sioc_io(7) sioc_io(7)
NAME [Toc] [Back]
sioc_io - SCSI pass-through interface
DESCRIPTION [Toc] [Back]
SCSI devices are controlled by a device-specific driver, when one
exists. Device-specific drivers, such as those for SCSI direct access
(disk) and sequential access (tape) devices, coordinate device and
driver states to accomplish correct logical device behavior. The
sioc_io pass-through interface enables the use of SCSI devices and
commands not normally supported by these device-specific drivers.
Superuser privileges or device write permissions are required to use
the SIOC_IO ioctl. All reserved fields in the sioc_io data structure
must be zero-filled.
The SIOC_IO ioctl allows an arbitrary SCSI command to be sent to a
device. All details of the SCSI command protocol are handled
automatically.
The data structure for the SIOC_IO ioctl is included from
<sys/scsi.h>:
/* SCSI device control ioctls */
#define SIOC_IO _IOWR('S', 22, struct sctl_io)
/* 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 char reserved[64];
};
The following flags can be used to specify the flags field value:
SCTL_READ Data-in phase expected if the data_length field is
non-zero. The absence of this flag implies that a
data-out phase is expected if the data_length
field is non-zero.
The cdb field specifies the SCSI command bytes. The number of command
bytes is specified by the cdb_length field. These command bytes are
Hewlett-Packard Company - 1 - HP-UX 11i Version 2: August 2003
sioc_io(7) sioc_io(7)
sent to the target device during the SCSI command phase.
The address of the data area for the data phase of the SCSI command is
specified by the data field. The data_length field specifies the
maximum number of data bytes to be transferred. A zero-valued
data_length indicates that no data phase should occur. Most SCSI
commands with a data phase expect the data length information to be
included somewhere in the command bytes. The caller is responsible
for correctly specifying both the data_length field and any cdb data
length values. The length may not be larger than SCSI_MAXPHYS and
some implementations further restrict this length.
The max_msecs field specifies the maximum time, in milliseconds, that
the device should need to complete the command. If this period of
time expires without command completion, the system might attempt
recovery procedures to regain the device's attention. These recovery
procedures might include abort tag, abort, and device and bus reset
operations. A zero value in the max_msec field indicates that the
timeout period is infinite and the system should wait indefinitely for
command completion.
When the SIOC_IO ioctl call returns, all command processing has been
completed. Most SIOC_IO ioctl calls will return zero (success). The
resulting detailed ioctl data should be used to evaluate ``success''
or ``failure'' from the caller's perspective. The cdb_status field
indicates the results of the cdb command. If the cdb_status field
indicates a S_CHECK_CONDITION status, the sense_status field indicates
the results of the SCSI REQUEST SENSE command used to collect the
associated sense data. These status fields will contain one of the
following values:
SCTL_INVALID_REQUEST The SCSI command request is invalid and
thus not attempted.
SCTL_SELECT_TIMEOUT The target device does not answer to
selection by the host SCSI interface
(the device does not exist or does not
respond).
SCTL_INCOMPLETE The device answered selection but the
command is not completed (the device
took too long or a communication failure
occurred).
S_GOOD Device successfully completed the
command.
S_CHECK_CONDITION Device indicated sense data is
available.
Hewlett-Packard Company - 2 - HP-UX 11i Version 2: August 2003
sioc_io(7) sioc_io(7)
S_CONDITION_MET Device successfully completed the
command and the requested (search or
pre-fetch) operation is satisfied.
S_BUSY Device indicated it is unable to accept
the command because it is busy doing
other operations.
S_INTERMEDIATE Device successfully completed this
command, which is one in a series of
linked commands (not supported, see
WARNINGS).
S_I_CONDITION_MET Device indicated both S_INTERMEDIATE and
S_CONDITION_MET (not supported, see
WARNINGS).
S_RESV_CONFLICT Device indicated the command conflicted
with an existing reservation.
S_COMMAND_TERMINATED Device indicated the command is
terminated early by the host system.
S_QUEUE_FULL Device indicated it is unable to accept
the command because its command queue is
currently full.
The data_xfer field indicates the number of data bytes actually
transferred during the data phase of the cdb command. This field is
valid only when the cdb_status field contains one of the following
values: S_GOOD or S_CHECK_CONDITION. The sense_xfer field indicates
the number of valid sense data bytes. This field is valid only when
the cdb_status field contains the value S_CHECK_CONDITION and the
sense_status field contains the value S_GOOD.
EXAMPLES [Toc] [Back]
Assume that fildes is a valid file descriptor for a SCSI device. The
first example attempts a SCSI INQUIRY command:
#include <sys/scsi.h>
struct sctl_io sctl_io;
#define MAX_LEN 255
unsigned char inquiry_data[MAX_LEN];
memset(sctl_io, 0, sizeof(sctl_io)); /* clear reserved fields */
sctl_io.flags = SCTL_READ; /* input data expected */
sctl_io.cdb[0] = 0x12; /* can use scsi.h CMDinquiry */
sctl_io.cdb[1] = 0x00;
sctl_io.cdb[2] = 0x00;
sctl_io.cdb[3] = 0x00;
Hewlett-Packard Company - 3 - HP-UX 11i Version 2: August 2003
sioc_io(7) sioc_io(7)
sctl_io.cdb[4] = MAX_LEN; /* allocation length */
sctl_io.cdb[5] = 0x00;
sctl_io.cdb_length = 6; /* 6 byte command */
sctl_io.data = &inquiry_data[0]; /* data buffer location */
sctl_io.data_length = MAX_LEN; /* maximum transfer length */
sctl_io.max_msecs = 10000; /* allow 10 seconds for cmd */
if (ioctl(fildes, SIOC_IO, &sctl_io) < 0)
{
/* request is invalid */
}
The following example attempts a SCSI TEST UNIT READY command and
checks to see if the device is ready, not ready, or in some other
state.
#include <sys/scsi.h>
struct sctl_io sctl_io;
memset(sctl_io, 0, sizeof(sctl_io)); /* clear reserved fields */
sctl_io.flags = 0; /* no data transfer expected */
sctl_io.cdb[0] = 0x00; /* can use CMDtest_unit_ready */
sctl_io.cdb[1] = 0x00;
sctl_io.cdb[2] = 0x00;
sctl_io.cdb[3] = 0x00;
sctl_io.cdb[4] = 0x00;
sctl_io.cdb[5] = 0x00;
sctl_io.cdb_length = 6; /* 6 byte command */
sctl_io.data = NULL; /* no data buffer is provided */
sctl_io.data_length = 0; /* do not transfer data */
sctl_io.max_msecs = 10000; /* allow 10 seconds for cmd */
if (ioctl(fildes, SIOC_IO, &sctl_io) < 0)
{
/* request is invalid */
}
else if (sctl_io.cdb_status == S_GOOD)
{
/* device is ready */
}
else if (sctl_io.cdb_status == S_BUSY ||
(sctl_io.cdb_status == S_CHECK_CONDITION &&
sctl_io.sense_status == S_GOOD &&
sctl_io.sense_xfer > 2 &&
(sctl_io.sense[2] & 0x0F) == 2)) /* can use sense_data */
{
/* device is not ready */
}
else
{
/* unknown state */
}
Hewlett-Packard Company - 4 - HP-UX 11i Version 2: August 2003
sioc_io(7) sioc_io(7)
WARNINGS [Toc] [Back]
Incorrect use of sioc_io operations (even those attempting access to
non-existent devices) can cause data loss, system panics, and device
damage.
The SIOC_EXCLUSIVE ioctl should be used to gain exclusive access to a
device prior to attempting SIOC_IO commands. If exclusive access is
not obtained, SIOC_IO commands will be intermixed with device-specific
driver commands, which can lead to undesirable results.
Device-specific drivers can reject inappropriate or troublesome
SIOC_IO commands. However, since not all such operations are known
and detected, care should be exercised to avoid disrupting devicespecific
drivers when using commands that modify internal device
states.
It is very easy to cause system deadlock through incorrect use of the
SIOC_PRIORITY_MODE ioctl. Normally it is necessary to lock the
calling process into memory (see plock(2)) prior to enabling priority
mode.
Most SCSI commands have a logical unit number (LUN) field. Parallel
SCSI implementations on the HP-UX operating system select logical
units via the SCSI IDENTIFY message. The LUN portion of the cdb
should normally be set to zero, even when the LUN being accessed is
not zero.
Use of linked commands is not supported.
Most SCSI commands with a data phase expect the data length
information to be included somewhere in the command bytes. Both the
data_length field and any cdb data length values must be correctly
specified to get correct command results.
Very large (or infinite) timeout values can cause a parallel SCSI bus
(potentially the entire system) to hang.
Device and/or bus reset operations can be used to regain a device's
attention when a timeout expires.
Resetting a device can cause I/O errors and/or loss of cached data.
This can result in loss of data and/or system panics.
Obtaining SCSI INQUIRY data by use of the SIOC_INQUIRY ioctl instead
of by use of the SIOC_IO ioctl is generally preferable since SCSI
implementations on the HP-UX operating system synchronize access of
inquiry data during driver open calls.
Since communication parameters can be affected by device-specific
driver capabilities, device-specific driver use might result in
communication parameter changes.
Hewlett-Packard Company - 5 - HP-UX 11i Version 2: August 2003
sioc_io(7) sioc_io(7)
FILES [Toc] [Back]
/usr/include/sys/scsi.h
/usr/include/sys/scsi_ctl.h
SEE ALSO [Toc] [Back]
ioctl(2), scsi(7), scsi_ctl(7).
Hewlett-Packard Company - 6 - HP-UX 11i Version 2: August 2003 [ Back ] |
