Date: Fri, 24 Mar 1995 08:53:10 -0700
From: ron@apple.com (Ron Hochsprung)
Subject: Item #264: PCI Binding, relocatable I/O below 64 KB

P1275 Open Firmware Working Group Proposal -- Proposal #264 Ver 1.5

Title:          I/O-space below 64K

Author:         Ron Hochsprung

Date:           March 24, 1995

Ed/Tech:        Technical

Synopsis:       Add interpretation of 't' bit for relocatable I/O

Doc & Version:  PCI Binding 1.4/1.5

Problem:        Devices are allowed (although, not documented!!!) to
                have I/O base registers that do not implemented their
                upper 16 bits.  I.e., they require that the upper 16
                bits are 0 and report their address space requirement
                by returning only the low-order 16 bits.

Proposal:

I am adding the proposed wording to the 1.5 draft, since I have to re-send
it anyway.  The wording proposed for this change is indicated by revision bars
on both the left and right.  It basically uses the 't'-bit to indicate that a
relocatable I/O Space address has to be allocated within the first 64 KB of
I/O space.  Note that this use of the 't'-bit is distinguished in the "reg"
property by being associated with a relocatable ('n'-bit = 0) entry;  the
corresponding "assigned-addresses" entry has the 't'-bit = 0.

Ron



[ P1275 Item #264 -- Received: Fri Mar 24 10:21:58 PST 1995 ]