[PATCH v2 1/6] of: overlay: Implement target index support

[Pantelis Antoniou <pantelis.antoniou@konsulko.com>]

Some applications require applying the same overlay to a different
target according to some external condition (for instance depending
on the slot a card has been inserted, the overlay target is different).

The target index functionality use requires using the new
of_overlay_create_target_index() API which uses an index argument.

The format changes as follow

	fragment@0 {
		target = <&foo_target>, <&bar_target>;
	};

Calling of_overlay_create_target_index() with a 0 index selects
the foo_target, while using an index of 1 selects the bar_target.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
---
 drivers/of/overlay.c | 65 ++++++++++++++++++++++++++++++++++++----------------
 include/linux/of.h   |  8 +++++++
 2 files changed, 53 insertions(+), 20 deletions(-)

diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index fdfc487..2efd4b7 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -75,6 +75,7 @@ struct of_overlay {
 	const struct attribute_group **attr_groups;
 	struct of_changeset cset;
 	struct kobject kobj;
+	int target_index;
 };
 
 /* master enable switch; once set to 0 can't be re-enabled */
@@ -222,30 +223,29 @@ static int of_overlay_apply(struct of_overlay *ov)
 
 /*
  * Find the target node using a number of different strategies
- * in order of preference
+ * in order of preference. Respects the target index if available.
  *
  * "target" property containing the phandle of the target
  * "target-path" property containing the path of the target
  */
-static struct device_node *find_target_node(struct device_node *info_node)
+static struct device_node *find_target_node(struct of_overlay *ov,
+		struct device_node *info_node, int index)
 {
 	const char *path;
 	u32 val;
 	int ret;
 
 	/* first try to go by using the target as a phandle */
-	ret = of_property_read_u32(info_node, "target", &val);
+	ret = of_property_read_u32_index(info_node, "target", index, &val);
 	if (ret == 0)
 		return of_find_node_by_phandle(val);
 
-	/* now try to locate by path */
-	ret = of_property_read_string(info_node, "target-path", &path);
+	/* failed, try to locate by path */
+	ret = of_property_read_string_index(info_node, "target-path", index,
+			&path);
 	if (ret == 0)
 		return of_find_node_by_path(path);
 
-	pr_err("%s: Failed to find target for node %p (%s)\n", __func__,
-		info_node, info_node->name);
-
 	return NULL;
 }
 
@@ -270,7 +270,7 @@ static int of_fill_overlay_info(struct of_overlay *ov,
 	if (ovinfo->overlay == NULL)
 		goto err_fail;
 
-	ovinfo->target = find_target_node(info_node);
+	ovinfo->target = find_target_node(ov, info_node, ov->target_index);
 	if (ovinfo->target == NULL)
 		goto err_fail;
 
@@ -473,17 +473,8 @@ static struct kobj_type of_overlay_ktype = {
 
 static struct kset *ov_kset;
 
-/**
- * of_overlay_create() - Create and apply an overlay
- * @tree:	Device node containing all the overlays
- *
- * Creates and applies an overlay while also keeping track
- * of the overlay in a list. This list can be used to prevent
- * illegal overlay removals.
- *
- * Returns the id of the created overlay, or a negative error number
- */
-int of_overlay_create(struct device_node *tree)
+static int __of_overlay_create(struct device_node *tree,
+		int target_index)
 {
 	struct of_overlay *ov;
 	int err, id;
@@ -498,6 +489,8 @@ int of_overlay_create(struct device_node *tree)
 		return -ENOMEM;
 	ov->id = -1;
 
+	ov->target_index = target_index;
+
 	INIT_LIST_HEAD(&ov->node);
 
 	of_changeset_init(&ov->cset);
@@ -577,8 +570,40 @@ err_destroy_trans:
 
 	return err;
 }
+
+/**
+ * of_overlay_create() - Create and apply an overlay
+ * @tree:	Device node containing all the overlays
+ *
+ * Creates and applies an overlay while also keeping track
+ * of the overlay in a list. This list can be used to prevent
+ * illegal overlay removals.
+ *
+ * Returns the id of the created overlay, or a negative error number
+ */
+int of_overlay_create(struct device_node *tree)
+{
+	return __of_overlay_create(tree, 0);
+}
 EXPORT_SYMBOL_GPL(of_overlay_create);
 
+/**
+ * of_overlay_create_target_index() - Create and apply an overlay
+ * @tree:	Device node containing all the overlays
+ * @index:	Index to use in the target properties
+ *
+ * Creates and applies an overlay while also keeping track
+ * of the overlay in a list. This list can be used to prevent
+ * illegal overlay removals.
+ *
+ * Returns the id of the created overlay, or a negative error number
+ */
+int of_overlay_create_target_index(struct device_node *tree, int index)
+{
+	return __of_overlay_create(tree, index);
+}
+EXPORT_SYMBOL_GPL(of_overlay_create_target_index);
+
 /* check whether the given node, lies under the given tree */
 static int overlay_subtree_check(struct device_node *tree,
 		struct device_node *dn)
diff --git a/include/linux/of.h b/include/linux/of.h
index 97ac5c8..4548773 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -1420,6 +1420,8 @@ int of_overlay_create(struct device_node *tree);
 int of_overlay_destroy(int id);
 int of_overlay_destroy_all(void);
 
+int of_overlay_create_target_index(struct device_node *tree, int index);
+
 #else
 
 static inline int of_overlay_create(struct device_node *tree)
@@ -1437,6 +1439,12 @@ static inline int of_overlay_destroy_all(void)
 	return -ENOTSUPP;
 }
 
+static inline int of_overlay_create_target_index(struct device_node *tree,
+		int index)
+{
+	return -ENOTSUPP;
+}
+
 #endif
 
 #endif /* _LINUX_OF_H */
-- 
1.7.12