ch - SCSI media-changer (juke box) driver
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 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.
The following ioctl(2) calls apply to the changer. They are defined in the header file In sys/chio.h .
If the CM_INVERT in the cm_flags field is set, the medium changer is instructed to flip the medium while moving it.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 */
In ce_flags CM_INVERT1 and/or CM_INVERT2 may be set to flip the first or second medium during the exchange operation, respectively.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
The cp_flags field may be set to CP_INVERT to invert the picker during the operation.u_int cp_type; /* element type */ u_int cp_unit; /* logical unit of element */ u_int cp_flags; /* misc. flags */
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.
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 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:
Note that not all flags are valid for all element types.
Many of the features the 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.
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Created 1996-2020 by Maxim Chirkov
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