// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Force feedback support for memoryless devices
 *
 *  Copyright (c) 2006 Anssi Hannula <anssi.hannula@gmail.com>
 *  Copyright (c) 2006 Dmitry Torokhov <dtor@mail.ru>
 */

/* #define DEBUG */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/export.h>
#include <linux/slab.h>
#include <linux/input.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/jiffies.h>
#include <linux/fixp-arith.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Anssi Hannula <anssi.hannula@gmail.com>");
MODULE_DESCRIPTION("Force feedback support for memoryless devices");

/* Number of effects handled with memoryless devices */
#define FF_MEMLESS_EFFECTS      16

/* Envelope update interval in ms */
#define FF_ENVELOPE_INTERVAL    50

#define FF_EFFECT_STARTED       0
#define FF_EFFECT_PLAYING       1
#define FF_EFFECT_ABORTING      2

struct ml_effect_state {
        struct ff_effect *effect;
        unsigned long flags;    /* effect state (STARTED, PLAYING, etc) */
        int count;              /* loop count of the effect */
        unsigned long play_at;  /* start time */
        unsigned long stop_at;  /* stop time */
        unsigned long adj_at;   /* last time the effect was sent */
};

struct ml_device {
        void *private;
        struct ml_effect_state states[FF_MEMLESS_EFFECTS];
        int gain;
        struct timer_list timer;
        struct input_dev *dev;

        int (*play_effect)(struct input_dev *dev, void *data,
                           struct ff_effect *effect);
};

static const struct ff_envelope *get_envelope(const struct ff_effect *effect)
{
        static const struct ff_envelope empty_envelope;

        switch (effect->type) {
        case FF_PERIODIC:
                return &effect->u.periodic.envelope;

        case FF_CONSTANT:
                return &effect->u.constant.envelope;

        default:
                return &empty_envelope;
        }
}

/*
 * Check for the next time envelope requires an update on memoryless devices
 */
static unsigned long calculate_next_time(struct ml_effect_state *state)
{
        const struct ff_envelope *envelope = get_envelope(state->effect);
        unsigned long attack_stop, fade_start, next_fade;

        if (envelope->attack_length) {
                attack_stop = state->play_at +
                        msecs_to_jiffies(envelope->attack_length);
                if (time_before(state->adj_at, attack_stop))
                        return state->adj_at +
                                        msecs_to_jiffies(FF_ENVELOPE_INTERVAL);
        }

        if (state->effect->replay.length) {
                if (envelope->fade_length) {
                        /* check when fading should start */
                        fade_start = state->stop_at -
                                        msecs_to_jiffies(envelope->fade_length);

                        if (time_before(state->adj_at, fade_start))
                                return fade_start;

                        /* already fading, advance to next checkpoint */
                        next_fade = state->adj_at +
                                        msecs_to_jiffies(FF_ENVELOPE_INTERVAL);
                        if (time_before(next_fade, state->stop_at))
                                return next_fade;
                }

                return state->stop_at;
        }

        return state->play_at;
}

static void ml_schedule_timer(struct ml_device *ml)
{
        struct ml_effect_state *state;
        unsigned long now = jiffies;
        unsigned long earliest = 0;
        unsigned long next_at;
        int events = 0;
        int i;

        pr_debug("calculating next timer\n");

        for (i = 0; i < FF_MEMLESS_EFFECTS; i++) {

                state = &ml->states[i];

                if (!test_bit(FF_EFFECT_STARTED, &state->flags))
                        continue;

                if (test_bit(FF_EFFECT_PLAYING, &state->flags))
                        next_at = calculate_next_time(state);
                else
                        next_at = state->play_at;

                if (time_before_eq(now, next_at) &&
                    (++events == 1 || time_before(next_at, earliest)))
                        earliest = next_at;
        }

        if (!events) {
                pr_debug("no actions\n");
                timer_delete(&ml->timer);
        } else {
                pr_debug("timer set\n");
                mod_timer(&ml->timer, earliest);
        }
}

/*
 * Apply an envelope to a value
 */
static int apply_envelope(struct ml_effect_state *state, int value,
                          struct ff_envelope *envelope)
{
        struct ff_effect *effect = state->effect;
        unsigned long now = jiffies;
        int time_from_level;
        int time_of_envelope;
        int envelope_level;
        int difference;

        if (envelope->attack_length &&
            time_before(now,
                        state->play_at + msecs_to_jiffies(envelope->attack_length))) {
                pr_debug("value = 0x%x, attack_level = 0x%x\n",
                         value, envelope->attack_level);
                time_from_level = jiffies_to_msecs(now - state->play_at);
                time_of_envelope = envelope->attack_length;
                envelope_level = min_t(u16, envelope->attack_level, 0x7fff);

        } else if (envelope->fade_length && effect->replay.length &&
                   time_after(now,
                              state->stop_at - msecs_to_jiffies(envelope->fade_length)) &&
                   time_before(now, state->stop_at)) {
                time_from_level = jiffies_to_msecs(state->stop_at - now);
                time_of_envelope = envelope->fade_length;
                envelope_level = min_t(u16, envelope->fade_level, 0x7fff);
        } else
                return value;

        difference = abs(value) - envelope_level;

        pr_debug("difference = %d\n", difference);
        pr_debug("time_from_level = 0x%x\n", time_from_level);
        pr_debug("time_of_envelope = 0x%x\n", time_of_envelope);

        difference = difference * time_from_level / time_of_envelope;

        pr_debug("difference = %d\n", difference);

        return value < 0 ?
                -(difference + envelope_level) : (difference + envelope_level);
}

/*
 * Return the type the effect has to be converted into (memless devices)
 */
static int get_compatible_type(struct ff_device *ff, int effect_type)
{

        if (test_bit(effect_type, ff->ffbit))
                return effect_type;

        if (effect_type == FF_PERIODIC && test_bit(FF_RUMBLE, ff->ffbit))
                return FF_RUMBLE;

        pr_err("invalid type in get_compatible_type()\n");

        return 0;
}

/*
 * Only left/right direction should be used (under/over 0x8000) for
 * forward/reverse motor direction (to keep calculation fast & simple).
 */
static u16 ml_calculate_direction(u16 direction, u16 force,
                                  u16 new_direction, u16 new_force)
{
        if (!force)
                return new_direction;
        if (!new_force)
                return direction;
        return (((u32)(direction >> 1) * force +
                 (new_direction >> 1) * new_force) /
                (force + new_force)) << 1;
}

#define FRAC_N 8
static inline s16 fixp_new16(s16 a)
{
        return ((s32)a) >> (16 - FRAC_N);
}

static inline s16 fixp_mult(s16 a, s16 b)
{
        a = ((s32)a * 0x100) / 0x7fff;
        return ((s32)(a * b)) >> FRAC_N;
}

/*
 * Combine two effects and apply gain.
 */
static void ml_combine_effects(struct ff_effect *effect,
                               struct ml_effect_state *state,
                               int gain)
{
        struct ff_effect *new = state->effect;
        unsigned int strong, weak, i;
        int x, y;
        s16 level;

        switch (new->type) {
        case FF_CONSTANT:
                i = new->direction * 360 / 0xffff;
                level = fixp_new16(apply_envelope(state,
                                        new->u.constant.level,
                                        &new->u.constant.envelope));
                x = fixp_mult(fixp_sin16(i), level) * gain / 0xffff;
                y = fixp_mult(-fixp_cos16(i), level) * gain / 0xffff;
                /*
                 * here we abuse ff_ramp to hold x and y of constant force
                 * If in future any driver wants something else than x and y
                 * in s8, this should be changed to something more generic
                 */
                effect->u.ramp.start_level =
                        clamp_val(effect->u.ramp.start_level + x, -0x80, 0x7f);
                effect->u.ramp.end_level =
                        clamp_val(effect->u.ramp.end_level + y, -0x80, 0x7f);
                break;

        case FF_RUMBLE:
                strong = (u32)new->u.rumble.strong_magnitude * gain / 0xffff;
                weak = (u32)new->u.rumble.weak_magnitude * gain / 0xffff;

                if (effect->u.rumble.strong_magnitude + strong)
                        effect->direction = ml_calculate_direction(
                                effect->direction,
                                effect->u.rumble.strong_magnitude,
                                new->direction, strong);
                else if (effect->u.rumble.weak_magnitude + weak)
                        effect->direction = ml_calculate_direction(
                                effect->direction,
                                effect->u.rumble.weak_magnitude,
                                new->direction, weak);
                else
                        effect->direction = 0;
                effect->u.rumble.strong_magnitude =
                        min(strong + effect->u.rumble.strong_magnitude,
                            0xffffU);
                effect->u.rumble.weak_magnitude =
                        min(weak + effect->u.rumble.weak_magnitude, 0xffffU);
                break;

        case FF_PERIODIC:
                i = apply_envelope(state, abs(new->u.periodic.magnitude),
                                   &new->u.periodic.envelope);

                /* here we also scale it 0x7fff => 0xffff */
                i = i * gain / 0x7fff;

                if (effect->u.rumble.strong_magnitude + i)
                        effect->direction = ml_calculate_direction(
                                effect->direction,
                                effect->u.rumble.strong_magnitude,
                                new->direction, i);
                else
                        effect->direction = 0;
                effect->u.rumble.strong_magnitude =
                        min(i + effect->u.rumble.strong_magnitude, 0xffffU);
                effect->u.rumble.weak_magnitude =
                        min(i + effect->u.rumble.weak_magnitude, 0xffffU);
                break;

        default:
                pr_err("invalid type in ml_combine_effects()\n");
                break;
        }

}


/*
 * Because memoryless devices have only one effect per effect type active
 * at one time we have to combine multiple effects into one
 */
static int ml_get_combo_effect(struct ml_device *ml,
                               unsigned long *effect_handled,
                               struct ff_effect *combo_effect)
{
        struct ff_effect *effect;
        struct ml_effect_state *state;
        int effect_type;
        int i;

        memset(combo_effect, 0, sizeof(struct ff_effect));

        for (i = 0; i < FF_MEMLESS_EFFECTS; i++) {
                if (__test_and_set_bit(i, effect_handled))
                        continue;

                state = &ml->states[i];
                effect = state->effect;

                if (!test_bit(FF_EFFECT_STARTED, &state->flags))
                        continue;

                if (time_before(jiffies, state->play_at))
                        continue;

                /*
                 * here we have started effects that are either
                 * currently playing (and may need be aborted)
                 * or need to start playing.
                 */
                effect_type = get_compatible_type(ml->dev->ff, effect->type);
                if (combo_effect->type != effect_type) {
                        if (combo_effect->type != 0) {
                                __clear_bit(i, effect_handled);
                                continue;
                        }
                        combo_effect->type = effect_type;
                }

                if (__test_and_clear_bit(FF_EFFECT_ABORTING, &state->flags)) {
                        __clear_bit(FF_EFFECT_PLAYING, &state->flags);
                        __clear_bit(FF_EFFECT_STARTED, &state->flags);
                } else if (effect->replay.length &&
                           time_after_eq(jiffies, state->stop_at)) {

                        __clear_bit(FF_EFFECT_PLAYING, &state->flags);

                        if (--state->count <= 0) {
                                __clear_bit(FF_EFFECT_STARTED, &state->flags);
                        } else {
                                state->play_at = jiffies +
                                        msecs_to_jiffies(effect->replay.delay);
                                state->stop_at = state->play_at +
                                        msecs_to_jiffies(effect->replay.length);
                        }
                } else {
                        __set_bit(FF_EFFECT_PLAYING, &state->flags);
                        state->adj_at = jiffies;
                        ml_combine_effects(combo_effect, state, ml->gain);
                }
        }

        return combo_effect->type != 0;
}

static void ml_play_effects(struct ml_device *ml)
{
        struct ff_effect effect;
        DECLARE_BITMAP(handled_bm, FF_MEMLESS_EFFECTS);

        memset(handled_bm, 0, sizeof(handled_bm));

        while (ml_get_combo_effect(ml, handled_bm, &effect))
                ml->play_effect(ml->dev, ml->private, &effect);

        ml_schedule_timer(ml);
}

static void ml_effect_timer(struct timer_list *t)
{
        struct ml_device *ml = timer_container_of(ml, t, timer);
        struct input_dev *dev = ml->dev;

        pr_debug("timer: updating effects\n");

        guard(spinlock_irqsave)(&dev->event_lock);
        ml_play_effects(ml);
}

/*
 * Sets requested gain for FF effects. Called with dev->event_lock held.
 */
static void ml_ff_set_gain(struct input_dev *dev, u16 gain)
{
        struct ml_device *ml = dev->ff->private;
        int i;

        ml->gain = gain;

        for (i = 0; i < FF_MEMLESS_EFFECTS; i++)
                __clear_bit(FF_EFFECT_PLAYING, &ml->states[i].flags);

        ml_play_effects(ml);
}

/*
 * Start/stop specified FF effect. Called with dev->event_lock held.
 */
static int ml_ff_playback(struct input_dev *dev, int effect_id, int value)
{
        struct ml_device *ml = dev->ff->private;
        struct ml_effect_state *state = &ml->states[effect_id];

        if (value > 0) {
                pr_debug("initiated play\n");

                __set_bit(FF_EFFECT_STARTED, &state->flags);
                state->count = value;
                state->play_at = jiffies +
                                 msecs_to_jiffies(state->effect->replay.delay);
                state->stop_at = state->play_at +
                                 msecs_to_jiffies(state->effect->replay.length);
                state->adj_at = state->play_at;

        } else {
                pr_debug("initiated stop\n");

                if (test_bit(FF_EFFECT_PLAYING, &state->flags))
                        __set_bit(FF_EFFECT_ABORTING, &state->flags);
                else
                        __clear_bit(FF_EFFECT_STARTED, &state->flags);
        }

        ml_play_effects(ml);

        return 0;
}

static int ml_ff_upload(struct input_dev *dev,
                        struct ff_effect *effect, struct ff_effect *old)
{
        struct ml_device *ml = dev->ff->private;
        struct ml_effect_state *state = &ml->states[effect->id];

        guard(spinlock_irq)(&dev->event_lock);

        if (test_bit(FF_EFFECT_STARTED, &state->flags)) {
                __clear_bit(FF_EFFECT_PLAYING, &state->flags);
                state->play_at = jiffies +
                                 msecs_to_jiffies(state->effect->replay.delay);
                state->stop_at = state->play_at +
                                 msecs_to_jiffies(state->effect->replay.length);
                state->adj_at = state->play_at;
                ml_schedule_timer(ml);
        }

        return 0;
}

static void ml_ff_destroy(struct ff_device *ff)
{
        struct ml_device *ml = ff->private;

        /*
         * Even though we stop all playing effects when tearing down
         * an input device (via input_device_flush() that calls into
         * input_ff_flush() that stops and erases all effects), we
         * do not actually stop the timer, and therefore we should
         * do it here.
         */
        timer_delete_sync(&ml->timer);

        kfree(ml->private);
}

/**
 * input_ff_create_memless() - create memoryless force-feedback device
 * @dev: input device supporting force-feedback
 * @data: driver-specific data to be passed into @play_effect
 * @play_effect: driver-specific method for playing FF effect
 */
int input_ff_create_memless(struct input_dev *dev, void *data,
                int (*play_effect)(struct input_dev *, void *, struct ff_effect *))
{
        struct ff_device *ff;
        int error;
        int i;

        struct ml_device *ml __free(kfree) = kzalloc_obj(*ml);
        if (!ml)
                return -ENOMEM;

        ml->dev = dev;
        ml->private = data;
        ml->play_effect = play_effect;
        ml->gain = 0xffff;
        timer_setup(&ml->timer, ml_effect_timer, 0);

        set_bit(FF_GAIN, dev->ffbit);

        error = input_ff_create(dev, FF_MEMLESS_EFFECTS);
        if (error)
                return error;

        ff = dev->ff;
        ff->upload = ml_ff_upload;
        ff->playback = ml_ff_playback;
        ff->set_gain = ml_ff_set_gain;
        ff->destroy = ml_ff_destroy;

        /* we can emulate periodic effects with RUMBLE */
        if (test_bit(FF_RUMBLE, ff->ffbit)) {
                set_bit(FF_PERIODIC, dev->ffbit);
                set_bit(FF_SINE, dev->ffbit);
                set_bit(FF_TRIANGLE, dev->ffbit);
                set_bit(FF_SQUARE, dev->ffbit);
        }

        for (i = 0; i < FF_MEMLESS_EFFECTS; i++)
                ml->states[i].effect = &ff->effects[i];

        ff->private = no_free_ptr(ml);

        return 0;
}
EXPORT_SYMBOL_GPL(input_ff_create_memless);