drivers/base/component.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Componentized device handling.
  *
  * This is work in progress.  We gather up the component devices into a list,
  * and bind them when instructed.  At the moment, we're specific to the DRM
  * subsystem, and only handles one master device, but this doesn't have to be
  * the case.
  */
 #include <linux/component.h>
 #include <linux/device.h>
 #include <linux/kref.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/debugfs.h>

 struct component;

 struct component_match_array {
 	void *data;
 	int (*compare)(struct device *, void *);
 	void (*release)(struct device *, void *);
 	struct component *component;
 	bool duplicate;
 };

 struct component_match {
 	size_t alloc;
 	size_t num;
 	struct component_match_array *compare;
 };

 struct master {
 	struct list_head node;
 	bool bound;

 	const struct component_master_ops *ops;
 	struct device *dev;
 	struct component_match *match;
 	struct dentry *dentry;
 };

 struct component {
 	struct list_head node;
 	struct master *master;
 	bool bound;

 	const struct component_ops *ops;
 	struct device *dev;
 };

 static DEFINE_MUTEX(component_mutex);
 static LIST_HEAD(component_list);
 static LIST_HEAD(masters);

 #ifdef CONFIG_DEBUG_FS

 static struct dentry *component_debugfs_dir;

 static int component_devices_show(struct seq_file *s, void *data)
 {
 	struct master *m = s->private;
 	struct component_match *match = m->match;
 	size_t i;

 	mutex_lock(&component_mutex);
 	seq_printf(s, "%-40s %20s\n", "master name", "status");
 	seq_puts(s, "-------------------------------------------------------------\n");
 	seq_printf(s, "%-40s %20s\n\n",
 		   dev_name(m->dev), m->bound ? "bound" : "not bound");

 	seq_printf(s, "%-40s %20s\n", "device name", "status");
 	seq_puts(s, "-------------------------------------------------------------\n");
 	for (i = 0; i < match->num; i++) {
 		struct device *d = (struct device *)match->compare[i].data;

 		seq_printf(s, "%-40s %20s\n", dev_name(d),
 			   match->compare[i].component ?
 			   "registered" : "not registered");
 	}
 	mutex_unlock(&component_mutex);

 	return 0;
 }

 DEFINE_SHOW_ATTRIBUTE(component_devices);

 static int __init component_debug_init(void)
 {
 	component_debugfs_dir = debugfs_create_dir("device_component", NULL);

 	return 0;
 }

 core_initcall(component_debug_init);

 static void component_master_debugfs_add(struct master *m)
 {
 	m->dentry = debugfs_create_file(dev_name(m->dev), 0444,
 					component_debugfs_dir,
 					m, &component_devices_fops);
 }

 static void component_master_debugfs_del(struct master *m)
 {
 	debugfs_remove(m->dentry);
 	m->dentry = NULL;
 }

 #else

 static void component_master_debugfs_add(struct master *m)
 { }

 static void component_master_debugfs_del(struct master *m)
 { }

 #endif

 static struct master *__master_find(struct device *dev,
 	const struct component_master_ops *ops)
 {
 	struct master *m;

 	list_for_each_entry(m, &masters, node)
 		if (m->dev == dev && (!ops || m->ops == ops))
 			return m;

 	return NULL;
 }

 static struct component *find_component(struct master *master,
 	int (*compare)(struct device *, void *), void *compare_data)
 {
 	struct component *c;

 	list_for_each_entry(c, &component_list, node) {
 		if (c->master && c->master != master)
 			continue;

 		if (compare(c->dev, compare_data))
 			return c;
 	}

 	return NULL;
 }

 static int find_components(struct master *master)
 {
 	struct component_match *match = master->match;
 	size_t i;
 	int ret = 0;

 	/*
 	 * Scan the array of match functions and attach
 	 * any components which are found to this master.
 	 */
 	for (i = 0; i < match->num; i++) {
 		struct component_match_array *mc = &match->compare[i];
 		struct component *c;

 		dev_dbg(master->dev, "Looking for component %zu\n", i);

 		if (match->compare[i].component)
 			continue;

 		c = find_component(master, mc->compare, mc->data);
 		if (!c) {
 			ret = -ENXIO;
 			break;
 		}

 		dev_dbg(master->dev, "found component %s, duplicate %u\n", dev_name(c->dev), !!c->master);

 		/* Attach this component to the master */
 		match->compare[i].duplicate = !!c->master;
 		match->compare[i].component = c;
 		c->master = master;
 	}
 	return ret;
 }

 /* Detach component from associated master */
 static void remove_component(struct master *master, struct component *c)
 {
 	size_t i;

 	/* Detach the component from this master. */
 	for (i = 0; i < master->match->num; i++)
 		if (master->match->compare[i].component == c)
 			master->match->compare[i].component = NULL;
 }

 /*
  * Try to bring up a master.  If component is NULL, we're interested in
  * this master, otherwise it's a component which must be present to try
  * and bring up the master.
  *
  * Returns 1 for successful bringup, 0 if not ready, or -ve errno.
  */
 static int try_to_bring_up_master(struct master *master,
 	struct component *component)
 {
 	int ret;

 	dev_dbg(master->dev, "trying to bring up master\n");

 	if (find_components(master)) {
 		dev_dbg(master->dev, "master has incomplete components\n");
 		return 0;
 	}

 	if (component && component->master != master) {
 		dev_dbg(master->dev, "master is not for this component (%s)\n",
 			dev_name(component->dev));
 		return 0;
 	}

 	if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
 		return -ENOMEM;

 	/* Found all components */
 	ret = master->ops->bind(master->dev);
 	if (ret < 0) {
 		devres_release_group(master->dev, NULL);
 		dev_info(master->dev, "master bind failed: %d\n", ret);
 		return ret;
 	}

 	master->bound = true;
 	return 1;
 }

 static int try_to_bring_up_masters(struct component *component)
 {
 	struct master *m;
 	int ret = 0;

 	list_for_each_entry(m, &masters, node) {
 		if (!m->bound) {
 			ret = try_to_bring_up_master(m, component);
 			if (ret != 0)
 				break;
 		}
 	}

 	return ret;
 }

 static void take_down_master(struct master *master)
 {
 	if (master->bound) {
 		master->ops->unbind(master->dev);
 		devres_release_group(master->dev, NULL);
 		master->bound = false;
 	}
 }

 static void component_match_release(struct device *master,
 	struct component_match *match)
 {
 	unsigned int i;

 	for (i = 0; i < match->num; i++) {
 		struct component_match_array *mc = &match->compare[i];

 		if (mc->release)
 			mc->release(master, mc->data);
 	}

 	kfree(match->compare);
 }

 static void devm_component_match_release(struct device *dev, void *res)
 {
 	component_match_release(dev, res);
 }

 static int component_match_realloc(struct device *dev,
 	struct component_match *match, size_t num)
 {
 	struct component_match_array *new;

 	if (match->alloc == num)
 		return 0;

 	new = kmalloc_array(num, sizeof(*new), GFP_KERNEL);
 	if (!new)
 		return -ENOMEM;

 	if (match->compare) {
 		memcpy(new, match->compare, sizeof(*new) *
 					    min(match->num, num));
 		kfree(match->compare);
 	}
 	match->compare = new;
 	match->alloc = num;

 	return 0;
 }

 /*
  * Add a component to be matched, with a release function.
  *
  * The match array is first created or extended if necessary.
  */
 void component_match_add_release(struct device *master,
 	struct component_match **matchptr,
 	void (*release)(struct device *, void *),
 	int (*compare)(struct device *, void *), void *compare_data)
 {
 	struct component_match *match = *matchptr;

 	if (IS_ERR(match))
 		return;

 	if (!match) {
 		match = devres_alloc(devm_component_match_release,
 				     sizeof(*match), GFP_KERNEL);
 		if (!match) {
 			*matchptr = ERR_PTR(-ENOMEM);
 			return;
 		}

 		devres_add(master, match);

 		*matchptr = match;
 	}

 	if (match->num == match->alloc) {
 		size_t new_size = match->alloc + 16;
 		int ret;

 		ret = component_match_realloc(master, match, new_size);
 		if (ret) {
 			*matchptr = ERR_PTR(ret);
 			return;
 		}
 	}

 	match->compare[match->num].compare = compare;
 	match->compare[match->num].release = release;
 	match->compare[match->num].data = compare_data;
 	match->compare[match->num].component = NULL;
 	match->num++;
 }
 EXPORT_SYMBOL(component_match_add_release);

 static void free_master(struct master *master)
 {
 	struct component_match *match = master->match;
 	int i;

 	component_master_debugfs_del(master);
 	list_del(&master->node);

 	if (match) {
 		for (i = 0; i < match->num; i++) {
 			struct component *c = match->compare[i].component;
 			if (c)
 				c->master = NULL;
 		}
 	}

 	kfree(master);
 }

 int component_master_add_with_match(struct device *dev,
 	const struct component_master_ops *ops,
 	struct component_match *match)
 {
 	struct master *master;
 	int ret;

 	/* Reallocate the match array for its true size */
 	ret = component_match_realloc(dev, match, match->num);
 	if (ret)
 		return ret;

 	master = kzalloc(sizeof(*master), GFP_KERNEL);
 	if (!master)
 		return -ENOMEM;

 	master->dev = dev;
 	master->ops = ops;
 	master->match = match;

 	component_master_debugfs_add(master);
 	/* Add to the list of available masters. */
 	mutex_lock(&component_mutex);
 	list_add(&master->node, &masters);

 	ret = try_to_bring_up_master(master, NULL);

 	if (ret < 0)
 		free_master(master);

 	mutex_unlock(&component_mutex);

 	return ret < 0 ? ret : 0;
 }
 EXPORT_SYMBOL_GPL(component_master_add_with_match);

 void component_master_del(struct device *dev,
 	const struct component_master_ops *ops)
 {
 	struct master *master;

 	mutex_lock(&component_mutex);
 	master = __master_find(dev, ops);
 	if (master) {
 		take_down_master(master);
 		free_master(master);
 	}
 	mutex_unlock(&component_mutex);
 }
 EXPORT_SYMBOL_GPL(component_master_del);

 static void component_unbind(struct component *component,
 	struct master *master, void *data)
 {
 	WARN_ON(!component->bound);

 	component->ops->unbind(component->dev, master->dev, data);
 	component->bound = false;

 	/* Release all resources claimed in the binding of this component */
 	devres_release_group(component->dev, component);
 }

 void component_unbind_all(struct device *master_dev, void *data)
 {
 	struct master *master;
 	struct component *c;
 	size_t i;

 	WARN_ON(!mutex_is_locked(&component_mutex));

 	master = __master_find(master_dev, NULL);
 	if (!master)
 		return;

 	/* Unbind components in reverse order */
 	for (i = master->match->num; i--; )
 		if (!master->match->compare[i].duplicate) {
 			c = master->match->compare[i].component;
 			component_unbind(c, master, data);
 		}
 }
 EXPORT_SYMBOL_GPL(component_unbind_all);

 static int component_bind(struct component *component, struct master *master,
 	void *data)
 {
 	int ret;

 	/*
 	 * Each component initialises inside its own devres group.
 	 * This allows us to roll-back a failed component without
 	 * affecting anything else.
 	 */
 	if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
 		return -ENOMEM;

 	/*
 	 * Also open a group for the device itself: this allows us
 	 * to release the resources claimed against the sub-device
 	 * at the appropriate moment.
 	 */
 	if (!devres_open_group(component->dev, component, GFP_KERNEL)) {
 		devres_release_group(master->dev, NULL);
 		return -ENOMEM;
 	}

 	dev_dbg(master->dev, "binding %s (ops %ps)\n",
 		dev_name(component->dev), component->ops);

 	ret = component->ops->bind(component->dev, master->dev, data);
 	if (!ret) {
 		component->bound = true;

 		/*
 		 * Close the component device's group so that resources
 		 * allocated in the binding are encapsulated for removal
 		 * at unbind.  Remove the group on the DRM device as we
 		 * can clean those resources up independently.
 		 */
 		devres_close_group(component->dev, NULL);
 		devres_remove_group(master->dev, NULL);

 		dev_info(master->dev, "bound %s (ops %ps)\n",
 			 dev_name(component->dev), component->ops);
 	} else {
 		devres_release_group(component->dev, NULL);
 		devres_release_group(master->dev, NULL);

 		dev_err(master->dev, "failed to bind %s (ops %ps): %d\n",
 			dev_name(component->dev), component->ops, ret);
 	}

 	return ret;
 }

 int component_bind_all(struct device *master_dev, void *data)
 {
 	struct master *master;
 	struct component *c;
 	size_t i;
 	int ret = 0;

 	WARN_ON(!mutex_is_locked(&component_mutex));

 	master = __master_find(master_dev, NULL);
 	if (!master)
 		return -EINVAL;

 	/* Bind components in match order */
 	for (i = 0; i < master->match->num; i++)
 		if (!master->match->compare[i].duplicate) {
 			c = master->match->compare[i].component;
 			ret = component_bind(c, master, data);
 			if (ret)
 				break;
 		}

 	if (ret != 0) {
 		for (; i > 0; i--)
 			if (!master->match->compare[i - 1].duplicate) {
 				c = master->match->compare[i - 1].component;
 				component_unbind(c, master, data);
 			}
 	}

 	return ret;
 }
 EXPORT_SYMBOL_GPL(component_bind_all);

 int component_add(struct device *dev, const struct component_ops *ops)
 {
 	struct component *component;
 	int ret;

 	component = kzalloc(sizeof(*component), GFP_KERNEL);
 	if (!component)
 		return -ENOMEM;

 	component->ops = ops;
 	component->dev = dev;

 	dev_dbg(dev, "adding component (ops %ps)\n", ops);

 	mutex_lock(&component_mutex);
 	list_add_tail(&component->node, &component_list);

 	ret = try_to_bring_up_masters(component);
 	if (ret < 0) {
 		if (component->master)
 			remove_component(component->master, component);
 		list_del(&component->node);

 		kfree(component);
 	}
 	mutex_unlock(&component_mutex);

 	return ret < 0 ? ret : 0;
 }
 EXPORT_SYMBOL_GPL(component_add);

 void component_del(struct device *dev, const struct component_ops *ops)
 {
 	struct component *c, *component = NULL;

 	mutex_lock(&component_mutex);
 	list_for_each_entry(c, &component_list, node)
 		if (c->dev == dev && c->ops == ops) {
 			list_del(&c->node);
 			component = c;
 			break;
 		}

 	if (component && component->master) {
 		take_down_master(component->master);
 		remove_component(component->master, component);
 	}

 	mutex_unlock(&component_mutex);

 	WARN_ON(!component);
 	kfree(component);
 }
 EXPORT_SYMBOL_GPL(component_del);

 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Componentized device handling.
	*
	* This is work in progress. We gather up the component devices into a list,
	* and bind them when instructed. At the moment, we're specific to the DRM
	* subsystem, and only handles one master device, but this doesn't have to be
	* the case.
	*/
	#include <linux/component.h>
	#include <linux/device.h>
	#include <linux/kref.h>
	#include <linux/list.h>
	#include <linux/module.h>
	#include <linux/mutex.h>
	#include <linux/slab.h>
	#include <linux/debugfs.h>

	struct component;

	struct component_match_array {
	void *data;
	int (compare)(struct device , void *);
	void (release)(struct device , void *);
	struct component *component;
	bool duplicate;
	};

	struct component_match {
	size_t alloc;
	size_t num;
	struct component_match_array *compare;
	};

	struct master {
	struct list_head node;
	bool bound;

	const struct component_master_ops *ops;
	struct device *dev;
	struct component_match *match;
	struct dentry *dentry;
	};

	struct component {
	struct list_head node;
	struct master *master;
	bool bound;

	const struct component_ops *ops;
	struct device *dev;
	};

	static DEFINE_MUTEX(component_mutex);
	static LIST_HEAD(component_list);
	static LIST_HEAD(masters);

	#ifdef CONFIG_DEBUG_FS

	static struct dentry *component_debugfs_dir;

	static int component_devices_show(struct seq_file s, void data)
	{
	struct master *m = s->private;
	struct component_match *match = m->match;
	size_t i;

	mutex_lock(&component_mutex);
	seq_printf(s, "%-40s %20s\n", "master name", "status");
	seq_puts(s, "-------------------------------------------------------------\n");
	seq_printf(s, "%-40s %20s\n\n",
	dev_name(m->dev), m->bound ? "bound" : "not bound");

	seq_printf(s, "%-40s %20s\n", "device name", "status");
	seq_puts(s, "-------------------------------------------------------------\n");
	for (i = 0; i < match->num; i++) {
	struct device d = (struct device )match->compare[i].data;

	seq_printf(s, "%-40s %20s\n", dev_name(d),
	match->compare[i].component ?
	"registered" : "not registered");
	}
	mutex_unlock(&component_mutex);

	return 0;
	}

	DEFINE_SHOW_ATTRIBUTE(component_devices);

	static int __init component_debug_init(void)
	{
	component_debugfs_dir = debugfs_create_dir("device_component", NULL);

	return 0;
	}

	core_initcall(component_debug_init);

	static void component_master_debugfs_add(struct master *m)
	{
	m->dentry = debugfs_create_file(dev_name(m->dev), 0444,
	component_debugfs_dir,
	m, &component_devices_fops);
	}

	static void component_master_debugfs_del(struct master *m)
	{
	debugfs_remove(m->dentry);
	m->dentry = NULL;
	}

	#else

	static void component_master_debugfs_add(struct master *m)
	{ }

	static void component_master_debugfs_del(struct master *m)
	{ }

	#endif

	static struct master __master_find(struct device dev,
	const struct component_master_ops *ops)
	{
	struct master *m;

	list_for_each_entry(m, &masters, node)
	if (m->dev == dev && (!ops \|\| m->ops == ops))
	return m;

	return NULL;
	}

	static struct component find_component(struct master master,
	int (compare)(struct device , void ), void compare_data)
	{
	struct component *c;

	list_for_each_entry(c, &component_list, node) {
	if (c->master && c->master != master)
	continue;

	if (compare(c->dev, compare_data))
	return c;
	}

	return NULL;
	}

	static int find_components(struct master *master)
	{
	struct component_match *match = master->match;
	size_t i;
	int ret = 0;

	/*
	* Scan the array of match functions and attach
	* any components which are found to this master.
	*/
	for (i = 0; i < match->num; i++) {
	struct component_match_array *mc = &match->compare[i];
	struct component *c;

	dev_dbg(master->dev, "Looking for component %zu\n", i);

	if (match->compare[i].component)
	continue;

	c = find_component(master, mc->compare, mc->data);
	if (!c) {
	ret = -ENXIO;
	break;
	}

	dev_dbg(master->dev, "found component %s, duplicate %u\n", dev_name(c->dev), !!c->master);

	/* Attach this component to the master */
	match->compare[i].duplicate = !!c->master;
	match->compare[i].component = c;
	c->master = master;
	}
	return ret;
	}

	/* Detach component from associated master */
	static void remove_component(struct master master, struct component c)
	{
	size_t i;

	/* Detach the component from this master. */
	for (i = 0; i < master->match->num; i++)
	if (master->match->compare[i].component == c)
	master->match->compare[i].component = NULL;
	}

	/*
	* Try to bring up a master. If component is NULL, we're interested in
	* this master, otherwise it's a component which must be present to try
	* and bring up the master.
	*
	* Returns 1 for successful bringup, 0 if not ready, or -ve errno.
	*/
	static int try_to_bring_up_master(struct master *master,
	struct component *component)
	{
	int ret;

	dev_dbg(master->dev, "trying to bring up master\n");

	if (find_components(master)) {
	dev_dbg(master->dev, "master has incomplete components\n");
	return 0;
	}

	if (component && component->master != master) {
	dev_dbg(master->dev, "master is not for this component (%s)\n",
	dev_name(component->dev));
	return 0;
	}

	if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
	return -ENOMEM;

	/* Found all components */
	ret = master->ops->bind(master->dev);
	if (ret < 0) {
	devres_release_group(master->dev, NULL);
	dev_info(master->dev, "master bind failed: %d\n", ret);
	return ret;
	}

	master->bound = true;
	return 1;
	}

	static int try_to_bring_up_masters(struct component *component)
	{
	struct master *m;
	int ret = 0;

	list_for_each_entry(m, &masters, node) {
	if (!m->bound) {
	ret = try_to_bring_up_master(m, component);
	if (ret != 0)
	break;
	}
	}

	return ret;
	}

	static void take_down_master(struct master *master)
	{
	if (master->bound) {
	master->ops->unbind(master->dev);
	devres_release_group(master->dev, NULL);
	master->bound = false;
	}
	}

	static void component_match_release(struct device *master,
	struct component_match *match)
	{
	unsigned int i;

	for (i = 0; i < match->num; i++) {
	struct component_match_array *mc = &match->compare[i];

	if (mc->release)
	mc->release(master, mc->data);
	}

	kfree(match->compare);
	}

	static void devm_component_match_release(struct device dev, void res)
	{
	component_match_release(dev, res);
	}

	static int component_match_realloc(struct device *dev,
	struct component_match *match, size_t num)
	{
	struct component_match_array *new;

	if (match->alloc == num)
	return 0;

	new = kmalloc_array(num, sizeof(*new), GFP_KERNEL);
	if (!new)
	return -ENOMEM;

	if (match->compare) {
	memcpy(new, match->compare, sizeof(new)
	min(match->num, num));
	kfree(match->compare);
	}
	match->compare = new;
	match->alloc = num;

	return 0;
	}

	/*
	* Add a component to be matched, with a release function.
	*
	* The match array is first created or extended if necessary.
	*/
	void component_match_add_release(struct device *master,
	struct component_match **matchptr,
	void (release)(struct device , void *),
	int (compare)(struct device , void ), void compare_data)
	{
	struct component_match match = matchptr;

	if (IS_ERR(match))
	return;

	if (!match) {
	match = devres_alloc(devm_component_match_release,
	sizeof(*match), GFP_KERNEL);
	if (!match) {
	*matchptr = ERR_PTR(-ENOMEM);
	return;
	}

	devres_add(master, match);

	*matchptr = match;
	}

	if (match->num == match->alloc) {
	size_t new_size = match->alloc + 16;
	int ret;

	ret = component_match_realloc(master, match, new_size);
	if (ret) {
	*matchptr = ERR_PTR(ret);
	return;
	}
	}

	match->compare[match->num].compare = compare;
	match->compare[match->num].release = release;
	match->compare[match->num].data = compare_data;
	match->compare[match->num].component = NULL;
	match->num++;
	}
	EXPORT_SYMBOL(component_match_add_release);

	static void free_master(struct master *master)
	{
	struct component_match *match = master->match;
	int i;

	component_master_debugfs_del(master);
	list_del(&master->node);

	if (match) {
	for (i = 0; i < match->num; i++) {
	struct component *c = match->compare[i].component;
	if (c)
	c->master = NULL;
	}
	}

	kfree(master);
	}

	int component_master_add_with_match(struct device *dev,
	const struct component_master_ops *ops,
	struct component_match *match)
	{
	struct master *master;
	int ret;

	/* Reallocate the match array for its true size */
	ret = component_match_realloc(dev, match, match->num);
	if (ret)
	return ret;

	master = kzalloc(sizeof(*master), GFP_KERNEL);
	if (!master)
	return -ENOMEM;

	master->dev = dev;
	master->ops = ops;
	master->match = match;

	component_master_debugfs_add(master);
	/* Add to the list of available masters. */
	mutex_lock(&component_mutex);
	list_add(&master->node, &masters);

	ret = try_to_bring_up_master(master, NULL);

	if (ret < 0)
	free_master(master);

	mutex_unlock(&component_mutex);

	return ret < 0 ? ret : 0;
	}
	EXPORT_SYMBOL_GPL(component_master_add_with_match);

	void component_master_del(struct device *dev,
	const struct component_master_ops *ops)
	{
	struct master *master;

	mutex_lock(&component_mutex);
	master = __master_find(dev, ops);
	if (master) {
	take_down_master(master);
	free_master(master);
	}
	mutex_unlock(&component_mutex);
	}
	EXPORT_SYMBOL_GPL(component_master_del);

	static void component_unbind(struct component *component,
	struct master master, void data)
	{
	WARN_ON(!component->bound);

	component->ops->unbind(component->dev, master->dev, data);
	component->bound = false;

	/* Release all resources claimed in the binding of this component */
	devres_release_group(component->dev, component);
	}

	void component_unbind_all(struct device master_dev, void data)
	{
	struct master *master;
	struct component *c;
	size_t i;

	WARN_ON(!mutex_is_locked(&component_mutex));

	master = __master_find(master_dev, NULL);
	if (!master)
	return;

	/* Unbind components in reverse order */
	for (i = master->match->num; i--; )
	if (!master->match->compare[i].duplicate) {
	c = master->match->compare[i].component;
	component_unbind(c, master, data);
	}
	}
	EXPORT_SYMBOL_GPL(component_unbind_all);

	static int component_bind(struct component component, struct master master,
	void *data)
	{
	int ret;

	/*
	* Each component initialises inside its own devres group.
	* This allows us to roll-back a failed component without
	* affecting anything else.
	*/
	if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
	return -ENOMEM;

	/*
	* Also open a group for the device itself: this allows us
	* to release the resources claimed against the sub-device
	* at the appropriate moment.
	*/
	if (!devres_open_group(component->dev, component, GFP_KERNEL)) {
	devres_release_group(master->dev, NULL);
	return -ENOMEM;
	}

	dev_dbg(master->dev, "binding %s (ops %ps)\n",
	dev_name(component->dev), component->ops);

	ret = component->ops->bind(component->dev, master->dev, data);
	if (!ret) {
	component->bound = true;

	/*
	* Close the component device's group so that resources
	* allocated in the binding are encapsulated for removal
	* at unbind. Remove the group on the DRM device as we
	* can clean those resources up independently.
	*/
	devres_close_group(component->dev, NULL);
	devres_remove_group(master->dev, NULL);

	dev_info(master->dev, "bound %s (ops %ps)\n",
	dev_name(component->dev), component->ops);
	} else {
	devres_release_group(component->dev, NULL);
	devres_release_group(master->dev, NULL);

	dev_err(master->dev, "failed to bind %s (ops %ps): %d\n",
	dev_name(component->dev), component->ops, ret);
	}

	return ret;
	}

	int component_bind_all(struct device master_dev, void data)
	{
	struct master *master;
	struct component *c;
	size_t i;
	int ret = 0;

	WARN_ON(!mutex_is_locked(&component_mutex));

	master = __master_find(master_dev, NULL);
	if (!master)
	return -EINVAL;

	/* Bind components in match order */
	for (i = 0; i < master->match->num; i++)
	if (!master->match->compare[i].duplicate) {
	c = master->match->compare[i].component;
	ret = component_bind(c, master, data);
	if (ret)
	break;
	}

	if (ret != 0) {
	for (; i > 0; i--)
	if (!master->match->compare[i - 1].duplicate) {
	c = master->match->compare[i - 1].component;
	component_unbind(c, master, data);
	}
	}

	return ret;
	}
	EXPORT_SYMBOL_GPL(component_bind_all);

	int component_add(struct device dev, const struct component_ops ops)
	{
	struct component *component;
	int ret;

	component = kzalloc(sizeof(*component), GFP_KERNEL);
	if (!component)
	return -ENOMEM;

	component->ops = ops;
	component->dev = dev;

	dev_dbg(dev, "adding component (ops %ps)\n", ops);

	mutex_lock(&component_mutex);
	list_add_tail(&component->node, &component_list);

	ret = try_to_bring_up_masters(component);
	if (ret < 0) {
	if (component->master)
	remove_component(component->master, component);
	list_del(&component->node);

	kfree(component);
	}
	mutex_unlock(&component_mutex);

	return ret < 0 ? ret : 0;
	}
	EXPORT_SYMBOL_GPL(component_add);

	void component_del(struct device dev, const struct component_ops ops)
	{
	struct component c, component = NULL;

	mutex_lock(&component_mutex);
	list_for_each_entry(c, &component_list, node)
	if (c->dev == dev && c->ops == ops) {
	list_del(&c->node);
	component = c;
	break;
	}

	if (component && component->master) {
	take_down_master(component->master);
	remove_component(component->master, component);
	}

	mutex_unlock(&component_mutex);

	WARN_ON(!component);
	kfree(component);
	}
	EXPORT_SYMBOL_GPL(component_del);

	MODULE_LICENSE("GPL v2");