1. Introduction
   1.1. Project/Component Working Name:
	SAS Phy Identifier Binary Representation Update

   1.2. Name of Document Author/Supplier:
	Tarl Neustaedter
        Stephen Ehring

   1.3. Date of This Document:
	05/10/2010
	
2. Project Summary

   This project modifies the SAS phy identifier binary representation in order
   to handle phys on SAS expanders.

3. Business Summary

   3.1. Problem Area:

        Some SPARC platforms (Serpa in this case) support different disk
        backplanes, some of which contain a SAS expander. With the current
        SAS binding implementation, there is currently no way to uniquely
        identify a disk in a static manner since the phy identifier binary
        representation only allows for one phy number. What is needed is some
        way to represent this nested phy identifier configuration.


4. Technical Description:

    4.1. Details:

        To solve this problem we are proposing an update the the SAS
        binding [1], specifically the section 3.1.1.1.2 "Phy Identifier
        Binary Representation". The new description will read:

3.1.1.1.2  Phy Identifier Binary Representation

This representation identifies a phy on the SAS adapter or a directly connected expander.

               Bit #   33222222 22221111 11111100 00000000
                       10987654 32109876 54321098 76543210

       sas.hi cell:    00000000 00000000 00000000 00000000
       sas.lo cell:    00000000 00000001 jjjjjjjj iiiiiiii
       lun.hi cell:    uuuuuuuu uuuuuuuu uuuuuuuu uuuuuuuu
       lun.lo cell:    uuuuuuuu uuuuuuuu uuuuuuuu uuuuuuuu

where:
   00..00        Bits with the value zero
       ii..ii          8-bit unsigned number phy identifier in the range
                       of 0..FE .
       jj..jj          Expander identifier. Either zero (indicating the PHY number
                       iiiiiiii is on the SAS adapter itself) or identifies the PHY
                       connecting to the expander, in which case iiiiiiii identifies
                       a PHY on a SAS expander. In the non-zero case, jjjjjjjj is an
                       8-bit unsigned number of the PHY plus one, in the range 1..FF
       uu..uu          64-bit unsigned number logical unit number

Note: The high order 47 bits sas.hi ... sas.lo are required to be zero in
this form, and bit 16 of sas.lo is required to be one.

    4.2 Exported Interfaces:

    Interface			Classification	Comments
    ------------------------    --------------- ----------------------------
    SAS Phy Identifier Binary   Uncommitted     New binding is located in materials
    Representation as described                 directory.
    in this document (4.1)

5. Reference Documents:

   [1] SAS Binding

   http://sac.eng/Archives/CaseLog/arc/FWARC/2008/013/commitment2.materials/sas-bindings-r1.9.txt