how CAM/HBA probe for devices?

[Dan Nelson]

In the last episode (Feb 08), Scott Long said:
> For iSCSI, this obviously won't work.  CAM has no concept of iSCSI
> addresses, and even if it did, doing a linear scan of even a small
> subnet would be prohibitively expensive.  What is really needed is a
> new XPT layer that understands iSCSI.  By this, I mean a layer that
> understands how to properly scan and detect targets, how to log into
> them, etc.  It should also have a certain amount of flexibility so
> that hardware-assisted solutions can plug in and pick-and-choose the
> pieces they need from the transport layer.
>
> Lucent did an iSCSI initiator for FreeBSD 4.x a while back and I
> think they got around all of this by telling CAM not to auto-scan at
> boot, followed by having the driver announce devices to CAM directly
> (look at the ATAPI-CAM code for an example of how to do this) and do
> all the detection and login work behind CAM's back.  This really
> should only be considered a hack though.  If you're interested, I
> might be able to dig up the link to it.  We never pursued integrating
> it to the FreeBSD tree because of very restrictive licensing terms on
> it.

The fibre-channel drivers (isp,mpt) must have been the first to have
hit this problem; do they do the same thing as atapicam?

-- 
	Dan Nelson
	dnelson at allantgroup.com