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* Force feedback support for memoryless devices
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* Copyright (c) 2006 Anssi Hannula <anssi.hannula@gmail.com>
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* Copyright (c) 2006 Dmitry Torokhov <dtor@mail.ru>
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/slab.h>
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#include <linux/input.h>
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/spinlock.h>
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#include <linux/jiffies.h>
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#include "fixp-arith.h"
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Anssi Hannula <anssi.hannula@gmail.com>");
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MODULE_DESCRIPTION("Force feedback support for memoryless devices");
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/* Number of effects handled with memoryless devices */
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#define FF_MEMLESS_EFFECTS 16
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/* Envelope update interval in ms */
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#define FF_ENVELOPE_INTERVAL 50
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#define FF_EFFECT_STARTED 0
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#define FF_EFFECT_PLAYING 1
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#define FF_EFFECT_ABORTING 2
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struct ml_effect_state {
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struct ff_effect *effect;
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unsigned long flags; /* effect state (STARTED, PLAYING, etc) */
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int count; /* loop count of the effect */
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unsigned long play_at; /* start time */
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unsigned long stop_at; /* stop time */
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unsigned long adj_at; /* last time the effect was sent */
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struct ml_effect_state states[FF_MEMLESS_EFFECTS];
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struct timer_list timer;
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struct input_dev *dev;
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int (*play_effect)(struct input_dev *dev, void *data,
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struct ff_effect *effect);
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static const struct ff_envelope *get_envelope(const struct ff_effect *effect)
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static const struct ff_envelope empty_envelope;
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switch (effect->type) {
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return &effect->u.periodic.envelope;
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return &effect->u.constant.envelope;
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return &empty_envelope;
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* Check for the next time envelope requires an update on memoryless devices
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static unsigned long calculate_next_time(struct ml_effect_state *state)
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const struct ff_envelope *envelope = get_envelope(state->effect);
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unsigned long attack_stop, fade_start, next_fade;
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if (envelope->attack_length) {
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attack_stop = state->play_at +
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msecs_to_jiffies(envelope->attack_length);
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if (time_before(state->adj_at, attack_stop))
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return state->adj_at +
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msecs_to_jiffies(FF_ENVELOPE_INTERVAL);
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if (state->effect->replay.length) {
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if (envelope->fade_length) {
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/* check when fading should start */
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fade_start = state->stop_at -
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msecs_to_jiffies(envelope->fade_length);
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if (time_before(state->adj_at, fade_start))
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/* already fading, advance to next checkpoint */
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next_fade = state->adj_at +
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msecs_to_jiffies(FF_ENVELOPE_INTERVAL);
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if (time_before(next_fade, state->stop_at))
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return state->stop_at;
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return state->play_at;
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static void ml_schedule_timer(struct ml_device *ml)
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struct ml_effect_state *state;
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unsigned long now = jiffies;
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unsigned long earliest = 0;
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unsigned long next_at;
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pr_debug("calculating next timer\n");
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for (i = 0; i < FF_MEMLESS_EFFECTS; i++) {
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state = &ml->states[i];
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if (!test_bit(FF_EFFECT_STARTED, &state->flags))
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if (test_bit(FF_EFFECT_PLAYING, &state->flags))
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next_at = calculate_next_time(state);
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next_at = state->play_at;
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if (time_before_eq(now, next_at) &&
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(++events == 1 || time_before(next_at, earliest)))
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pr_debug("no actions\n");
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del_timer(&ml->timer);
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pr_debug("timer set\n");
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mod_timer(&ml->timer, earliest);
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* Apply an envelope to a value
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static int apply_envelope(struct ml_effect_state *state, int value,
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struct ff_envelope *envelope)
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struct ff_effect *effect = state->effect;
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unsigned long now = jiffies;
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int time_of_envelope;
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if (envelope->attack_length &&
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state->play_at + msecs_to_jiffies(envelope->attack_length))) {
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pr_debug("value = 0x%x, attack_level = 0x%x\n",
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value, envelope->attack_level);
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time_from_level = jiffies_to_msecs(now - state->play_at);
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time_of_envelope = envelope->attack_length;
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envelope_level = min_t(__s16, envelope->attack_level, 0x7fff);
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} else if (envelope->fade_length && effect->replay.length &&
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state->stop_at - msecs_to_jiffies(envelope->fade_length)) &&
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time_before(now, state->stop_at)) {
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time_from_level = jiffies_to_msecs(state->stop_at - now);
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time_of_envelope = envelope->fade_length;
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envelope_level = min_t(__s16, envelope->fade_level, 0x7fff);
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difference = abs(value) - envelope_level;
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pr_debug("difference = %d\n", difference);
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pr_debug("time_from_level = 0x%x\n", time_from_level);
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pr_debug("time_of_envelope = 0x%x\n", time_of_envelope);
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difference = difference * time_from_level / time_of_envelope;
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pr_debug("difference = %d\n", difference);
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-(difference + envelope_level) : (difference + envelope_level);
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* Return the type the effect has to be converted into (memless devices)
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static int get_compatible_type(struct ff_device *ff, int effect_type)
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if (test_bit(effect_type, ff->ffbit))
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if (effect_type == FF_PERIODIC && test_bit(FF_RUMBLE, ff->ffbit))
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pr_err("invalid type in get_compatible_type()\n");
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* Only left/right direction should be used (under/over 0x8000) for
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* forward/reverse motor direction (to keep calculation fast & simple).
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static u16 ml_calculate_direction(u16 direction, u16 force,
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u16 new_direction, u16 new_force)
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return new_direction;
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return (((u32)(direction >> 1) * force +
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(new_direction >> 1) * new_force) /
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(force + new_force)) << 1;
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* Combine two effects and apply gain.
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static void ml_combine_effects(struct ff_effect *effect,
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struct ml_effect_state *state,
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struct ff_effect *new = state->effect;
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unsigned int strong, weak, i;
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i = new->direction * 360 / 0xffff;
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level = fixp_new16(apply_envelope(state,
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new->u.constant.level,
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&new->u.constant.envelope));
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x = fixp_mult(fixp_sin(i), level) * gain / 0xffff;
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y = fixp_mult(-fixp_cos(i), level) * gain / 0xffff;
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* here we abuse ff_ramp to hold x and y of constant force
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* If in future any driver wants something else than x and y
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* in s8, this should be changed to something more generic
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effect->u.ramp.start_level =
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clamp_val(effect->u.ramp.start_level + x, -0x80, 0x7f);
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effect->u.ramp.end_level =
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clamp_val(effect->u.ramp.end_level + y, -0x80, 0x7f);
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strong = (u32)new->u.rumble.strong_magnitude * gain / 0xffff;
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weak = (u32)new->u.rumble.weak_magnitude * gain / 0xffff;
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if (effect->u.rumble.strong_magnitude + strong)
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effect->direction = ml_calculate_direction(
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effect->u.rumble.strong_magnitude,
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new->direction, strong);
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else if (effect->u.rumble.weak_magnitude + weak)
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effect->direction = ml_calculate_direction(
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effect->u.rumble.weak_magnitude,
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new->direction, weak);
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effect->direction = 0;
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effect->u.rumble.strong_magnitude =
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min(strong + effect->u.rumble.strong_magnitude,
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effect->u.rumble.weak_magnitude =
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min(weak + effect->u.rumble.weak_magnitude, 0xffffU);
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i = apply_envelope(state, abs(new->u.periodic.magnitude),
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&new->u.periodic.envelope);
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/* here we also scale it 0x7fff => 0xffff */
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i = i * gain / 0x7fff;
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if (effect->u.rumble.strong_magnitude + i)
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effect->direction = ml_calculate_direction(
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effect->u.rumble.strong_magnitude,
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effect->direction = 0;
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effect->u.rumble.strong_magnitude =
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min(i + effect->u.rumble.strong_magnitude, 0xffffU);
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effect->u.rumble.weak_magnitude =
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min(i + effect->u.rumble.weak_magnitude, 0xffffU);
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pr_err("invalid type in ml_combine_effects()\n");
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* Because memoryless devices have only one effect per effect type active
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* at one time we have to combine multiple effects into one
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static int ml_get_combo_effect(struct ml_device *ml,
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unsigned long *effect_handled,
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struct ff_effect *combo_effect)
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struct ff_effect *effect;
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struct ml_effect_state *state;
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memset(combo_effect, 0, sizeof(struct ff_effect));
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for (i = 0; i < FF_MEMLESS_EFFECTS; i++) {
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if (__test_and_set_bit(i, effect_handled))
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state = &ml->states[i];
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effect = state->effect;
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if (!test_bit(FF_EFFECT_STARTED, &state->flags))
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if (time_before(jiffies, state->play_at))
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* here we have started effects that are either
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* currently playing (and may need be aborted)
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* or need to start playing.
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effect_type = get_compatible_type(ml->dev->ff, effect->type);
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if (combo_effect->type != effect_type) {
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if (combo_effect->type != 0) {
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__clear_bit(i, effect_handled);
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combo_effect->type = effect_type;
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if (__test_and_clear_bit(FF_EFFECT_ABORTING, &state->flags)) {
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__clear_bit(FF_EFFECT_PLAYING, &state->flags);
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__clear_bit(FF_EFFECT_STARTED, &state->flags);
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} else if (effect->replay.length &&
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time_after_eq(jiffies, state->stop_at)) {
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__clear_bit(FF_EFFECT_PLAYING, &state->flags);
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if (--state->count <= 0) {
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__clear_bit(FF_EFFECT_STARTED, &state->flags);
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state->play_at = jiffies +
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msecs_to_jiffies(effect->replay.delay);
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state->stop_at = state->play_at +
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msecs_to_jiffies(effect->replay.length);
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__set_bit(FF_EFFECT_PLAYING, &state->flags);
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state->adj_at = jiffies;
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ml_combine_effects(combo_effect, state, ml->gain);
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return combo_effect->type != 0;
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static void ml_play_effects(struct ml_device *ml)
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struct ff_effect effect;
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DECLARE_BITMAP(handled_bm, FF_MEMLESS_EFFECTS);
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memset(handled_bm, 0, sizeof(handled_bm));
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while (ml_get_combo_effect(ml, handled_bm, &effect))
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ml->play_effect(ml->dev, ml->private, &effect);
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ml_schedule_timer(ml);
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static void ml_effect_timer(unsigned long timer_data)
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struct input_dev *dev = (struct input_dev *)timer_data;
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struct ml_device *ml = dev->ff->private;
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pr_debug("timer: updating effects\n");
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spin_lock_irqsave(&dev->event_lock, flags);
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spin_unlock_irqrestore(&dev->event_lock, flags);
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* Sets requested gain for FF effects. Called with dev->event_lock held.
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static void ml_ff_set_gain(struct input_dev *dev, u16 gain)
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struct ml_device *ml = dev->ff->private;
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for (i = 0; i < FF_MEMLESS_EFFECTS; i++)
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__clear_bit(FF_EFFECT_PLAYING, &ml->states[i].flags);
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* Start/stop specified FF effect. Called with dev->event_lock held.
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static int ml_ff_playback(struct input_dev *dev, int effect_id, int value)
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struct ml_device *ml = dev->ff->private;
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struct ml_effect_state *state = &ml->states[effect_id];
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pr_debug("initiated play\n");
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__set_bit(FF_EFFECT_STARTED, &state->flags);
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state->count = value;
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state->play_at = jiffies +
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msecs_to_jiffies(state->effect->replay.delay);
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state->stop_at = state->play_at +
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msecs_to_jiffies(state->effect->replay.length);
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state->adj_at = state->play_at;
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pr_debug("initiated stop\n");
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if (test_bit(FF_EFFECT_PLAYING, &state->flags))
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__set_bit(FF_EFFECT_ABORTING, &state->flags);
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__clear_bit(FF_EFFECT_STARTED, &state->flags);
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static int ml_ff_upload(struct input_dev *dev,
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struct ff_effect *effect, struct ff_effect *old)
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struct ml_device *ml = dev->ff->private;
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struct ml_effect_state *state = &ml->states[effect->id];
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spin_lock_irq(&dev->event_lock);
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if (test_bit(FF_EFFECT_STARTED, &state->flags)) {
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__clear_bit(FF_EFFECT_PLAYING, &state->flags);
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state->play_at = jiffies +
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msecs_to_jiffies(state->effect->replay.delay);
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state->stop_at = state->play_at +
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msecs_to_jiffies(state->effect->replay.length);
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state->adj_at = state->play_at;
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ml_schedule_timer(ml);
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spin_unlock_irq(&dev->event_lock);
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static void ml_ff_destroy(struct ff_device *ff)
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struct ml_device *ml = ff->private;
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* input_ff_create_memless() - create memoryless force-feedback device
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* @dev: input device supporting force-feedback
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* @data: driver-specific data to be passed into @play_effect
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* @play_effect: driver-specific method for playing FF effect
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int input_ff_create_memless(struct input_dev *dev, void *data,
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int (*play_effect)(struct input_dev *, void *, struct ff_effect *))
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struct ml_device *ml;
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struct ff_device *ff;
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ml = kzalloc(sizeof(struct ml_device), GFP_KERNEL);
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ml->play_effect = play_effect;
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setup_timer(&ml->timer, ml_effect_timer, (unsigned long)dev);
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set_bit(FF_GAIN, dev->ffbit);
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error = input_ff_create(dev, FF_MEMLESS_EFFECTS);
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ff->upload = ml_ff_upload;
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ff->playback = ml_ff_playback;
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ff->set_gain = ml_ff_set_gain;
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ff->destroy = ml_ff_destroy;
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/* we can emulate periodic effects with RUMBLE */
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if (test_bit(FF_RUMBLE, ff->ffbit)) {
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set_bit(FF_PERIODIC, dev->ffbit);
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set_bit(FF_SINE, dev->ffbit);
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set_bit(FF_TRIANGLE, dev->ffbit);
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set_bit(FF_SQUARE, dev->ffbit);
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for (i = 0; i < FF_MEMLESS_EFFECTS; i++)
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ml->states[i].effect = &ff->effects[i];
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EXPORT_SYMBOL_GPL(input_ff_create_memless);