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mc(7) [osf1 man page]

mc(7)							 Miscellaneous Information Manual						     mc(7)

NAME

       mc - SCSI medium changer interface

DESCRIPTION

       The  medium  changer  (mc)  interface  provides	a  means for applications to control the robotic medium changers found in tape and optical
       libraries or jukeboxes.

       The mc driver may be used for any supported Small Computer System Interface (SCSI) medium changer devices, and potentially for other  SCSI-
       compliant  changer  devices.   Applications  use  Unix I/O calls (open, close, ioctl) to access changer devices, by means of device special
       files.  Changer device special files are typically created in the /dev/changer directory by the dsfmgr utility on system startup. Refer	to
       the  dsfmgr(8)  Reference  Page	and the System Administration Guide if you need to recreate device special files that are deleted acciden-
       tally. The rz(7) and tz(7) Reference Pages provide information on how device names map to SCSI CAM lun addresses.

       The format of a a medium changer device special file name is: /dev/changer/mcN where N is an  integer  representing  the  instance  of  the
       device that is assigned by dsfmgr at system startup.

       The  driver  supports a number of ioctl commands that move media in the library or return information about the media.  See the header file
       /usr/sys/include/io/cam/mchanger.h for the ioctl commands and their associated structs.

       An application opens the device special file corresponding to the changer device, executes appropriate  ioctl  commands,  then  closes  the
       device  special file.  Typically, changer devices are not shared between applications, but this is not due to any limitation on the changer
       or mc driver, but rather to the possibility of confusing which media belong to which application.  An application on a  non-cluster  system
       can  assure that only it can use a changer by opening that changer's device special file for exclusive access, by including the O_EXCL flag
       in the open call, and leaving the file open until the application is completely done using the changer.	However, if the changer  is  on  a
       shared  bus  in	a  cluster,  it  is  possible for an application on each cluster member to open the device, even if each specifies O_EXCL,
       because that only grants exclusive access on the local host.  In this case it may be useful for the application to use a SCSI device reser-
       vation to assure exclusive access.  (An ioctl command is provided to facilitate reserving a changer.)

       Refer to the Software Product Description for a list of supported devices under the heading of SCSI CAM Layered Components.  Facilities are
       provided in the operating system to allow the addition of some third-party SCSI-compliant medium changers.  Under  Digital  Unix  v4.0  and
       later,  refer to the ddr_config(8) and ddr.dbase(4) reference pages for instructions.  Under Digital Unix v3.x, new devices can be added to
       /sys/data/cam_data.c.  See that file for instructions.

FILES

       changer device special file header file for changer ioctl commands

RELATED INFORMATION

       Commands: mcutil(1), mcicap(4), dsfmgr(8), scu(8), uerf(8)

       Interfaces: op(7), tz(7), SCSI(7)

       delim off

																	     mc(7)

Check Out this Related Man Page

CD(9)							   BSD Kernel Developer's Manual						     CD(9)

NAME

     cd -- CDROM driver for the CAM SCSI subsystem

DESCRIPTION

     The cd device driver provides a read only interface for CDROM drives (SCSI type 5) and WORM drives (SCSI type 4) that support CDROM type com-
     mands.  Some drives do not behave as the driver expects.  See the QUIRKS section for information on possible flags.

QUIRKS

     Each CD-ROM device can have different interpretations of the SCSI spec.  This can lead to drives requiring special handling in the driver.
     The following is a list of quirks that the driver recognize.

     CD_Q_NO_TOUCH    This flag tell the driver not to probe the drive at attach time to see if there is a disk in the drive and find out what
		      size it is.  This flag is currently unimplemented in the CAM cd driver.

     CD_Q_BCD_TRACKS  This flag is for broken drives that return the track numbers in packed BCD instead of straight decimal.  If the drive seems
		      to skip tracks (tracks 10-15 are skipped) then you have a drive that is in need of this flag.

     CD_Q_NO_CHANGER  This flag tells the driver that the device in question is not a changer.	This is only necessary for a CDROM device with
		      multiple luns that are not a part of a changer.

     CD_Q_CHANGER     This flag tells the driver that the given device is a multi-lun changer.	In general, the driver will figure this out auto-
		      matically when it sees a LUN greater than 0.  Setting this flag only has the effect of telling the driver to run the initial
		      read capacity command for LUN 0 of the changer through the changer scheduling code.

     CD_Q_10_BYTE_ONLY
		      This flag tells the driver that the given device only accepts 10 byte MODE SENSE/MODE SELECT commands.  In general these
		      types of quirks should not be added to the cd(4) driver.	The reason is that the driver does several things to attempt to
		      determine whether the drive in question needs 10 byte commands.  First, it issues a CAM Path Inquiry command to determine
		      whether the protocol that the drive speaks typically only allows 10 byte commands.  (ATAPI and USB are two prominent exam-
		      ples of protocols where you generally only want to send 10 byte commands.)  Then, if it gets an ILLEGAL REQUEST error back
		      from a 6 byte MODE SENSE or MODE SELECT command, it attempts to send the 10 byte version of the command instead.	The only
		      reason you would need a quirk is if your drive uses a protocol (e.g., SCSI) that typically does not have a problem with 6
		      byte commands.

FILES

     /sys/cam/scsi/scsi_cd.c  is the driver source file.

SEE ALSO

     cd(4), scsi(4)

HISTORY

     The cd manual page first appeared in FreeBSD 2.2.

AUTHORS

     This manual page was written by John-Mark Gurney <gurney_j@efn.org>.  It was updated for CAM and FreeBSD 3.0 by Kenneth Merry
     <ken@FreeBSD.org>.

BSD
								 September 2, 2003							       BSD
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