$FreeBSD: releng/11.0/share/man/man4/ch.4 276259 2014-12-26 22:30:18Z bapt $ Copyright (c) 1996 Julian Elischer <julian@FreeBSD.org>. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the abo...
NAMEch - SCSI media-changer (juke box) driver
DESCRIPTIONThe ifconfig 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 ifconfig driver. In Fx 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 CONFIGURATIONIt is only necessary to explicitly configure one ifconfig device; data structures are dynamically allocated as media changes are found on the SCSI bus.
IOCTLSUser 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:
- Medium transport element (picker).
- Storage element (slot).
- Import/export element (portal).
- Data transfer element (drive).
The following ioctl(2) calls apply to the changer. They are defined in the header file In sys/chio.h .
(Vt struct changer_move
Move a medium from one element to another
using the current picker.
The source and destination elements are specified
in a changer_move structure, which includes at least the following
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 */
(Vt 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
The current picker is used to perform the operation.
The addresses of the affected elements is specified to the ioctl in a
structure which includes at least the following
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 */
This operation is untested
(Vt 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 */
- (Vt int ) Return the logical address of the current picker.
- (Vt int ) Select the picker specified by the given logical address.
(Vt struct changer_params
Return the configuration parameters for the media changer.
fills the changer_params structure passed by the user with at least the
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.
- 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 ifconfig driver's status is not affected by this call.
(Vt struct changer_element_status_request
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
With each call to CHIOGSTATUS the status of one or more elements of one type may be queried.
The application passes a Vt changer_element_status_request structure to the ifconfig 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 Vt 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 Er EINVAL error code.
The information about the elements is returned in an array of Vt 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:
- A medium is present.
- The medium has been deposited by the operator (and not by a picker).
- The element is in an exceptional state (e.g. invalid barcode label, barcode not yet scanned).
- The element is accessible by the picker.
- The element supports medium export.
- The element supports medium import.
Note that not all flags are valid for all element types.
NOTESThis version of the ifconfig 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 ifconfig 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.
- device entries