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TARG(4)               DragonFly 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 (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 <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.


<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.


/usr/share/examples/scsi_target, isp(4), scsi(4) FreeBSD Target Information, http://www.root.org/~nate/freebsd/.


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>.


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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