Merge tag 'driver-core-4.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core updates from Greg KH:
 "Here are all of the driver core and related patches for 4.19-rc1.

  Nothing huge here, just a number of small cleanups and the ability to
  now stop the deferred probing after init happens.

  All of these have been in linux-next for a while with only a merge
  issue reported"

* tag 'driver-core-4.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (21 commits)
  base: core: Remove WARN_ON from link dependencies check
  drivers/base: stop new probing during shutdown
  drivers: core: Remove glue dirs from sysfs earlier
  driver core: remove unnecessary function extern declare
  sysfs.h: fix non-kernel-doc comment
  PM / Domains: Stop deferring probe at the end of initcall
  iommu: Remove IOMMU_OF_DECLARE
  iommu: Stop deferring probe at end of initcalls
  pinctrl: Support stopping deferred probe after initcalls
  dt-bindings: pinctrl: add a 'pinctrl-use-default' property
  driver core: allow stopping deferred probe after init
  driver core: add a debugfs entry to show deferred devices
  sysfs: Fix internal_create_group() for named group updates
  base: fix order of OF initialization
  linux/device.h: fix kernel-doc notation warning
  Documentation: update firmware loader fallback reference
  kobject: Replace strncpy with memcpy
  drivers: base: cacheinfo: use OF property_read_u32 instead of get_property,read_number
  kernfs: Replace strncpy with memcpy
  device: Add #define dev_fmt similar to #define pr_fmt
  ...

Documentation/admin-guide/kernel-parameters.txt

@@ -812,6 +812,15 @@
 			Defaults to the default architecture's huge page size
 			if not specified.
 
+	deferred_probe_timeout=
+			[KNL] Debugging option to set a timeout in seconds for
+			deferred probe to give up waiting on dependencies to
+			probe. Only specific dependencies (subsystems or
+			drivers) that have opted in will be ignored. A timeout of 0
+			will timeout at the end of initcalls. This option will also
+			dump out devices still on the deferred probe list after
+			retrying.
+
 	dhash_entries=	[KNL]
 			Set number of hash buckets for dentry cache.
 

Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt

@@ -103,6 +103,12 @@ Optional properties:
 #pinctrl-cells:	Number of pin control cells in addition to the index within the
 		pin controller device instance
 
+pinctrl-use-default: Boolean. Indicates that the OS can use the boot default
+		pin configuration. This allows using an OS that does not have a
+		driver for the pin controller. This property can be set either
+		globally for the pin controller or in child nodes for individual
+		pin group control.
+
 Pin controller devices should contain the pin configuration nodes that client
 devices reference.
 

Documentation/driver-api/firmware/fallback-mechanisms.rst

@@ -92,7 +92,7 @@ the loading file.
 
 The firmware device used to help load firmware using sysfs is only created if
 direct firmware loading fails and if the fallback mechanism is enabled for your
-firmware request, this is set up with fw_load_from_user_helper().  It is
+firmware request, this is set up with :c:func:`firmware_fallback_sysfs`. It is
 important to re-iterate that no device is created if a direct filesystem lookup
 succeeded.
 
@@ -108,6 +108,11 @@ firmware_data_read() and firmware_loading_show() are just provided for the
 test_firmware driver for testing, they are not called in normal use or
 expected to be used regularly by userspace.
 
+firmware_fallback_sysfs
+-----------------------
+.. kernel-doc:: drivers/base/firmware_loader/fallback.c
+   :functions: firmware_fallback_sysfs
+
 Firmware kobject uevent fallback mechanism
 ==========================================
 

drivers/base/base.h

@@ -84,8 +84,6 @@ struct device_private {
 #define to_device_private_bus(obj)	\
 	container_of(obj, struct device_private, knode_bus)
 
-extern int device_private_init(struct device *dev);
-
 /* initialisation functions */
 extern int devices_init(void);
 extern int buses_init(void);

drivers/base/cacheinfo.c

@@ -74,52 +74,48 @@ static inline int get_cacheinfo_idx(enum cache_type type)
 static void cache_size(struct cacheinfo *this_leaf, struct device_node *np)
 {
 	const char *propname;
-	const __be32 *cache_size;
 	int ct_idx;
 
 	ct_idx = get_cacheinfo_idx(this_leaf->type);
 	propname = cache_type_info[ct_idx].size_prop;
 
-	cache_size = of_get_property(np, propname, NULL);
-	if (cache_size)
-		this_leaf->size = of_read_number(cache_size, 1);
+	if (of_property_read_u32(np, propname, &this_leaf->size))
+		this_leaf->size = 0;
 }
 
 /* not cache_line_size() because that's a macro in include/linux/cache.h */
 static void cache_get_line_size(struct cacheinfo *this_leaf,
 				struct device_node *np)
 {
-	const __be32 *line_size;
 	int i, lim, ct_idx;
 
 	ct_idx = get_cacheinfo_idx(this_leaf->type);
 	lim = ARRAY_SIZE(cache_type_info[ct_idx].line_size_props);
 
 	for (i = 0; i < lim; i++) {
+		int ret;
+		u32 line_size;
 		const char *propname;
 
 		propname = cache_type_info[ct_idx].line_size_props[i];
-		line_size = of_get_property(np, propname, NULL);
-		if (line_size)
+		ret = of_property_read_u32(np, propname, &line_size);
+		if (!ret) {
+			this_leaf->coherency_line_size = line_size;
 			break;
+		}
 	}
-
-	if (line_size)
-		this_leaf->coherency_line_size = of_read_number(line_size, 1);
 }
 
 static void cache_nr_sets(struct cacheinfo *this_leaf, struct device_node *np)
 {
 	const char *propname;
-	const __be32 *nr_sets;
 	int ct_idx;
 
 	ct_idx = get_cacheinfo_idx(this_leaf->type);
 	propname = cache_type_info[ct_idx].nr_sets_prop;
 
-	nr_sets = of_get_property(np, propname, NULL);
-	if (nr_sets)
-		this_leaf->number_of_sets = of_read_number(nr_sets, 1);
+	if (of_property_read_u32(np, propname, &this_leaf->number_of_sets))
+		this_leaf->number_of_sets = 0;
 }
 
 static void cache_associativity(struct cacheinfo *this_leaf)

drivers/base/core.c

@@ -105,7 +105,7 @@ static int device_is_dependent(struct device *dev, void *target)
 	struct device_link *link;
 	int ret;
 
-	if (WARN_ON(dev == target))
+	if (dev == target)
 		return 1;
 
 	ret = device_for_each_child(dev, target, device_is_dependent);
@@ -113,7 +113,7 @@ static int device_is_dependent(struct device *dev, void *target)
 		return ret;
 
 	list_for_each_entry(link, &dev->links.consumers, s_node) {
-		if (WARN_ON(link->consumer == target))
+		if (link->consumer == target)
 			return 1;
 
 		ret = device_is_dependent(link->consumer, target);
@@ -1647,6 +1647,8 @@ static void cleanup_glue_dir(struct device *dev, struct kobject *glue_dir)
 		return;
 
 	mutex_lock(&gdp_mutex);
+	if (!kobject_has_children(glue_dir))
+		kobject_del(glue_dir);
 	kobject_put(glue_dir);
 	mutex_unlock(&gdp_mutex);
 }
@@ -1786,7 +1788,7 @@ static void device_remove_sys_dev_entry(struct device *dev)
 	}
 }
 
-int device_private_init(struct device *dev)
+static int device_private_init(struct device *dev)
 {
 	dev->p = kzalloc(sizeof(*dev->p), GFP_KERNEL);
 	if (!dev->p)
@@ -2859,6 +2861,9 @@ void device_shutdown(void)
 {
 	struct device *dev, *parent;
 
+	wait_for_device_probe();
+	device_block_probing();
+
 	spin_lock(&devices_kset->list_lock);
 	/*
 	 * Walk the devices list backward, shutting down each in turn.
@@ -3052,12 +3057,12 @@ void func(const struct device *dev, const char *fmt, ...)	\
 }								\
 EXPORT_SYMBOL(func);
 
-define_dev_printk_level(dev_emerg, KERN_EMERG);
-define_dev_printk_level(dev_alert, KERN_ALERT);
-define_dev_printk_level(dev_crit, KERN_CRIT);
-define_dev_printk_level(dev_err, KERN_ERR);
-define_dev_printk_level(dev_warn, KERN_WARNING);
-define_dev_printk_level(dev_notice, KERN_NOTICE);
+define_dev_printk_level(_dev_emerg, KERN_EMERG);
+define_dev_printk_level(_dev_alert, KERN_ALERT);
+define_dev_printk_level(_dev_crit, KERN_CRIT);
+define_dev_printk_level(_dev_err, KERN_ERR);
+define_dev_printk_level(_dev_warn, KERN_WARNING);
+define_dev_printk_level(_dev_notice, KERN_NOTICE);
 define_dev_printk_level(_dev_info, KERN_INFO);
 
 #endif

drivers/base/dd.c

@@ -16,6 +16,7 @@
  * Copyright (c) 2007-2009 Novell Inc.
  */
 
+#include <linux/debugfs.h>
 #include <linux/device.h>
 #include <linux/delay.h>
 #include <linux/dma-mapping.h>
@@ -53,6 +54,7 @@ static DEFINE_MUTEX(deferred_probe_mutex);
 static LIST_HEAD(deferred_probe_pending_list);
 static LIST_HEAD(deferred_probe_active_list);
 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
+static struct dentry *deferred_devices;
 static bool initcalls_done;
 
 /*
@@ -62,26 +64,6 @@ static bool initcalls_done;
  */
 static bool defer_all_probes;
 
-/*
- * For initcall_debug, show the deferred probes executed in late_initcall
- * processing.
- */
-static void deferred_probe_debug(struct device *dev)
-{
-	ktime_t calltime, delta, rettime;
-	unsigned long long duration;
-
-	printk(KERN_DEBUG "deferred probe %s @ %i\n", dev_name(dev),
-	       task_pid_nr(current));
-	calltime = ktime_get();
-	bus_probe_device(dev);
-	rettime = ktime_get();
-	delta = ktime_sub(rettime, calltime);
-	duration = (unsigned long long) ktime_to_ns(delta) >> 10;
-	printk(KERN_DEBUG "deferred probe %s returned after %lld usecs\n",
-	       dev_name(dev), duration);
-}
-
 /*
  * deferred_probe_work_func() - Retry probing devices in the active list.
  */
@@ -125,11 +107,7 @@ static void deferred_probe_work_func(struct work_struct *work)
 		device_pm_move_to_tail(dev);
 
 		dev_dbg(dev, "Retrying from deferred list\n");
-		if (initcall_debug && !initcalls_done)
-			deferred_probe_debug(dev);
-		else
-			bus_probe_device(dev);
-
+		bus_probe_device(dev);
 		mutex_lock(&deferred_probe_mutex);
 
 		put_device(dev);
@@ -224,6 +202,69 @@ void device_unblock_probing(void)
 	driver_deferred_probe_trigger();
 }
 
+/*
+ * deferred_devs_show() - Show the devices in the deferred probe pending list.
+ */
+static int deferred_devs_show(struct seq_file *s, void *data)
+{
+	struct device_private *curr;
+
+	mutex_lock(&deferred_probe_mutex);
+
+	list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
+		seq_printf(s, "%s\n", dev_name(curr->device));
+
+	mutex_unlock(&deferred_probe_mutex);
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(deferred_devs);
+
+static int deferred_probe_timeout = -1;
+static int __init deferred_probe_timeout_setup(char *str)
+{
+	deferred_probe_timeout = simple_strtol(str, NULL, 10);
+	return 1;
+}
+__setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
+
+/**
+ * driver_deferred_probe_check_state() - Check deferred probe state
+ * @dev: device to check
+ *
+ * Returns -ENODEV if init is done and all built-in drivers have had a chance
+ * to probe (i.e. initcalls are done), -ETIMEDOUT if deferred probe debug
+ * timeout has expired, or -EPROBE_DEFER if none of those conditions are met.
+ *
+ * Drivers or subsystems can opt-in to calling this function instead of directly
+ * returning -EPROBE_DEFER.
+ */
+int driver_deferred_probe_check_state(struct device *dev)
+{
+	if (initcalls_done) {
+		if (!deferred_probe_timeout) {
+			dev_WARN(dev, "deferred probe timeout, ignoring dependency");
+			return -ETIMEDOUT;
+		}
+		dev_warn(dev, "ignoring dependency for device, assuming no driver");
+		return -ENODEV;
+	}
+	return -EPROBE_DEFER;
+}
+
+static void deferred_probe_timeout_work_func(struct work_struct *work)
+{
+	struct device_private *private, *p;
+
+	deferred_probe_timeout = 0;
+	driver_deferred_probe_trigger();
+	flush_work(&deferred_probe_work);
+
+	list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)
+		dev_info(private->device, "deferred probe pending");
+}
+static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
+
 /**
  * deferred_probe_initcall() - Enable probing of deferred devices
  *
@@ -233,15 +274,36 @@ void device_unblock_probing(void)
  */
 static int deferred_probe_initcall(void)
 {
+	deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL,
+					       NULL, &deferred_devs_fops);
+
 	driver_deferred_probe_enable = true;
 	driver_deferred_probe_trigger();
 	/* Sort as many dependencies as possible before exiting initcalls */
 	flush_work(&deferred_probe_work);
 	initcalls_done = true;
+
+	/*
+	 * Trigger deferred probe again, this time we won't defer anything
+	 * that is optional
+	 */
+	driver_deferred_probe_trigger();
+	flush_work(&deferred_probe_work);
+
+	if (deferred_probe_timeout > 0) {
+		schedule_delayed_work(&deferred_probe_timeout_work,
+			deferred_probe_timeout * HZ);
+	}
 	return 0;
 }
 late_initcall(deferred_probe_initcall);
 
+static void __exit deferred_probe_exit(void)
+{
+	debugfs_remove_recursive(deferred_devices);
+}
+__exitcall(deferred_probe_exit);
+
 /**
  * device_is_bound() - Check if device is bound to a driver
  * @dev: device to check
@@ -519,6 +581,23 @@ done:
 	return ret;
 }
 
+/*
+ * For initcall_debug, show the driver probe time.
+ */
+static int really_probe_debug(struct device *dev, struct device_driver *drv)
+{
+	ktime_t calltime, delta, rettime;
+	int ret;
+
+	calltime = ktime_get();
+	ret = really_probe(dev, drv);
+	rettime = ktime_get();
+	delta = ktime_sub(rettime, calltime);
+	printk(KERN_DEBUG "probe of %s returned %d after %lld usecs\n",
+	       dev_name(dev), ret, (s64) ktime_to_us(delta));
+	return ret;
+}
+
 /**
  * driver_probe_done
  * Determine if the probe sequence is finished or not.
@@ -577,7 +656,10 @@ int driver_probe_device(struct device_driver *drv, struct device *dev)
 		pm_runtime_get_sync(dev->parent);
 
 	pm_runtime_barrier(dev);
-	ret = really_probe(dev, drv);
+	if (initcall_debug)
+		ret = really_probe_debug(dev, drv);
+	else
+		ret = really_probe(dev, drv);
 	pm_request_idle(dev);
 
 	if (dev->parent)

drivers/base/init.c

@@ -30,9 +30,9 @@ void __init driver_init(void)
 	/* These are also core pieces, but must come after the
 	 * core core pieces.
 	 */
+	of_core_init();
 	platform_bus_init();
 	cpu_dev_init();
 	memory_dev_init();
 	container_dev_init();
-	of_core_init();
 }

drivers/base/power/domain.c

@@ -2253,7 +2253,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
 		mutex_unlock(&gpd_list_lock);
 		dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
 			__func__, PTR_ERR(pd));
-		return -EPROBE_DEFER;
+		return driver_deferred_probe_check_state(dev);
 	}
 
 	dev_dbg(dev, "adding to PM domain %s\n", pd->name);

drivers/iommu/arm-smmu-v3.c

@@ -2915,8 +2915,6 @@ static struct platform_driver arm_smmu_driver = {
 };
 module_platform_driver(arm_smmu_driver);
 
-IOMMU_OF_DECLARE(arm_smmuv3, "arm,smmu-v3");
-
 MODULE_DESCRIPTION("IOMMU API for ARM architected SMMUv3 implementations");
 MODULE_AUTHOR("Will Deacon <will.deacon@arm.com>");
 MODULE_LICENSE("GPL v2");

drivers/iommu/arm-smmu.c

@@ -2211,13 +2211,6 @@ static struct platform_driver arm_smmu_driver = {
 };
 module_platform_driver(arm_smmu_driver);
 
-IOMMU_OF_DECLARE(arm_smmuv1, "arm,smmu-v1");
-IOMMU_OF_DECLARE(arm_smmuv2, "arm,smmu-v2");
-IOMMU_OF_DECLARE(arm_mmu400, "arm,mmu-400");
-IOMMU_OF_DECLARE(arm_mmu401, "arm,mmu-401");
-IOMMU_OF_DECLARE(arm_mmu500, "arm,mmu-500");
-IOMMU_OF_DECLARE(cavium_smmuv2, "cavium,smmu-v2");
-
 MODULE_DESCRIPTION("IOMMU API for ARM architected SMMU implementations");
 MODULE_AUTHOR("Will Deacon <will.deacon@arm.com>");
 MODULE_LICENSE("GPL v2");

drivers/iommu/exynos-iommu.c

@@ -1390,5 +1390,3 @@ err_reg_driver:
 	return ret;
 }
 core_initcall(exynos_iommu_init);
-
-IOMMU_OF_DECLARE(exynos_iommu_of, "samsung,exynos-sysmmu");

drivers/iommu/ipmmu-vmsa.c

@@ -1108,9 +1108,6 @@ static void __exit ipmmu_exit(void)
 subsys_initcall(ipmmu_init);
 module_exit(ipmmu_exit);
 
-IOMMU_OF_DECLARE(ipmmu_vmsa_iommu_of, "renesas,ipmmu-vmsa");
-IOMMU_OF_DECLARE(ipmmu_r8a7795_iommu_of, "renesas,ipmmu-r8a7795");
-
 MODULE_DESCRIPTION("IOMMU API for Renesas VMSA-compatible IPMMU");
 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 MODULE_LICENSE("GPL v2");

drivers/iommu/msm_iommu.c

@@ -877,7 +877,5 @@ static void __exit msm_iommu_driver_exit(void)
 subsys_initcall(msm_iommu_driver_init);
 module_exit(msm_iommu_driver_exit);
 
-IOMMU_OF_DECLARE(msm_iommu_of, "qcom,apq8064-iommu");
-
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Stepan Moskovchenko <stepanm@codeaurora.org>");

drivers/iommu/of_iommu.c

@@ -27,9 +27,6 @@
 
 #define NO_IOMMU	1
 
-static const struct of_device_id __iommu_of_table_sentinel
-	__used __section(__iommu_of_table_end);
-
 /**
  * of_get_dma_window - Parse *dma-window property and returns 0 if found.
  *
@@ -98,19 +95,6 @@ int of_get_dma_window(struct device_node *dn, const char *prefix, int index,
 }
 EXPORT_SYMBOL_GPL(of_get_dma_window);
 
-static bool of_iommu_driver_present(struct device_node *np)
-{
-	/*
-	 * If the IOMMU still isn't ready by the time we reach init, assume
-	 * it never will be. We don't want to defer indefinitely, nor attempt
-	 * to dereference __iommu_of_table after it's been freed.
-	 */
-	if (system_state >= SYSTEM_RUNNING)
-		return false;
-
-	return of_match_node(&__iommu_of_table, np);
-}
-
 static int of_iommu_xlate(struct device *dev,
 			  struct of_phandle_args *iommu_spec)
 {
@@ -120,8 +104,7 @@ static int of_iommu_xlate(struct device *dev,
 
 	ops = iommu_ops_from_fwnode(fwnode);
 	if ((ops && !ops->of_xlate) ||
-	    !of_device_is_available(iommu_spec->np) ||
-	    (!ops && !of_iommu_driver_present(iommu_spec->np)))
+	    !of_device_is_available(iommu_spec->np))
 		return NO_IOMMU;
 
 	err = iommu_fwspec_init(dev, &iommu_spec->np->fwnode, ops);
@@ -133,7 +116,7 @@ static int of_iommu_xlate(struct device *dev,
 	 * a proper probe-ordering dependency mechanism in future.
 	 */
 	if (!ops)
-		return -EPROBE_DEFER;
+		return driver_deferred_probe_check_state(dev);
 
 	return ops->of_xlate(dev, iommu_spec);
 }

drivers/iommu/qcom_iommu.c

@@ -945,7 +945,5 @@ static void __exit qcom_iommu_exit(void)
 module_init(qcom_iommu_init);
 module_exit(qcom_iommu_exit);
 
-IOMMU_OF_DECLARE(qcom_iommu_dev, "qcom,msm-iommu-v1");
-
 MODULE_DESCRIPTION("IOMMU API for QCOM IOMMU v1 implementations");
 MODULE_LICENSE("GPL v2");

drivers/iommu/rockchip-iommu.c

@@ -1284,8 +1284,6 @@ static int __init rk_iommu_init(void)
 }
 subsys_initcall(rk_iommu_init);
 
-IOMMU_OF_DECLARE(rk_iommu_of, "rockchip,iommu");
-
 MODULE_DESCRIPTION("IOMMU API for Rockchip");
 MODULE_AUTHOR("Simon Xue <xxm@rock-chips.com> and Daniel Kurtz <djkurtz@chromium.org>");
 MODULE_ALIAS("platform:rockchip-iommu");

drivers/pinctrl/devicetree.c

@@ -111,17 +111,24 @@ static int dt_to_map_one_config(struct pinctrl *p,
 	int ret;
 	struct pinctrl_map *map;
 	unsigned num_maps;
+	bool allow_default = false;
 
 	/* Find the pin controller containing np_config */
 	np_pctldev = of_node_get(np_config);
 	for (;;) {
+		if (!allow_default)
+			allow_default = of_property_read_bool(np_pctldev,
+							      "pinctrl-use-default");
+
 		np_pctldev = of_get_next_parent(np_pctldev);
 		if (!np_pctldev || of_node_is_root(np_pctldev)) {
-			dev_info(p->dev, "could not find pctldev for node %pOF, deferring probe\n",
-				np_config);
 			of_node_put(np_pctldev);
-			/* OK let's just assume this will appear later then */
-			return -EPROBE_DEFER;
+			ret = driver_deferred_probe_check_state(p->dev);
+			/* keep deferring if modules are enabled unless we've timed out */
+			if (IS_ENABLED(CONFIG_MODULES) && !allow_default && ret == -ENODEV)
+				ret = -EPROBE_DEFER;
+
+			return ret;
 		}
 		/* If we're creating a hog we can use the passed pctldev */
 		if (hog_pctldev && (np_pctldev == p->dev->of_node)) {

fs/kernfs/symlink.c

@@ -97,7 +97,7 @@ static int kernfs_get_target_path(struct kernfs_node *parent,
 		int slen = strlen(kn->name);
 
 		len -= slen;
-		strncpy(s + len, kn->name, slen);
+		memcpy(s + len, kn->name, slen);
 		if (len)
 			s[--len] = '/';
 

fs/sysfs/group.c

@@ -124,13 +124,22 @@ static int internal_create_group(struct kobject *kobj, int update,
 	}
 	kobject_get_ownership(kobj, &uid, &gid);
 	if (grp->name) {
-		kn = kernfs_create_dir_ns(kobj->sd, grp->name,
-					  S_IRWXU | S_IRUGO | S_IXUGO,
-					  uid, gid, kobj, NULL);
-		if (IS_ERR(kn)) {
-			if (PTR_ERR(kn) == -EEXIST)
-				sysfs_warn_dup(kobj->sd, grp->name);
-			return PTR_ERR(kn);
+		if (update) {
+			kn = kernfs_find_and_get(kobj->sd, grp->name);
+			if (!kn) {
+				pr_warn("Can't update unknown attr grp name: %s/%s\n",
+					kobj->name, grp->name);
+				return -EINVAL;
+			}
+		} else {
+			kn = kernfs_create_dir_ns(kobj->sd, grp->name,
+						  S_IRWXU | S_IRUGO | S_IXUGO,
+						  uid, gid, kobj, NULL);
+			if (IS_ERR(kn)) {
+				if (PTR_ERR(kn) == -EEXIST)
+					sysfs_warn_dup(kobj->sd, grp->name);
+				return PTR_ERR(kn);
+			}
 		}
 	} else
 		kn = kobj->sd;
@@ -141,6 +150,10 @@ static int internal_create_group(struct kobject *kobj, int update,
 			kernfs_remove(kn);
 	}
 	kernfs_put(kn);
+
+	if (grp->name && update)
+		kernfs_put(kn);
+
 	return error;
 }
 
@@ -205,7 +218,8 @@ EXPORT_SYMBOL_GPL(sysfs_create_groups);
  * of the attribute files being created already exist.  Furthermore,
  * if the visibility of the files has changed through the is_visible()
  * callback, it will update the permissions and add or remove the
- * relevant files.
+ * relevant files. Changing a group's name (subdirectory name under
+ * kobj's directory in sysfs) is not allowed.
  *
  * The primary use for this function is to call it after making a change
  * that affects group visibility.