HP-UX Reference (11i v1 00/12) - 5 Miscellaneous Topics, 7 Device (Special) Files, 9 General Information, Index (vol 9)

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scsi_pt(7) scsi_pt(7)

(Series 800 Only)

NAME

scsi_pt - SCSI pass-through device driver for Series 800 NIO based systems

DESCRIPTION

SCSI devices are normally controlled by a device-type-speciﬁc driver when the appropriate device-type-

speciﬁc driver exists. Device-type-speciﬁc drivers, such as those for SCSI direct access (disk) and sequen-

tial access (tape) devices, coordinate device and driver states to accomplish correct logical device behavior.

The SCSI pass-through driver (also called spt) enables use of SCSI devices and commands that are not sup-

ported by these device-type-speciﬁc drivers.

A successful scsi_pt open() call requires no device I/O operations. Once open, ioctl() calls can be

used to change SCSI communication parameters, attempt SCSI commands, or other SCSI operations.

Since the SCSI pass-through driver does not attempt to logically understand the target device, read()

and write() calls are not supported. Super-user privileges or device write permissions are required to

use these ioctls. All reserved ﬁelds in the data structures associated with these ioctls must be zero-

ﬁlled.

Since the SCSI pass-through driver is a separate device driver, the default device-type-speciﬁc driver can-

not be used for the same device at the same time as the pass-through driver.

SCSI Commands and Operations

Only two ioctl commands are supported by the NIO SCSI pass through driver; the SIOC_EXCLUSIVE

command and the SIOC_IO command.

The SIOC_EXCLUSIVE ioctl provides a mechanism to prevent other opens of a device. This allows

exclusive access by the locking application. There are two different levels of locks supported; SCSI target

level and SCSI lun level. These levels are speciﬁed via the

data ﬁeld of the ioctl() call:

0 release exclusive access to SCSI lun

1 gain exclusive access to SCSI lun

2 release exclusive access to SCSI target

3 gain exclusive access to SCSI target

For example, to lock the device (SCSI target):

three = 3;

if (err = ioctl(fd, SIOC_EXCLUSIVE, &three)) {

/* Could not lock the device -- check err */

}

NOTE: The corresponding unlock must be made for the acquired lock. An unlock of the SCSI target (data

== 2) will NOT unlock all of the individual SCSI luns (data == 0).

The

SIOC_IO ioctl allows an arbitrary SCSI command to be sent to a device. All details of the SCSI com-

mand protocol are handled automatically. See EXAMPLE mentioned below.

The header ﬁle <sys/scsi.h> has useful information for SCSI device control. The following is an

excerpt from it:

/* SCSI device control ioctls */

#define SIOC_IO _IOWR(’S’, 22, struct sctl_io)

#define SIOC_EXCLUSIVE _IOW(’S’, 68, int)

/* Structure for SIOC_IO ioctl */

struct sctl_io

{

unsigned flags;

unsigned char cdb_length;

unsigned char cdb[16];

void *data;

unsigned data_length;

unsigned max_msecs;

unsigned data_xfer;

unsigned cdb_status;

unsigned char sense[256];

unsigned sense_status;

unsigned char sense_xfer;

unsigned reserved[16];

HP-UX Release 11i: December 2000 − 1 − Section 7−−125

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