of: overlay: add per overlay sysfs attributes

* A per overlay can_remove sysfs attribute that reports whether
the overlay can be removed or not due to another overlapping overlay.

* A target sysfs attribute listing the target of each fragment,
in a group named after the name of the fragment.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[geert: Setup ovinfo[cnt].info for symbols]
[geert: Spelling s/changset/changeset/]
[geert: Rebase on top of commit 39a751a4

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

drivers/of/overlay.c

@@ -25,6 +25,20 @@
 
 #include "of_private.h"
 
+/* fwd. decl */
+struct overlay_changeset;
+struct fragment;
+
+/* an attribute for each fragment */
+struct fragment_attribute {
+	struct attribute attr;
+	ssize_t (*show)(struct kobject *kobj, struct fragment_attribute *fattr,
+			char *buf);
+	ssize_t (*store)(struct kobject *kobj, struct fragment_attribute *fattr,
+			 const char *buf, size_t count);
+	struct fragment *fragment;
+};
+
 /**
  * struct target - info about current target node as recursing through overlay
  * @np:			node where current level of overlay will be applied
@@ -47,12 +61,18 @@ struct target {
 
 /**
  * struct fragment - info about fragment nodes in overlay expanded device tree
+ * @info:	info node that contains the target and overlay
  * @target:	target of the overlay operation
  * @overlay:	pointer to the __overlay__ node
  */
 struct fragment {
 	struct device_node *overlay;
 	struct device_node *target;
+	struct overlay_changeset *ovcs;
+	struct device_node *info;
+	struct attribute_group attr_group;
+	struct attribute *attrs[2];
+	struct fragment_attribute target_attr;
 };
 
 /**
@@ -73,6 +93,7 @@ struct overlay_changeset {
 	struct device_node *overlay_tree;
 	int count;
 	struct fragment *fragments;
+	const struct attribute_group **attr_groups;
 	bool symbols_fragment;
 	struct of_changeset cset;
 	struct kobject kobj;
@@ -106,6 +127,7 @@ static int devicetree_corrupt(void)
 
 static int build_changeset_next_level(struct overlay_changeset *ovcs,
 		struct target *target, const struct device_node *overlay_node);
+static int overlay_removal_is_ok(struct overlay_changeset *ovcs);
 
 /*
  * of_resolve_phandles() finds the largest phandle in the live tree.
@@ -727,6 +749,16 @@ static struct device_node *find_target(struct device_node *info_node)
 	return NULL;
 }
 
+static ssize_t target_show(struct kobject *kobj,
+			   struct fragment_attribute *fattr, char *buf)
+{
+	struct fragment *fragment = fattr->fragment;
+
+	return snprintf(buf, PAGE_SIZE, "%pOF\n", fragment->target);
+}
+
+static const struct fragment_attribute target_template_attr = __ATTR_RO(target);
+
 /**
  * init_overlay_changeset() - initialize overlay changeset from overlay tree
  * @ovcs:	Overlay changeset to build
@@ -746,7 +778,7 @@ static int init_overlay_changeset(struct overlay_changeset *ovcs,
 	struct device_node *node, *overlay_node;
 	struct fragment *fragment;
 	struct fragment *fragments;
-	int cnt, id, ret;
+	int i, cnt, id, ret;
 
 	/*
 	 * Warn for some issues.  Can not return -EINVAL for these until
@@ -811,6 +843,7 @@ static int init_overlay_changeset(struct overlay_changeset *ovcs,
 			goto err_free_fragments;
 		}
 
+		fragment->info = of_node_get(node);
 		cnt++;
 	}
 
@@ -831,6 +864,7 @@ static int init_overlay_changeset(struct overlay_changeset *ovcs,
 			goto err_free_fragments;
 		}
 
+		fragment->info = of_node_get(node);
 		cnt++;
 	}
 
@@ -844,6 +878,34 @@ static int init_overlay_changeset(struct overlay_changeset *ovcs,
 	ovcs->count = cnt;
 	ovcs->fragments = fragments;
 
+	ovcs->attr_groups = kcalloc(cnt + 1, sizeof(struct attribute_group *),
+				    GFP_KERNEL);
+	if (ovcs->attr_groups == NULL) {
+		ret = -ENOMEM;
+		goto err_free_fragments;
+	}
+
+	for (i = 0; i < cnt; i++) {
+		fragment = &ovcs->fragments[i];
+
+		ovcs->attr_groups[i] = &fragment->attr_group;
+
+		fragment->target_attr = target_template_attr;
+		/* make lockdep happy */
+		sysfs_attr_init(&fragment->target_attr.attr);
+		fragment->target_attr.fragment = fragment;
+
+		fragment->attrs[0] = &fragment->target_attr.attr;
+		fragment->attrs[1] = NULL;
+
+		/* NOTE: direct reference to the full_name */
+		fragment->attr_group.name =
+			kbasename(fragment->info->full_name);
+		fragment->attr_group.attrs = fragment->attrs;
+
+	}
+	ovcs->attr_groups[i] = NULL;
+
 	return 0;
 
 err_free_fragments:
@@ -866,9 +928,12 @@ static void free_overlay_changeset(struct overlay_changeset *ovcs)
 	if (ovcs->id)
 		idr_remove(&ovcs_idr, ovcs->id);
 
+	kfree(ovcs->attr_groups);
+
 	for (i = 0; i < ovcs->count; i++) {
 		of_node_put(ovcs->fragments[i].target);
 		of_node_put(ovcs->fragments[i].overlay);
+		of_node_put(ovcs->fragments[i].info);
 	}
 	kfree(ovcs->fragments);
 	kobject_put(&ovcs->kobj);
@@ -922,8 +987,25 @@ static const struct attribute *overlay_global_attrs[] = {
 	NULL
 };
 
+static ssize_t can_remove_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct overlay_changeset *ovcs = kobj_to_ovcs(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", overlay_removal_is_ok(ovcs));
+}
+
+static struct kobj_attribute can_remove_attr = __ATTR_RO(can_remove);
+
+static struct attribute *overlay_changeset_attrs[] = {
+	&can_remove_attr.attr,
+	NULL
+};
+
 static struct kobj_type overlay_changeset_ktype = {
 	.release = overlay_changeset_release,
+	.sysfs_ops = &kobj_sysfs_ops,	/* default kobj sysfs ops */
+	.default_attrs = overlay_changeset_attrs,
 };
 
 static struct kset *ov_kset;
@@ -1046,15 +1128,14 @@ static int of_overlay_apply(const void *fdt, struct device_node *tree,
 	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;
+		goto err_revert;
+	}
+
+	ret = sysfs_create_groups(&ovcs->kobj, ovcs->attr_groups);
+	if (ret != 0) {
+		pr_err("%s: sysfs_create_groups() failed for tree@%s\n",
+				__func__, tree->full_name);
+		goto err_revert;
 	}
 
 	ret = __of_changeset_apply_notify(&ovcs->cset);
@@ -1075,6 +1156,14 @@ static int of_overlay_apply(const void *fdt, struct device_node *tree,
 
 	goto out_unlock;
 
+err_revert:
+	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;
+	}
+
 err_free_tree:
 	kfree(fdt);
 	kfree(tree);
@@ -1299,6 +1388,8 @@ int of_overlay_remove(int *ovcs_id)
 
 	list_del(&ovcs->ovcs_list);
 
+	sysfs_remove_groups(&ovcs->kobj, ovcs->attr_groups);
+
 	ret_apply = 0;
 	ret = __of_changeset_revert_entries(&ovcs->cset, &ret_apply);
 	if (ret) {