/*
   *  Force feedback support for memoryless devices
   *
   *  Copyright (c) 2006 Anssi Hannula <anssi.hannula@gmail.com>
   *  Copyright (c) 2006 Dmitry Torokhov <dtor@mail.ru>
   */
  
  /*
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
   */
  
  /* #define DEBUG */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #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
  ");
  
  	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
  ");
  		del_timer(&ml->timer);
  	} else {
  		pr_debug("timer set
  ");
  		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
  ",
  			 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
  ", difference);
  	pr_debug("time_from_level = 0x%x
  ", time_from_level);
  	pr_debug("time_of_envelope = 0x%x
  ", time_of_envelope);
  
  	difference = difference * time_from_level / time_of_envelope;
  
  	pr_debug("difference = %d
  ", 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()
  ");
  
  	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()
  ");
  		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(unsigned long timer_data)
  {
  	struct input_dev *dev = (struct input_dev *)timer_data;
  	struct ml_device *ml = dev->ff->private;
  	unsigned long flags;
  
  	pr_debug("timer: updating effects
  ");
  
  	spin_lock_irqsave(&dev->event_lock, flags);
  	ml_play_effects(ml);
  	spin_unlock_irqrestore(&dev->event_lock, flags);
  }
  
  /*
   * 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
  ");
  
  		__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
  ");
  
  		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];
  
  	spin_lock_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);
  	}
  
  	spin_unlock_irq(&dev->event_lock);
  
  	return 0;
  }
  
  static void ml_ff_destroy(struct ff_device *ff)
  {
  	struct ml_device *ml = ff->private;
  
  	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 ml_device *ml;
  	struct ff_device *ff;
  	int error;
  	int i;
  
  	ml = kzalloc(sizeof(struct ml_device), GFP_KERNEL);
  	if (!ml)
  		return -ENOMEM;
  
  	ml->dev = dev;
  	ml->private = data;
  	ml->play_effect = play_effect;
  	ml->gain = 0xffff;
  	setup_timer(&ml->timer, ml_effect_timer, (unsigned long)dev);
  
  	set_bit(FF_GAIN, dev->ffbit);
  
  	error = input_ff_create(dev, FF_MEMLESS_EFFECTS);
  	if (error) {
  		kfree(ml);
  		return error;
  	}
  
  	ff = dev->ff;
  	ff->private = ml;
  	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];
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(input_ff_create_memless);