scsi_target - a SCSI target emulator
-------

This code is a rewrite of /sys/cam/scsi/scsi_target* and
/usr/share/examples/scsi_target/.  The kernel driver allows a user
process to enable target mode and then pass CCBs to and from the HBA
via read(2) and write(2).  The included user program uses this
to emulate a disk drive (RBC).  All reads/writes to and from the emulated
drive access data in a file.

Requirements
---
One or two PCs
One SCSI dual bus HBA or two single bus HBAs
Cable to connect both HBAs
FreeBSD 4.8-RELEASE or 5-CURRENT

SCSI Adapters
---
The HBA you use for emulating a target must have target mode support.
Drivers that have good target mode support are ahc(4) and isp(4).
Drivers that may support target mode in the future are sym(4), ahd(4),
and mpt(4).

1. Tested HBAs
Cards based on Adaptec 7890 (Ultra2), 7899 (Ultra 160)
Qlogic SCSI 1280

2. Untested but should work
Cards based on Adaptec 7891, 7896, 7897 (Ultra2)
Cards based on Adaptec 7892 (Ultra 160)
Qlogic Fibre Channel cards (2100, 2200, 2300, 2312)
Qlogic SCSI cards

3. May work in the future
Other isp(4) cards
sym(4)
mpt(4)
ahd(4)

Usage
---
1. Add the following to your kernel config if not present:
   device scbus
   device da
   # SCSI target emulator
   device targ
   # Blackhole target driver
   device targbh
   options CAMDEBUG
   # Enable asynch IO (or just do "kldload aio")
   options VFS_AIO
2. Add the appropriate option for your HBA to enable target mode.
For the ahc(4) cards, this is:
   options AHC_TMODE_ENABLE=0x8
... where the supplied value is a bitmask of the SCSI target ids you wish
to enable target mode support on.  If you're using multiple HBAs in the
same box or a dual bus HBA, be sure to only enable target mode support for
the card you wish to use as the target since some drivers don't support
simultaneous initiator/target roles.
For the isp(4) cards:
   options ISP_TARGET_MODE
Note that most isp(4) cards can do simultaneous init/target operations
and you must use the init id as the target id.  For instance, if
your card is configured to be initiator id 7 (in the BIOS), you
should use 7 as the target id you emulate.
3. Build a kernel with the new driver the ordinary way.
4. Reboot
5. cd /usr/share/examples/scsi_target; make
6. Build a backing store file
   dd if=/dev/zero of=test_file bs=1m count=20
7. Run the usermode, specifying the appropriate bus/target/lun you wish
the emulated drive to appear on:
   ./scsi_target -d 0:3:0 test_file
8. Go to the initiator HBA and rescan for the new drive using the other
HBA's bus number as below:
   camcontrol rescan 1
9. You should see some debugging messages on the target as commands are
received and processed and then the drive should appear on the initiator
as shown below:
   camcontrol devlist
   <FreeBSD Emulated Disk 0.1>   at scbus1 target 3 lun 0 (pass0,da0)
12. You can now fdisk, disklabel, newfs, and mount the emulated drive.
(Assuming everything is working ok :)

Please report any problems to nate AT root.org

KNOWN BUGS:
none, although much more testing is needed