of: implement of_prepend_property

Like of_append_property for adding at the end of properties, implement
of_prepend_property for placing data into the front.

This is especially useful to fixup most-specific compatibles into
existing nodes.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20220912155436.1565755-1-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

3 files changed, 39 insertions, 1 deletions

diff --git a/drivers/of/base.c b/drivers/of/base.c
index d2e7ea4ae7..9b32215740 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2378,6 +2378,36 @@ int of_append_property(struct device_node *np, const char *name, const void *val
 	return 0;
 }
 
+int of_prepend_property(struct device_node *np, const char *name, const void *val, int len)
+{
+	struct property *pp;
+	const void *oldval;
+	void *buf;
+	int oldlen;
+
+	pp = of_find_property(np, name, &oldlen);
+	if (!pp) {
+		of_new_property(np, name, val, len);
+		return 0;
+	}
+
+	oldval = of_property_get_value(pp);
+
+	buf = malloc(len + oldlen);
+	if (!buf)
+		return -ENOMEM;
+
+	memcpy(buf, val, len);
+	memcpy(buf + len, oldval, oldlen);
+
+	free(pp->value);
+	pp->value = buf;
+	pp->length = len + oldlen;
+	pp->value_const = NULL;
+
+	return 0;
+}
+
 int of_property_sprintf(struct device_node *np,
 			const char *propname, const char *fmt, ...)
 {
diff --git a/include/of.h b/include/of.h
index 392227e755..2c3b52d156 100644
--- a/include/of.h
+++ b/include/of.h
@@ -135,6 +135,8 @@ extern int of_set_property(struct device_node *node, const char *p,
 			const void *val, int len, int create);
 extern int of_append_property(struct device_node *np, const char *p,
 			      const void *val, int len);
+extern int of_prepend_property(struct device_node *np, const char *name,
+			       const void *val, int len);
 extern struct property *of_new_property(struct device_node *node,
 				const char *name, const void *data, int len);
 extern struct property *of_new_property_const(struct device_node *node,
@@ -538,6 +540,12 @@ static inline int of_append_property(struct device_node *np, const char *p,
 	return -ENOSYS;
 }
 
+static inline int of_prepend_property(struct device_node *np, const char *name,
+				      const void *val, int len)
+{
+	return -ENOSYS;
+}
+
 static inline struct property *of_new_property(struct device_node *node,
 				const char *name, const void *data, int len)
 {
diff --git a/test/self/of_manipulation.c b/test/self/of_manipulation.c
index 7e30a60ca6..f7f95fa269 100644
--- a/test/self/of_manipulation.c
+++ b/test/self/of_manipulation.c
@@ -103,9 +103,9 @@ static void test_of_property_strings(struct device_node *root)
 
 	of_append_property(np4, "property-single", "ayy", 4);
 
-	of_append_property(np4, "property-multi", "ayy", 4);
 	of_append_property(np4, "property-multi", "bee", 4);
 	of_append_property(np4, "property-multi", "sea", 4);
+	of_prepend_property(np4, "property-multi", "ayy", 4);
 
 	assert_equal(np3, np4);
 }