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CH(4) | Device Drivers Manual | CH(4) |
NAME¶
ch
—
SCSI media-changer (juke box) driver
SYNOPSIS¶
device ch
DESCRIPTION¶
Thech
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 onech
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).
<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 */
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 */
CM_INVERT1
and/orCM_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 */
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 */
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 thech
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;
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, theCHIOGSTATUS
ioctl returns theEINVAL
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) */
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.
NOTES¶
This version of thech
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 thech
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¶
Thech
driver appeared in
386BSD-0.1.
AUTHORS¶
Thech
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⟩.May 14, 1998 | Debian |