SCSI_ADDRESS(9S) Data Structures for Drivers SCSI_ADDRESS(9S)

NAME

scsi_address - SCSI address structure

SYNOPSIS

#include <sys/scsi/scsi.h>

INTERFACE LEVEL

illumos architecture specific (illumos DDI)

DESCRIPTION

A scsi_address structure defines the addressing components for a SCSI
target device. The address of the target device is separated into two
components: target number and logical unit number. The two addressing
components are used to uniquely identify any type of SCSI device;
however, most devices can be addressed with the target component of the
address.

In the case where only the target component is used to address the
device, the logical unit should be set to 0. If the SCSI target device
supports logical units, then the HBA must interpret the logical units
field of the data structure.

The pkt_address member of a scsi_pkt(9S) is initialized by
scsi_init_pkt(9F).

Complex Addressing

HBA drivers may set the flag SCSI_HBA_ADDR_COMPLEX in the hba_flags
argument to scsi_hba_attach_setup(9F). When the flag is set, the way
this structure is used changes. While the a_hba_tran member is still
accessible for accessing the scsi_hba_tran(9S) structure, the nature of
addressing changes.

When using complex addressing, a particular device is addressed through
a unit address which takes the shape of a string. When using complex
addressing, the target and lun fields are inaccessible and instead a
device driver can obtain the scsi_device(9S) structure that this
address corresponds to. In the complex addressing world, this is
generally a direct mapping. To obtain this structure, a driver would
call the scsi_address_device(9F) function.

With the scsi_device(9S) structure, the device driver can then get to
the device-specific private data through the
scsi_device_hba_private_get(9F) function.

STRUCTURE MEMBERS

scsi_hba_tran_t *a_hba_tran; /* Transport vectors for the SCSI bus */
ushort_t a_target; /* SCSI target id */
uchar_t a_lun; /* SCSI logical unit */

a_hba_tran is a pointer to the controlling HBA's transport vector
structure. The SCSA interface uses this field to pass any transport
requests from the SCSI target device drivers to the HBA driver. This
member is accessible regardless of whether the device driver uses
complex addressing or not.

a_target is the target component of the SCSI address. This member is
not accessible when the device driver uses complex addressing.

a_lun is the logical unit component of the SCSI address. The logical
unit is used to further distinguish a SCSI target device that supports
multiple logical units from one that does not. This member is not
accessible when the device driver uses complex addressing.

SEE ALSO

scsi_address_device(9F), scsi_device_hba_private_get(9F),
scsi_hba_attach_setup(9F), scsi_init_pkt(9F), scsi_device(9S),
scsi_hba_tran(9S), scsi_pkt(9S)


Writing Device Drivers.

illumos January 29, 2022 illumos