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TARG(4)			 BSD Kernel Interfaces Manual		       TARG(4)

     targ -- SCSI target emulator driver

     device targ

     The targ driver provides an interface for usermode	programs to emulate
     SCSI target devices.  A sample program that emulates a disk drive (simi-
     lar to da(4)) can be found	in /usr/share/examples/scsi_target.

     The targ driver supplies control devices, /dev/targ0, /dev/targ1, etc.
     If	a device is already in use, open(2) will fail and errno	will be	set to
     EBUSY.  After opening the device, the file	descriptor must	be bound to a
     specific bus/target/LUN and enabled to process CCBs using the
     TARGIOCENABLE ioctl.  The process then uses write(2) to send CCBs to the
     SIM and poll(2) or	kqueue(2) to see if responses are ready.  Pointers to
     completed CCBs are	returned via read(2).  Any data	transfers requested by
     the user CCBs are done via	zero-copy IO.

     The following ioctl(2) calls are defined in the header file

     TARGIOCENABLE   (struct ioc_enable_lun) Enable target mode	on the LUN
		     specified by the following	structure:

			   struct ioc_enable_lun {
				   path_id_t	   path_id;
				   target_id_t	   target_id;
				   lun_id_t	   lun_id;
				   int		   grp6_len;
				   int		   grp7_len;

		     The selected path (bus), target, and LUN must not already
		     be	in use or EADDRINUSE is	returned.  If grp6_len or
		     grp7_len are non-zero, reception of vendor-specific com-
		     mands is enabled.

     TARGIOCDISABLE  Disable target mode and abort all pending CCBs.  The CCBs
		     may optionally be read as they complete.  TARGIOCENABLE
		     can then be called	to activate a different	LUN.  Multiple
		     disable calls have	no effect.  The	close(2) system	call
		     automatically disables target mode	if enabled.

     TARGIOCDEBUG    (int) Enables CAM_PERIPH debugging	if the argument	is
		     non-zero, otherwise disables it.

     <cam/scsi/scsi_targetio.h>	  describes the	usermode interface.
     /sys/cam/scsi/scsi_target.c  is the driver	source file.
     /dev/targ*			  are the control devices.

     /usr/share/examples/scsi_target, ahc(4), isp(4), scsi(4)

     FreeBSD Target Information,

     Currently,	only the ahc(4)	and isp(4) drivers fully support target	mode.

     The ahc(4)	driver does not	support	tagged queuing in target mode.

     The targ driver first appeared in FreeBSD 3.0 and was written by Justin
     T.	Gibbs.	It was rewritten for FreeBSD 5.0 by Nate Lawson

BSD			       November	15, 2002			   BSD


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