of: Make device nodes kobjects so they show up in sysfs

Device tree nodes are already treated as objects, and we already want to
expose them to userspace which is done using the /proc filesystem today.
Right now the kernel has to do a lot of work to keep the /proc view in
sync with the in-kernel representation. If device_nodes are switched to
be kobjects then the device tree code can be a whole lot simpler. It
also turns out that switching to using /sysfs from /proc results in
smaller code and data size, and the userspace ABI won't change if
/proc/device-tree symlinks to /sys/firmware/devicetree/base.

v7: Add missing sysfs_bin_attr_init()
v6: Add __of_add_property() early init fixes from Pantelis
v5: Rename firmware/ofw to firmware/devicetree
    Fix updating property values in sysfs
v4: Fixed build error on Powerpc
    Fixed handling of dynamic nodes on powerpc
v3: Fixed handling of duplicate attribute and child node names
v2: switch to using sysfs bin_attributes which solve the problem of
    reporting incorrect property size.
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Tested-by: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>

Documentation/ABI/testing/sysfs-firmware-ofw

+What:		/sys/firmware/devicetree/*
+Date:		November 2013
+Contact:	Grant Likely <grant.likely@linaro.org>
+Description:
+		When using OpenFirmware or a Flattened Device Tree to enumerate
+		hardware, the device tree structure will be exposed in this
+		directory.
+
+		It is possible for multiple device-tree directories to exist.
+		Some device drivers use a separate detached device tree which
+		have no attachment to the system tree and will appear in a
+		different subdirectory under /sys/firmware/devicetree.
+
+		Userspace must not use the /sys/firmware/devicetree/base
+		path directly, but instead should follow /proc/device-tree
+		symlink. It is possible that the absolute path will change
+		in the future, but the symlink is the stable ABI.
+
+		The /proc/device-tree symlink replaces the devicetree /proc
+		filesystem support, and has largely the same semantics and
+		should be compatible with existing userspace.
+
+		The contents of /sys/firmware/devicetree/ is a
+		hierarchy of directories, one per device tree node. The
+		directory name is the resolved path component name (node
+		name plus address). Properties are represented as files
+		in the directory. The contents of each file is the exact
+		binary data from the device tree.

arch/powerpc/platforms/pseries/dlpar.c

@@ -11,7 +11,6 @@
  */
 
 #include <linux/kernel.h>
-#include <linux/kref.h>
 #include <linux/notifier.h>
 #include <linux/spinlock.h>
 #include <linux/cpu.h>
@@ -87,7 +86,6 @@ static struct device_node *dlpar_parse_cc_node(struct cc_workarea *ccwa,
 	}
 
 	of_node_set_flag(dn, OF_DYNAMIC);
-	kref_init(&dn->kref);
 
 	return dn;
 }

arch/powerpc/platforms/pseries/reconfig.c

@@ -12,7 +12,6 @@
  */
 
 #include <linux/kernel.h>
-#include <linux/kref.h>
 #include <linux/notifier.h>
 #include <linux/proc_fs.h>
 #include <linux/slab.h>
@@ -70,7 +69,6 @@ static int pSeries_reconfig_add_node(const char *path, struct property *proplist
 
 	np->properties = proplist;
 	of_node_set_flag(np, OF_DYNAMIC);
-	kref_init(&np->kref);
 
 	np->parent = derive_parent(path);
 	if (IS_ERR(np->parent)) {

arch/powerpc/sysdev/msi_bitmap.c

@@ -202,7 +202,7 @@ void __init test_of_node(void)
 
 	/* There should really be a struct device_node allocator */
 	memset(&of_node, 0, sizeof(of_node));
-	kref_init(&of_node.kref);
+	kref_init(&of_node.kobj.kref);
 	of_node.full_name = node_name;
 
 	check(0 == msi_bitmap_alloc(&bmp, size, &of_node));

drivers/of/base.c

@@ -23,6 +23,7 @@
 #include <linux/of.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
+#include <linux/string.h>
 #include <linux/proc_fs.h>
 
 #include "of_private.h"
@@ -35,6 +36,12 @@ struct device_node *of_chosen;
 struct device_node *of_aliases;
 static struct device_node *of_stdout;
 
+static struct kset *of_kset;
+
+/*
+ * Used to protect the of_aliases; but also overloaded to hold off addition of
+ * nodes to sysfs
+ */
 DEFINE_MUTEX(of_aliases_mutex);
 
 /* use when traversing tree through the allnext, child, sibling,
@@ -92,14 +99,14 @@ int __weak of_node_to_nid(struct device_node *np)
 struct device_node *of_node_get(struct device_node *node)
 {
 	if (node)
-		kref_get(&node->kref);
+		kobject_get(&node->kobj);
 	return node;
 }
 EXPORT_SYMBOL(of_node_get);
 
-static inline struct device_node *kref_to_device_node(struct kref *kref)
+static inline struct device_node *kobj_to_device_node(struct kobject *kobj)
 {
-	return container_of(kref, struct device_node, kref);
+	return container_of(kobj, struct device_node, kobj);
 }
 
 /**
@@ -109,16 +116,15 @@ static inline struct device_node *kref_to_device_node(struct kref *kref)
  *	In of_node_put() this function is passed to kref_put()
  *	as the destructor.
  */
-static void of_node_release(struct kref *kref)
+static void of_node_release(struct kobject *kobj)
 {
-	struct device_node *node = kref_to_device_node(kref);
+	struct device_node *node = kobj_to_device_node(kobj);
 	struct property *prop = node->properties;
 
 	/* We should never be releasing nodes that haven't been detached. */
 	if (!of_node_check_flag(node, OF_DETACHED)) {
 		pr_err("ERROR: Bad of_node_put() on %s\n", node->full_name);
 		dump_stack();
-		kref_init(&node->kref);
 		return;
 	}
 
@@ -151,11 +157,140 @@ static void of_node_release(struct kref *kref)
 void of_node_put(struct device_node *node)
 {
 	if (node)
-		kref_put(&node->kref, of_node_release);
+		kobject_put(&node->kobj);
 }
 EXPORT_SYMBOL(of_node_put);
+#else
+static void of_node_release(struct kobject *kobj)
+{
+	/* Without CONFIG_OF_DYNAMIC, no nodes gets freed */
+}
 #endif /* CONFIG_OF_DYNAMIC */
 
+struct kobj_type of_node_ktype = {
+	.release = of_node_release,
+};
+
+static ssize_t of_node_property_read(struct file *filp, struct kobject *kobj,
+				struct bin_attribute *bin_attr, char *buf,
+				loff_t offset, size_t count)
+{
+	struct property *pp = container_of(bin_attr, struct property, attr);
+	return memory_read_from_buffer(buf, count, &offset, pp->value, pp->length);
+}
+
+static const char *safe_name(struct kobject *kobj, const char *orig_name)
+{
+	const char *name = orig_name;
+	struct kernfs_node *kn;
+	int i = 0;
+
+	/* don't be a hero. After 16 tries give up */
+	while (i < 16 && (kn = sysfs_get_dirent(kobj->sd, name))) {
+		sysfs_put(kn);
+		if (name != orig_name)
+			kfree(name);
+		name = kasprintf(GFP_KERNEL, "%s#%i", orig_name, ++i);
+	}
+
+	if (name != orig_name)
+		pr_warn("device-tree: Duplicate name in %s, renamed to \"%s\"\n",
+			kobject_name(kobj), name);
+	return name;
+}
+
+static int __of_add_property_sysfs(struct device_node *np, struct property *pp)
+{
+	int rc;
+
+	/* Important: Don't leak passwords */
+	bool secure = strncmp(pp->name, "security-", 9) == 0;
+
+	sysfs_bin_attr_init(&pp->attr);
+	pp->attr.attr.name = safe_name(&np->kobj, pp->name);
+	pp->attr.attr.mode = secure ? S_IRUSR : S_IRUGO;
+	pp->attr.size = secure ? 0 : pp->length;
+	pp->attr.read = of_node_property_read;
+
+	rc = sysfs_create_bin_file(&np->kobj, &pp->attr);
+	WARN(rc, "error adding attribute %s to node %s\n", pp->name, np->full_name);
+	return rc;
+}
+
+static int __of_node_add(struct device_node *np)
+{
+	const char *name;
+	struct property *pp;
+	int rc;
+
+	np->kobj.kset = of_kset;
+	if (!np->parent) {
+		/* Nodes without parents are new top level trees */
+		rc = kobject_add(&np->kobj, NULL, safe_name(&of_kset->kobj, "base"));
+	} else {
+		name = safe_name(&np->parent->kobj, kbasename(np->full_name));
+		if (!name || !name[0])
+			return -EINVAL;
+
+		rc = kobject_add(&np->kobj, &np->parent->kobj, "%s", name);
+	}
+	if (rc)
+		return rc;
+
+	for_each_property_of_node(np, pp)
+		__of_add_property_sysfs(np, pp);
+
+	return 0;
+}
+
+int of_node_add(struct device_node *np)
+{
+	int rc = 0;
+	kobject_init(&np->kobj, &of_node_ktype);
+	mutex_lock(&of_aliases_mutex);
+	if (of_kset)
+		rc = __of_node_add(np);
+	mutex_unlock(&of_aliases_mutex);
+	return rc;
+}
+
+#if defined(CONFIG_OF_DYNAMIC)
+static void of_node_remove(struct device_node *np)
+{
+	struct property *pp;
+
+	for_each_property_of_node(np, pp)
+		sysfs_remove_bin_file(&np->kobj, &pp->attr);
+
+	kobject_del(&np->kobj);
+}
+#endif
+
+static int __init of_init(void)
+{
+	struct device_node *np;
+
+	/* Create the kset, and register existing nodes */
+	mutex_lock(&of_aliases_mutex);
+	of_kset = kset_create_and_add("devicetree", NULL, firmware_kobj);
+	if (!of_kset) {
+		mutex_unlock(&of_aliases_mutex);
+		return -ENOMEM;
+	}
+	for_each_of_allnodes(np)
+		__of_node_add(np);
+	mutex_unlock(&of_aliases_mutex);
+
+#if !defined(CONFIG_PROC_DEVICETREE)
+	/* Symlink to the new tree when PROC_DEVICETREE is disabled */
+	if (of_allnodes)
+		proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
+#endif /* CONFIG_PROC_DEVICETREE */
+
+	return 0;
+}
+core_initcall(of_init);
+
 static struct property *__of_find_property(const struct device_node *np,
 					   const char *name, int *lenp)
 {
@@ -1546,6 +1681,14 @@ int of_add_property(struct device_node *np, struct property *prop)
 	raw_spin_lock_irqsave(&devtree_lock, flags);
 	rc = __of_add_property(np, prop);
 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
+	if (rc)
+		return rc;
+
+	/* at early boot, bail hear and defer setup to of_init() */
+	if (!of_kset)
+		return 0;
+
+	__of_add_property_sysfs(np, prop);
 
 #ifdef CONFIG_PROC_DEVICETREE
 	/* try to add to proc as well if it was initialized */
@@ -1593,6 +1736,12 @@ int of_remove_property(struct device_node *np, struct property *prop)
 	if (!found)
 		return -ENODEV;
 
+	/* at early boot, bail hear and defer setup to of_init() */
+	if (!of_kset)
+		return 0;
+
+	sysfs_remove_bin_file(&np->kobj, &prop->attr);
+
 #ifdef CONFIG_PROC_DEVICETREE
 	/* try to remove the proc node as well */
 	if (np->pde)
@@ -1643,13 +1792,20 @@ int of_update_property(struct device_node *np, struct property *newprop)
 		next = &(*next)->next;
 	}
 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
+	if (rc)
+		return rc;
+
+	/* Update the sysfs attribute */
+	if (oldprop)
+		sysfs_remove_bin_file(&np->kobj, &oldprop->attr);
+	__of_add_property_sysfs(np, newprop);
 
 	if (!found)
 		return -ENODEV;
 
 #ifdef CONFIG_PROC_DEVICETREE
 	/* try to add to proc as well if it was initialized */
-	if (!rc && np->pde)
+	if (np->pde)
 		proc_device_tree_update_prop(np->pde, newprop, oldprop);
 #endif /* CONFIG_PROC_DEVICETREE */
 
@@ -1723,6 +1879,7 @@ int of_attach_node(struct device_node *np)
 	of_node_clear_flag(np, OF_DETACHED);
 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
 
+	of_node_add(np);
 	of_add_proc_dt_entry(np);
 	return 0;
 }
@@ -1795,6 +1952,7 @@ int of_detach_node(struct device_node *np)
 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
 
 	of_remove_proc_dt_entry(np);
+	of_node_remove(np);
 	return rc;
 }
 #endif /* defined(CONFIG_OF_DYNAMIC) */

drivers/of/fdt.c

@@ -232,7 +232,6 @@ static void * unflatten_dt_node(struct boot_param_header *blob,
 				dad->next->sibling = np;
 			dad->next = np;
 		}
-		kref_init(&np->kref);
 	}
 	/* process properties */
 	while (1) {
@@ -327,6 +326,8 @@ static void * unflatten_dt_node(struct boot_param_header *blob,
 			np->name = "<NULL>";
 		if (!np->type)
 			np->type = "<NULL>";
+
+		of_node_add(np);
 	}
 	while (tag == OF_DT_BEGIN_NODE || tag == OF_DT_NOP) {
 		if (tag == OF_DT_NOP)

drivers/of/pdt.c

@@ -179,8 +179,6 @@ static struct device_node * __init of_pdt_create_node(phandle node,
 	of_pdt_incr_unique_id(dp);
 	dp->parent = parent;
 
-	kref_init(&dp->kref);
-
 	dp->name = of_pdt_get_one_property(node, "name");
 	dp->type = of_pdt_get_one_property(node, "device_type");
 	dp->phandle = node;
@@ -215,6 +213,7 @@ static struct device_node * __init of_pdt_build_tree(struct device_node *parent,
 		*nextp = &dp->allnext;
 
 		dp->full_name = of_pdt_build_full_name(dp);
+		of_node_add(dp);
 
 		dp->child = of_pdt_build_tree(dp,
 				of_pdt_prom_ops->getchild(node), nextp);
@@ -245,6 +244,7 @@ void __init of_pdt_build_devicetree(phandle root_node, struct of_pdt_ops *ops)
 	of_allnodes->path_component_name = "";
 #endif
 	of_allnodes->full_name = "/";
+	of_node_add(of_allnodes);
 
 	nextp = &of_allnodes->allnext;
 	of_allnodes->child = of_pdt_build_tree(of_allnodes,

drivers/of/testcase-data/tests-phandle.dtsi

 
 / {
 	testcase-data {
+		security-password = "password";
+		duplicate-name = "duplicate";
+		duplicate-name { };
 		phandle-tests {
 			provider0: provider0 {
 				#phandle-cells = <0>;

include/linux/of.h

@@ -18,7 +18,7 @@
 #include <linux/types.h>
 #include <linux/bitops.h>
 #include <linux/errno.h>
-#include <linux/kref.h>
+#include <linux/kobject.h>
 #include <linux/mod_devicetable.h>
 #include <linux/spinlock.h>
 #include <linux/topology.h>
@@ -37,6 +37,7 @@ struct property {
 	struct property *next;
 	unsigned long _flags;
 	unsigned int unique_id;
+	struct bin_attribute attr;
 };
 
 #if defined(CONFIG_SPARC)
@@ -57,7 +58,7 @@ struct device_node {
 	struct	device_node *next;	/* next device of same type */
 	struct	device_node *allnext;	/* next in list of all nodes */
 	struct	proc_dir_entry *pde;	/* this node's proc directory */
-	struct	kref kref;
+	struct	kobject kobj;
 	unsigned long _flags;
 	void	*data;
 #if defined(CONFIG_SPARC)
@@ -74,6 +75,8 @@ struct of_phandle_args {
 	uint32_t args[MAX_PHANDLE_ARGS];
 };
 
+extern int of_node_add(struct device_node *node);
+
 #ifdef CONFIG_OF_DYNAMIC
 extern struct device_node *of_node_get(struct device_node *node);
 extern void of_node_put(struct device_node *node);
@@ -187,6 +190,8 @@ static inline const char *of_node_full_name(const struct device_node *np)
 	return np ? np->full_name : "<no-node>";
 }
 
+#define for_each_of_allnodes(dn) \
+	for (dn = of_allnodes; dn; dn = dn->allnext)
 extern struct device_node *of_find_node_by_name(struct device_node *from,
 	const char *name);
 extern struct device_node *of_find_node_by_type(struct device_node *from,