of: overlay: kobjectify overlay objects

We are going to need the overlays to appear on sysfs with runtime
global properties (like master enable) so turn them into kobjects.

They have to be in sysfs so that people can have information about the
overlays applied in the system, i.e. where their targets are and whether
removal is possible. In a future more attributes can be added
in a backwards compatible manner.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[geert: Rebase to v4.15-rc1]
[Fengguang Wu: Make overlay_changeset_release() static]
[geert: Rebase on top of commit 39a751a4

 ("of: change overlay apply input data from unflattened to FDT")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

drivers/of/base.c

@@ -166,6 +166,7 @@ void __of_phandle_cache_inv_entry(phandle handle)
 void __init of_core_init(void)
 {
 	struct device_node *np;
+	int ret;
 
 
 	/* Create the kset, and register existing nodes */
@@ -186,6 +187,10 @@ void __init of_core_init(void)
 	/* Symlink in /proc as required by userspace ABI */
 	if (of_root)
 		proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
+
+	ret = of_overlay_init();
+	if (ret != 0)
+		pr_warn("of_init: of_overlay_init failed!\n");
 }
 
 static struct property *__of_find_property(const struct device_node *np,

drivers/of/of_private.h

@@ -169,4 +169,13 @@ static inline int of_dma_get_range(struct device_node *np,
 }
 #endif
 
+#if defined(CONFIG_OF_OVERLAY)
+extern int of_overlay_init(void);
+#else
+static inline int of_overlay_init(void)
+{
+	return 0;
+}
+#endif
+
 #endif /* _LINUX_OF_PRIVATE_H */

drivers/of/overlay.c

@@ -20,6 +20,7 @@
 #include <linux/libfdt.h>
 #include <linux/err.h>
 #include <linux/idr.h>
+#include <linux/sysfs.h>
 
 #include "of_private.h"
 
@@ -73,6 +74,7 @@ struct overlay_changeset {
 	struct fragment *fragments;
 	bool symbols_fragment;
 	struct of_changeset cset;
+	struct kobject kobj;
 };
 
 /* flags are sticky - once set, do not reset */
@@ -858,6 +860,18 @@ static void free_overlay_changeset(struct overlay_changeset *ovcs)
 		of_node_put(ovcs->fragments[i].overlay);
 	}
 	kfree(ovcs->fragments);
+	kobject_put(&ovcs->kobj);
+}
+
+static inline struct overlay_changeset *kobj_to_ovcs(struct kobject *kobj)
+{
+	return container_of(kobj, struct overlay_changeset, kobj);
+}
+
+static void overlay_changeset_release(struct kobject *kobj)
+{
+	struct overlay_changeset *ovcs = kobj_to_ovcs(kobj);
+
 	/*
 	 * There should be no live pointers into ovcs->overlay_tree and
 	 * ovcs->fdt due to the policy that overlay notifiers are not allowed
@@ -868,6 +882,12 @@ static void free_overlay_changeset(struct overlay_changeset *ovcs)
 	kfree(ovcs);
 }
 
+static struct kobj_type overlay_changeset_ktype = {
+	.release = overlay_changeset_release,
+};
+
+static struct kset *ov_kset;
+
 /*
  * internal documentation
  *
@@ -938,6 +958,8 @@ static int of_overlay_apply(const void *fdt, struct device_node *tree,
 		goto out;
 	}
 
+	kobject_init(&ovcs->kobj, &overlay_changeset_ktype);
+
 	of_overlay_mutex_lock();
 	mutex_lock(&of_mutex);
 
@@ -975,6 +997,22 @@ static int of_overlay_apply(const void *fdt, struct device_node *tree,
 		goto err_free_overlay_changeset;
 	}
 
+	ovcs->kobj.kset = ov_kset;
+	ret = kobject_add(&ovcs->kobj, NULL, "%d", ovcs->id);
+	if (ret != 0) {
+		pr_err("%s: kobject_add() failed for tree@%s\n", __func__,
+				tree->full_name);
+		ret_tmp = 0;
+		ret_revert = __of_changeset_revert_entries(&ovcs->cset,
+							   &ret_tmp);
+		if (ret_revert) {
+			pr_debug("overlay changeset revert error %d\n",
+				 ret_revert);
+			devicetree_state_flags |= DTSF_REVERT_FAIL;
+		}
+		goto err_free_overlay_changeset;
+	}
+
 	ret = __of_changeset_apply_notify(&ovcs->cset);
 	if (ret)
 		pr_err("overlay apply changeset entry notify error %d\n", ret);
@@ -1274,3 +1312,13 @@ int of_overlay_remove_all(void)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(of_overlay_remove_all);
+
+/* called from of_init() */
+int of_overlay_init(void)
+{
+	ov_kset = kset_create_and_add("overlays", NULL, &of_kset->kobj);
+	if (!ov_kset)
+		return -ENOMEM;
+
+	return 0;
+}