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AIX Version 4.3 Kernel and Subsystems Technical Reference, Volume 2

SCIOSTARTTGT (Start Target) SCSI Adapter Device Driver ioctl Operation


Opens a logical path to a SCSI initiator device.


The SCIOSTARTTGT operation opens a logical path to a SCSI initiator device. The host SCSI adapter acts as a target. This operation causes the adapter device driver to allocate and initialize device-dependent information areas needed to manage data received from the initiator. It also makes the adapter device driver allocate system buffer areas to hold data received from the initiator. Finally, it makes the host adapter ready to receive data from the initiator.

This operation may only be called from a kernel process or device driver, as it requires that both the caller and the SCSI adapter device driver be able to directly access each other's code in memory.

Note: This operation is not supported by all SCSI I/O controllers. If not supported, errno is set to ENXIO and a value of -1 is returned.

The arg parameter to the SCIOSTARTTGT ioctl operation should be set to the address of an sc_strt_tgt structure, which is defined in the /usr/include/sys/scsi.h file. The caller fills in the ID field with the SCSI ID of the SCSI initiator and sets the logical unit number (LUN) field to 0 , as the initiator LUN is ignored for received data.

The caller sets the buf_size field to the desired size for all receive buffers allocated for this host target instance. This is an adapter-dependent parameter, which should be set to 4096 bytes for the SCSI I/O Controller. The num_bufs field is set to indicate how many buffers the caller wishes to have allocated for the device. This is also an adapter-dependent parameter. For the SCSI I/O Controller, it should be set to 16 or greater.

The caller fills in the recv_func field with the address of a pinned routine from its module, which the adapter device driver calls to pass received-data information structures. These structures tell the caller where the data is located and if any errors occurred.

The tm_correlator field can optionally be used by the caller to provide an efficient means of associating received data with the appropriate device. This field is saved by the SCSI adapter device driver and is returned, with information passed back to the caller's recv_func routine.

The free_func field is an output parameter for this operation. The SCSI adapter device driver fills this field with the address of a pinned routine in its module, which the caller calls to pass processed received-data information structures.

Currently, the host SCSI adapter acts only as LUN 0 when accessed from other SCSI initiators. This means the remotely-attached SCSI initiator can only direct data at one logical connection per host SCSI adapter. At most, only one calling process can open the logical path from the host SCSI adapter to a remote SCSI initiator. This does not prevent a single process from having multiple target devices opened simultaneously.

Note: Two or more SCSI target devices can have the same SCSI ID if they are physically attached to separate SCSI adapters.

Return Values

When completed successfully, this operation returns a value of 0. Otherwise, a value of -1 is returned and the errno global variable is set to one of the following values:

EINVAL An SCIOSTARTTGT command has already been issued to this SCSI ID, the passed SCSI ID is the same as that of the adapter, the LUN field is not set to 0, the buf_size field is greater than 4096 bytes, the num_bufs field is less than 16, or the recv_func field is set to null.
EIO Indicates an I/O error or kernel service failure occurred, preventing the device driver from enabling the selected SCSI ID.
ENOMEM Indicates that a memory allocation error has occurred.
EPERM Indicates the caller is not running in kernel mode, which is the only mode allowed to execute this operation.


/dev/scsi0, /dev/scsi1,...,/dev/scsin Provide an interface to allow SCSI device drivers to access SCSI devices or adapters.
/dev/vscsi0, /dev/vscsi1,..., /dev/vscsin Provide an interface to allow SCSI-2 Fast/Wide Adapter/A and SCSI-2 Differential Fast/Wide Adapter/A device drivers to access SCSI devices or adapters.

Related Information

The rmt SCSI device driver, scdisk SCSI device driver, SCSI Adapter device driver, tmscsi SCSI device driver.

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