P1394 Mail Archive: Re: P1394> SBP-2 Targets

P1394 Mail Archive: Re: P1394> SBP-2 Targets

Re: P1394> SBP-2 Targets

From: Eric Anderson (ewa@apple.com)
Date: Tue Sep 12 2000 - 14:50:49 EDT

  • Next message: Peter Johansson: "Re: P1394> SBP-2 Targets"

    Multiple targets, represented by multiple Unit Directories, are
    fully allowed by the SBP-2 and 1394 specs. A computer, in
    particular, is likely to publish multiple SBP-2 units for
    unrelated purposes.

    In principle, multiple targets represented by multiple unit
    directories would be fully independent, aside from sharing
    a node's characteristics such as node ID and GUID. In practice
    the level of independence depends on the sophistication of
    your microcontroller.

    I haven't kept up with the 1212r work; it may change the
    terminology somewhat. But I don't believe it adds any
    restrictions or limits to what 1394 and SBP-2 allow. In
    particular if you have multiple instance directories, and
    each one has a (different) unit directory associated with
    it, I believe that would represent multiple targets.

    Multiple instance directories, each pointing to the same unit
    directory, would be different (if 1212r allows that). The unit
    directory would have a single management agent; each node is
    limited to at most one login to that agent (by SBP-2); this would
    effectively be a single target.

    I'm not sure if I'm on the t10@t10.org mailing list (or if I can
    post to it), by the way.

    Eric Anderson
    Apple Computer

    >Hi All,
    >Recently I have been involved in some discussions about what
    >constitutes an SBP-2 Target; these discussions have pointed out
    >some areas of the SBP-2 spec that are kind of fuzzy. I'm posting
    >this question to get an idea of how this issue is viewed by the
    >rest of the industry.
    > target: A node that receives device service or management
    >requests from an initiator....
    >This has been interpreted to mean that there is only one SBP-2 target
    >per node.
    >4.1 Unit Architecture
    >In CSR architecture and Serial Bus terminology, targets implemented
    >to this standard are units. A Serial Bus node that implements a
    >target has a unit directory in configuration ROM that identifies the
    >presence and capabilities of the target.
    >This implies that each SBP-2 unit directory is a separate target.
    >The case not covered by the SBP-2 specification is the one where
    >there are multiple instance directories each containing an SBP-2
    >unit directory. Is this one target or multiple targets? I have
    >been assuming that this represents multiple targets; are my
    >assumptions correct?
    >Chuck Rice
    >Software Engineer
    >Hewlett Packard Company
    >Vancouver Division
    >18110 SE 34th Street
    >Vancouver, WA 98683

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