NAME¶
ch —
SCSI media-changer (juke box)
driver
SYNOPSIS¶
device ch
DESCRIPTION¶
The
ch driver provides support for a
SCSI
media changer. It allows many slots of media to be multiplexed between a
number of drives. The changer device may optionally be equipped with a bar
code reader, which reads label information attached to the media.
A SCSI adapter must also be separately configured into the system before a SCSI
changer can be configured.
As the SCSI adapter is probed during boot, the
SCSI bus is
scanned for devices. Any devices found which answer as 'Changer' type devices
will be 'attached' to the
ch driver. In
FreeBSD releases prior to 2.1, the first found will be
attached as
ch0 and the next,
ch1 etc.
Beginning in 2.1 it is possible to specify what ch unit a device should come
on line as; refer to
scsi(4) for details on kernel
configuration.
KERNEL CONFIGURATION¶
It is only necessary to explicitly configure one
ch device;
data structures are dynamically allocated as media changes are found on the
SCSI bus.
IOCTLS¶
User mode programs communicate with the changer driver through a number of
ioctls which are described below. Changer element addresses used in the
communication between the kernel and the changer device are mapped to
zero-based logical addresses. Element types are specified as follows:
CHET_MT
- Medium transport element (picker).
CHET_ST
- Storage element (slot).
CHET_IE
- Import/export element (portal).
CHET_DT
- Data transfer element (drive).
The following
ioctl(2) calls apply to the changer. They are
defined in the header file
<sys/chio.h>.
CHIOMOVE
- (struct changer_move) Move a medium
from one element to another (MOVE MEDIUM) using the
current picker. The source and destination elements are specified in a
changer_move structure, which includes at least the following fields:
u_int cm_fromtype; /* element type to move from */
u_int cm_fromunit; /* logical unit of from element */
u_int cm_totype; /* element type to move to */
u_int cm_tounit; /* logical unit of to element */
u_int cm_flags; /* misc. flags */
If the CM_INVERT
in the
cm_flags field is set, the medium changer is
instructed to flip the medium while moving it.
CHIOEXCHANGE
- (struct changer_exchange) Move the
medium located in the source element to the first destination element, and
move the medium that had been in the first destination element to the
second destination element. In case of a simple exchange, the source and
second destination elements should be the same. The current picker is used
to perform the operation. The addresses of the affected elements is
specified to the ioctl in a changer_exchange
structure which includes at least the following fields:
u_int ce_srctype; /* element type of source */
u_int ce_srcunit; /* logical unit of source */
u_int ce_fdsttype; /* element type of first destination */
u_int ce_fdstunit; /* logical unit of first destination */
u_int ce_sdsttype; /* element type of second destination */
u_int ce_sdstunit; /* logical unit of second destination */
u_int ce_flags; /* misc. flags */
In ce_flags, CM_INVERT1
and/or
CM_INVERT2
may be set to flip the first or second
medium during the exchange operation, respectively.
This operation is untested.
CHIOPOSITION
- (struct changer_position) Position
the current picker in front of the specified element. The element is
specified with a changer_position structure, which includes at least the
following elements:
u_int cp_type; /* element type */
u_int cp_unit; /* logical unit of element */
u_int cp_flags; /* misc. flags */
The cp_flags field may be set to
CP_INVERT
to invert the picker during the
operation.
CHIOGPICKER
- (int) Return the logical address of
the current picker.
CHIOSPICKER
- (int) Select the picker specified by
the given logical address.
CHIOGPARAMS
- (struct changer_params) Return the
configuration parameters for the media changer. This ioctl fills the
changer_params structure passed by the user with at least the following
fields:
u_int cp_npickers; /* number of pickers */
u_int cp_nslots; /* number of slots */
u_int cp_nportals; /* number of import/export portals */
u_int cp_ndrives; /* number of drives */
This call can be used by applications to query the dimensions of the jukebox
before using the CHIGSTATUS
ioctl to query the
jukebox' status.
CHIOIELEM
- Perform the INITIALIZE ELEMENT STATUS
call on the media changer device. This forces the media changer to update
its internal status information with respect to loaded media. It also
scans any barcode labels provided that it has a label reader. The
ch driver's status is not affected by this call.
CHIOGSTATUS
- (struct
changer_element_status_request) Perform the READ
ELEMENT STATUS call on the media changer device. This call reads the
element status information of the media changer and converts it to an
array of changer_element_status structures.
With each call to
CHIOGSTATUS
, the status of one or
more elements of one type may be queried.
The application passes a
changer_element_status_request structure to the
ch driver which contains the following fields:
u_int cesr_element_type;
u_int cesr_element_base;
u_int cesr_element_count;
u_int cesr_flags;
struct changer_element_status *cesr_element_status;
This structure is read by the driver to determine the type, logical base
address and number of elements for which information is to be returned in
the array of changer_element_status structures
pointed to by the cesr_element_status field. The
application must allocate enough memory for
cesr_element_count status structures (see below).
The cesr_flags can optionally be set to
CESR_VOLTAGS
to indicate that volume tag (bar
code) information is to be read from the jukebox and returned.
The cesr_element_base and
cesr_element_count fields must be valid with respect
to the physical configuration of the changer. If they are not, the
CHIOGSTATUS
ioctl returns the
EINVAL
error code.
The information about the elements is returned in an array of
changer_element_status structures. This structure
include at least the following fields:
u_int ces_addr; /* element address in media changer */
u_char ces_flags; /* see CESTATUS definitions below */
u_char ces_sensecode; /* additional sense code for element */
u_char ces_sensequal; /* additional sense code qualifier */
u_char ces_invert; /* invert bit */
u_char ces_svalid; /* source address (ces_source) valid */
u_short ces_source; /* source address of medium */
changer_voltag_t ces_pvoltag; /* primary volume tag */
changer_voltag_t ces_avoltag; /* alternate volume tag */
u_char ces_idvalid; /* ces_scsi_id is valid */
u_char ces_scsi_id; /* SCSI id of element (if ces_idvalid is nonzero) */
u_char ces_lunvalid; /* ces_scsi_lun is valid */
u_char ces_scsi_lun; /* SCSI lun of element (if ces_lunvalid is nonzero) */
The ces_addr field contains the address of the element
in the coordinate system of the media changer. It is not used by the
driver, and should be used for diagnostic purposes only.
The following flags are defined for the ces_flags
field:
CESTATUS_FULL
- A medium is present.
CESTATUS_IMPEXP
- The medium has been deposited by the operator (and not
by a picker).
CESTATUS_EXCEPT
- The element is in an exceptional state (e.g. invalid
barcode label, barcode not yet scanned).
CESTATUS_ACCESS
- The element is accessible by the picker.
CESTATUS_EXENAB
- The element supports medium export.
CESTATUS_INENAB
- The element supports medium import.
Note that not all flags are valid for all element types.
NOTES¶
This version of the
ch driver has been tested with a DEC TZ875
(5 slot, one DLT drive) and a Breece Hill Q47 (60 slot, four DLT drives,
barcode reader).
Many of the features the
ch driver supports are not thoroughly
tested due to the fact that the devices available for testing do not support
the necessary commands. This is true for alternate volume tags, media
flipping, import/export element handling, multiple picker operation and other
things.
FILES¶
- /dev/ch[0-9]
- device entries
DIAGNOSTICS¶
If the media changer does not support features requested by the
ch driver, it will produce both console error messages and
failure return codes to the ioctls described here.
SEE ALSO¶
cam(4),
chio(1),
cd(4),
da(4),
sa(4)
HISTORY¶
The
ch driver appeared in
386BSD-0.1.
AUTHORS¶
The
ch driver was written by
Jason R.
Thorpe ⟨thorpej@and.com⟩ for And Communications,
http://www.and.com/. It was added to the system by
Stefan Grefen
⟨grefen@goofy.zdv.uni-mainz.de⟩ who apparently had such a
device. It was ported to CAM by
Kenneth Merry
⟨ken@FreeBSD.org⟩. It was updated to support volume tags by
Hans Huebner ⟨hans@artcom.de⟩.