uscsi - user SCSI command interface
ioctl(int fildes, int request, struct uscsi_cmd *cmd);
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 driver for SCSI disks and ATAPI CD-ROM drives, and
by the st 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 com-
mand, 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
The I/O direction and other details of how to carry
out the SCSI command. Possible values are described
The SCSI status byte returned by the device is
returned in this field.
Time in seconds to allow for completion of the com-
A pointer to the SCSI CDB (command descriptor block)
to be transferred to the device in command phase.
The user buffer containing the data to be read from or
written to the device.
The length of uscsi_bufaddr.
If a data transfer terminates without transferring the
entire requested amount, the remainder, or residue, is
returned in this field.
The length of the SCSI CDB to be transferred to the
device in command phase.
The length of uscsi_rqbuf, the application's Request
The SCSI status byte returned for the Request Sense
command executed automatically by the driver in
response to a Check Condition status return.
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).
Points to a buffer in application address space to
which the results of an automatic Request Sense com-
mand are written.
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_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:
Data will be written from the initiator to the target.
The driver should not print any console error messages
or warnings regarding failures associated with this
The driver should not attempt any retries or other
recovery mechanisms if this SCSI command terminates
abnormally in any way.
This SCSI command should not be executed with other
Data will be read from the target to the initiator.
Set the SCSI bus to asynchronous mode before running
Set the SCSI bus to synchronous mode before running
Send a SCSI Bus Device Reset Message to this target.
Cause a SCSI Bus Reset on the bus associated with this
Enable Request Sense extensions. If the user applica-
tion 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.
Tells USCSI to renegotiate wide mode and synchronous
transfer speed before the transmitted SCSI command is
executed. This flag in effects 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 ioctl supported by drivers providing the uscsi interface
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.
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 ioctl.
The uscsi_cmd itself, the uscsi_cdb, the uscsi_buf, or
the uscsi_rqbuf point to an invalid address.
See attributes(5) for descriptions of the following attri-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Availability | SUNWhea |
ioctl(2), attributes(5), sd(7D), st(7D)
ANSI Small Computer System Interface-2 (SCSI-2)
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 con-
fuse 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
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.
Man(1) output converted with