[PATCH] of: implement of_prepend_property

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

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>
---
 drivers/of/base.c           | 35 +++++++++++++++++++++++++++++++++++
 include/of.h                |  8 ++++++++
 test/self/of_manipulation.c |  2 +-
 3 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 212b226eb55c..e208949b08bd 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2378,6 +2378,41 @@ 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;
+	int orig_len;
+	const void *orig_buf;
+	void *buf;
+
+	if (!np)
+		return -ENOENT;
+
+	pp = of_find_property(np, name, NULL);
+	if (!pp) {
+		of_new_property(np, name, val, len);
+		return 0;
+	}
+
+	orig_len = pp->length;
+	buf = realloc(pp->value, orig_len + len);
+	if (!buf)
+		return -ENOMEM;
+
+	orig_buf = pp->value_const ?: buf;
+	if (orig_buf) {
+		memmove(buf + len, orig_buf, orig_len);
+		pp->value_const = NULL;
+	}
+
+	memcpy(buf, val, len);
+
+	pp->value = buf;
+	pp->length += len;
+
+	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 153e75d3e51d..052d5fcad84c 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,
@@ -536,6 +538,12 @@ 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 7e30a60ca687..f7f95fa269af 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);
 }
-- 
2.30.2