// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/drivers/devfreq/governor_userspace.c
 *
 *  Copyright (C) 2011 Samsung Electronics
 *      MyungJoo Ham <myungjoo.ham@samsung.com>
 */

#include <linux/slab.h>
#include <linux/device.h>
#include <linux/devfreq.h>
#include <linux/devfreq-governor.h>
#include <linux/kstrtox.h>
#include <linux/pm.h>
#include <linux/mutex.h>
#include <linux/module.h>

struct userspace_data {
        unsigned long user_frequency;
        bool valid;
};

static int devfreq_userspace_func(struct devfreq *df, unsigned long *freq)
{
        struct userspace_data *data = df->governor_data;

        if (data->valid)
                *freq = data->user_frequency;
        else
                *freq = df->previous_freq; /* No user freq specified yet */

        return 0;
}

static ssize_t set_freq_store(struct device *dev, struct device_attribute *attr,
                              const char *buf, size_t count)
{
        struct devfreq *devfreq = to_devfreq(dev);
        struct userspace_data *data;
        unsigned long wanted;
        int err = 0;

        err = kstrtoul(buf, 0, &wanted);
        if (err)
                return err;

        mutex_lock(&devfreq->lock);
        data = devfreq->governor_data;

        data->user_frequency = wanted;
        data->valid = true;
        err = update_devfreq(devfreq);
        if (err == 0)
                err = count;
        mutex_unlock(&devfreq->lock);
        return err;
}

static ssize_t set_freq_show(struct device *dev,
                             struct device_attribute *attr, char *buf)
{
        struct devfreq *devfreq = to_devfreq(dev);
        struct userspace_data *data;
        int err = 0;

        mutex_lock(&devfreq->lock);
        data = devfreq->governor_data;

        if (data->valid)
                err = sprintf(buf, "%lu\n", data->user_frequency);
        else
                err = sprintf(buf, "undefined\n");
        mutex_unlock(&devfreq->lock);
        return err;
}

static DEVICE_ATTR_RW(set_freq);
static struct attribute *dev_entries[] = {
        &dev_attr_set_freq.attr,
        NULL,
};
static const struct attribute_group dev_attr_group = {
        .name   = DEVFREQ_GOV_USERSPACE,
        .attrs  = dev_entries,
};

static int userspace_init(struct devfreq *devfreq)
{
        int err = 0;
        struct userspace_data *data = kzalloc_obj(struct userspace_data);

        if (!data) {
                err = -ENOMEM;
                goto out;
        }
        data->valid = false;
        devfreq->governor_data = data;

        err = sysfs_create_group(&devfreq->dev.kobj, &dev_attr_group);
out:
        return err;
}

static void userspace_exit(struct devfreq *devfreq)
{
        /*
         * Remove the sysfs entry, unless this is being called after
         * device_del(), which should have done this already via kobject_del().
         */
        if (devfreq->dev.kobj.sd)
                sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);

        kfree(devfreq->governor_data);
        devfreq->governor_data = NULL;
}

static int devfreq_userspace_handler(struct devfreq *devfreq,
                        unsigned int event, void *data)
{
        int ret = 0;

        switch (event) {
        case DEVFREQ_GOV_START:
                ret = userspace_init(devfreq);
                break;
        case DEVFREQ_GOV_STOP:
                userspace_exit(devfreq);
                break;
        default:
                break;
        }

        return ret;
}

static struct devfreq_governor devfreq_userspace = {
        .name = DEVFREQ_GOV_USERSPACE,
        .get_target_freq = devfreq_userspace_func,
        .event_handler = devfreq_userspace_handler,
};

static int __init devfreq_userspace_init(void)
{
        return devfreq_add_governor(&devfreq_userspace);
}
subsys_initcall(devfreq_userspace_init);

static void __exit devfreq_userspace_exit(void)
{
        int ret;

        ret = devfreq_remove_governor(&devfreq_userspace);
        if (ret)
                pr_err("%s: failed remove governor %d\n", __func__, ret);

        return;
}
module_exit(devfreq_userspace_exit);
MODULE_DESCRIPTION("DEVFREQ Userspace governor");
MODULE_LICENSE("GPL");