From: Michael Segapeli <mikes@austin.ibm.com>
Subject: Item #280: Device Support Extensions V0.2, Req. for SCSI Devices
Date: Wed, 02 Aug 95 15:25:27 -0600


P1275 Open Firmware Working Group Proposal -- Proposal #280 Ver 1

Title:		Additional Requirements for SCSI devices

Author:		Mike Segapeli

Date:		August 2, 1995

Ed/Tech:	     Technical

Synopsis:	     Clarify requirements for SCSI devices 

Doc & Version:	Device Support Extensions Version 0.2 Draft

Problem:	     For SCSI devices, it is not quite clear which
               methods are required.  

Proposal:	

 Add the following text as new sections to the Device Support Extensions 
 Document:

  New Section: Additional Requirements for SCSI Devices

       A node representing a SCSI-II device shall implement all the 
       methods and properties specified in Annex E, sections E.1 through
       E.5 of [1] (This is the Core Requirements Specifications)


  New Section: Additional Requirements for Block and Byte Devices

       The "disk-label" standard support package and packages of device
       type "block" and "byte" shall implement the following method:

       size  ( -- d )                                      M

       Return the size of the device in bytes.

       Return, as a double number "d", the number of bytes of storage
       associated with the device or instance.  If the size cannot be
       determined, return the double number -1.

       Packages of device type "block" and "byte" shall implement the 
       following method:

       #blocks  ( -- u )                                    M

       Return the size of the device in blocks.

       Return, as an unsigned number "u", the number of blocks of storage
       associated with the device or instance, where a "block" is a unit
       of storage consisting of the number of bytes returned by the package's
       "block-size" method.  If the size cannot be determined, or if the
       number of blocks exceeds the range of an unsigned number, return
       the maximum unsigned integer (which, because of Open Firmware's
       assumption of two's complement arithmetic) is equivalent to the
       signed number -1).


  New Section: Additional Requirements for Block Devices

       The "disk-label" standard support package and packages of device
       type "block" shall implement the following methods:
       offset-low : returns least significant cell of the double number
                    denoting the beginning offset of the disk partition
                    that was specified when the "disk-label" support 
		    package was opened.  In general that offset is
		    obtained by executing the "offset" method of the
		    "disk-label" support package with an agrument of
		    zero.  It is permissable for the disk package to
		    execute the "disk-label" support package's "offset"
		    method once after opening that support package,
		    storing the result for later use.

       offset-high : returns most significant cell of the double number
                     denoting the beginning offset of the disk partition
                     that was specified when the "disk-label" support 
		     package was opened.  In general that offset is
		     obtained by executing the "offset" method of the
		     "disk-label" support package with an agrument of
		     zero.  It is permissable for the disk package to
		     execute the "disk-label" support package's
		     "offset" method once after opening that support
		     package, storing the result for later use.


[ P1275 Item #280 -- Received: Wed Aug  2 13:29:07 PDT 1995 ]