/*
   * Componentized device handling.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * 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>
  
  struct master {
  	struct list_head node;
  	struct list_head components;
  	bool bound;
  
  	const struct component_master_ops *ops;
  	struct device *dev;
  };
  
  struct component {
  	struct list_head node;
  	struct list_head master_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);
  
  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;
  }
  
  /* Attach an unattached component to a master. */
  static void component_attach_master(struct master *master, struct component *c)
  {
  	c->master = master;
  
  	list_add_tail(&c->master_node, &master->components);
  }
  
  /* Detach a component from a master. */
  static void component_detach_master(struct master *master, struct component *c)
  {
  	list_del(&c->master_node);
  
  	c->master = NULL;
  }
  
  int component_master_add_child(struct master *master,
  	int (*compare)(struct device *, void *), void *compare_data)
  {
  	struct component *c;
  	int ret = -ENXIO;
  
  	list_for_each_entry(c, &component_list, node) {
  		if (c->master)
  			continue;
  
  		if (compare(c->dev, compare_data)) {
  			component_attach_master(master, c);
  			ret = 0;
  			break;
  		}
  	}
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(component_master_add_child);
  
  /* Detach all attached components from this master */
  static void master_remove_components(struct master *master)
  {
  	while (!list_empty(&master->components)) {
  		struct component *c = list_first_entry(&master->components,
  					struct component, master_node);
  
  		WARN_ON(c->master != master);
  
  		component_detach_master(master, c);
  	}
  }
  
  /*
   * 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 = 0;
  
  	if (!master->bound) {
  		/*
  		 * Search the list of components, looking for components that
  		 * belong to this master, and attach them to the master.
  		 */
  		if (master->ops->add_components(master->dev, master)) {
  			/* Failed to find all components */
  			master_remove_components(master);
  			ret = 0;
  			goto out;
  		}
  
  		if (component && component->master != master) {
  			master_remove_components(master);
  			ret = 0;
  			goto out;
  		}
  
  		if (!devres_open_group(master->dev, NULL, GFP_KERNEL)) {
  			ret = -ENOMEM;
  			goto out;
  		}
  
  		/* 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
  ", ret);
  			master_remove_components(master);
  			goto out;
  		}
  
  		master->bound = true;
  		ret = 1;
  	}
  out:
  
  	return ret;
  }
  
  static int try_to_bring_up_masters(struct component *component)
  {
  	struct master *m;
  	int ret = 0;
  
  	list_for_each_entry(m, &masters, node) {
  		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;
  	}
  
  	master_remove_components(master);
  }
  
  int component_master_add(struct device *dev,
  	const struct component_master_ops *ops)
  {
  	struct master *master;
  	int ret;
  
  	master = kzalloc(sizeof(*master), GFP_KERNEL);
  	if (!master)
  		return -ENOMEM;
  
  	master->dev = dev;
  	master->ops = ops;
  	INIT_LIST_HEAD(&master->components);
  
  	/* 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) {
  		/* Delete off the list if we weren't successful */
  		list_del(&master->node);
  		kfree(master);
  	}
  	mutex_unlock(&component_mutex);
  
  	return ret < 0 ? ret : 0;
  }
  EXPORT_SYMBOL_GPL(component_master_add);
  
  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);
  
  		list_del(&master->node);
  		kfree(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;
  
  	WARN_ON(!mutex_is_locked(&component_mutex));
  
  	master = __master_find(master_dev, NULL);
  	if (!master)
  		return;
  
  	list_for_each_entry_reverse(c, &master->components, master_node)
  		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)
  ",
  		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)
  ",
  			 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
  ",
  			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;
  	int ret = 0;
  
  	WARN_ON(!mutex_is_locked(&component_mutex));
  
  	master = __master_find(master_dev, NULL);
  	if (!master)
  		return -EINVAL;
  
  	list_for_each_entry(c, &master->components, master_node) {
  		ret = component_bind(c, master, data);
  		if (ret)
  			break;
  	}
  
  	if (ret != 0) {
  		list_for_each_entry_continue_reverse(c, &master->components,
  						     master_node)
  			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)
  ", ops);
  
  	mutex_lock(&component_mutex);
  	list_add_tail(&component->node, &component_list);
  
  	ret = try_to_bring_up_masters(component);
  	if (ret < 0) {
  		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);
  
  	mutex_unlock(&component_mutex);
  
  	WARN_ON(!component);
  	kfree(component);
  }
  EXPORT_SYMBOL_GPL(component_del);
  
  MODULE_LICENSE("GPL v2");