/*
 * devfreq-event: a framework to provide raw data and events of devfreq devices
 *
 * Copyright (C) 2015 Samsung Electronics
 * Author: Chanwoo Choi <cw00.choi@samsung.com>
 *
 * 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 driver is based on drivers/devfreq/devfreq.c.
 */

#include <linux/devfreq-event.h>
#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/of.h>

static struct class *devfreq_event_class;

/* The list of all devfreq event list */
static LIST_HEAD(devfreq_event_list);
static DEFINE_MUTEX(devfreq_event_list_lock);

#define to_devfreq_event(DEV) container_of(DEV, struct devfreq_event_dev, dev)

/**
 * devfreq_event_enable_edev() - Enable the devfreq-event dev and increase
 *                               the enable_count of devfreq-event dev.
 * @edev        : the devfreq-event device
 *
 * Note that this function increase the enable_count and enable the
 * devfreq-event device. The devfreq-event device should be enabled before
 * using it by devfreq device.
 */
int devfreq_event_enable_edev(struct devfreq_event_dev *edev)
{
        int ret = 0;

        if (!edev || !edev->desc)
                return -EINVAL;

        mutex_lock(&edev->lock);
        if (edev->desc->ops && edev->desc->ops->enable
                        && edev->enable_count == 0) {
                ret = edev->desc->ops->enable(edev);
                if (ret < 0)
                        goto err;
        }
        edev->enable_count++;
err:
        mutex_unlock(&edev->lock);

        return ret;
}
EXPORT_SYMBOL_GPL(devfreq_event_enable_edev);

/**
 * devfreq_event_disable_edev() - Disable the devfreq-event dev and decrease
 *                                the enable_count of the devfreq-event dev.
 * @edev        : the devfreq-event device
 *
 * Note that this function decrease the enable_count and disable the
 * devfreq-event device. After the devfreq-event device is disabled,
 * devfreq device can't use the devfreq-event device for get/set/reset
 * operations.
 */
int devfreq_event_disable_edev(struct devfreq_event_dev *edev)
{
        int ret = 0;

        if (!edev || !edev->desc)
                return -EINVAL;

        mutex_lock(&edev->lock);
        if (edev->enable_count <= 0) {
                dev_warn(&edev->dev, "unbalanced enable_count\n");
                ret = -EIO;
                goto err;
        }

        if (edev->desc->ops && edev->desc->ops->disable
                        && edev->enable_count == 1) {
                ret = edev->desc->ops->disable(edev);
                if (ret < 0)
                        goto err;
        }
        edev->enable_count--;
err:
        mutex_unlock(&edev->lock);

        return ret;
}
EXPORT_SYMBOL_GPL(devfreq_event_disable_edev);

/**
 * devfreq_event_is_enabled() - Check whether devfreq-event dev is enabled or
 *                              not.
 * @edev        : the devfreq-event device
 *
 * Note that this function check whether devfreq-event dev is enabled or not.
 * If return true, the devfreq-event dev is enabeld. If return false, the
 * devfreq-event dev is disabled.
 */
bool devfreq_event_is_enabled(struct devfreq_event_dev *edev)
{
        bool enabled = false;

        if (!edev || !edev->desc)
                return enabled;

        mutex_lock(&edev->lock);

        if (edev->enable_count > 0)
                enabled = true;

        mutex_unlock(&edev->lock);

        return enabled;
}
EXPORT_SYMBOL_GPL(devfreq_event_is_enabled);

/**
 * devfreq_event_set_event() - Set event to devfreq-event dev to start.
 * @edev        : the devfreq-event device
 *
 * Note that this function set the event to the devfreq-event device to start
 * for getting the event data which could be various event type.
 */
int devfreq_event_set_event(struct devfreq_event_dev *edev)
{
        int ret;

        if (!edev || !edev->desc)
                return -EINVAL;

        if (!edev->desc->ops || !edev->desc->ops->set_event)
                return -EINVAL;

        if (!devfreq_event_is_enabled(edev))
                return -EPERM;

        mutex_lock(&edev->lock);
        ret = edev->desc->ops->set_event(edev);
        mutex_unlock(&edev->lock);

        return ret;
}
EXPORT_SYMBOL_GPL(devfreq_event_set_event);

/**
 * devfreq_event_get_event() - Get {load|total}_count from devfreq-event dev.
 * @edev        : the devfreq-event device
 * @edata       : the calculated data of devfreq-event device
 *
 * Note that this function get the calculated event data from devfreq-event dev
 * after stoping the progress of whole sequence of devfreq-event dev.
 */
int devfreq_event_get_event(struct devfreq_event_dev *edev,
                            struct devfreq_event_data *edata)
{
        int ret;

        if (!edev || !edev->desc)
                return -EINVAL;

        if (!edev->desc->ops || !edev->desc->ops->get_event)
                return -EINVAL;

        if (!devfreq_event_is_enabled(edev))
                return -EINVAL;

        edata->total_count = edata->load_count = 0;

        mutex_lock(&edev->lock);
        ret = edev->desc->ops->get_event(edev, edata);
        if (ret < 0)
                edata->total_count = edata->load_count = 0;
        mutex_unlock(&edev->lock);

        return ret;
}
EXPORT_SYMBOL_GPL(devfreq_event_get_event);

/**
 * devfreq_event_reset_event() - Reset all opeations of devfreq-event dev.
 * @edev        : the devfreq-event device
 *
 * Note that this function stop all operations of devfreq-event dev and reset
 * the current event data to make the devfreq-event device into initial state.
 */
int devfreq_event_reset_event(struct devfreq_event_dev *edev)
{
        int ret = 0;

        if (!edev || !edev->desc)
                return -EINVAL;

        if (!devfreq_event_is_enabled(edev))
                return -EPERM;

        mutex_lock(&edev->lock);
        if (edev->desc->ops && edev->desc->ops->reset)
                ret = edev->desc->ops->reset(edev);
        mutex_unlock(&edev->lock);

        return ret;
}
EXPORT_SYMBOL_GPL(devfreq_event_reset_event);

/**
 * devfreq_event_get_edev_by_phandle() - Get the devfreq-event dev from
 *                                       devicetree.
 * @dev         : the pointer to the given device
 * @index       : the index into list of devfreq-event device
 *
 * Note that this function return the pointer of devfreq-event device.
 */
struct devfreq_event_dev *devfreq_event_get_edev_by_phandle(struct device *dev,
                                                      int index)
{
        struct device_node *node;
        struct devfreq_event_dev *edev;

        if (!dev->of_node)
                return ERR_PTR(-EINVAL);

        node = of_parse_phandle(dev->of_node, "devfreq-events", index);
        if (!node)
                return ERR_PTR(-ENODEV);

        mutex_lock(&devfreq_event_list_lock);
        list_for_each_entry(edev, &devfreq_event_list, node) {
                if (edev->dev.parent && edev->dev.parent->of_node == node)
                        goto out;
        }

        list_for_each_entry(edev, &devfreq_event_list, node) {
                if (!strcmp(edev->desc->name, node->name))
                        goto out;
        }
        edev = NULL;
out:
        mutex_unlock(&devfreq_event_list_lock);

        if (!edev) {
                of_node_put(node);
                return ERR_PTR(-ENODEV);
        }

        of_node_put(node);

        return edev;
}
EXPORT_SYMBOL_GPL(devfreq_event_get_edev_by_phandle);

/**
 * devfreq_event_get_edev_count() - Get the count of devfreq-event dev
 * @dev         : the pointer to the given device
 *
 * Note that this function return the count of devfreq-event devices.
 */
int devfreq_event_get_edev_count(struct device *dev)
{
        int count;

        if (!dev->of_node) {
                dev_err(dev, "device does not have a device node entry\n");
                return -EINVAL;
        }

        count = of_property_count_elems_of_size(dev->of_node, "devfreq-events",
                                                sizeof(u32));
        if (count < 0) {
                dev_err(dev,
                        "failed to get the count of devfreq-event in %s node\n",
                        dev->of_node->full_name);
                return count;
        }

        return count;
}
EXPORT_SYMBOL_GPL(devfreq_event_get_edev_count);

static void devfreq_event_release_edev(struct device *dev)
{
        struct devfreq_event_dev *edev = to_devfreq_event(dev);

        kfree(edev);
}

/**
 * devfreq_event_add_edev() - Add new devfreq-event device.
 * @dev         : the device owning the devfreq-event device being created
 * @desc        : the devfreq-event device's decriptor which include essential
 *                data for devfreq-event device.
 *
 * Note that this function add new devfreq-event device to devfreq-event class
 * list and register the device of the devfreq-event device.
 */
struct devfreq_event_dev *devfreq_event_add_edev(struct device *dev,
                                                struct devfreq_event_desc *desc)
{
        struct devfreq_event_dev *edev;
        static atomic_t event_no = ATOMIC_INIT(-1);
        int ret;

        if (!dev || !desc)
                return ERR_PTR(-EINVAL);

        if (!desc->name || !desc->ops)
                return ERR_PTR(-EINVAL);

        if (!desc->ops->set_event || !desc->ops->get_event)
                return ERR_PTR(-EINVAL);

        edev = kzalloc(sizeof(struct devfreq_event_dev), GFP_KERNEL);
        if (!edev)
                return ERR_PTR(-ENOMEM);

        mutex_init(&edev->lock);
        edev->desc = desc;
        edev->enable_count = 0;
        edev->dev.parent = dev;
        edev->dev.class = devfreq_event_class;
        edev->dev.release = devfreq_event_release_edev;

        dev_set_name(&edev->dev, "event%d", atomic_inc_return(&event_no));
        ret = device_register(&edev->dev);
        if (ret < 0) {
                put_device(&edev->dev);
                return ERR_PTR(ret);
        }
        dev_set_drvdata(&edev->dev, edev);

        INIT_LIST_HEAD(&edev->node);

        mutex_lock(&devfreq_event_list_lock);
        list_add(&edev->node, &devfreq_event_list);
        mutex_unlock(&devfreq_event_list_lock);

        return edev;
}
EXPORT_SYMBOL_GPL(devfreq_event_add_edev);

/**
 * devfreq_event_remove_edev() - Remove the devfreq-event device registered.
 * @dev         : the devfreq-event device
 *
 * Note that this function remove the registered devfreq-event device.
 */
int devfreq_event_remove_edev(struct devfreq_event_dev *edev)
{
        if (!edev)
                return -EINVAL;

        WARN_ON(edev->enable_count);

        mutex_lock(&devfreq_event_list_lock);
        list_del(&edev->node);
        mutex_unlock(&devfreq_event_list_lock);

        device_unregister(&edev->dev);

        return 0;
}
EXPORT_SYMBOL_GPL(devfreq_event_remove_edev);

static int devm_devfreq_event_match(struct device *dev, void *res, void *data)
{
        struct devfreq_event_dev **r = res;

        if (WARN_ON(!r || !*r))
                return 0;

        return *r == data;
}

static void devm_devfreq_event_release(struct device *dev, void *res)
{
        devfreq_event_remove_edev(*(struct devfreq_event_dev **)res);
}

/**
 * devm_devfreq_event_add_edev() - Resource-managed devfreq_event_add_edev()
 * @dev         : the device owning the devfreq-event device being created
 * @desc        : the devfreq-event device's decriptor which include essential
 *                data for devfreq-event device.
 *
 * Note that this function manages automatically the memory of devfreq-event
 * device using device resource management and simplify the free operation
 * for memory of devfreq-event device.
 */
struct devfreq_event_dev *devm_devfreq_event_add_edev(struct device *dev,
                                                struct devfreq_event_desc *desc)
{
        struct devfreq_event_dev **ptr, *edev;

        ptr = devres_alloc(devm_devfreq_event_release, sizeof(*ptr),
                                GFP_KERNEL);
        if (!ptr)
                return ERR_PTR(-ENOMEM);

        edev = devfreq_event_add_edev(dev, desc);
        if (IS_ERR(edev)) {
                devres_free(ptr);
                return ERR_PTR(-ENOMEM);
        }

        *ptr = edev;
        devres_add(dev, ptr);

        return edev;
}
EXPORT_SYMBOL_GPL(devm_devfreq_event_add_edev);

/**
 * devm_devfreq_event_remove_edev()- Resource-managed devfreq_event_remove_edev()
 * @dev         : the device owning the devfreq-event device being created
 * @edev        : the devfreq-event device
 *
 * Note that this function manages automatically the memory of devfreq-event
 * device using device resource management.
 */
void devm_devfreq_event_remove_edev(struct device *dev,
                                struct devfreq_event_dev *edev)
{
        WARN_ON(devres_release(dev, devm_devfreq_event_release,
                               devm_devfreq_event_match, edev));
}
EXPORT_SYMBOL_GPL(devm_devfreq_event_remove_edev);

/*
 * Device attributes for devfreq-event class.
 */
static ssize_t name_show(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct devfreq_event_dev *edev = to_devfreq_event(dev);

        if (!edev || !edev->desc)
                return -EINVAL;

        return sprintf(buf, "%s\n", edev->desc->name);
}
static DEVICE_ATTR_RO(name);

static ssize_t enable_count_show(struct device *dev,
                                  struct device_attribute *attr, char *buf)
{
        struct devfreq_event_dev *edev = to_devfreq_event(dev);

        if (!edev || !edev->desc)
                return -EINVAL;

        return sprintf(buf, "%d\n", edev->enable_count);
}
static DEVICE_ATTR_RO(enable_count);

static struct attribute *devfreq_event_attrs[] = {
        &dev_attr_name.attr,
        &dev_attr_enable_count.attr,
        NULL,
};
ATTRIBUTE_GROUPS(devfreq_event);

static int __init devfreq_event_init(void)
{
        devfreq_event_class = class_create(THIS_MODULE, "devfreq-event");
        if (IS_ERR(devfreq_event_class)) {
                pr_err("%s: couldn't create class\n", __FILE__);
                return PTR_ERR(devfreq_event_class);
        }

        devfreq_event_class->dev_groups = devfreq_event_groups;

        return 0;
}
subsys_initcall(devfreq_event_init);