[PATCH 3/3] of: implement new of_property_sprintf

[Ahmad Fatoum]

Board code may compute values for device tree properties and write them
as strings. Make this easier by adding a of_property_write_string
variant that does formatted output. This also saves an allocation,
because asprintf buffer is reused.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
 drivers/of/base.c | 57 ++++++++++++++++++++++++++++++++++++++---------
 include/of.h      |  2 ++
 2 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 065265ec9756..321022f2b391 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2157,6 +2157,21 @@ struct device_node *of_new_node(struct device_node *parent, const char *name)
 	return node;
 }
 
+static struct property *__of_new_property(struct device_node *node, const char *name,
+		void *data, int len)
+{
+	struct property *prop;
+
+	prop = xzalloc(sizeof(*prop));
+	prop->name = xstrdup(name);
+	prop->length = len;
+	prop->value = data;
+
+	list_add_tail(&prop->list, &node->properties);
+
+	return prop;
+}
+
 /**
  * of_new_property - Add a new property to a node
  * @node:	device node to which the property is added
@@ -2172,19 +2187,13 @@ struct device_node *of_new_node(struct device_node *parent, const char *name)
 struct property *of_new_property(struct device_node *node, const char *name,
 		const void *data, int len)
 {
-	struct property *prop;
-
-	prop = xzalloc(sizeof(*prop));
-	prop->name = xstrdup(name);
-	prop->length = len;
-	prop->value = xzalloc(len);
+	char *buf;
 
+	buf = xzalloc(len);
 	if (data)
-		memcpy(prop->value, data, len);
+		memcpy(buf, data, len);
 
-	list_add_tail(&prop->list, &node->properties);
-
-	return prop;
+	return __of_new_property(node, name, buf, len);
 }
 
 /**
@@ -2256,6 +2265,34 @@ int of_set_property(struct device_node *np, const char *name, const void *val, i
 	return 0;
 }
 
+int of_property_sprintf(struct device_node *np,
+			const char *propname, const char *fmt, ...)
+{
+	struct property *pp;
+	struct va_format vaf;
+	char *buf = NULL;
+	va_list args;
+	int len;
+
+	if (!np)
+		return -ENOENT;
+
+	va_start(args, fmt);
+	vaf.fmt = fmt;
+	vaf.va = &args;
+	len = asprintf(&buf, "%pV", &vaf);
+	va_end(args);
+
+	if (len < 0)
+		return -ENOMEM;
+
+	pp = of_find_property(np, propname, NULL);
+	of_delete_property(pp);
+
+	__of_new_property(np, propname, buf, len);
+	return len;
+}
+
 static int mem_bank_num;
 
 int of_add_memory(struct device_node *node, bool dump)
diff --git a/include/of.h b/include/of.h
index 1b7392cdb3b9..e5df4cab4afc 100644
--- a/include/of.h
+++ b/include/of.h
@@ -241,6 +241,8 @@ extern int of_property_write_string(struct device_node *np, const char *propname
 				    const char *value);
 extern int of_property_write_strings(struct device_node *np, const char *propname,
 				    ...) __attribute__((__sentinel__));
+int of_property_sprintf(struct device_node *np, const char *propname, const char *fmt, ...)
+	__attribute__ ((format(__printf__, 3, 4)));
 
 extern struct device_node *of_parse_phandle(const struct device_node *np,
 					    const char *phandle_name,
-- 
2.30.2