linux-kernel - [RFC PATCH 18/77] dtc-parser.y: Avoid an empty proplist

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Message-ID: <20260112142009.1006236-19-herve.codina@bootlin.com>
Date: Mon, 12 Jan 2026 15:19:08 +0100
From: Herve Codina <herve.codina@...tlin.com>
To: David Gibson <david@...son.dropbear.id.au>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>
Cc: Ayush Singh <ayush@...gleboard.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	devicetree-compiler@...r.kernel.org,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	devicetree-spec@...r.kernel.org,
	Hui Pu <hui.pu@...ealthcare.com>,
	Ian Ray <ian.ray@...ealthcare.com>,
	Luca Ceresoli <luca.ceresoli@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Herve Codina <herve.codina@...tlin.com>
Subject: [RFC PATCH 18/77] dtc-parser.y: Avoid an empty proplist

In the dts parser grammar, a nodedef is defined by
  '{' proplist subnodes '}' ';'
with both proplist and subnodes that can be empty lists.

Soon a new list will be added in the nodedef related to export symbol
list.

Having all those lists with support for empty lists will lead to some
Bison warnings:
  warning: 4 shift/reduce conflicts [-Wconflicts-sr]
  warning: 1 reduce/reduce conflict [-Wconflicts-rr]

The simpler way to remove those warning and thus have a robust parsing
is to avoid those empty lists.

Update the proplist definition and nodedef definition to avoid those
multiple empty lists. Instead of allowing a proplist to be an empty
list, force the list to be a non empty one and update the nodedef to
handle explicitly the absence of the proplist to support the case where
no properties are available, i.e. the case of a node composed only of
sub-nodes.

This doesn't change the functional behavior.

Signed-off-by: Herve Codina <herve.codina@...tlin.com>
---
 dtc-parser.y | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/dtc-parser.y b/dtc-parser.y
index d8914d2..2e152b0 100644
--- a/dtc-parser.y
+++ b/dtc-parser.y
@@ -272,12 +272,16 @@ nodedef:
 		{
 			$$ = build_node($2, $3, &@$);
 		}
+	| '{' subnodes '}' ';'
+		{
+			$$ = build_node(NULL, $2, &@$);
+		}
 	;

 proplist:
-	  /* empty */
+	  propdef
 		{
-			$$ = NULL;
+			$$ = chain_property($1, NULL);
 		}
 	| proplist propdef
 		{
-- 
2.52.0