Date: Wed, 17 Jun 1998 12:40:34 -0700 (PDT)
From: David Kahn <dmk@eng.sun.com>
Subject: Item #440: clarify SET-CALLBACK unset value


P1275 Openboot Working Group Proposal -- Proposal #:440 Ver 1

Title:          Clarification of set-callback client interface

Author:         David Kahn

Date:           Tue Jun 16 17:47:11 PDT 1998

Ed/Tech:        Technical

Synopsis:       Clarify the return value from SET-CALLBACK when the
		callback handler is unset.

Doc & Version:  Core Errata

Problem:        The definition of the SET-CALLBACK client interface,
		in section 6.3.2.6 of the core document states:

			The service sets the callback handler to
			*newfunc* and returns as *oldfunc* the address
			of the entry point of the previously installed
			callback handler function.

		The purpose of returning *oldfunc* is to allow the
		client program to insert a callback handler in a chain
		of callback handlers.

		The text fails to specify the value returned when
		the previous callback handler is unset.

		Sun's existing practice uses the value zero to indicate
		'unset'.

Proposal:       

	Add the following to the core errata:

	The following text augments the definition of the SET-CALLBACK
	client interface, originally defined in section 6.3.2.6 of
	the core specification.

	Change the last sentence of the first paragraph of text in
	the SET-CALLBACK description to:

		The service sets the callback handler to *newfunc*
		and returns in *oldfunc* the address of the entry
		point of the previously installed callback handler
		or the value zero if there is no previously installed
		callback handler.


[ P1275 Item #440 -- Received: Wed Jun 17 12:43:56 PDT 1998 ]