NAME
targ —
SCSI target emulator driver
SYNOPSIS
device targ
DESCRIPTION
Thetarg 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
EADDRINUSEis 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.
TARGIOCENABLEcan 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_PERIPHdebugging 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.