// SPDX-License-Identifier: GPL-2.0-only
/*
 * Generic gameport layer
 *
 * Copyright (c) 1999-2002 Vojtech Pavlik
 * Copyright (c) 2005 Dmitry Torokhov
 */


#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/export.h>
#include <linux/stddef.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/gameport.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/workqueue.h>
#include <linux/sched.h>        /* HZ */
#include <linux/mutex.h>
#include <linux/timekeeping.h>

MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
MODULE_DESCRIPTION("Generic gameport layer");
MODULE_LICENSE("GPL");

static bool use_ktime = true;
module_param(use_ktime, bool, 0400);
MODULE_PARM_DESC(use_ktime, "Use ktime for measuring I/O speed");

/*
 * gameport_mutex protects entire gameport subsystem and is taken
 * every time gameport port or driver registrered or unregistered.
 */
static DEFINE_MUTEX(gameport_mutex);

static LIST_HEAD(gameport_list);

static const struct bus_type gameport_bus;

static void gameport_add_port(struct gameport *gameport);
static void gameport_attach_driver(struct gameport_driver *drv);
static void gameport_reconnect_port(struct gameport *gameport);
static void gameport_disconnect_port(struct gameport *gameport);

#if defined(__i386__)

#include <linux/i8253.h>

#define DELTA(x,y)      ((y)-(x)+((y)<(x)?1193182/HZ:0))
#define GET_TIME(x)     do { x = get_time_pit(); } while (0)

static unsigned int get_time_pit(void)
{
        unsigned long flags;
        unsigned int count;

        raw_spin_lock_irqsave(&i8253_lock, flags);
        outb_p(0x00, 0x43);
        count = inb_p(0x40);
        count |= inb_p(0x40) << 8;
        raw_spin_unlock_irqrestore(&i8253_lock, flags);

        return count;
}

#endif



/*
 * gameport_measure_speed() measures the gameport i/o speed.
 */

static int gameport_measure_speed(struct gameport *gameport)
{
        unsigned int i, t, tx;
        u64 t1, t2, t3;
        unsigned long flags;

        if (gameport_open(gameport, NULL, GAMEPORT_MODE_RAW))
                return 0;

        tx = ~0;

        for (i = 0; i < 50; i++) {
                local_irq_save(flags);
                t1 = ktime_get_ns();
                for (t = 0; t < 50; t++)
                        gameport_read(gameport);
                t2 = ktime_get_ns();
                t3 = ktime_get_ns();
                local_irq_restore(flags);
                udelay(i * 10);
                t = (t2 - t1) - (t3 - t2);
                if (t < tx)
                        tx = t;
        }

        gameport_close(gameport);
        t = 1000000 * 50;
        if (tx)
                t /= tx;
        return t;
}

static int old_gameport_measure_speed(struct gameport *gameport)
{
#if defined(__i386__)

        unsigned int i, t, t1, t2, t3, tx;
        unsigned long flags;

        if (gameport_open(gameport, NULL, GAMEPORT_MODE_RAW))
                return 0;

        tx = 1 << 30;

        for(i = 0; i < 50; i++) {
                local_irq_save(flags);
                GET_TIME(t1);
                for (t = 0; t < 50; t++) gameport_read(gameport);
                GET_TIME(t2);
                GET_TIME(t3);
                local_irq_restore(flags);
                udelay(i * 10);
                if ((t = DELTA(t2,t1) - DELTA(t3,t2)) < tx) tx = t;
        }

        gameport_close(gameport);
        return 59659 / (tx < 1 ? 1 : tx);

#elif defined (__x86_64__)

        unsigned int i, t;
        unsigned long tx, t1, t2, flags;

        if (gameport_open(gameport, NULL, GAMEPORT_MODE_RAW))
                return 0;

        tx = 1 << 30;

        for(i = 0; i < 50; i++) {
                local_irq_save(flags);
                t1 = rdtsc();
                for (t = 0; t < 50; t++) gameport_read(gameport);
                t2 = rdtsc();
                local_irq_restore(flags);
                udelay(i * 10);
                if (t2 - t1 < tx) tx = t2 - t1;
        }

        gameport_close(gameport);
        return (this_cpu_read(cpu_info.loops_per_jiffy) *
                (unsigned long)HZ / (1000 / 50)) / (tx < 1 ? 1 : tx);

#else

        unsigned int j, t = 0;

        if (gameport_open(gameport, NULL, GAMEPORT_MODE_RAW))
                return 0;

        j = jiffies; while (j == jiffies);
        j = jiffies; while (j == jiffies) { t++; gameport_read(gameport); }

        gameport_close(gameport);
        return t * HZ / 1000;

#endif
}

void gameport_start_polling(struct gameport *gameport)
{
        spin_lock(&gameport->timer_lock);

        if (!gameport->poll_cnt++) {
                BUG_ON(!gameport->poll_handler);
                BUG_ON(!gameport->poll_interval);
                mod_timer(&gameport->poll_timer, jiffies + msecs_to_jiffies(gameport->poll_interval));
        }

        spin_unlock(&gameport->timer_lock);
}
EXPORT_SYMBOL(gameport_start_polling);

void gameport_stop_polling(struct gameport *gameport)
{
        spin_lock(&gameport->timer_lock);

        if (!--gameport->poll_cnt)
                timer_delete(&gameport->poll_timer);

        spin_unlock(&gameport->timer_lock);
}
EXPORT_SYMBOL(gameport_stop_polling);

static void gameport_run_poll_handler(struct timer_list *t)
{
        struct gameport *gameport = timer_container_of(gameport, t,
                                                       poll_timer);

        gameport->poll_handler(gameport);
        if (gameport->poll_cnt)
                mod_timer(&gameport->poll_timer, jiffies + msecs_to_jiffies(gameport->poll_interval));
}

/*
 * Basic gameport -> driver core mappings
 */

static int gameport_bind_driver(struct gameport *gameport, struct gameport_driver *drv)
{
        int error;

        gameport->dev.driver = &drv->driver;
        if (drv->connect(gameport, drv)) {
                gameport->dev.driver = NULL;
                return -ENODEV;
        }

        error = device_bind_driver(&gameport->dev);
        if (error) {
                dev_warn(&gameport->dev,
                         "device_bind_driver() failed for %s (%s) and %s, error: %d\n",
                        gameport->phys, gameport->name,
                        drv->description, error);
                drv->disconnect(gameport);
                gameport->dev.driver = NULL;
                return error;
        }

        return 0;
}

static void gameport_find_driver(struct gameport *gameport)
{
        int error;

        error = device_attach(&gameport->dev);
        if (error < 0)
                dev_warn(&gameport->dev,
                         "device_attach() failed for %s (%s), error: %d\n",
                         gameport->phys, gameport->name, error);
}


/*
 * Gameport event processing.
 */

enum gameport_event_type {
        GAMEPORT_REGISTER_PORT,
        GAMEPORT_ATTACH_DRIVER,
};

struct gameport_event {
        enum gameport_event_type type;
        void *object;
        struct module *owner;
        struct list_head node;
};

static DEFINE_SPINLOCK(gameport_event_lock);    /* protects gameport_event_list */
static LIST_HEAD(gameport_event_list);

static struct gameport_event *gameport_get_event(void)
{
        struct gameport_event *event = NULL;
        unsigned long flags;

        spin_lock_irqsave(&gameport_event_lock, flags);

        if (!list_empty(&gameport_event_list)) {
                event = list_first_entry(&gameport_event_list,
                                         struct gameport_event, node);
                list_del_init(&event->node);
        }

        spin_unlock_irqrestore(&gameport_event_lock, flags);
        return event;
}

static void gameport_free_event(struct gameport_event *event)
{
        module_put(event->owner);
        kfree(event);
}

static void gameport_remove_duplicate_events(struct gameport_event *event)
{
        struct gameport_event *e, *next;
        unsigned long flags;

        spin_lock_irqsave(&gameport_event_lock, flags);

        list_for_each_entry_safe(e, next, &gameport_event_list, node) {
                if (event->object == e->object) {
                        /*
                         * If this event is of different type we should not
                         * look further - we only suppress duplicate events
                         * that were sent back-to-back.
                         */
                        if (event->type != e->type)
                                break;

                        list_del_init(&e->node);
                        gameport_free_event(e);
                }
        }

        spin_unlock_irqrestore(&gameport_event_lock, flags);
}


static void gameport_handle_events(struct work_struct *work)
{
        struct gameport_event *event;

        mutex_lock(&gameport_mutex);

        /*
         * Note that we handle only one event here to give swsusp
         * a chance to freeze kgameportd thread. Gameport events
         * should be pretty rare so we are not concerned about
         * taking performance hit.
         */
        if ((event = gameport_get_event())) {

                switch (event->type) {

                case GAMEPORT_REGISTER_PORT:
                        gameport_add_port(event->object);
                        break;

                case GAMEPORT_ATTACH_DRIVER:
                        gameport_attach_driver(event->object);
                        break;
                }

                gameport_remove_duplicate_events(event);
                gameport_free_event(event);
        }

        mutex_unlock(&gameport_mutex);
}

static DECLARE_WORK(gameport_event_work, gameport_handle_events);

static int gameport_queue_event(void *object, struct module *owner,
                                enum gameport_event_type event_type)
{
        unsigned long flags;
        struct gameport_event *event;
        int retval = 0;

        spin_lock_irqsave(&gameport_event_lock, flags);

        /*
         * Scan event list for the other events for the same gameport port,
         * starting with the most recent one. If event is the same we
         * do not need add new one. If event is of different type we
         * need to add this event and should not look further because
         * we need to preserve sequence of distinct events.
         */
        list_for_each_entry_reverse(event, &gameport_event_list, node) {
                if (event->object == object) {
                        if (event->type == event_type)
                                goto out;
                        break;
                }
        }

        event = kmalloc_obj(*event, GFP_ATOMIC);
        if (!event) {
                pr_err("Not enough memory to queue event %d\n", event_type);
                retval = -ENOMEM;
                goto out;
        }

        if (!try_module_get(owner)) {
                pr_warn("Can't get module reference, dropping event %d\n",
                        event_type);
                kfree(event);
                retval = -EINVAL;
                goto out;
        }

        event->type = event_type;
        event->object = object;
        event->owner = owner;

        list_add_tail(&event->node, &gameport_event_list);
        queue_work(system_long_wq, &gameport_event_work);

out:
        spin_unlock_irqrestore(&gameport_event_lock, flags);
        return retval;
}

/*
 * Remove all events that have been submitted for a given object,
 * be it a gameport port or a driver.
 */
static void gameport_remove_pending_events(void *object)
{
        struct gameport_event *event, *next;
        unsigned long flags;

        spin_lock_irqsave(&gameport_event_lock, flags);

        list_for_each_entry_safe(event, next, &gameport_event_list, node) {
                if (event->object == object) {
                        list_del_init(&event->node);
                        gameport_free_event(event);
                }
        }

        spin_unlock_irqrestore(&gameport_event_lock, flags);
}

/*
 * Destroy child gameport port (if any) that has not been fully registered yet.
 *
 * Note that we rely on the fact that port can have only one child and therefore
 * only one child registration request can be pending. Additionally, children
 * are registered by driver's connect() handler so there can't be a grandchild
 * pending registration together with a child.
 */
static struct gameport *gameport_get_pending_child(struct gameport *parent)
{
        struct gameport_event *event;
        struct gameport *gameport, *child = NULL;
        unsigned long flags;

        spin_lock_irqsave(&gameport_event_lock, flags);

        list_for_each_entry(event, &gameport_event_list, node) {
                if (event->type == GAMEPORT_REGISTER_PORT) {
                        gameport = event->object;
                        if (gameport->parent == parent) {
                                child = gameport;
                                break;
                        }
                }
        }

        spin_unlock_irqrestore(&gameport_event_lock, flags);
        return child;
}

/*
 * Gameport port operations
 */

static ssize_t gameport_description_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct gameport *gameport = to_gameport_port(dev);

        return sprintf(buf, "%s\n", gameport->name);
}
static DEVICE_ATTR(description, S_IRUGO, gameport_description_show, NULL);

static ssize_t drvctl_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
        struct gameport *gameport = to_gameport_port(dev);
        struct device_driver *drv;
        int error;

        error = mutex_lock_interruptible(&gameport_mutex);
        if (error)
                return error;

        if (!strncmp(buf, "none", count)) {
                gameport_disconnect_port(gameport);
        } else if (!strncmp(buf, "reconnect", count)) {
                gameport_reconnect_port(gameport);
        } else if (!strncmp(buf, "rescan", count)) {
                gameport_disconnect_port(gameport);
                gameport_find_driver(gameport);
        } else if ((drv = driver_find(buf, &gameport_bus)) != NULL) {
                gameport_disconnect_port(gameport);
                error = gameport_bind_driver(gameport, to_gameport_driver(drv));
        } else {
                error = -EINVAL;
        }

        mutex_unlock(&gameport_mutex);

        return error ? error : count;
}
static DEVICE_ATTR_WO(drvctl);

static struct attribute *gameport_device_attrs[] = {
        &dev_attr_description.attr,
        &dev_attr_drvctl.attr,
        NULL,
};
ATTRIBUTE_GROUPS(gameport_device);

static void gameport_release_port(struct device *dev)
{
        struct gameport *gameport = to_gameport_port(dev);

        kfree(gameport);
        module_put(THIS_MODULE);
}

void gameport_set_phys(struct gameport *gameport, const char *fmt, ...)
{
        va_list args;

        va_start(args, fmt);
        vsnprintf(gameport->phys, sizeof(gameport->phys), fmt, args);
        va_end(args);
}
EXPORT_SYMBOL(gameport_set_phys);

static void gameport_default_trigger(struct gameport *gameport)
{
#ifdef CONFIG_HAS_IOPORT
        outb(0xff, gameport->io);
#endif
}

static unsigned char gameport_default_read(struct gameport *gameport)
{
#ifdef CONFIG_HAS_IOPORT
        return inb(gameport->io);
#else
        return 0xff;
#endif
}

static void gameport_setup_default_handlers(struct gameport *gameport)
{
        if ((!gameport->trigger || !gameport->read) &&
            !IS_ENABLED(CONFIG_HAS_IOPORT))
                dev_err(&gameport->dev,
                        "I/O port access is required for %s (%s) but is not available\n",
                        gameport->phys, gameport->name);

        if (!gameport->trigger)
                gameport->trigger = gameport_default_trigger;
        if (!gameport->read)
                gameport->read = gameport_default_read;
}

/*
 * Prepare gameport port for registration.
 */
static void gameport_init_port(struct gameport *gameport)
{
        static atomic_t gameport_no = ATOMIC_INIT(-1);

        __module_get(THIS_MODULE);

        mutex_init(&gameport->drv_mutex);
        device_initialize(&gameport->dev);
        dev_set_name(&gameport->dev, "gameport%lu",
                        (unsigned long)atomic_inc_return(&gameport_no));
        gameport->dev.bus = &gameport_bus;
        gameport->dev.release = gameport_release_port;
        if (gameport->parent)
                gameport->dev.parent = &gameport->parent->dev;

        gameport_setup_default_handlers(gameport);
        INIT_LIST_HEAD(&gameport->node);
        spin_lock_init(&gameport->timer_lock);
        timer_setup(&gameport->poll_timer, gameport_run_poll_handler, 0);
}

/*
 * Complete gameport port registration.
 * Driver core will attempt to find appropriate driver for the port.
 */
static void gameport_add_port(struct gameport *gameport)
{
        int error;

        if (gameport->parent)
                gameport->parent->child = gameport;

        gameport->speed = use_ktime ?
                gameport_measure_speed(gameport) :
                old_gameport_measure_speed(gameport);

        list_add_tail(&gameport->node, &gameport_list);

        if (gameport->io)
                dev_info(&gameport->dev, "%s is %s, io %#x, speed %dkHz\n",
                         gameport->name, gameport->phys, gameport->io, gameport->speed);
        else
                dev_info(&gameport->dev, "%s is %s, speed %dkHz\n",
                        gameport->name, gameport->phys, gameport->speed);

        error = device_add(&gameport->dev);
        if (error)
                dev_err(&gameport->dev,
                        "device_add() failed for %s (%s), error: %d\n",
                        gameport->phys, gameport->name, error);
}

/*
 * gameport_destroy_port() completes deregistration process and removes
 * port from the system
 */
static void gameport_destroy_port(struct gameport *gameport)
{
        struct gameport *child;

        child = gameport_get_pending_child(gameport);
        if (child) {
                gameport_remove_pending_events(child);
                put_device(&child->dev);
        }

        if (gameport->parent) {
                gameport->parent->child = NULL;
                gameport->parent = NULL;
        }

        if (device_is_registered(&gameport->dev))
                device_del(&gameport->dev);

        list_del_init(&gameport->node);

        gameport_remove_pending_events(gameport);
        put_device(&gameport->dev);
}

/*
 * Reconnect gameport port and all its children (re-initialize attached devices)
 */
static void gameport_reconnect_port(struct gameport *gameport)
{
        do {
                if (!gameport->drv || !gameport->drv->reconnect || gameport->drv->reconnect(gameport)) {
                        gameport_disconnect_port(gameport);
                        gameport_find_driver(gameport);
                        /* Ok, old children are now gone, we are done */
                        break;
                }
                gameport = gameport->child;
        } while (gameport);
}

/*
 * gameport_disconnect_port() unbinds a port from its driver. As a side effect
 * all child ports are unbound and destroyed.
 */
static void gameport_disconnect_port(struct gameport *gameport)
{
        struct gameport *s, *parent;

        if (gameport->child) {
                /*
                 * Children ports should be disconnected and destroyed
                 * first, staring with the leaf one, since we don't want
                 * to do recursion
                 */
                for (s = gameport; s->child; s = s->child)
                        /* empty */;

                do {
                        parent = s->parent;

                        device_release_driver(&s->dev);
                        gameport_destroy_port(s);
                } while ((s = parent) != gameport);
        }

        /*
         * Ok, no children left, now disconnect this port
         */
        device_release_driver(&gameport->dev);
}

/*
 * Submits register request to kgameportd for subsequent execution.
 * Note that port registration is always asynchronous.
 */
void __gameport_register_port(struct gameport *gameport, struct module *owner)
{
        gameport_init_port(gameport);
        gameport_queue_event(gameport, owner, GAMEPORT_REGISTER_PORT);
}
EXPORT_SYMBOL(__gameport_register_port);

/*
 * Synchronously unregisters gameport port.
 */
void gameport_unregister_port(struct gameport *gameport)
{
        mutex_lock(&gameport_mutex);
        gameport_disconnect_port(gameport);
        gameport_destroy_port(gameport);
        mutex_unlock(&gameport_mutex);
}
EXPORT_SYMBOL(gameport_unregister_port);


/*
 * Gameport driver operations
 */

static ssize_t description_show(struct device_driver *drv, char *buf)
{
        struct gameport_driver *driver = to_gameport_driver(drv);
        return sprintf(buf, "%s\n", driver->description ? driver->description : "(none)");
}
static DRIVER_ATTR_RO(description);

static struct attribute *gameport_driver_attrs[] = {
        &driver_attr_description.attr,
        NULL
};
ATTRIBUTE_GROUPS(gameport_driver);

static int gameport_driver_probe(struct device *dev)
{
        struct gameport *gameport = to_gameport_port(dev);
        struct gameport_driver *drv = to_gameport_driver(dev->driver);

        drv->connect(gameport, drv);
        return gameport->drv ? 0 : -ENODEV;
}

static void gameport_driver_remove(struct device *dev)
{
        struct gameport *gameport = to_gameport_port(dev);
        struct gameport_driver *drv = to_gameport_driver(dev->driver);

        drv->disconnect(gameport);
}

static void gameport_attach_driver(struct gameport_driver *drv)
{
        int error;

        error = driver_attach(&drv->driver);
        if (error)
                pr_err("driver_attach() failed for %s, error: %d\n",
                        drv->driver.name, error);
}

int __gameport_register_driver(struct gameport_driver *drv, struct module *owner,
                                const char *mod_name)
{
        int error;

        drv->driver.bus = &gameport_bus;
        drv->driver.owner = owner;
        drv->driver.mod_name = mod_name;

        /*
         * Temporarily disable automatic binding because probing
         * takes long time and we are better off doing it in kgameportd
         */
        drv->ignore = true;

        error = driver_register(&drv->driver);
        if (error) {
                pr_err("driver_register() failed for %s, error: %d\n",
                        drv->driver.name, error);
                return error;
        }

        /*
         * Reset ignore flag and let kgameportd bind the driver to free ports
         */
        drv->ignore = false;
        error = gameport_queue_event(drv, NULL, GAMEPORT_ATTACH_DRIVER);
        if (error) {
                driver_unregister(&drv->driver);
                return error;
        }

        return 0;
}
EXPORT_SYMBOL(__gameport_register_driver);

void gameport_unregister_driver(struct gameport_driver *drv)
{
        struct gameport *gameport;

        mutex_lock(&gameport_mutex);

        drv->ignore = true;     /* so gameport_find_driver ignores it */
        gameport_remove_pending_events(drv);

start_over:
        list_for_each_entry(gameport, &gameport_list, node) {
                if (gameport->drv == drv) {
                        gameport_disconnect_port(gameport);
                        gameport_find_driver(gameport);
                        /* we could've deleted some ports, restart */
                        goto start_over;
                }
        }

        driver_unregister(&drv->driver);

        mutex_unlock(&gameport_mutex);
}
EXPORT_SYMBOL(gameport_unregister_driver);

static int gameport_bus_match(struct device *dev, const struct device_driver *drv)
{
        const struct gameport_driver *gameport_drv = to_gameport_driver(drv);

        return !gameport_drv->ignore;
}

static const struct bus_type gameport_bus = {
        .name           = "gameport",
        .dev_groups     = gameport_device_groups,
        .drv_groups     = gameport_driver_groups,
        .match          = gameport_bus_match,
        .probe          = gameport_driver_probe,
        .remove         = gameport_driver_remove,
};

static void gameport_set_drv(struct gameport *gameport, struct gameport_driver *drv)
{
        mutex_lock(&gameport->drv_mutex);
        gameport->drv = drv;
        mutex_unlock(&gameport->drv_mutex);
}

int gameport_open(struct gameport *gameport, struct gameport_driver *drv, int mode)
{
        if (gameport->open) {
                if (gameport->open(gameport, mode)) {
                        return -1;
                }
        } else {
                if (mode != GAMEPORT_MODE_RAW)
                        return -1;
        }

        gameport_set_drv(gameport, drv);
        return 0;
}
EXPORT_SYMBOL(gameport_open);

void gameport_close(struct gameport *gameport)
{
        timer_delete_sync(&gameport->poll_timer);
        gameport->poll_handler = NULL;
        gameport->poll_interval = 0;
        gameport_set_drv(gameport, NULL);
        if (gameport->close)
                gameport->close(gameport);
}
EXPORT_SYMBOL(gameport_close);

static int __init gameport_init(void)
{
        int error;

        error = bus_register(&gameport_bus);
        if (error) {
                pr_err("failed to register gameport bus, error: %d\n", error);
                return error;
        }


        return 0;
}

static void __exit gameport_exit(void)
{
        bus_unregister(&gameport_bus);

        /*
         * There should not be any outstanding events but work may
         * still be scheduled so simply cancel it.
         */
        cancel_work_sync(&gameport_event_work);
}

subsys_initcall(gameport_init);
module_exit(gameport_exit);