/*
 * 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 component_match {
        size_t alloc;
        size_t num;
        struct {
                void *data;
                int (*fn)(struct device *, void *);
        } compare[0];
};

struct master {
        struct list_head node;
        struct list_head components;
        bool bound;

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

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;
}

/*
 * Add a component to a master, finding the component via the compare
 * function and compare data.  This is safe to call for duplicate matches
 * and will not result in the same component being added multiple times.
 */
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 && c->master != master)
                        continue;

                if (compare(c->dev, compare_data)) {
                        if (!c->master)
                                component_attach_master(master, c);
                        ret = 0;
                        break;
                }
        }

        return ret;
}
EXPORT_SYMBOL_GPL(component_master_add_child);

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

        if (!match) {
                /*
                 * Search the list of components, looking for components that
                 * belong to this master, and attach them to the master.
                 */
                return master->ops->add_components(master->dev, master);
        }

        /*
         * Scan the array of match functions and attach
         * any components which are found to this master.
         */
        for (i = 0; i < match->num; i++) {
                ret = component_master_add_child(master,
                                                 match->compare[i].fn,
                                                 match->compare[i].data);
                if (ret)
                        break;
        }
        return ret;
}

/* 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;

        if (master->bound)
                return 0;

        /*
         * Search the list of components, looking for components that
         * belong to this master, and attach them to the master.
         */
        if (find_components(master)) {
                /* Failed to find all components */
                ret = 0;
                goto out;
        }

        if (component && component->master != 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\n", ret);
                goto out;
        }

        master->bound = true;
        return 1;

out:
        master_remove_components(master);

        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);
}

static size_t component_match_size(size_t num)
{
        return offsetof(struct component_match, compare[num]);
}

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

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

        new = devm_kmalloc(dev, component_match_size(num), GFP_KERNEL);
        if (!new)
                return ERR_PTR(-ENOMEM);

        if (match) {
                memcpy(new, match, component_match_size(min(match->num, num)));
                devm_kfree(dev, match);
        } else {
                new->num = 0;
        }

        new->alloc = num;

        return new;
}

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

        if (IS_ERR(match))
                return;

        if (!match || match->num == match->alloc) {
                size_t new_size = match ? match->alloc + 16 : 15;

                match = component_match_realloc(dev, match, new_size);

                *matchptr = match;

                if (IS_ERR(match))
                        return;
        }

        match->compare[match->num].fn = compare;
        match->compare[match->num].data = compare_data;
        match->num++;
}
EXPORT_SYMBOL(component_match_add);

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

        if (ops->add_components && match)
                return -EINVAL;

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

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

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

int component_master_add(struct device *dev,
        const struct component_master_ops *ops)
{
        return component_master_add_with_match(dev, ops, NULL);
}
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)\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;
        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)\n", 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");