Re: [RFC]: 64 bit LUN/Tags, dummy device in host_queue, host_lock <-> LLDD reentrancy

Mike Anderson
2002-08-26T17:27:46Z

James Bottomley [James.Bottomley@SteelEye.com] wrote:
> ARZEH@de.ibm.com said:
> > Does the use of driverfs-names mean that the HBA driver somehow comes
> > into the discovery-loop for devices (e.g. scan_scsis somehow interacts
> > with the HBA driver to determine which driverfs entry to create.)?
>
> Well, scanning is really only for legacy. Way into the future, I'd like to
> see hotplug notification for device attach events, so no fibre controller ever
> need be troubled by the scan. All they'd do is send a device attach
> notification into SCSI when they detect one. (SCSI would probably then turn
> around and ask for a REPORT_LUNS).
>

There will probably still need to be some form of scan through the
hotplug scripts based on a HAs capability (parallel SCSI, FC loop). A
CAM-3 like indication that the HA is capable of auto discovery or needs
a probe from min-max.

> > Shouldn't there be some sort of rule for LUN (or unit) naming within
> > at least the same hardware class? That is for: parallel, iSCSI, FC,
> > etc. Will the SCSI stack automatically try to discover all devices
> > behind the HBA (e.g, on the FC SAN)? Or will there be an interface to
> > restrict the range, etc?
>
> Yes, there should. But such a rule would only be for maintaining consistency
> within driverfs, and therefore could happily become Patric Mochel's problem.
> If we go the whole hotplug route, discovery would be up to the scsi hotplug
> scripts.
>
> > Lastly, how will you keep track of LUNs in the SCSI stack? Will the
> > current LUN field disappear in favour of a generic character string?
>
> Internally to Scsi_Device, LUNs will be linked by pointers. How we know
> whether such a linkage needs to occur, I'm not yet sure about. In the worst
> case we could use driverfs matching to see if a newly discovered device's PUN
> matches an existing device, or there might be a way for the HBA driver to
> supply the information.
>

James I do not follow the usage of LUNs linked by pointers, can you
explain further?

-Mike
--
Michael Anderson
andmike@us.ibm.com