HP-UX Reference (11i v2 04/09) - 7 Device (Special) Files, 9 General Information, Index (vol 10)

a
autochanger(7) autochanger(7)
NAME
autochanger - SCSI interfaces for medium changer device and magneto-optical autochanger surface dev-
ice
DESCRIPTION
An autochanger is a SCSI mass storage device, consisting of a mechanical changer device, one or more
data transfer devices (such as optical disk drives), and media (such as optical disks) for data storage. The
mechanical changer moves media between storage and usage locations within the autochanger.
Depending on system architecture, one of two medium changer drivers (
schgr or
autox0)provides
access to the medium changer device; a module (
ssrfc) provides access to the surfaces of the optical
disks.
Two levels of functionality are provided by the medium changer drivers. The mechanical changer device
can be accessed directly to move media within the autochanger. Alternatively, media surfaces can be
accessed as unique devices, causing the changer driver to move the media into a drive to perform an I/O
request.
The
schgr and autox0 medium changer device drivers follow the SCSI specification for medium
changer devices to provide a generic medium changer interface, making it feasible to construct an appli-
cation level driver for any mechanical changer, jukebox, library, or autochanger device (MO, tape, CD-
ROM).
However, the
ssrfc module is provided specifically to support Hewlett-Packard magneto-optical disk
autochanger products.
Device Naming Convention
The device naming convention for the autochanger driver enables accessing the changer device, as well as
individual media surfaces. Block devices for autochangers reside in
/dev/ac, character devices reside
in /dev/rac. Within these directories, names are derived from the "c#t#d#" device naming convention
(explained in intro (7)), with the surface descriptor appended at the end. Unique device names are deter-
mined by the card instance, target address of the SCSI changer device, LUN of the SCSI changer device,
and the surface descriptor.
The surface descriptor can be zero or non-specified for the changer device. Also, there is no block special
file for the changer itself. For example,
/dev/rac/c1t5d0
is the character special file for the changer at SCSI target address 5 and LUN 0, attached to SCSI card
instance 1, and is equivalent to /dev/rac/c1t5d0_0
.
Any given surface is described by the card instance, SCSI target address and SCSI LUN of the changer,
and then appended with a surface descriptor for the slot number and side. For example,
/dev/ac/c1t5d0_1a
is the block special file for surface 1a of the autochanger just mentioned and
/dev/rac/c1t5d0_1a
is the character special file for the same surface 1a.
Major and Minor Number Descriptions
The following shows the bit assignments (
dev_t format) used by the changer drivers to access the
changer device and each surface within an autochanger:
0-7 8-15 16-19 20-22 23-31
MAJOR INSTANCE TARGET LUN SURFACE
MAJOR is the major number of the appropriate driver, INSTANCE is the card instance of the SCSI inter-
face to which the changer device is attached, TARGET is the SCSI target address of the changer device,
LUN is the SCSI LUN of the changer device, and SURFACE is the unique descriptor of each surface in
the autochanger, as described in the following table. (Note, the surface descriptors refer to bits 23-31.)
Section 7−−4 Hewlett-Packard Company − 1 − HP-UX 11i Version 2: September 2004