// SPDX-License-Identifier: GPL-2.0-only
/*
 * Windfarm PowerMac thermal control. Core
 *
 * (c) Copyright 2005 Benjamin Herrenschmidt, IBM Corp.
 *                    <benh@kernel.crashing.org>
 *
 * This core code tracks the list of sensors & controls, register
 * clients, and holds the kernel thread used for control.
 *
 * TODO:
 *
 * Add some information about sensor/control type and data format to
 * sensors/controls, and have the sysfs attribute stuff be moved
 * generically here instead of hard coded in the platform specific
 * driver as it us currently
 *
 * This however requires solving some annoying lifetime issues with
 * sysfs which doesn't seem to have lifetime rules for struct attribute,
 * I may have to create full features kobjects for every sensor/control
 * instead which is a bit of an overkill imho
 */

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/kthread.h>
#include <linux/jiffies.h>
#include <linux/reboot.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/mutex.h>
#include <linux/freezer.h>

#include "windfarm.h"

#define VERSION "0.2"

#undef DEBUG

#ifdef DEBUG
#define DBG(args...)    printk(args)
#else
#define DBG(args...)    do { } while(0)
#endif

static LIST_HEAD(wf_controls);
static LIST_HEAD(wf_sensors);
static DEFINE_MUTEX(wf_lock);
static BLOCKING_NOTIFIER_HEAD(wf_client_list);
static int wf_client_count;
static unsigned int wf_overtemp;
static unsigned int wf_overtemp_counter;
static struct task_struct *wf_thread;

static struct platform_device wf_platform_device = {
        .name   = "windfarm",
};

/*
 * Utilities & tick thread
 */

static inline void wf_notify(int event, void *param)
{
        blocking_notifier_call_chain(&wf_client_list, event, param);
}

static int wf_critical_overtemp(void)
{
        static char const critical_overtemp_path[] = "/sbin/critical_overtemp";
        char *argv[] = { (char *)critical_overtemp_path, NULL };
        static char *envp[] = { "HOME=/",
                                "TERM=linux",
                                "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
                                NULL };

        return call_usermodehelper(critical_overtemp_path,
                                   argv, envp, UMH_WAIT_EXEC);
}

static int wf_thread_func(void *data)
{
        unsigned long next, delay;

        next = jiffies;

        DBG("wf: thread started\n");

        set_freezable();
        while (!kthread_should_stop()) {
                try_to_freeze();

                if (time_after_eq(jiffies, next)) {
                        wf_notify(WF_EVENT_TICK, NULL);
                        if (wf_overtemp) {
                                wf_overtemp_counter++;
                                /* 10 seconds overtemp, notify userland */
                                if (wf_overtemp_counter > 10)
                                        wf_critical_overtemp();
                                /* 30 seconds, shutdown */
                                if (wf_overtemp_counter > 30) {
                                        printk(KERN_ERR "windfarm: Overtemp "
                                               "for more than 30"
                                               " seconds, shutting down\n");
                                        machine_power_off();
                                }
                        }
                        next += HZ;
                }

                delay = next - jiffies;
                if (delay <= HZ)
                        schedule_timeout_interruptible(delay);
        }

        DBG("wf: thread stopped\n");

        return 0;
}

static void wf_start_thread(void)
{
        wf_thread = kthread_run(wf_thread_func, NULL, "kwindfarm");
        if (IS_ERR(wf_thread)) {
                printk(KERN_ERR "windfarm: failed to create thread,err %ld\n",
                       PTR_ERR(wf_thread));
                wf_thread = NULL;
        }
}


static void wf_stop_thread(void)
{
        if (wf_thread)
                kthread_stop(wf_thread);
        wf_thread = NULL;
}

/*
 * Controls
 */

static void wf_control_release(struct kref *kref)
{
        struct wf_control *ct = container_of(kref, struct wf_control, ref);

        DBG("wf: Deleting control %s\n", ct->name);

        if (ct->ops && ct->ops->release)
                ct->ops->release(ct);
        else
                kfree(ct);
}

static ssize_t wf_show_control(struct device *dev,
                               struct device_attribute *attr, char *buf)
{
        struct wf_control *ctrl = container_of(attr, struct wf_control, attr);
        const char *typestr;
        s32 val = 0;
        int err;

        err = ctrl->ops->get_value(ctrl, &val);
        if (err < 0) {
                if (err == -EFAULT)
                        return sprintf(buf, "<HW FAULT>\n");
                return err;
        }
        switch(ctrl->type) {
        case WF_CONTROL_RPM_FAN:
                typestr = " RPM";
                break;
        case WF_CONTROL_PWM_FAN:
                typestr = " %";
                break;
        default:
                typestr = "";
        }
        return sprintf(buf, "%d%s\n", val, typestr);
}

/* This is really only for debugging... */
static ssize_t wf_store_control(struct device *dev,
                                struct device_attribute *attr,
                                const char *buf, size_t count)
{
        struct wf_control *ctrl = container_of(attr, struct wf_control, attr);
        int val;
        int err;
        char *endp;

        val = simple_strtoul(buf, &endp, 0);
        while (endp < buf + count && (*endp == ' ' || *endp == '\n'))
                ++endp;
        if (endp - buf < count)
                return -EINVAL;
        err = ctrl->ops->set_value(ctrl, val);
        if (err < 0)
                return err;
        return count;
}

int wf_register_control(struct wf_control *new_ct)
{
        struct wf_control *ct;

        mutex_lock(&wf_lock);
        list_for_each_entry(ct, &wf_controls, link) {
                if (!strcmp(ct->name, new_ct->name)) {
                        printk(KERN_WARNING "windfarm: trying to register"
                               " duplicate control %s\n", ct->name);
                        mutex_unlock(&wf_lock);
                        return -EEXIST;
                }
        }
        kref_init(&new_ct->ref);
        list_add(&new_ct->link, &wf_controls);

        sysfs_attr_init(&new_ct->attr.attr);
        new_ct->attr.attr.name = new_ct->name;
        new_ct->attr.attr.mode = 0644;
        new_ct->attr.show = wf_show_control;
        new_ct->attr.store = wf_store_control;
        if (device_create_file(&wf_platform_device.dev, &new_ct->attr))
                printk(KERN_WARNING "windfarm: device_create_file failed"
                        " for %s\n", new_ct->name);
                /* the subsystem still does useful work without the file */

        DBG("wf: Registered control %s\n", new_ct->name);

        wf_notify(WF_EVENT_NEW_CONTROL, new_ct);
        mutex_unlock(&wf_lock);

        return 0;
}
EXPORT_SYMBOL_GPL(wf_register_control);

void wf_unregister_control(struct wf_control *ct)
{
        mutex_lock(&wf_lock);
        list_del(&ct->link);
        mutex_unlock(&wf_lock);

        DBG("wf: Unregistered control %s\n", ct->name);

        kref_put(&ct->ref, wf_control_release);
}
EXPORT_SYMBOL_GPL(wf_unregister_control);

int wf_get_control(struct wf_control *ct)
{
        if (!try_module_get(ct->ops->owner))
                return -ENODEV;
        kref_get(&ct->ref);
        return 0;
}
EXPORT_SYMBOL_GPL(wf_get_control);

void wf_put_control(struct wf_control *ct)
{
        struct module *mod = ct->ops->owner;
        kref_put(&ct->ref, wf_control_release);
        module_put(mod);
}
EXPORT_SYMBOL_GPL(wf_put_control);


/*
 * Sensors
 */


static void wf_sensor_release(struct kref *kref)
{
        struct wf_sensor *sr = container_of(kref, struct wf_sensor, ref);

        DBG("wf: Deleting sensor %s\n", sr->name);

        if (sr->ops && sr->ops->release)
                sr->ops->release(sr);
        else
                kfree(sr);
}

static ssize_t wf_show_sensor(struct device *dev,
                              struct device_attribute *attr, char *buf)
{
        struct wf_sensor *sens = container_of(attr, struct wf_sensor, attr);
        s32 val = 0;
        int err;

        err = sens->ops->get_value(sens, &val);
        if (err < 0)
                return err;
        return sprintf(buf, "%d.%03d\n", FIX32TOPRINT(val));
}

int wf_register_sensor(struct wf_sensor *new_sr)
{
        struct wf_sensor *sr;

        mutex_lock(&wf_lock);
        list_for_each_entry(sr, &wf_sensors, link) {
                if (!strcmp(sr->name, new_sr->name)) {
                        printk(KERN_WARNING "windfarm: trying to register"
                               " duplicate sensor %s\n", sr->name);
                        mutex_unlock(&wf_lock);
                        return -EEXIST;
                }
        }
        kref_init(&new_sr->ref);
        list_add(&new_sr->link, &wf_sensors);

        sysfs_attr_init(&new_sr->attr.attr);
        new_sr->attr.attr.name = new_sr->name;
        new_sr->attr.attr.mode = 0444;
        new_sr->attr.show = wf_show_sensor;
        new_sr->attr.store = NULL;
        if (device_create_file(&wf_platform_device.dev, &new_sr->attr))
                printk(KERN_WARNING "windfarm: device_create_file failed"
                        " for %s\n", new_sr->name);
                /* the subsystem still does useful work without the file */

        DBG("wf: Registered sensor %s\n", new_sr->name);

        wf_notify(WF_EVENT_NEW_SENSOR, new_sr);
        mutex_unlock(&wf_lock);

        return 0;
}
EXPORT_SYMBOL_GPL(wf_register_sensor);

void wf_unregister_sensor(struct wf_sensor *sr)
{
        mutex_lock(&wf_lock);
        list_del(&sr->link);
        mutex_unlock(&wf_lock);

        DBG("wf: Unregistered sensor %s\n", sr->name);

        wf_put_sensor(sr);
}
EXPORT_SYMBOL_GPL(wf_unregister_sensor);

int wf_get_sensor(struct wf_sensor *sr)
{
        if (!try_module_get(sr->ops->owner))
                return -ENODEV;
        kref_get(&sr->ref);
        return 0;
}
EXPORT_SYMBOL_GPL(wf_get_sensor);

void wf_put_sensor(struct wf_sensor *sr)
{
        struct module *mod = sr->ops->owner;
        kref_put(&sr->ref, wf_sensor_release);
        module_put(mod);
}
EXPORT_SYMBOL_GPL(wf_put_sensor);


/*
 * Client & notification
 */

int wf_register_client(struct notifier_block *nb)
{
        int rc;
        struct wf_control *ct;
        struct wf_sensor *sr;

        mutex_lock(&wf_lock);
        rc = blocking_notifier_chain_register(&wf_client_list, nb);
        if (rc != 0)
                goto bail;
        wf_client_count++;
        list_for_each_entry(ct, &wf_controls, link)
                wf_notify(WF_EVENT_NEW_CONTROL, ct);
        list_for_each_entry(sr, &wf_sensors, link)
                wf_notify(WF_EVENT_NEW_SENSOR, sr);
        if (wf_client_count == 1)
                wf_start_thread();
 bail:
        mutex_unlock(&wf_lock);
        return rc;
}
EXPORT_SYMBOL_GPL(wf_register_client);

int wf_unregister_client(struct notifier_block *nb)
{
        mutex_lock(&wf_lock);
        blocking_notifier_chain_unregister(&wf_client_list, nb);
        wf_client_count--;
        if (wf_client_count == 0)
                wf_stop_thread();
        mutex_unlock(&wf_lock);

        return 0;
}
EXPORT_SYMBOL_GPL(wf_unregister_client);

void wf_set_overtemp(void)
{
        mutex_lock(&wf_lock);
        wf_overtemp++;
        if (wf_overtemp == 1) {
                printk(KERN_WARNING "windfarm: Overtemp condition detected !\n");
                wf_overtemp_counter = 0;
                wf_notify(WF_EVENT_OVERTEMP, NULL);
        }
        mutex_unlock(&wf_lock);
}
EXPORT_SYMBOL_GPL(wf_set_overtemp);

void wf_clear_overtemp(void)
{
        mutex_lock(&wf_lock);
        WARN_ON(wf_overtemp == 0);
        if (wf_overtemp == 0) {
                mutex_unlock(&wf_lock);
                return;
        }
        wf_overtemp--;
        if (wf_overtemp == 0) {
                printk(KERN_WARNING "windfarm: Overtemp condition cleared !\n");
                wf_notify(WF_EVENT_NORMALTEMP, NULL);
        }
        mutex_unlock(&wf_lock);
}
EXPORT_SYMBOL_GPL(wf_clear_overtemp);

static int __init windfarm_core_init(void)
{
        DBG("wf: core loaded\n");

        platform_device_register(&wf_platform_device);
        return 0;
}

static void __exit windfarm_core_exit(void)
{
        BUG_ON(wf_client_count != 0);

        DBG("wf: core unloaded\n");

        platform_device_unregister(&wf_platform_device);
}


module_init(windfarm_core_init);
module_exit(windfarm_core_exit);

MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
MODULE_DESCRIPTION("Core component of PowerMac thermal control");
MODULE_LICENSE("GPL");