[PATCH 1/2] dtc: Add /append-property/

[Ayush Singh <ayush@beagleboard.org>]

Allow appending values to a property instead of overriding the previous
values of property.

Currently, we have /delete-node/ and /delete-property/, but lack
/append-property/. Hence we end up having to repeat all existing values
when appending to a property (e.g. see [1] appending to clocks from
[2]).

This functionality is also important for creating a device tree based
implementation to support different types of addon-boards such as
mikroBUS, Grove [3], etc.

[3] https://lore.kernel.org/linux-arm-kernel/20240702164403.29067-1-afd@ti.com/
[2] https://elixir.bootlin.com/linux/latest/source/arch/arm64/boot/dts/renesas/r8a77951-salvator-xs.dts#L39
[1] https://elixir.bootlin.com/linux/latest/source/arch/arm64/boot/dts/renesas/r8a77951.dtsi#L3334

Signed-off-by: Ayush Singh <ayush@beagleboard.org>
---
 dtc-lexer.l  |  7 +++++++
 dtc-parser.y |  6 ++++++
 dtc.h        |  3 +++
 livetree.c   | 30 +++++++++++++++++++++++++-----
 4 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/dtc-lexer.l b/dtc-lexer.l
index de60a70..5da4ca5 100644
--- a/dtc-lexer.l
+++ b/dtc-lexer.l
@@ -137,6 +137,13 @@ static void PRINTF(1, 2) lexical_error(const char *fmt, ...);
 			return DT_DEL_NODE;
 		}
 
+<*>"/append-property/"	{
+			DPRINT("Keyword: /append-property/\n");
+			DPRINT("<PROPNODENAME>\n");
+			BEGIN(PROPNODENAME);
+			return DT_APP_PROP;
+		}
+
 <*>"/omit-if-no-ref/"	{
 			DPRINT("Keyword: /omit-if-no-ref/\n");
 			DPRINT("<PROPNODENAME>\n");
diff --git a/dtc-parser.y b/dtc-parser.y
index 4d5eece..94ce405 100644
--- a/dtc-parser.y
+++ b/dtc-parser.y
@@ -58,6 +58,7 @@ static bool is_ref_relative(const char *ref)
 %token DT_BITS
 %token DT_DEL_PROP
 %token DT_DEL_NODE
+%token DT_APP_PROP
 %token DT_OMIT_NO_REF
 %token <propnodename> DT_PROPNODENAME
 %token <integer> DT_LITERAL
@@ -296,6 +297,11 @@ propdef:
 			$$ = build_property_delete($2);
 			free($2);
 		}
+	| DT_APP_PROP DT_PROPNODENAME '=' propdata ';'
+		{
+			$$ = build_property_append($2, $4, &@$);
+			free($2);
+		}
 	| DT_LABEL propdef
 		{
 			add_label(&$2->labels, $1);
diff --git a/dtc.h b/dtc.h
index 4c4aaca..06771c5 100644
--- a/dtc.h
+++ b/dtc.h
@@ -205,6 +205,7 @@ struct bus_type {
 
 struct property {
 	bool deleted;
+	bool append;
 	char *name;
 	struct data val;
 
@@ -263,6 +264,8 @@ void delete_labels(struct label **labels);
 struct property *build_property(const char *name, struct data val,
 				struct srcpos *srcpos);
 struct property *build_property_delete(const char *name);
+struct property *build_property_append(const char *name, struct data val,
+				       struct srcpos *srcpos);
 struct property *chain_property(struct property *first, struct property *list);
 struct property *reverse_properties(struct property *first);
 
diff --git a/livetree.c b/livetree.c
index 49f7230..74eca1b 100644
--- a/livetree.c
+++ b/livetree.c
@@ -62,6 +62,20 @@ struct property *build_property_delete(const char *name)
 	return new;
 }
 
+struct property *build_property_append(const char *name, struct data val,
+				       struct srcpos *srcpos)
+{
+	struct property *new = xmalloc(sizeof(*new));
+
+	memset(new, 0, sizeof(*new));
+	new->name = xstrdup(name);
+	new->append = true;
+	new->val = val;
+	new->srcpos = srcpos_copy(srcpos);
+
+	return new;
+}
+
 struct property *chain_property(struct property *first, struct property *list)
 {
 	assert(first->next == NULL);
@@ -151,8 +165,8 @@ struct node *merge_nodes(struct node *old_node, struct node *new_node)
 	for_each_label_withdel(new_node->labels, l)
 		add_label(&old_node->labels, l->label);
 
-	/* Move properties from the new node to the old node.  If there
-	 * is a collision, replace the old value with the new */
+	/* Move properties from the new node to the old node. If there
+	 * is a collision, replace/append the old value with the new */
 	while (new_node->proplist) {
 		/* Pop the property off the list */
 		new_prop = new_node->proplist;
@@ -165,15 +179,21 @@ struct node *merge_nodes(struct node *old_node, struct node *new_node)
 			continue;
 		}
 
-		/* Look for a collision, set new value if there is */
+		/* Look for a collision, set new value/append if there is */
 		for_each_property_withdel(old_node, old_prop) {
 			if (streq(old_prop->name, new_prop->name)) {
 				/* Add new labels to old property */
 				for_each_label_withdel(new_prop->labels, l)
 					add_label(&old_prop->labels, l->label);
 
-				old_prop->val = new_prop->val;
-				old_prop->deleted = 0;
+				if (new_prop->append) {
+					old_prop->val = data_merge(old_prop->val, new_prop->val);
+				} else {
+					old_prop->val = new_prop->val;
+				}
+
+				old_prop->deleted = false;
+				old_prop->append = false;
 				free(old_prop->srcpos);
 				old_prop->srcpos = new_prop->srcpos;
 				free(new_prop);

-- 
2.46.0