Re: FireWire/SBP2 Target mode

[Stefan Richter <stefanr@s5r6.in-berlin.de>]

On Aug 17 Chris Boot wrote:
> Now that we have a nice SCSI target framework in the kernel, and drivers 
> either in-tree or being worked on for iSCSI, FC, FCoE, SAS and iSER, I 
> was wondering about the possibility of adding FireWire to that list. 
> Apple Macs have had a FireWire Target Disk mode for a long time, and 

Side note:  This target mode is a feature of their OpenFirmware and EFI
firmwares, not of the Mac OS and the OS X.  Though both firmware- and
operating-system-implemented SBP-2 targets certainly have their use cases.
Aside from the SBP-2 target in Macs and from Oracle Endpoint, I only know
of SBP-2 targets that are built upon dedicated bus bridge silicon.

> there is even a program called Endpoint[1] that apparently does this on 
> Linux though it looks completely untouched since 2003 and no longer 
> works as it depends on the old FireWire stack.

It can be made to work again if it and libraw1394 are slightly extended to
use a different API for Configuration ROM changes.  Or Endpoint could be
ported from libraw1394 to <linux/firewire-cdev.h>.  But then it would of
course not benefit from the generic SCSI target infrastructure, e.g. WRT
administration, backing storage choices, or command set support.

> I would very much like to see something like this added to the kernel, 
> and would very much like to contribute to writing this feature. However 
> my kernel development knowledge is very limited indeed so this would 
> require a lot hand-holding and mentoring.
> 
> What's the interest in such a feature?

People keep asking for it; very infrequently though.

> Would anyone be able to give some (a lot?) of their time to help write
> this?
> 
> Thanks,
> Chris
> 
> [1] http://oss.oracle.com/projects/endpoint/

I for one can answer questions about firewire-core's driver API but do not
have much spare time for more, for the time being.

BTW, a kernelspace SBP-2 target drivers would use several of the FireWire
features that the firewire-net driver uses too.  So the sources of that
driver may be of help where the firewire-core kerneldoc comments are
missing or are not providing the bigger picture.
-- 
Stefan Richter
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http://arcgraph.de/sr/