NAME¶
targ —
SCSI target emulator
driver
SYNOPSIS¶
To compile this driver into the kernel, place the following line in your kernel
configuration file:
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
<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¶
- <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.
SEE ALSO¶
/usr/share/examples/scsi_target,
ahc(4),
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
ahc(4) and
isp(4)
drivers fully support target mode.
The
ahc(4) driver does not support tagged queuing in target
mode.
