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 the control
device /dev/targ. 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
<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.
<cam/scsi/scsi_targetio.h>
- describes the usermode interface.
- /sys/cam/scsi/scsi_target.c
- is the driver source file.
- /dev/targ
- is the control device.
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
ahc(4) and
isp(4)
drivers fully support target mode.
The
ahc(4)
driver does not support tagged queuing in target mode.