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 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.
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
- is the control device.
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.