/*
 * V4L2 clock service
 *
 * Copyright (C) 2012-2013, Guennadi Liakhovetski <g.liakhovetski@gmx.de>
 *
 * 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.
 */

#include <linux/atomic.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/string.h>

#include <media/v4l2-clk.h>
#include <media/v4l2-subdev.h>

static DEFINE_MUTEX(clk_lock);
static LIST_HEAD(clk_list);

static struct v4l2_clk *v4l2_clk_find(const char *dev_id, const char *id)
{
        struct v4l2_clk *clk;

        list_for_each_entry(clk, &clk_list, list) {
                if (strcmp(dev_id, clk->dev_id))
                        continue;

                if (!id || !clk->id || !strcmp(clk->id, id))
                        return clk;
        }

        return ERR_PTR(-ENODEV);
}

struct v4l2_clk *v4l2_clk_get(struct device *dev, const char *id)
{
        struct v4l2_clk *clk;

        mutex_lock(&clk_lock);
        clk = v4l2_clk_find(dev_name(dev), id);

        if (!IS_ERR(clk))
                atomic_inc(&clk->use_count);
        mutex_unlock(&clk_lock);

        return clk;
}
EXPORT_SYMBOL(v4l2_clk_get);

void v4l2_clk_put(struct v4l2_clk *clk)
{
        struct v4l2_clk *tmp;

        if (IS_ERR(clk))
                return;

        mutex_lock(&clk_lock);

        list_for_each_entry(tmp, &clk_list, list)
                if (tmp == clk)
                        atomic_dec(&clk->use_count);

        mutex_unlock(&clk_lock);
}
EXPORT_SYMBOL(v4l2_clk_put);

static int v4l2_clk_lock_driver(struct v4l2_clk *clk)
{
        struct v4l2_clk *tmp;
        int ret = -ENODEV;

        mutex_lock(&clk_lock);

        list_for_each_entry(tmp, &clk_list, list)
                if (tmp == clk) {
                        ret = !try_module_get(clk->ops->owner);
                        if (ret)
                                ret = -EFAULT;
                        break;
                }

        mutex_unlock(&clk_lock);

        return ret;
}

static void v4l2_clk_unlock_driver(struct v4l2_clk *clk)
{
        module_put(clk->ops->owner);
}

int v4l2_clk_enable(struct v4l2_clk *clk)
{
        int ret = v4l2_clk_lock_driver(clk);

        if (ret < 0)
                return ret;

        mutex_lock(&clk->lock);

        if (++clk->enable == 1 && clk->ops->enable) {
                ret = clk->ops->enable(clk);
                if (ret < 0)
                        clk->enable--;
        }

        mutex_unlock(&clk->lock);

        return ret;
}
EXPORT_SYMBOL(v4l2_clk_enable);

/*
 * You might Oops if you try to disabled a disabled clock, because then the
 * driver isn't locked and could have been unloaded by now, so, don't do that
 */
void v4l2_clk_disable(struct v4l2_clk *clk)
{
        int enable;

        mutex_lock(&clk->lock);

        enable = --clk->enable;
        if (WARN(enable < 0, "Unbalanced %s() on %s:%s!\n", __func__,
                 clk->dev_id, clk->id))
                clk->enable++;
        else if (!enable && clk->ops->disable)
                clk->ops->disable(clk);

        mutex_unlock(&clk->lock);

        v4l2_clk_unlock_driver(clk);
}
EXPORT_SYMBOL(v4l2_clk_disable);

unsigned long v4l2_clk_get_rate(struct v4l2_clk *clk)
{
        int ret = v4l2_clk_lock_driver(clk);

        if (ret < 0)
                return ret;

        mutex_lock(&clk->lock);
        if (!clk->ops->get_rate)
                ret = -ENOSYS;
        else
                ret = clk->ops->get_rate(clk);
        mutex_unlock(&clk->lock);

        v4l2_clk_unlock_driver(clk);

        return ret;
}
EXPORT_SYMBOL(v4l2_clk_get_rate);

int v4l2_clk_set_rate(struct v4l2_clk *clk, unsigned long rate)
{
        int ret = v4l2_clk_lock_driver(clk);

        if (ret < 0)
                return ret;

        mutex_lock(&clk->lock);
        if (!clk->ops->set_rate)
                ret = -ENOSYS;
        else
                ret = clk->ops->set_rate(clk, rate);
        mutex_unlock(&clk->lock);

        v4l2_clk_unlock_driver(clk);

        return ret;
}
EXPORT_SYMBOL(v4l2_clk_set_rate);

struct v4l2_clk *v4l2_clk_register(const struct v4l2_clk_ops *ops,
                                   const char *dev_id,
                                   const char *id, void *priv)
{
        struct v4l2_clk *clk;
        int ret;

        if (!ops || !dev_id)
                return ERR_PTR(-EINVAL);

        clk = kzalloc(sizeof(struct v4l2_clk), GFP_KERNEL);
        if (!clk)
                return ERR_PTR(-ENOMEM);

        clk->id = kstrdup(id, GFP_KERNEL);
        clk->dev_id = kstrdup(dev_id, GFP_KERNEL);
        if ((id && !clk->id) || !clk->dev_id) {
                ret = -ENOMEM;
                goto ealloc;
        }
        clk->ops = ops;
        clk->priv = priv;
        atomic_set(&clk->use_count, 0);
        mutex_init(&clk->lock);

        mutex_lock(&clk_lock);
        if (!IS_ERR(v4l2_clk_find(dev_id, id))) {
                mutex_unlock(&clk_lock);
                ret = -EEXIST;
                goto eexist;
        }
        list_add_tail(&clk->list, &clk_list);
        mutex_unlock(&clk_lock);

        return clk;

eexist:
ealloc:
        kfree(clk->id);
        kfree(clk->dev_id);
        kfree(clk);
        return ERR_PTR(ret);
}
EXPORT_SYMBOL(v4l2_clk_register);

void v4l2_clk_unregister(struct v4l2_clk *clk)
{
        if (WARN(atomic_read(&clk->use_count),
                 "%s(): Refusing to unregister ref-counted %s:%s clock!\n",
                 __func__, clk->dev_id, clk->id))
                return;

        mutex_lock(&clk_lock);
        list_del(&clk->list);
        mutex_unlock(&clk_lock);

        kfree(clk->id);
        kfree(clk->dev_id);
        kfree(clk);
}
EXPORT_SYMBOL(v4l2_clk_unregister);

struct v4l2_clk_fixed {
        unsigned long rate;
        struct v4l2_clk_ops ops;
};

static unsigned long fixed_get_rate(struct v4l2_clk *clk)
{
        struct v4l2_clk_fixed *priv = clk->priv;
        return priv->rate;
}

struct v4l2_clk *__v4l2_clk_register_fixed(const char *dev_id,
                const char *id, unsigned long rate, struct module *owner)
{
        struct v4l2_clk *clk;
        struct v4l2_clk_fixed *priv = kzalloc(sizeof(*priv), GFP_KERNEL);

        if (!priv)
                return ERR_PTR(-ENOMEM);

        priv->rate = rate;
        priv->ops.get_rate = fixed_get_rate;
        priv->ops.owner = owner;

        clk = v4l2_clk_register(&priv->ops, dev_id, id, priv);
        if (IS_ERR(clk))
                kfree(priv);

        return clk;
}
EXPORT_SYMBOL(__v4l2_clk_register_fixed);

void v4l2_clk_unregister_fixed(struct v4l2_clk *clk)
{
        kfree(clk->priv);
        v4l2_clk_unregister(clk);
}
EXPORT_SYMBOL(v4l2_clk_unregister_fixed);