Re: [PATCH] allow a transport to pre-initialize starget_data

[James Bottomley <jejb@steeleye.com>]

On Mon, 2005-08-15 at 11:41 -0400, Luben Tuikov wrote:
> Hmm, you've 
>     "found an actual use for channel (exposing underlying physical discs
>      of raid devices)".
> 
> I'm completely befuddled James.

For RAID cards in the SCSI subsystem that export RAID devices as SCSI
devices, there's a need of a standard way to get at the underlying
devices (for DV, parameter setting or configuration).  The idea is to
expose these devices on a non zero channel.

> What if we didn't have "channel" (SPI leftover) in the first place?
> Or, if an LU is implemented as a RAID device, how do you find out its
> individual disks?

It's not a SPI leftover.  It's used by HBA's that have two channels that
genuinely share resources.  Although most modern SCSI cards simply have
two chips (and hence two separate HBAs) per channel, there are a few, of
which the qlogic fc card is one, that still have this one chip per two
channels model.

> Is there a spec or standard that you're following in doing this?

It's an OS abstraction, so no.

James