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TARG(4)               DragonFly Kernel Interfaces Manual               TARG(4)


NAME

     targ - SCSI target emulator driver


SYNOPSIS

     device targ


DESCRIPTION

     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.


IOCTLS

     The following ioctl(2) calls are defined in the header file
     <bus/cam/scsi/scsi_targetio.h>.

     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.


FILES

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


SEE ALSO

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

     FreeBSD Target Information, http://www.root.org/~nate/freebsd/.


AUTHORS

     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
     <nate@root.org>.


BUGS

     Currently, only the isp(4) driver fully supports target mode.

DragonFly 5.9-DEVELOPMENT      November 15, 2002     DragonFly 5.9-DEVELOPMENT

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