Fr b
followed by a decimal number field width indicates a bit field of that width.
The bit fields are packed as tightly as possible beginning with the
high bit (so that it reads the same as the SCSI spec), and a new byte of
the CDB is started whenever a byte fills completely or when an
.Fr i
field is encountered.
.Pp
A field width specifier consisting of the letter
.Fr i
followed by either
1, 2, 3 or 4 indicates a 1, 2, 3 or 4 byte integral value that must
be swapped into SCSI byte order (MSB first).
.Pp
For the
.Fr v
field specifier the next integer argument is taken from the variable argument
list and that value is used swapped into SCSI byte order.
.Pp
.Fn scsireq_decode
is used to decode information from the data in phase of the SCSI
transfer.
.Pp
The decoding is similar to
the command specifier processing of
.Fn scsireq_build
except that the data is extracted from the data pointed to by
.Fr scsireq->databuf.
The stdarg list should be pointers to integers instead of integer
values.
A seek field type and a suppression modifier are added.
The
.Fr *
suppression modifier (e.g.,
.Fr *i3
or
.Fr *b4 )
suppresses assignment from the field and can be used to skip
over bytes or bits in the data, without having to copy
them to a dummy variable in the arg list.
.Pp
The seek field type
.Fr s
permits you to skip over data.
This seeks to an absolute position (
.Fr s3 )
or a relative position (
.Fr s+3 )
in the data, based on whether or not the presence of the '+' sign.
The seek value can be specified as
.Fr v
and the next integer value from the argument list will be
used as the seek value.
.Pp
.Fn scsireq_buff_decode
decodes an arbitrary data buffer using the method
described above in
.Fn scsireq_decode .
.Pp
.Fn scsireq_encode
encodes the data phase section of the structure.  The encoding is
handled identically as the encoding of the CDB structure by
.Fn scsireq_build
.Pp
.Fn scsireq_enter
submits the built up structure for processing using
the SCIOCCOMMAND ioctl.
.Pp
.Fn SCSIREQ_ERROR
is a macro that determines if the result of the SCIOCCOMMAND ioctl may
have been
in error by examining the host adapter return code, whether sense was sent
or not, and so on.
.Pp
.Fn scsi_open
checks environment variables and initializes the library for
consistent library use and then calls the regular open system call.
.Pp
.Fn scsi_debug
prints the results of a scsireq_enter function to the specified stdio
stream.
.Pp
.Fn scsi_debug_output
requests that the results of all transactions be debugged to the
supplied file using
.Fn scsi_debug .
.Sh RETURN VALUES
The function
.Fn scsireq_new
returns a pointer to storage allocated from malloc, and therefore
potentially a NULL.
.Pp
The functions
.Fn scsireq_build
and
.Fn scsireq_reset
return the same pointer as the one passed in.
.Pp
The functions
.Fn scsireq_buff_decode and
.Fn scsireq_decode
return the number of assignments performed.
.Pp
.Fn scsireq_encode
returns the number of fields processed.
.Pp
The function
.Fn scsireq_enter
returns the result of the ioctl call.
.Sh SEE ALSO
.Xr scsi 8 ,
.Xr scsi 4
.Sh BUGS
This only works completely for the 1542C.  The host adapter code
that sets up the residual amount of data transfer has to be added
to each individual adapter.  This library is usable on the other
host adapters, however, the SCSI driver pretends that the proper
amount of data is always transferred.  If you have an Adaptec 174x
and can hack contact dufault@hda.com and you can have the code to
calculate residual data for the 174x series to integrate and test.
.Sh HISTORY
Many systems have comparable interfaces to permit a user to construct a
SCSI command in user space.
.Pp
The data structure is almost identical to the SGI /dev/scsi data
structure.  If anyone knows the name of the authors it should
go here; Peter Dufault first read about it in a 1989 Sun Expert magazine.
.Pp
Peter Dufault implemented a clone of SGI's interface in 386bsd that
led to this library and the related kernel ioctl.
If anyone needs that for compatability contact dufault@hda.com.