scst/qla2x00t/qla2x00-target

Target driver for Qlogic 2200/2300 Fibre Channel cards
======================================================

Version 1.0.1, XX XXXX 2008
---------------------------

This driver has all required features and looks to be quite stable (for
beta) and useful. It consists from two parts: the target mode driver
itself and the changed initiator driver from Linux kernel, which is,
particularly, intended to perform all the initialization and shutdown
tasks. This driver was changed to provide the target mode support and
all necessary callbacks, but it's still capable to work as initiator
only. Mode, when a host acts as the initiator and the target
simultaneously, is supported as well.

This version is compatible with SCST core version 1.0.1 and higher and
Linux kernel 2.6.27 and higher. Backport patches to kernels earlier than
2.6.27 are welcome.

The original initiator driver was taken from the kernel 2.6.27.

If you need to use this driver on kernels prior 2.6.27, it is
recommended to use version 1.0.0.x of this driver, taken from branch
1.0.0.x. For 2.6.26 you can also use version of this driver from SVN
trunk/ revision 577.

See also "ToDo" file for list of known issues and unimplemented 
features.

Installation
------------

Only vanilla kernels from kernel.org and RHEL/CentOS 5.2 kernels are
supported, but SCST should work on other (vendors') kernels, if you
manage to successfully compile on them. The main problem with vendors'
kernels is that they often contain patches, which will appear only in
the next version of the vanilla kernel, therefore it's quite hard to
track such changes. Thus, if during compilation for some vendor kernel
your compiler complains about redefinition of some symbol, you should
either switch to vanilla kernel, or add or change as necessary the
corresponding to that symbol "#if LINUX_VERSION_CODE" statement.

At first, make sure that the link "/lib/modules/`you_kernel_version`/build" 
points to the source code for your currently running kernel.

Then you should replace (or link) by the initiator driver from this
package "qla2xxx" subdirectory in kernel_source/drivers/scsi/ of the
currently running kernel and using your favorite kernel configuration
tool enable in the QLogic QLA2XXX Fibre Channel driver target mode
support (CONFIG_SCSI_QLA2XXX_TARGET). Then rebuild the kernel and its
modules. During this step you will compile the initiator driver. To
install it, install the built kernel and its modules.

Then edit qla2x00-target/Makefile and set SCST_INC_DIR variable to point
to the directory, where SCST's public include files are located. If you
install QLA2x00 target driver's source code in the SCST's directory,
then SCST_INC_DIR will be set correctly for you.

Also you can set SCST_DIR variable to the directory, where SCST was
built, but this is optional. If you don't set it or set incorrectly,
during the compilation you will get a bunch of harmless warnings like
"WARNING: "scst_rx_data" [/XXX/qla2x00tgt.ko] undefined!"

To compile the target driver, type 'make' in qla2x00-target/
subdirectory. It will build qla2x00tgt.ko module.

To install the target driver, type 'make install' in qla2x00-target/
subdirectory. The target driver will be installed in
/lib/modules/`you_kernel_version`/extra. To uninstall it, type 'make
uninstall'.

After the drivers are loaded and adapters successfully initialized by
the initiator driver, including firmware image load, the target mode
should be enabled via a sysfs interface on a per card basis. Under the
appropriate scsi_host there is an entry target_mode_enabled, where you
should write "1", like:

echo "1" >/sys/class/scsi_host/host0/target_mode_enabled

Then you should configure exported devices using the corresponding
interface of SCST core. It is highly recommended to use scstadmin
utility for that purpose.

Compilation options
-------------------

There are the following compilation options, that could be commented
in/out in Makefile:

 - CONFIG_SCST_DEBUG - turns on some debugging code, including some logging.
   Makes the driver considerably bigger and slower, producing large amount of
   log data.

 - CONFIG_SCST_TRACING - turns on ability to log events. Makes the driver
   considerably bigger and leads to some performance loss.

 - CONFIG_QLA_TGT_DEBUG_WORK_IN_THREAD - makes SCST process incoming
   commands from the qla2x00t target driver and call the driver's
   callbacks in internal SCST threads context instead of SIRQ context,
   where those commands were received. Useful for debugging and lead to
   some performance loss.
   
Credits
-------

Thanks to 

 * Nathaniel Clark <nate@misrule.us> for porting to new 2.6 kernel
initiator driver.

 * Mark Buechler <mark.buechler@gmail.com> for the original
WWN-based authentification, a lot of useful suggestions, bug reports and
help in debugging.

 * Ming Zhang <mingz@ele.uri.edu> for his fixes.

Vladislav Bolkhovitin <vst@vlnb.net>, http://scst.sourceforge.net