SBP2 Rev 4 Issues: Speed to Use for Fetches and Unit_Unique_ID definition

Nagaraj G GNagaraj at wipinfo.soft.net
Mon Sep 13 23:59:52 PDT 1999


* From the T10 Reflector (t10 at t10.org), posted by:
* "Nagaraj G" <GNagaraj at wipinfo.soft.net>
*
Hi All,

I have some questions about SBP2 Specification Rev 4.

Question 1: Speed of Fetching

Section 8.2 says,

"The speed at which the block write request to the MANAGEMENT_AGENT register
is received shall determine the speed used by the target for all subsequent
requests to read the initiator's configuration ROM, fetch ORB's from
initiator memory or store status at the initiator's status_FIFO. Command
block ORB's separately specify the speed for requests addressed to the data
buffer or page table".

And section 8.3 says,

"The speed at which the block write request to the MANAGEMENT_AGENT register
is received shall determine the speed used by the target for all subsequent
requests to read the initiator's configuration ROM, fetch ORB's from
initiator memory or store status at the initiator's status_FIFO. This
replaces the speed most recently obtained from the prior login or reconnect
request".

My question is, if this was designed with IEEE 1394-1995 also in mind, where
is the speed code available on the receiver side and where is it on the
transmitter side. The packet formats in IEEE Standard 1394-1995 and P1394a
Draft (latest) do not have any speed field in the packet formats. So how do
you think that this mandating (shall) be achieved by the SBP2
implementations when it does not have access to speed definitions.

Do you intend to have this feature mandated by the hardware LINK layer
implementations (like OHCI) so that the interfaces provide such support?

Question 2: Unit Unique ID in Configuration ROM

Section 7.4.12 says,

"The Unit_Unique_ID entry is an optional leaf entry in the unit directory
that describes the location of the unit unique ID leaf within configuration
ROM. If a vendor implements a device with multiple Serial Bus access paths,
i.e., multiple links to Serial Bus each of which receives a distinct node_ID
as the result of Serial Bus initialization or bus enumeration, the
Unit_Unique_ID entry shall be implemented".

And section 7.6 says,

"Although the node unique ID (EUI-64) present in the bus information block
is sufficient to uniquely identify nodes attached to Serial Bus, it is
insufficient to identify a target when a vendor implements a device with
multiple Serial Bus node connections. In this case initiator software
requires information by which a particular target may be uniquely
identified, regardless of the Serial Bus access path used".

My question is, if the initiator identifies the target (having multiple
serial bus access paths) as a single unit with the Unit_Unique_ID, then how
should it identify the Logical Units on the target unit in each serial bus
access path.

For example take the case of a target unit having two serial bus access
paths and having two Logical Units (LUN0 and LUN1) on each path (i.e., it
has four LUNs two on each access path). Since it should have the same
Unit_Unique_ID in the Configuration ROM in both the serial bus access paths,
the initiator identifies the target unit as a single unit. But now there are
two LUNs in each access path which are not linked together on the target
unit side. Suppose the initiator wants to login into each of the LUNs, how
should it go about? Should the initiator keep a map of the LUNs on each
serial bus access path and login separately on that path or should this be
taken care at the target side with a mapping of the LUNs of one path on the
other.

Hope you have understood the questions. If you need more clarification, pls.
reply.



Pls reply. I hope the working group of T10 is still in sync with the SBP2
specification and I hopw to get a reply

Thanks in advance

G. Nagaraj
Senior Software Engineer
EnThink Inc.
37, Castle Street, Ashok Nagar,
Bangalore - 560 025, India
Phone: +91-80-536-7297 Ext: 211
Fax: +91-80-557-6032
www.EnThink.com


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