[RFC PATCH v3 1/5] of: dynamic: Add of_changeset_update_prop_string

[Chen-Yu Tsai <wenst@chromium.org>]

Add a helper function to add string property updates to an OF changeset.
This is similar to of_changeset_add_prop_string(), but instead of adding
the property (and failing if it exists), it will update the property.

This shall be used later in the DT hardware prober.

Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>

---
New patch added in v3.
---
 drivers/of/dynamic.c | 47 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/of.h   |  3 +++
 2 files changed, 50 insertions(+)

diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
index f63250c650ca..d22aad938667 100644
--- a/drivers/of/dynamic.c
+++ b/drivers/of/dynamic.c
@@ -1039,3 +1039,50 @@ int of_changeset_add_prop_u32_array(struct of_changeset *ocs,
 	return ret;
 }
 EXPORT_SYMBOL_GPL(of_changeset_add_prop_u32_array);
+
+static int of_changeset_update_prop_helper(struct of_changeset *ocs,
+					   struct device_node *np,
+					   const struct property *pp)
+{
+	struct property *new_pp;
+	int ret;
+
+	new_pp = __of_prop_dup(pp, GFP_KERNEL);
+	if (!new_pp)
+		return -ENOMEM;
+
+	ret = of_changeset_update_property(ocs, np, new_pp);
+	if (ret) {
+		kfree(new_pp->name);
+		kfree(new_pp->value);
+		kfree(new_pp);
+	}
+
+	return ret;
+}
+
+/**
+ * of_changeset_update_prop_string - Add a string property update to a changeset
+ *
+ * @ocs:	changeset pointer
+ * @np:		device node pointer
+ * @prop_name:	name of the property to be updated
+ * @str:	pointer to null terminated string
+ *
+ * Create a string property to be updated and add it to a changeset.
+ *
+ * Return: 0 on success, a negative error value in case of an error.
+ */
+int of_changeset_update_prop_string(struct of_changeset *ocs,
+				    struct device_node *np,
+				    const char *prop_name, const char *str)
+{
+	struct property prop;
+
+	prop.name = (char *)prop_name;
+	prop.length = strlen(str) + 1;
+	prop.value = (void *)str;
+
+	return of_changeset_update_prop_helper(ocs, np, &prop);
+}
+EXPORT_SYMBOL_GPL(of_changeset_update_prop_string);
diff --git a/include/linux/of.h b/include/linux/of.h
index 6a9ddf20e79a..c69bc7da380e 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -1601,6 +1601,9 @@ static inline int of_changeset_add_prop_u32(struct of_changeset *ocs,
 {
 	return of_changeset_add_prop_u32_array(ocs, np, prop_name, &val, 1);
 }
+int of_changeset_update_prop_string(struct of_changeset *ocs,
+				    struct device_node *np,
+				    const char *prop_name, const char *str);
 
 #else /* CONFIG_OF_DYNAMIC */
 static inline int of_reconfig_notifier_register(struct notifier_block *nb)
-- 
2.43.0.rc1.413.gea7ed67945-goog