Tribblix: manual page: uscsi.4i

USCSI(4I) Ioctl Requests USCSI(4I)

NAME

uscsi - user SCSI command interface

SYNOPSIS

#include <sys/scsi/impl/uscsi.h>

ioctl(int filedes, int request, struct uscsi_cmd *cmd);

DESCRIPTION

The uscsi command is very powerful and somewhat dangerous; therefore it
has some permission restrictions. See WARNINGS for more details.

Drivers supporting this ioctl(2) provide a general interface allowing
user-level applications to cause individual SCSI commands to be
directed to a particular SCSI or ATAPI device under control of that
driver. The uscsi command is supported by the sd(4D) driver for SCSI
disks and ATAPI CD-ROM drives, and by the st(4D) driver for SCSI tape
drives. uscsi may also be supported by other device drivers; see the
specific device driver manual page for complete information.

Applications must not assume that all Solaris disk device drivers
support the uscsi ioctl command. The SCSI command may include a data
transfer to or from that device, if appropriate for that command. Upon
completion of the command, the user application can determine how many
bytes were transferred and the status returned by the device. Also,
optionally, if the command returns a Check Condition status, the driver
will automatically issue a Request Sense command and return the sense
data along with the original status. See the USCSI_RQENABLE flag below
for this Request Sense processing. The uscsi_cmd structure is defined
in <sys/scsi/impl/uscsi.h> and includes the following members:

int uscsi_flags; /* read, write, etc. see below */
short uscsi_status; /* resulting status */
short uscsi_timeout; /* Command Timeout */
caddr_t uscsi_cdb /* CDB to send to target */
caddr_t uscsi_bufaddr; /* i/o source/destination */
size_t uscsi_buflen; /* size of i/o to take place*/
size_t uscsi_resid; /* resid from i/o operation */
uchar_t uscsi_cdblen; /* # of valid CDB bytes */
uchar_t uscsi_rqlen; /* size of uscsi_rqbuf */
uchar_t uscsi_rqstatus; /* status of request sense cmd */
uchar_t uscsi_rqresid; /* resid of request sense cmd */
caddr_t uscsi_rqbuf; /* request sense buffer */
void *uscsi_reserved_5; /* Reserved for future use */

The fields of the uscsi_cmd structure have the following meanings:

uscsi_flags The I/O direction and other details of how to carry
out the SCSI command. Possible values are described
below.

uscsi_status The SCSI status byte returned by the device is
returned in this field.

uscsi_timeout Time in seconds to allow for completion of the
command.

uscsi_cdb A pointer to the SCSI CDB (command descriptor block)
to be transferred to the device in command phase.

uscsi_bufaddr The user buffer containing the data to be read from
or written to the device.

uscsi_buflen The length of uscsi_bufaddr.

uscsi_resid If a data transfer terminates without transferring
the entire requested amount, the remainder, or
residue, is returned in this field.

uscsi_cdblen The length of the SCSI CDB to be transferred to the
device in command phase.

uscsi_rqlen The length of uscsi_rqbuf, the application's Request
Sense buffer.

uscsi_rqstatus The SCSI status byte returned for the Request Sense
command executed automatically by the driver in
response to a Check Condition status return.

uscsi_rqresid The residue, or untransferred data length, of the
Request Sense data transfer (the number of bytes,
less than or equal to uscsi_rqlen, which were not
filled with sense data).

uscsi_rqbuf Points to a buffer in application address space to
which the results of an automatic Request Sense
command are written.

uscsi_reserved_5 Reserved for future use.

The uscsi_flags field defines the following:

USCSI_WRITE /* send data to device */
USCSI_SILENT /* no error messages */
USCSI_DIAGNOSE /* fail if any error occurs */
USCSI_ISOLATE /* isolate from normal commands */
USCSI_READ /* get data from device */
USCSI_ASYNC /* set bus to asynchronous mode */
USCSI_SYNC /* return bus to sync mode if possible */
USCSI_RESET /* reset target */
USCSI_RESET_TARGET /* reset target */
USCSI_RESET_LUN /* reset logical unit */
USCSI_RESET_ALL /* reset all targets */
USCSI_RQENABLE /* enable request sense extensions */
USCSI_RENEGOT /* renegotiate wide/sync on next I/O */

The uscsi_flags bits have the following interpretation:

USCSI_WRITE Data will be written from the initiator to the
target.

USCSI_SILENT The driver should not print any console error
messages or warnings regarding failures associated
with this SCSI command.

USCSI_DIAGNOSE The driver should not attempt any retries or other
recovery mechanisms if this SCSI command terminates
abnormally in any way.

USCSI_ISOLATE This SCSI command should not be executed with other
commands.

USCSI_READ Data will be read from the target to the initiator.

USCSI_ASYNC Set the SCSI bus to asynchronous mode before
running this command.

USCSI_SYNC Set the SCSI bus to synchronous mode before running
this command.

USCSI_RESET Send a SCSI bus device reset message to this
target.

USCSI_RESET_TARGET Same as USCSI_RESET. Use this flag to request
TARGET RESET. (USCSI_RESET is maintained only for
compatibility with old applications).

USCSI_RESET_LUN Send a SCSI logical unit reset message to this
target.

USCSI_RESET_ALL USCSI_RESET_ALL, USCSI_RESET/USCSI_RESET_TARGET,
and USCSI_RESET_LUN are mutually exclusive options
and issuing them in any simultaneous combination
will result in implementation-dependent behavior
When a USCSI reset request is combined with other
SCSI commands, the following semantics take effect:
If the USCSI RESET flag is specified, the other
fields (other than uscsi_flags) in the uscsi_cmd
are ignored. The uscsi_cdblen field must be set to
zero.

USCSI_RQENABLE Enable Request Sense extensions. If the user
application is prepared to receive sense data, this
bit must be set, the fields uscsi_rqbuf and
uscsi_rqbuflen must be non-zero, and the
uscsi_rqbuf must point to memory writable by the
application.

USCSI_RENEGOT Tells USCSI to renegotiate wide mode and
synchronous transfer speed before the transmitted
SCSI command is executed. This flag in effect
tells the target driver to pass the
FLAG_RENEGOTIATE_WIDE_SYNC flag in the SCSI packet
before passing the command to an adapter driver for
transport. See the scsi_pkt(9S) flag
FLAG_RENEGOTIATE_WIDE_SYNC for more information.

The uscsi_xfer_t is a type definition that corresponds to a 64-bit
unsigned integer. It should be used for the USCSIMAXXFER ioctls. This
is used for determining the maximum transfer size that can be performed
in a single USCSICMD ioctl. If the SCSI request is larger than the
specified size, then it may not work, depending on the hardware
platform.

IOCTLS

The ioctl() supported by drivers providing the uscsi interface is:

USCSICMD The argument is a pointer to a uscsi_cmd structure. The
SCSI device addressed by that driver is selected, and
given the SCSI command addressed by uscsi_cdb. If this
command requires a data phase, the uscsi_buflen and
uscsi_bufaddr fields must be set appropriately; if data
phase occurs, the uscsi_resid is returned as the number
of bytes not transferred. The status of the command, as
returned by the device, is returned in the uscsi_status
field. If the command terminates with Check Condition
status, and Request Sense is enabled, the sense data
itself is returned in uscsi_rqbuf. The uscsi_rqresid
provides the residue of the Request Sense data transfer.

USCSIMAXXFER The argument is a pointer to a uscsi_xfer_t value. The
maximum transfer size that can be used with the USCSICMD
ioctl for the current device will be returned in the
uscsi_xfer_t.

Not all devices which support the USCSICMD ioctl also
support the USCSIMAXXFER ioctl.

ERRORS

EINVAL A parameter has an incorrect, or unsupported, value.

EIO An error occurred during the execution of the command.

EPERM A process without root credentials tried to execute the
USCSICMD or USCSIMAXXFER ioctl.

EFAULT The uscsi_cmd itself, the uscsi_cdb, the uscsi_buf, the
uscsi_rqbuf, or the uscsi_xfer_t point to an invalid address.

STABILITY

Committed

WARNINGS

The uscsi command is very powerful, but somewhat dangerous, and so its
use is restricted to processes running as root, regardless of the file
permissions on the device node. The device driver code expects to own
the device state, and uscsi commands can change the state of the device
and confuse the device driver. It is best to use uscsi commands only
with no side effects, and avoid commands such as Mode Select, as they
may cause damage to data stored on the drive or system panics. Also,
as the commands are not checked in any way by the device driver, any
block may be overwritten, and the block numbers are absolute block
numbers on the drive regardless of which slice number is used to send
the command.

The uscsi interface is not recommended for very large data transfers
(typically more than 16MB). If the requested transfer size exceeds the
maximum transfer size of the DMA engine, it will not be broken up into
multiple transfers and DMA errors may result. The USCSIMAXXFER ioctl
can be used to determine the maximum transfer size.

The USCSICMD ioctl associates a struct uscsi_cmd with a device by using
an open file descriptor to the device. Other APIs might provide the
same struct uscsi_cmd programming interface, but perform device
association in some other manner.

illumos March 13, 2022 illumos