ff-memless.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 *  Force feedback support for memoryless devices
  4 *
  5 *  Copyright (c) 2006 Anssi Hannula <anssi.hannula@gmail.com>
  6 *  Copyright (c) 2006 Dmitry Torokhov <dtor@mail.ru>
  7 */
  8
  9/* #define DEBUG */
 10
 11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 12
 13#include <linux/export.h>
 14#include <linux/slab.h>
 15#include <linux/input.h>
 16#include <linux/module.h>
 17#include <linux/mutex.h>
 18#include <linux/spinlock.h>
 19#include <linux/jiffies.h>
 20#include <linux/fixp-arith.h>
 21
 22MODULE_LICENSE("GPL");
 23MODULE_AUTHOR("Anssi Hannula <anssi.hannula@gmail.com>");
 24MODULE_DESCRIPTION("Force feedback support for memoryless devices");
 25
 26/* Number of effects handled with memoryless devices */
 27#define FF_MEMLESS_EFFECTS	16
 28
 29/* Envelope update interval in ms */
 30#define FF_ENVELOPE_INTERVAL	50
 31
 32#define FF_EFFECT_STARTED	0
 33#define FF_EFFECT_PLAYING	1
 34#define FF_EFFECT_ABORTING	2
 35
 36struct ml_effect_state {
 37	struct ff_effect *effect;
 38	unsigned long flags;	/* effect state (STARTED, PLAYING, etc) */
 39	int count;		/* loop count of the effect */
 40	unsigned long play_at;	/* start time */
 41	unsigned long stop_at;	/* stop time */
 42	unsigned long adj_at;	/* last time the effect was sent */
 43};
 44
 45struct ml_device {
 46	void *private;
 47	struct ml_effect_state states[FF_MEMLESS_EFFECTS];
 48	int gain;
 49	struct timer_list timer;
 50	struct input_dev *dev;
 51
 52	int (*play_effect)(struct input_dev *dev, void *data,
 53			   struct ff_effect *effect);
 54};
 55
 56static const struct ff_envelope *get_envelope(const struct ff_effect *effect)
 57{
 58	static const struct ff_envelope empty_envelope;
 59
 60	switch (effect->type) {
 61	case FF_PERIODIC:
 62		return &effect->u.periodic.envelope;
 63
 64	case FF_CONSTANT:
 65		return &effect->u.constant.envelope;
 66
 67	default:
 68		return &empty_envelope;
 69	}
 70}
 71
 72/*
 73 * Check for the next time envelope requires an update on memoryless devices
 74 */
 75static unsigned long calculate_next_time(struct ml_effect_state *state)
 76{
 77	const struct ff_envelope *envelope = get_envelope(state->effect);
 78	unsigned long attack_stop, fade_start, next_fade;
 79
 80	if (envelope->attack_length) {
 81		attack_stop = state->play_at +
 82			msecs_to_jiffies(envelope->attack_length);
 83		if (time_before(state->adj_at, attack_stop))
 84			return state->adj_at +
 85					msecs_to_jiffies(FF_ENVELOPE_INTERVAL);
 86	}
 87
 88	if (state->effect->replay.length) {
 89		if (envelope->fade_length) {
 90			/* check when fading should start */
 91			fade_start = state->stop_at -
 92					msecs_to_jiffies(envelope->fade_length);
 93
 94			if (time_before(state->adj_at, fade_start))
 95				return fade_start;
 96
 97			/* already fading, advance to next checkpoint */
 98			next_fade = state->adj_at +
 99					msecs_to_jiffies(FF_ENVELOPE_INTERVAL);
100			if (time_before(next_fade, state->stop_at))
101				return next_fade;
102		}
103
104		return state->stop_at;
105	}
106
107	return state->play_at;
108}
109
110static void ml_schedule_timer(struct ml_device *ml)
111{
112	struct ml_effect_state *state;
113	unsigned long now = jiffies;
114	unsigned long earliest = 0;
115	unsigned long next_at;
116	int events = 0;
117	int i;
118
119	pr_debug("calculating next timer\n");
120
121	for (i = 0; i < FF_MEMLESS_EFFECTS; i++) {
122
123		state = &ml->states[i];
124
125		if (!test_bit(FF_EFFECT_STARTED, &state->flags))
126			continue;
127
128		if (test_bit(FF_EFFECT_PLAYING, &state->flags))
129			next_at = calculate_next_time(state);
130		else
131			next_at = state->play_at;
132
133		if (time_before_eq(now, next_at) &&
134		    (++events == 1 || time_before(next_at, earliest)))
135			earliest = next_at;
136	}
137
138	if (!events) {
139		pr_debug("no actions\n");
140		timer_delete(&ml->timer);
141	} else {
142		pr_debug("timer set\n");
143		mod_timer(&ml->timer, earliest);
144	}
145}
146
147/*
148 * Apply an envelope to a value
149 */
150static int apply_envelope(struct ml_effect_state *state, int value,
151			  struct ff_envelope *envelope)
152{
153	struct ff_effect *effect = state->effect;
154	unsigned long now = jiffies;
155	int time_from_level;
156	int time_of_envelope;
157	int envelope_level;
158	int difference;
159
160	if (envelope->attack_length &&
161	    time_before(now,
162			state->play_at + msecs_to_jiffies(envelope->attack_length))) {
163		pr_debug("value = 0x%x, attack_level = 0x%x\n",
164			 value, envelope->attack_level);
165		time_from_level = jiffies_to_msecs(now - state->play_at);
166		time_of_envelope = envelope->attack_length;
167		envelope_level = min_t(u16, envelope->attack_level, 0x7fff);
168
169	} else if (envelope->fade_length && effect->replay.length &&
170		   time_after(now,
171			      state->stop_at - msecs_to_jiffies(envelope->fade_length)) &&
172		   time_before(now, state->stop_at)) {
173		time_from_level = jiffies_to_msecs(state->stop_at - now);
174		time_of_envelope = envelope->fade_length;
175		envelope_level = min_t(u16, envelope->fade_level, 0x7fff);
176	} else
177		return value;
178
179	difference = abs(value) - envelope_level;
180
181	pr_debug("difference = %d\n", difference);
182	pr_debug("time_from_level = 0x%x\n", time_from_level);
183	pr_debug("time_of_envelope = 0x%x\n", time_of_envelope);
184
185	difference = difference * time_from_level / time_of_envelope;
186
187	pr_debug("difference = %d\n", difference);
188
189	return value < 0 ?
190		-(difference + envelope_level) : (difference + envelope_level);
191}
192
193/*
194 * Return the type the effect has to be converted into (memless devices)
195 */
196static int get_compatible_type(struct ff_device *ff, int effect_type)
197{
198
199	if (test_bit(effect_type, ff->ffbit))
200		return effect_type;
201
202	if (effect_type == FF_PERIODIC && test_bit(FF_RUMBLE, ff->ffbit))
203		return FF_RUMBLE;
204
205	pr_err("invalid type in get_compatible_type()\n");
206
207	return 0;
208}
209
210/*
211 * Only left/right direction should be used (under/over 0x8000) for
212 * forward/reverse motor direction (to keep calculation fast & simple).
213 */
214static u16 ml_calculate_direction(u16 direction, u16 force,
215				  u16 new_direction, u16 new_force)
216{
217	if (!force)
218		return new_direction;
219	if (!new_force)
220		return direction;
221	return (((u32)(direction >> 1) * force +
222		 (new_direction >> 1) * new_force) /
223		(force + new_force)) << 1;
224}
225
226#define FRAC_N 8
227static inline s16 fixp_new16(s16 a)
228{
229	return ((s32)a) >> (16 - FRAC_N);
230}
231
232static inline s16 fixp_mult(s16 a, s16 b)
233{
234	a = ((s32)a * 0x100) / 0x7fff;
235	return ((s32)(a * b)) >> FRAC_N;
236}
237
238/*
239 * Combine two effects and apply gain.
240 */
241static void ml_combine_effects(struct ff_effect *effect,
242			       struct ml_effect_state *state,
243			       int gain)
244{
245	struct ff_effect *new = state->effect;
246	unsigned int strong, weak, i;
247	int x, y;
248	s16 level;
249
250	switch (new->type) {
251	case FF_CONSTANT:
252		i = new->direction * 360 / 0xffff;
253		level = fixp_new16(apply_envelope(state,
254					new->u.constant.level,
255					&new->u.constant.envelope));
256		x = fixp_mult(fixp_sin16(i), level) * gain / 0xffff;
257		y = fixp_mult(-fixp_cos16(i), level) * gain / 0xffff;
258		/*
259		 * here we abuse ff_ramp to hold x and y of constant force
260		 * If in future any driver wants something else than x and y
261		 * in s8, this should be changed to something more generic
262		 */
263		effect->u.ramp.start_level =
264			clamp_val(effect->u.ramp.start_level + x, -0x80, 0x7f);
265		effect->u.ramp.end_level =
266			clamp_val(effect->u.ramp.end_level + y, -0x80, 0x7f);
267		break;
268
269	case FF_RUMBLE:
270		strong = (u32)new->u.rumble.strong_magnitude * gain / 0xffff;
271		weak = (u32)new->u.rumble.weak_magnitude * gain / 0xffff;
272
273		if (effect->u.rumble.strong_magnitude + strong)
274			effect->direction = ml_calculate_direction(
275				effect->direction,
276				effect->u.rumble.strong_magnitude,
277				new->direction, strong);
278		else if (effect->u.rumble.weak_magnitude + weak)
279			effect->direction = ml_calculate_direction(
280				effect->direction,
281				effect->u.rumble.weak_magnitude,
282				new->direction, weak);
283		else
284			effect->direction = 0;
285		effect->u.rumble.strong_magnitude =
286			min(strong + effect->u.rumble.strong_magnitude,
287			    0xffffU);
288		effect->u.rumble.weak_magnitude =
289			min(weak + effect->u.rumble.weak_magnitude, 0xffffU);
290		break;
291
292	case FF_PERIODIC:
293		i = apply_envelope(state, abs(new->u.periodic.magnitude),
294				   &new->u.periodic.envelope);
295
296		/* here we also scale it 0x7fff => 0xffff */
297		i = i * gain / 0x7fff;
298
299		if (effect->u.rumble.strong_magnitude + i)
300			effect->direction = ml_calculate_direction(
301				effect->direction,
302				effect->u.rumble.strong_magnitude,
303				new->direction, i);
304		else
305			effect->direction = 0;
306		effect->u.rumble.strong_magnitude =
307			min(i + effect->u.rumble.strong_magnitude, 0xffffU);
308		effect->u.rumble.weak_magnitude =
309			min(i + effect->u.rumble.weak_magnitude, 0xffffU);
310		break;
311
312	default:
313		pr_err("invalid type in ml_combine_effects()\n");
314		break;
315	}
316
317}
318
319
320/*
321 * Because memoryless devices have only one effect per effect type active
322 * at one time we have to combine multiple effects into one
323 */
324static int ml_get_combo_effect(struct ml_device *ml,
325			       unsigned long *effect_handled,
326			       struct ff_effect *combo_effect)
327{
328	struct ff_effect *effect;
329	struct ml_effect_state *state;
330	int effect_type;
331	int i;
332
333	memset(combo_effect, 0, sizeof(struct ff_effect));
334
335	for (i = 0; i < FF_MEMLESS_EFFECTS; i++) {
336		if (__test_and_set_bit(i, effect_handled))
337			continue;
338
339		state = &ml->states[i];
340		effect = state->effect;
341
342		if (!test_bit(FF_EFFECT_STARTED, &state->flags))
343			continue;
344
345		if (time_before(jiffies, state->play_at))
346			continue;
347
348		/*
349		 * here we have started effects that are either
350		 * currently playing (and may need be aborted)
351		 * or need to start playing.
352		 */
353		effect_type = get_compatible_type(ml->dev->ff, effect->type);
354		if (combo_effect->type != effect_type) {
355			if (combo_effect->type != 0) {
356				__clear_bit(i, effect_handled);
357				continue;
358			}
359			combo_effect->type = effect_type;
360		}
361
362		if (__test_and_clear_bit(FF_EFFECT_ABORTING, &state->flags)) {
363			__clear_bit(FF_EFFECT_PLAYING, &state->flags);
364			__clear_bit(FF_EFFECT_STARTED, &state->flags);
365		} else if (effect->replay.length &&
366			   time_after_eq(jiffies, state->stop_at)) {
367
368			__clear_bit(FF_EFFECT_PLAYING, &state->flags);
369
370			if (--state->count <= 0) {
371				__clear_bit(FF_EFFECT_STARTED, &state->flags);
372			} else {
373				state->play_at = jiffies +
374					msecs_to_jiffies(effect->replay.delay);
375				state->stop_at = state->play_at +
376					msecs_to_jiffies(effect->replay.length);
377			}
378		} else {
379			__set_bit(FF_EFFECT_PLAYING, &state->flags);
380			state->adj_at = jiffies;
381			ml_combine_effects(combo_effect, state, ml->gain);
382		}
383	}
384
385	return combo_effect->type != 0;
386}
387
388static void ml_play_effects(struct ml_device *ml)
389{
390	struct ff_effect effect;
391	DECLARE_BITMAP(handled_bm, FF_MEMLESS_EFFECTS);
392
393	memset(handled_bm, 0, sizeof(handled_bm));
394
395	while (ml_get_combo_effect(ml, handled_bm, &effect))
396		ml->play_effect(ml->dev, ml->private, &effect);
397
398	ml_schedule_timer(ml);
399}
400
401static void ml_effect_timer(struct timer_list *t)
402{
403	struct ml_device *ml = timer_container_of(ml, t, timer);
404	struct input_dev *dev = ml->dev;
405
406	pr_debug("timer: updating effects\n");
407
408	guard(spinlock_irqsave)(&dev->event_lock);
409	ml_play_effects(ml);
410}
411
412/*
413 * Sets requested gain for FF effects. Called with dev->event_lock held.
414 */
415static void ml_ff_set_gain(struct input_dev *dev, u16 gain)
416{
417	struct ml_device *ml = dev->ff->private;
418	int i;
419
420	ml->gain = gain;
421
422	for (i = 0; i < FF_MEMLESS_EFFECTS; i++)
423		__clear_bit(FF_EFFECT_PLAYING, &ml->states[i].flags);
424
425	ml_play_effects(ml);
426}
427
428/*
429 * Start/stop specified FF effect. Called with dev->event_lock held.
430 */
431static int ml_ff_playback(struct input_dev *dev, int effect_id, int value)
432{
433	struct ml_device *ml = dev->ff->private;
434	struct ml_effect_state *state = &ml->states[effect_id];
435
436	if (value > 0) {
437		pr_debug("initiated play\n");
438
439		__set_bit(FF_EFFECT_STARTED, &state->flags);
440		state->count = value;
441		state->play_at = jiffies +
442				 msecs_to_jiffies(state->effect->replay.delay);
443		state->stop_at = state->play_at +
444				 msecs_to_jiffies(state->effect->replay.length);
445		state->adj_at = state->play_at;
446
447	} else {
448		pr_debug("initiated stop\n");
449
450		if (test_bit(FF_EFFECT_PLAYING, &state->flags))
451			__set_bit(FF_EFFECT_ABORTING, &state->flags);
452		else
453			__clear_bit(FF_EFFECT_STARTED, &state->flags);
454	}
455
456	ml_play_effects(ml);
457
458	return 0;
459}
460
461static int ml_ff_upload(struct input_dev *dev,
462			struct ff_effect *effect, struct ff_effect *old)
463{
464	struct ml_device *ml = dev->ff->private;
465	struct ml_effect_state *state = &ml->states[effect->id];
466
467	guard(spinlock_irq)(&dev->event_lock);
468
469	if (test_bit(FF_EFFECT_STARTED, &state->flags)) {
470		__clear_bit(FF_EFFECT_PLAYING, &state->flags);
471		state->play_at = jiffies +
472				 msecs_to_jiffies(state->effect->replay.delay);
473		state->stop_at = state->play_at +
474				 msecs_to_jiffies(state->effect->replay.length);
475		state->adj_at = state->play_at;
476		ml_schedule_timer(ml);
477	}
478
479	return 0;
480}
481
482static void ml_ff_destroy(struct ff_device *ff)
483{
484	struct ml_device *ml = ff->private;
485
486	/*
487	 * Even though we stop all playing effects when tearing down
488	 * an input device (via input_device_flush() that calls into
489	 * input_ff_flush() that stops and erases all effects), we
490	 * do not actually stop the timer, and therefore we should
491	 * do it here.
492	 */
493	timer_delete_sync(&ml->timer);
494
495	kfree(ml->private);
496}
497
498/**
499 * input_ff_create_memless() - create memoryless force-feedback device
500 * @dev: input device supporting force-feedback
501 * @data: driver-specific data to be passed into @play_effect
502 * @play_effect: driver-specific method for playing FF effect
503 */
504int input_ff_create_memless(struct input_dev *dev, void *data,
505		int (*play_effect)(struct input_dev *, void *, struct ff_effect *))
506{
507	struct ff_device *ff;
508	int error;
509	int i;
510
511	struct ml_device *ml __free(kfree) = kzalloc(sizeof(*ml), GFP_KERNEL);
512	if (!ml)
513		return -ENOMEM;
514
515	ml->dev = dev;
516	ml->private = data;
517	ml->play_effect = play_effect;
518	ml->gain = 0xffff;
519	timer_setup(&ml->timer, ml_effect_timer, 0);
520
521	set_bit(FF_GAIN, dev->ffbit);
522
523	error = input_ff_create(dev, FF_MEMLESS_EFFECTS);
524	if (error)
525		return error;
526
527	ff = dev->ff;
528	ff->upload = ml_ff_upload;
529	ff->playback = ml_ff_playback;
530	ff->set_gain = ml_ff_set_gain;
531	ff->destroy = ml_ff_destroy;
532
533	/* we can emulate periodic effects with RUMBLE */
534	if (test_bit(FF_RUMBLE, ff->ffbit)) {
535		set_bit(FF_PERIODIC, dev->ffbit);
536		set_bit(FF_SINE, dev->ffbit);
537		set_bit(FF_TRIANGLE, dev->ffbit);
538		set_bit(FF_SQUARE, dev->ffbit);
539	}
540
541	for (i = 0; i < FF_MEMLESS_EFFECTS; i++)
542		ml->states[i].effect = &ff->effects[i];
543
544	ff->private = no_free_ptr(ml);
545
546	return 0;
547}
548EXPORT_SYMBOL_GPL(input_ff_create_memless);