Date: Tue, 21 Mar 1995 13:57:05 -0800
From: brianh@pongo.West.Sun.COM (Brian Horn)
Subject: Item #255: Virtual mode rules for PowerPC should be revised

P1275 Open Firmware Working Group Proposal -- Proposal #255 Ver 1.0

Title:		Alteration of Virtual Mode rules

Author:		Brian.Horn@west.sun.com

Date:		March 21, 1995

Ed/Tech:	Technical

Synopsis:	The OpenFirmware virtual mode rules are inappropriate

Doc & Version:	PowerPC binding to OpenFirmware Draft 1.0 2/16/95

Problem:	Use of BATs could be allowed (assuming other restrictions)

Proposal:	Page 6 line 28 states:

		shall not use BATs during client of user interface operations.

		The real issue is granularity and mapping modes allowed.

		Suggestion: drop that line and substitute:

		OpenFirmware may use any virtual mode mapping method it wishes
		up to the point where the client takes over memory management.
		The client indicates this by doing the "set-callback" service
		after which OpenFirmware will do *no* further direction
		manipulation of memory, but rather request the client implement
		the requests.

		[ed. note this allows any use of the segment registers as well
		 as the BAT registers that OpenFirmware might find useful]

[ P1275 Item #255 -- Received: Tue Mar 21 13:59:21 PST 1995 ]