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     targ — SCSI target emulator driver


     To compile this driver into the kernel, place the following line in your
     kernel configuration file:

           device targ


     The targ driver provides an interface for usermode programs to emulate
     SCSI target devices.  A sample program that emulates a disk drive
     (similar 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
                     commands 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,


     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


     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.