From: "John O'Quin" <oquin@austin.ibm.com>
Subject: Item #403: Re: Item #402: Interrupt Mapping 0.9
Date: Wed, 8 Jan 1997 14:40:05 -0600 (CST)


Ron,

You need to initialize the unit-interrupt-specifier before the begin
for the case where there is no interrupt-parent. The proposal below
does not seem to support the CHRP platform example where the PCI device
nodes do not have interrupt-parent properties and the bridge has the
interrupt-map.

Should the test be to see if the interrupt-map property is present
instead of the #address-cells property? Open Firmware allows for
bridges to not include #address-cells if the value is 2. So you could
have a device node without an interrupt-parent that has a parant that
has an interrupt-map, no #address-cells, and is not an
interrupt-controller.  This applies to all three test of
#address-cells.

Both the present psuedo-code and proposed pseudo-code disallow an
interrupt-map property in an interrupt-controller node. Was this
intentional? Section 3.3 does not read that this is not allowed.

In general, should this not allow skipping nodes that have neither
interrupt-map or interrupt-controller properties?


>	To: Mail list p1275-wg
>	From: <ron@apple.com>
>
>P1275 Open Firmware Working Group Proposal -- Proposal #402 Ver 1
>
>Title:          map-interrupt procedure change
>
>Author:         Ron Hochsprung
>
>Date:           1/7/97
>
>Ed/Tech:        Technical
>
>Synopsis:
>	Updates the map-interrupt procedure to handle common special case
>	of direct interrupt-parent.
>
>Doc & Version:  Interrupt Mapping recommended practice 0.9
>
>Problem:
>
>	We have run in to a common case where a device can directly point to
>	an interrupt controller (via the "interrupt-parent" property), where
>	the interpretation of its "interrupts" property should be the resulting
>	unit-interrupt-specifier, without having its unit-address used.
>
>Proposal:
>
>	Change the map-interrupt procedure to include code at the front that
>	checks if the device-node contains an "interrupt-parent" property.  If 
>so,
>	use the parent's node to determine if the unit-address of the device-node
>	should be considered part of the unit-interrupt-specifier.
>
>The following code shows the updated procedure:
>
>***** BEGIN CODE *****
>procedure map-interrupt( device-node, interrupt-specifier )
>
>	this-node = device-node
>	unit-address = valueof( "reg"[0], this-node )
>	if present( "interrupt-parent", this-node )
>		parent-node = valueof( "interrupt-parent", this-node )
>		if present( "#address-cells", parent-node )
>			unit-interrupt-specifier = cat( unit-address, interrupt-specifier )
>		  else
>			unit-interrupt-specifier = interrupt-specifier
>		this-node = parent-node
>
>	begin				\ loop up tree until we reach the root
>
>		if present( "interrupt-controller", this-node )
>			if present( "interrupt-parent", this-node )
>				parent-node = valueof( "interrupt-parent", this-node )
>				if present( "#address-cells", parent-node )
>					unit-address = valueof( "reg"[0], this-node )
>				  else
>					unit-address = NULL
>				  then
>				interrupt-specifier = valueof( "interrupts", this-node )
>				unit-interrupt-specifier = cat( unit-address, interrupt-specifier )
>				this-node = parent-node
>			  else		\ this is the root node, we're done
>				return( unit-interrupt-specifier )
>			  then
>
>		else			\ not "interrupt-controller"
>		if present( "interrupt-map", this-node )	\ we have a mapping to perform
>			if present( "interrupt-map-mask", this-node )
>				mask = valueof( "interrupt-map-mask" )
>				unit-interrupt-specifier = unit-interrupt-specifier & mask
>			  then
>			init-decode-cells( "interrupt-map", this-node )
>			found? = false
>			begin
>				child-specifier = decode-cells( sizeof( unit-interrupt-specifier ) )
>				parent-node = decode-cells( 1 )
>				if present( "#address-cells", parent-node )
>					#cells = valueof( "#address-cells", parent-node )
>				  else
>					#cells = 0
>				  then
>				#cells = #cells + valueof( "#interrupt-cells", parent-node )
>				if child-specifier == unit-interrupt-specifier
>					found? = true
>				  else
>					dummy = decode-cells( #cells )
>				  then
>				until found?
>			interrupt-specifier = decode-cells( #cells )
>			if present( "#address-cells", parent-node)
>				unit-address = valueof( "reg"[0], this-node )
>			  else
>				unit-address = NULL
>			  then
>			unit-interrupt-specifier = cat( unit-address, interrupt-specifier )
>			this-node = parent-node
>
>        else            \ no "interrupt-map" table
>        if present( "interrupt-parent", this-node )
>            this-node = valueof( "interrupt-parent", this-node )
>
>        else            \ by default, use our device-tree parent
>            this-node = device-tree-parent( this-node )
>        then
>        again
>***** END CODE *****
>
>[ P1275 Item #402 -- Received: Tue Jan  7 11:10:51 PST 1997 ]

[ P1275 Item #403 -- Received: Wed Jan  8 12:39:59 PST 1997 ]