[PATCH 0/5] Add ff-memless-next and make hid-lg4ff use it

[PATCH 0/5] Add ff-memless-next and make hid-lg4ff use it

[Michal Malý]

Hi everybody,

this patch series is a result of my work to improve FFB support for memoryless
devices. ff-memless-next is an improvement over the currently available
ff-memless which is well suited for joypads but cannot handle more advanced
devices such as racing wheels properly. As I have explained in one of RFCs
regarding ff-memless-next, the extent of changes makes implementing
ff-memless-next as a patch to ff-memless unfeasible. As of now there is a total
of 27 drivers using ff-memless (including lg4ff) - a lot of them joypads.
I do not have access to any FFB joypad at the moment so I cannot
implement the functionality required to handle joypads properly - namely FF_RUMBLE
and emulation of FF_PERIODIC through FF_RUMBLE.
The plan is to implement the missing functionality and replace ff-memless completely
in the future. 

Second part of this series ports lg4ff driver over to ff-memless-next.
The immediate benefit of this is support of all periodic effects and ramp effect.

Michal M.

 Michal Malý (5):
  INPUT: Add ff-memless-next module
  HID: Port hid-lg4ff to ff-memless-next
  HID: Add support for periodic effects in hid-lg4ff
  HID: Add support for ramp effect in hid-lg4ff
  INPUT: Remove the note that no driver currently uses ff-memless-next from KConfig

 Documentation/input/ff-memless-next.txt | 149 ++++++
 drivers/hid/Kconfig                     |   2 +-
 drivers/hid/hid-lg4ff.c                 |  93 ++--
 drivers/input/Kconfig                   |  11 +
 drivers/input/Makefile                  |   2 +
 drivers/input/ff-memless-next.c         | 793 ++++++++++++++++++++++++++++++++
 include/linux/input/ff-memless-next.h   |  31 ++
 7 files changed, 1045 insertions(+), 36 deletions(-)
--
 1.8.5.3

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[PATCH 1/5] Add ff-memless-next

[Michal Malý]

Introduce ff-memless-next module as a possible future replacement for
ff-memless.

Tested-by: Elias Vanderstuyft <elias.vds@gmail.com>
Signed-off-by: Michal Malý <madcatxster@prifuk.cz>
---
 Documentation/input/ff-memless-next.txt | 149 ++++++
 drivers/input/Kconfig                   |  12 +
 drivers/input/Makefile                  |   2 +
 drivers/input/ff-memless-next.c         | 793 ++++++++++++++++++++++++++++++++
 include/linux/input/ff-memless-next.h   |  31 ++
 5 files changed, 987 insertions(+)
 create mode 100644 Documentation/input/ff-memless-next.txt
 create mode 100644 drivers/input/ff-memless-next.c
 create mode 100644 include/linux/input/ff-memless-next.h

diff --git a/Documentation/input/ff-memless-next.txt b/Documentation/input/ff-memless-next.txt
new file mode 100644
index 0000000..699dc04
--- /dev/null
+++ b/Documentation/input/ff-memless-next.txt
@@ -0,0 +1,149 @@
+"ff-memless-next" force feedback module for memoryless devices.
+By Michal Malý <madcatxster@prifuk.cz> on 2013/12/21
+----------------------------------------------------------------------------
+
+1. Introduction
+~~~~~~~~~~~~~~~
+This document describes basic working principles of the "ff-memless-next"
+module and its purpose. This document also contains a summary
+of the "ff-memless-next" API and brief instructions on how to use it to write
+a hardware-specific backend with "ff-memless-next". Some specifics
+of ff-memless-next that might be of interest for userspace developers
+are also discussed.
+
+2. Basic principles of ff-memless-next
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+A lot of commonly used force feedback devices do not have a memory of their
+own. This means that it is not possible to upload a force feedback effect
+to such a device and let the device's CPU handle the playback. Instead,
+the device relies solely on its driver to tell it what force to generate.
+"ff-memless-next" was written to serve in this capacity. Its purpose is to
+calculate the overall force the device should apply and pass the result to
+a hardware-specific backend which then submits the appropriate command to
+the device.
+
+"ff-memless-next" differentiates between two types of force feedback effects,
+"combinable" and "uncombinable".
+"Combinable" effects are effects that generate a force of a given
+magnitude and direction. The magnitude can change in time according to the
+envelope of the effect and its waveform; the latter applies only to periodic
+effects. Force generated by "combinable" effect does not depend on the position
+of the device. Forces generated by each "combinable" effect that is active
+are periodically recalculated as needed and superposed into one overall force.
+"Combinable" effects are FF_CONSTANT, FF_PERIODIC and FF_RAMP.
+
+"Uncombinable" effects generate a force that depends on the position of
+the device. "ff-memless-next" assumes that the device takes care of processing
+such an effect. However, a device might have a limit on how many "uncombinable"
+effects can be active at once and this limit might be lower than the maximum
+effect count set in "ff-memless-next". "ff-memless-next" allows a
+hardware-specific driver to check whether the device is able to play
+an "uncombinable" effect. Error is reported back to userspace if the device
+cannot play the effect. The hardware-specific driver may choose not to
+perform this check in which case the userspace will have no way of knowing
+whether an "uncombinable" effect is really being played or not.
+"Uncombinable" effects are FF_DAMPER, FF_FRICTION, FF_INERTIA and FF_SPRING.
+
+FF_CUSTOM is currently not handled by "ff-memless-next".
+
+3. API provided by "ff-memless-next"
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+"ff-memless-next" provides an API for developers of hardware-specific
+drivers. In order to use the API, the hardware-specific driver should
+include <linux/input/ff-memless-next.h>
+Functions and structs defined by this API are:
+
+int input_ff_create_mlnx(struct input_dev *dev, void *data,
+			 int(*control_effect)(struct input_dev *, void *, const struct mlnx_effect_command *),
+			 const u16 update_rate)
+- Any hardware-specific driver that wants to use "ff-memless-next" must call
+this function. The function takes care of creating and registering a force
+feedback device within the kernel. It also initializes resources needed by
+"ff-memless-next" to handle a new device. No other initialization steps are necessary.
+	Parameters:
+	* dev - pointer to valid struct input_dev
+	* data - pointer to custom data the hardware-specific backend
+		 might need to pass to the control_effect() callback function
+		 (discussed later). * data will be freed automatically by
+		 "ff-memless-next" upon device's destruction.
+	* control_effect - A callback function. "ff-memless-next" will call
+			   this function when it is done processing effects.
+			   Implementation of control_effect() in the
+			   hardware-specific driver should create an appropriate
+			   command and submit it to the device.
+			   This function is called with dev->event_lock
+			   spinlock held.
+	update_rate - Rate in milliseconds at which envelopes and periodic
+		      effects are recalculated. Minimum value is limited by the
+		      kernel timer resolution and changes with value of
+		      CONFIG_HZ.
+
+struct mlnx_effect_command
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+- This struct is passed to the hardware-specific backend in
+the control_effect() function. See "ff-memless-next.h" for details.
+
+enum mlnx_commands
+^^^^^^^^^^^^^^^^^^
+- Types of commands generated by ff-memless-next
+	MLNX_START_COMBINED - Start or update "combinable" effect
+	MLNX_STOP_COMBINED - Stop "combinable" effect. In most cases this means
+			     to set the force to zero.
+	MLNX_UPLOAD_UNCOMB - Check if the device can accept and play
+			     "uncombinable" effect.
+			     Hardware-specific driver should return 0
+			     on success.
+	MLNX_START_UNCOMB - Start playback of "uncombinable" effect.
+	MLNX_STOP_UNCOMB - Stop playback of "uncombinable" effect.
+
+struct mlnx_simple_force
+^^^^^^^^^^^^^^^^^^^^^^^^
+	x - overall force along X axis
+	y - overall force along Y axis
+
+struct mlnx_uncomb_effect
+^^^^^^^^^^^^^^^^^^^^^^^^^
+- Information about "uncombinable" effect.
+	id - internal ID of the effect
+	* effect - pointer to the internal copy of the effect kept by
+		   "ff-memless-next". This pointer will remain valid until
+		   the effect is removed.
+
+Sample implementation of a dummy driver that uses "ff-memless-next" is
+available at "git://prifuk.cz/ff-dummy-device". Link to the source will
+be kept up to date.
+
+Direction of the effect's force translates to Cartesian coordinates system
+as follows:
+  Direction = 0: Down
+  Direction (0; 16384): 3rd quadrant
+  Direction = 16384: Left
+  Direction (16385; 32768): 2nd quadrant
+  Direction = 32768: Up
+  Direction (32769; 49152): 1st quadrant
+  Direction = 49152: Right
+  Direction (49153; 65535) :4th quadrant
+  Direction = 65565: Down
+
+4. Specifics of "ff-memless-next" for userspace developers
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+None of the persons involved in development or testing of "ff-memless-next"
+is aware of any reference force feedback specifications. "ff-memless-next"
+tries to adhere to Microsoft's DirectInput specifications because we
+believe that is what most developers have experience with.
+
+- Waveforms of periodic effects do not start at the origin, but as follows:
+	SAW_UP: At minimum
+	SAW_DOWN: At maximum
+	SQUARE: At maximum
+	TRIANGLE: At maximum
+	SINE: At origin
+
+- Updating periodic effects:
+	- All periodic effects are restarted when their parameters are updated.
+
+- Updating effects of finite duration:
+	- Once an effect of finite length finishes playing, it is considered
+	  stopped. Only effects that are playing can be updated on the fly.
+	  Therefore effects of finite duration can be updated only until
+	  they finish playing.
diff --git a/drivers/input/Kconfig b/drivers/input/Kconfig
index a11ff74..4371a12 100644
--- a/drivers/input/Kconfig
+++ b/drivers/input/Kconfig
@@ -77,6 +77,18 @@ config INPUT_MATRIXKMAP
 	  To compile this driver as a module, choose M here: the
 	  module will be called matrix-keymap.
 
+config INPUT_FF_MEMLESS_NEXT
+	tristate "New version of support for memoryless force feedback devices"
+	help
+	  Say Y here if you want to enable support for various memoryless
+	  force feedback devices (as of now there is no hardware-specific
+	  driver that supports this).
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ff-memless-next.
+
 comment "Userland interfaces"
 
 config INPUT_MOUSEDEV
diff --git a/drivers/input/Makefile b/drivers/input/Makefile
index 5ca3f63..269a22d 100644
--- a/drivers/input/Makefile
+++ b/drivers/input/Makefile
@@ -16,6 +16,8 @@ obj-$(CONFIG_INPUT_MOUSEDEV)	+= mousedev.o
 obj-$(CONFIG_INPUT_JOYDEV)	+= joydev.o
 obj-$(CONFIG_INPUT_EVDEV)	+= evdev.o
 obj-$(CONFIG_INPUT_EVBUG)	+= evbug.o
+obj-$(CONFIG_INPUT_MATRIXKMAP)	+= matrix-keymap.o
+obj-$(CONFIG_INPUT_FF_MEMLESS_NEXT)	+= ff-memless-next.o
 
 obj-$(CONFIG_INPUT_KEYBOARD)	+= keyboard/
 obj-$(CONFIG_INPUT_MOUSE)	+= mouse/
diff --git a/drivers/input/ff-memless-next.c b/drivers/input/ff-memless-next.c
new file mode 100644
index 0000000..97de791
--- /dev/null
+++ b/drivers/input/ff-memless-next.c
@@ -0,0 +1,793 @@
+/*
+ * Force feedback support for memoryless devices
+ *
+ * This module is based on "ff-memless" orignally written by Anssi Hannula.
+ * It is extended to support all force feedback effects currently supported
+ * by the Linux input stack.
+ *
+ * Copyright(c) 2013 Michal Maly <madcatxster@prifuk.cz>
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
+#include <linux/jiffies.h>
+#include <linux/fixp-arith.h>
+#include <linux/input/ff-memless-next.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Michal \"MadCatX\" Maly");
+MODULE_DESCRIPTION("Force feedback support for memoryless force feedback devices");
+
+#define FF_MAX_EFFECTS 16
+#define FF_MIN_EFFECT_LENGTH ((1000 / CONFIG_HZ) + 1)
+#define FF_EFFECT_STARTED 1
+#define FF_EFFECT_PLAYING 2
+
+
+struct mlnx_effect {
+	struct ff_effect effect;
+	unsigned long flags;
+	unsigned long begin_at;
+	unsigned long stop_at;
+	unsigned long updated_at;
+	unsigned long attack_stop;
+	unsigned long fade_begin;
+	int repeat;
+	u16 playback_time;
+};
+
+struct mlnx_device {
+	u8 combinable_playing;
+	unsigned long update_rate_jiffies;
+	void *private;
+	struct mlnx_effect effects[FF_MAX_EFFECTS];
+	int gain;
+	struct timer_list timer;
+	struct input_dev *dev;
+
+	int (*control_effect)(struct input_dev *, void *,
+			      const struct mlnx_effect_command *);
+};
+
+static s32 mlnx_calculate_x_force(const s32 level,
+						  const u16 direction)
+{
+	s32 new = (level * -fixp_sin(direction)) >> FRAC_N;
+	pr_debug("x force: %d\n", new);
+	return new;
+}
+
+static s32 mlnx_calculate_y_force(const s32 level,
+						  const u16 direction)
+{
+	s32 new = (level * -fixp_cos(direction)) >> FRAC_N;
+	pr_debug("y force: %d\n", new);
+	return new;
+}
+
+static bool mlnx_is_combinable(const struct ff_effect *effect)
+{
+	switch (effect->type) {
+	case FF_CONSTANT:
+	case FF_PERIODIC:
+	case FF_RAMP:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool mlnx_is_conditional(const struct ff_effect *effect)
+{
+	switch (effect->type) {
+	case FF_DAMPER:
+	case FF_FRICTION:
+	case FF_INERTIA:
+	case FF_SPRING:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool mlnx_is_square(const struct ff_effect *effect)
+{
+	if (effect->type == FF_PERIODIC)
+		return effect->u.periodic.waveform == FF_SQUARE;
+	return false;
+}
+
+static void mlnx_clr_playing(struct mlnx_effect *mlnxeff)
+{
+	__clear_bit(FF_EFFECT_PLAYING, &mlnxeff->flags);
+}
+
+static void mlnx_clr_started(struct mlnx_effect *mlnxeff)
+{
+	__clear_bit(FF_EFFECT_STARTED, &mlnxeff->flags);
+}
+
+static bool mlnx_is_playing(const struct mlnx_effect *mlnxeff)
+{
+	return test_bit(FF_EFFECT_PLAYING, &mlnxeff->flags);
+}
+
+static bool mlnx_is_started(const struct mlnx_effect *mlnxeff)
+{
+	return test_bit(FF_EFFECT_STARTED, &mlnxeff->flags);
+}
+
+static bool mlnx_test_set_playing(struct mlnx_effect *mlnxeff)
+{
+	return test_and_set_bit(FF_EFFECT_PLAYING, &mlnxeff->flags);
+}
+
+static const struct ff_envelope *mlnx_get_envelope(const struct ff_effect *effect)
+{
+	static const struct ff_envelope empty;
+
+	switch (effect->type) {
+	case FF_CONSTANT:
+		return &effect->u.constant.envelope;
+	case FF_PERIODIC:
+		return &effect->u.periodic.envelope;
+	case FF_RAMP:
+		return &effect->u.ramp.envelope;
+	default:
+		return &empty;
+	}
+}
+
+/* Some devices might have a limit on how many uncombinable effects
+ * can be played at once */
+static int mlnx_upload_conditional(struct mlnx_device *mlnxdev,
+				   const struct ff_effect *effect)
+{
+	struct mlnx_effect_command ecmd = {
+		.cmd = MLNX_UPLOAD_UNCOMB,
+		.u.uncomb.id = effect->id,
+		.u.uncomb.effect = effect
+	};
+	return mlnxdev->control_effect(mlnxdev->dev, mlnxdev->private, &ecmd);
+}
+
+static void mlnx_set_envelope_times(struct mlnx_effect *mlnxeff)
+{
+	const struct ff_effect *effect = &mlnxeff->effect;
+	const struct ff_envelope *envelope = mlnx_get_envelope(effect);
+
+	if (envelope->attack_length) {
+		unsigned long j = msecs_to_jiffies(envelope->attack_length);
+		mlnxeff->attack_stop = mlnxeff->begin_at + j;
+	}
+	if (effect->replay.length && envelope->fade_length) {
+		unsigned long j = msecs_to_jiffies(envelope->fade_length);
+		mlnxeff->fade_begin = mlnxeff->stop_at - j;
+	}
+}
+
+static void mlnx_set_trip_times(struct mlnx_effect *mlnxeff,
+				const unsigned long now)
+{
+	const struct ff_effect *effect = &mlnxeff->effect;
+	const u16 replay_delay = effect->replay.delay;
+	const u16 replay_length = effect->replay.length;
+
+	mlnxeff->begin_at = now + msecs_to_jiffies(replay_delay);
+	mlnxeff->stop_at = mlnxeff->begin_at + msecs_to_jiffies(replay_length);
+	mlnxeff->updated_at = mlnxeff->begin_at;
+	if (effect->type == FF_PERIODIC)
+		mlnxeff->playback_time = effect->u.periodic.phase;
+}
+
+static void mlnx_start_effect(struct mlnx_effect *mlnxeff)
+{
+	const unsigned long now = jiffies;
+
+	mlnx_set_trip_times(mlnxeff, now);
+	mlnx_set_envelope_times(mlnxeff);
+	__set_bit(FF_EFFECT_STARTED, &mlnxeff->flags);
+}
+
+static void mlnx_stop_effect(struct mlnx_device *mlnxdev,
+			     const struct mlnx_effect *mlnxeff)
+{
+	switch (mlnxeff->effect.type) {
+	case FF_CONSTANT:
+	case FF_PERIODIC:
+	case FF_RAMP:
+		if (--mlnxdev->combinable_playing == 0) {
+			const struct mlnx_effect_command c = {
+				.cmd = MLNX_STOP_COMBINED
+			};
+			mlnxdev->control_effect(mlnxdev->dev, mlnxdev->private,
+						&c);
+		}
+		return;
+	case FF_DAMPER:
+	case FF_FRICTION:
+	case FF_INERTIA:
+	case FF_SPRING:
+	{
+		const struct mlnx_effect_command c = {
+			.cmd = MLNX_STOP_UNCOMB,
+			.u.uncomb.id = mlnxeff->effect.id,
+			.u.uncomb.effect = &mlnxeff->effect
+		};
+		mlnxdev->control_effect(mlnxdev->dev, mlnxdev->private, &c);
+		return;
+	}
+	default:
+		return;
+	}
+}
+
+static int mlnx_restart_effect(struct mlnx_device *mlnxdev,
+			       struct mlnx_effect *mlnxeff)
+{
+	const struct ff_effect *effect = &mlnxeff->effect;
+	const unsigned long now = jiffies;
+
+	if (mlnx_is_combinable(effect)) {
+		if (effect->replay.delay)
+			mlnx_stop_effect(mlnxdev, mlnxeff);
+		else
+			mlnxdev->combinable_playing--;
+	} else if (mlnx_is_conditional(effect)) {
+		int ret;
+		if (effect->replay.delay)
+			mlnx_stop_effect(mlnxdev, mlnxeff);
+
+		ret = mlnx_upload_conditional(mlnxdev, &mlnxeff->effect);
+		if (ret)
+			return ret;
+	}
+
+	mlnx_set_trip_times(mlnxeff, now);
+	mlnx_set_envelope_times(mlnxeff);
+
+	return 0;
+}
+
+static s32 mlnx_apply_envelope(const struct mlnx_effect *mlnxeff,
+			       const s32 level)
+{
+	const struct ff_effect *effect = &mlnxeff->effect;
+	const struct ff_envelope *envelope = mlnx_get_envelope(effect);
+	const unsigned long now = jiffies;
+	const s32 alevel = abs(level);
+
+	/* Effect has an envelope with nonzero attack time */
+	if (envelope->attack_length && time_before(now, mlnxeff->attack_stop)) {
+		const s32 clength = jiffies_to_msecs(now - mlnxeff->begin_at);
+		const s32 alength = envelope->attack_length;
+		const s32 dlevel = (alevel - envelope->attack_level)
+				 * clength / alength;
+		return level < 0 ? -(dlevel + envelope->attack_level) :
+				    (dlevel + envelope->attack_level);
+	} else if (envelope->fade_length && time_before_eq(mlnxeff->fade_begin, now)) {
+		const s32 clength = jiffies_to_msecs(now - mlnxeff->fade_begin);
+		const s32 flength = envelope->fade_length;
+		const s32 dlevel = (envelope->fade_level - alevel)
+				 * clength / flength;
+		return level < 0 ? -(dlevel + alevel) : (dlevel + alevel);
+	}
+
+	return level;
+}
+
+static s32 mlnx_calculate_periodic(struct mlnx_effect *mlnxeff, const s32 level)
+{
+	const struct ff_effect *effect = &mlnxeff->effect;
+	const unsigned long now = jiffies;
+	const u16 period = effect->u.periodic.period;
+	const unsigned long dt = jiffies_to_msecs(now - mlnxeff->updated_at);
+	const s16 offset = effect->u.periodic.offset;
+	s32 new = level;
+	u16 t;
+
+	mlnxeff->playback_time += dt;
+	t = mlnxeff->playback_time % period;
+
+	switch (effect->u.periodic.waveform) {
+	case FF_SINE:
+	{
+		u16 degrees = (360 * t) / period;
+		new = ((level * fixp_sin(degrees)) >> FRAC_N) + offset;
+		break;
+	}
+	case FF_SQUARE:
+	{
+		u16 degrees = (360 * t) / period;
+		new = level * (degrees < 180 ? 1 : -1) + offset;
+		break;
+	}
+	case FF_SAW_UP:
+		new = 2 * level * t / period - level + offset;
+		break;
+	case FF_SAW_DOWN:
+		new = level - 2 * level * t / period + offset;
+		break;
+	case FF_TRIANGLE:
+	{
+		new = (2 * abs(level - (2 * level * t) / period));
+		new = new - level + offset;
+		break;
+	}
+	case FF_CUSTOM:
+		pr_debug("Custom waveform is not handled by this driver\n");
+		return level;
+	default:
+		pr_err("Invalid waveform\n");
+		return level;
+	}
+
+	mlnxeff->playback_time = t;
+	/* Ensure that the offset did not make the value exceed s16 range */
+	new = clamp(new, -0x7fff, 0x7fff);
+	pr_debug("level: %d, playback: %u, t: %u, dt: %lu\n",
+		 new, mlnxeff->playback_time, t, dt);
+	return new;
+}
+
+static s32 mlnx_calculate_ramp(const struct mlnx_effect *mlnxeff)
+{
+	const struct ff_effect *effect = &mlnxeff->effect;
+	const struct ff_envelope *envelope = mlnx_get_envelope(effect);
+	const unsigned long now = jiffies;
+	const u16 length = effect->replay.length;
+	const s16 mean = (effect->u.ramp.start_level + effect->u.ramp.end_level) / 2;
+	const u16 t = jiffies_to_msecs(now - mlnxeff->begin_at);
+	s32 start = effect->u.ramp.start_level;
+	s32 end = effect->u.ramp.end_level;
+	s32 new;
+
+	if (envelope->attack_length && time_before(now, mlnxeff->attack_stop)) {
+		const s32 clength = jiffies_to_msecs(now - mlnxeff->begin_at);
+		const s32 alength = envelope->attack_length;
+		s32 attack_level;
+		if (end > start)
+			attack_level = mean - envelope->attack_level;
+		else
+			attack_level = mean + envelope->attack_level;
+		start = (start - attack_level) * clength / alength
+		      + attack_level;
+	} else if (envelope->fade_length && time_before_eq(mlnxeff->fade_begin, now)) {
+		const s32 clength = jiffies_to_msecs(now - mlnxeff->fade_begin);
+		const s32 flength = envelope->fade_length;
+		s32 fade_level;
+		if (end > start)
+			fade_level = mean + envelope->fade_level;
+		else
+			fade_level = mean - envelope->fade_level;
+		end = (fade_level - end) * clength / flength + end;
+	}
+
+	new = ((end - start) * t) / length + start;
+	new = clamp(new, -0x7fff, 0x7fff);
+	pr_debug("RAMP level: %d, t: %u\n", new, t);
+	return new;
+}
+
+static void mlnx_destroy(struct ff_device *dev)
+{
+	struct mlnx_device *mlnxdev = dev->private;
+	del_timer_sync(&mlnxdev->timer);
+
+	kfree(mlnxdev->private);
+}
+
+static unsigned long mlnx_get_envelope_update_time(const struct mlnx_effect *mlnxeff,
+						   const unsigned long update_rate_jiffies)
+{
+	const struct ff_effect *effect = &mlnxeff->effect;
+	const struct ff_envelope *envelope = mlnx_get_envelope(effect);
+	const unsigned long now = jiffies;
+	unsigned long fade_next;
+
+	/* Effect has an envelope with nonzero attack time */
+	if (envelope->attack_length && time_before(now, mlnxeff->attack_stop)) {
+		if (time_before(mlnxeff->updated_at + update_rate_jiffies, mlnxeff->attack_stop))
+			return mlnxeff->updated_at + update_rate_jiffies;
+
+		return mlnxeff->attack_stop;
+	}
+
+	/* Effect has an envelope with nonzero fade time */
+	if (mlnxeff->effect.replay.length) {
+		if (!envelope->fade_length)
+			return mlnxeff->stop_at;
+
+		/* Schedule the next update when the fade begins */
+		if (time_before(mlnxeff->updated_at, mlnxeff->fade_begin))
+			return mlnxeff->fade_begin;
+
+		/* Already fading */
+		fade_next = mlnxeff->updated_at + update_rate_jiffies;
+
+		/* Schedule update when the effect stops */
+		if (time_after(fade_next, mlnxeff->stop_at))
+			return mlnxeff->stop_at;
+		/* Schedule update at the next checkpoint */
+			return fade_next;
+	}
+
+	/* There is no envelope */
+
+	/* Prevent the effect from being started twice */
+	if (mlnxeff->begin_at == now && mlnx_is_playing(mlnxeff))
+		return now - 1;
+
+	return mlnxeff->begin_at;
+}
+
+static unsigned long mlnx_get_update_time(const struct mlnx_effect *mlnxeff,
+				const unsigned long update_rate_jiffies)
+{
+	const unsigned long now = jiffies;
+	unsigned long time, update_periodic;
+
+	switch (mlnxeff->effect.type) {
+	/* Constant effect does not change with time, but it can have
+	 * an envelope and a duration */
+	case FF_CONSTANT:
+		return mlnx_get_envelope_update_time(mlnxeff,
+						     update_rate_jiffies);
+	/* Periodic and ramp effects have to be periodically updated */
+	case FF_PERIODIC:
+	case FF_RAMP:
+		time = mlnx_get_envelope_update_time(mlnxeff,
+						     update_rate_jiffies);
+
+		if (mlnx_is_square(&mlnxeff->effect)) {
+			const u16 half_T = mlnxeff->effect.u.periodic.period/2;
+			update_periodic = msecs_to_jiffies(half_T)
+					  + mlnxeff->updated_at;
+		} else
+			update_periodic = mlnxeff->updated_at
+					  + update_rate_jiffies;
+
+		/* Periodic effect has to be updated earlier than envelope
+		 * or envelope update time is in the past */
+		if (time_before(update_periodic, time) || time_before(time, now))
+			return update_periodic;
+		/* Envelope needs to be updated */
+		return time;
+	case FF_DAMPER:
+	case FF_FRICTION:
+	case FF_INERTIA:
+	case FF_SPRING:
+	default:
+		if (time_after_eq(mlnxeff->begin_at, now))
+			return mlnxeff->begin_at;
+
+		return mlnxeff->stop_at;
+	}
+}
+
+static void mlnx_schedule_playback(struct mlnx_device *mlnxdev)
+{
+	struct mlnx_effect *mlnxeff;
+	const unsigned long now = jiffies;
+	int events = 0;
+	int i;
+	unsigned long earliest = 0;
+	unsigned long time;
+
+	/* Iterate over all effects and determine the earliest
+	 * time when we have to attend to any */
+	for (i = 0; i < FF_MAX_EFFECTS; i++) {
+		mlnxeff = &mlnxdev->effects[i];
+
+		if (!mlnx_is_started(mlnxeff))
+			continue; /* Effect is not started, skip it */
+
+		if (mlnx_is_playing(mlnxeff))
+			time = mlnx_get_update_time(mlnxeff,
+						mlnxdev->update_rate_jiffies);
+		else
+			time = mlnxeff->begin_at;
+
+		pr_debug("Update time for effect %d: %lu\n", i, time);
+
+		/* Scheduled time is in the future and is either
+		 * before the current earliest time or it is
+		 * the first valid time value in this pass */
+		if (time_before_eq(now, time) &&
+		    (++events == 1 || time_before(time, earliest)))
+			earliest = time;
+	}
+
+	if (events) {
+		pr_debug("Events: %d, earliest: %lu\n", events, earliest);
+		mod_timer(&mlnxdev->timer, earliest);
+	}
+}
+
+static void mlnx_add_force(struct mlnx_effect *mlnxeff, s32 *cfx, s32 *cfy,
+			   const u16 gain)
+{
+	const struct ff_effect *effect = &mlnxeff->effect;
+	u16 direction;
+	s32 level;
+
+	pr_debug("Processing effect type %d, ID %d\n",
+		 mlnxeff->effect.type, mlnxeff->effect.id);
+
+	direction = mlnxeff->effect.direction * 360 / 0xffff;
+	pr_debug("Direction deg: %u\n", direction);
+
+	switch (mlnxeff->effect.type) {
+	case FF_CONSTANT:
+		level = mlnx_apply_envelope(mlnxeff, effect->u.constant.level);
+		break;
+	case FF_PERIODIC:
+		level = mlnx_apply_envelope(mlnxeff,
+					    effect->u.periodic.magnitude);
+		level = mlnx_calculate_periodic(mlnxeff, level);
+		break;
+	case FF_RAMP:
+		level = mlnx_calculate_ramp(mlnxeff);
+		break;
+	default:
+		pr_err("Effect %d not handled by mlnx_add_force\n",
+		       mlnxeff->effect.type);
+		return;
+	}
+
+	*cfx += mlnx_calculate_x_force(level, direction) * gain / 0xffff;
+	*cfy += mlnx_calculate_y_force(level, direction) * gain / 0xffff;
+}
+
+static void mlnx_play_effects(struct mlnx_device *mlnxdev)
+{
+	const u16 gain = mlnxdev->gain;
+	const unsigned long now = jiffies;
+	int i;
+	int cfx = 0;
+	int cfy = 0;
+
+	for (i = 0; i < FF_MAX_EFFECTS; i++) {
+		struct mlnx_effect *mlnxeff = &mlnxdev->effects[i];
+
+		if (!mlnx_is_started(mlnxeff)) {
+			pr_debug("Effect %hd/%d not started\n",
+				 mlnxeff->effect.id, i);
+			continue;
+		}
+
+		if (time_before(now, mlnxeff->begin_at)) {
+			pr_debug("Effect %hd/%d begins at a later time\n",
+				 mlnxeff->effect.id, i);
+			continue;
+		}
+
+		if (time_before_eq(mlnxeff->stop_at, now) && mlnxeff->effect.replay.length) {
+			pr_debug("Effect %hd/%d has to be stopped\n",
+				 mlnxeff->effect.id, i);
+
+			mlnx_clr_playing(mlnxeff);
+			if (--mlnxeff->repeat > 0)
+				mlnx_restart_effect(mlnxdev, mlnxeff);
+			else {
+				mlnx_clr_started(mlnxeff);
+				mlnx_stop_effect(mlnxdev, mlnxeff);
+			}
+
+			continue;
+		}
+
+		switch (mlnxeff->effect.type) {
+		case FF_CONSTANT:
+		case FF_PERIODIC:
+		case FF_RAMP:
+			if (!mlnx_test_set_playing(mlnxeff)) {
+				mlnxdev->combinable_playing++;
+				pr_debug("Starting combinable effect, total %u\n",
+					 mlnxdev->combinable_playing);
+			}
+			mlnx_add_force(mlnxeff, &cfx, &cfy, gain);
+			break;
+		case FF_DAMPER:
+		case FF_FRICTION:
+		case FF_INERTIA:
+		case FF_SPRING:
+			if (!mlnx_test_set_playing(mlnxeff)) {
+				const struct mlnx_effect_command ecmd = {
+					.cmd = MLNX_START_UNCOMB,
+					.u.uncomb.id = i,
+					.u.uncomb.effect = &mlnxeff->effect
+				};
+				mlnxdev->control_effect(mlnxdev->dev,
+						      mlnxdev->private, &ecmd);
+			}
+			break;
+		default:
+			pr_debug("Unhandled type of effect\n");
+		}
+		mlnxeff->updated_at = now;
+	}
+
+	if (mlnxdev->combinable_playing) {
+		const struct mlnx_effect_command ecmd = {
+			.cmd = MLNX_START_COMBINED,
+			.u.simple_force = {
+				.x = clamp(cfx, -0x7fff, 0x7fff),
+				.y = clamp(cfy, -0x7fff, 0x7fff)
+			}
+		};
+		mlnxdev->control_effect(mlnxdev->dev, mlnxdev->private, &ecmd);
+	}
+
+	mlnx_schedule_playback(mlnxdev);
+}
+
+static void mlnx_set_gain(struct input_dev *dev, u16 gain)
+{
+	struct mlnx_device *mlnxdev = dev->ff->private;
+	int i;
+
+	mlnxdev->gain = gain;
+
+	for (i = 0; i < FF_MAX_EFFECTS; i++)
+		mlnx_clr_playing(&mlnxdev->effects[i]);
+
+	mlnx_play_effects(mlnxdev);
+}
+
+static int mlnx_startstop(struct input_dev *dev, int effect_id, int repeat)
+{
+	struct mlnx_device *mlnxdev = dev->ff->private;
+	struct mlnx_effect *mlnxeff = &mlnxdev->effects[effect_id];
+
+	if (repeat > 0) {
+		pr_debug("Starting effect ID %d\n", effect_id);
+		mlnxeff->repeat = repeat;
+		if (!mlnx_is_started(mlnxeff))
+			mlnx_start_effect(mlnxeff);
+	} else {
+		pr_debug("Stopping effect ID %d\n", effect_id);
+		if (mlnx_is_started(mlnxeff)) {
+			if (mlnx_is_playing(mlnxeff)) {
+				mlnx_clr_playing(mlnxeff);
+				mlnx_stop_effect(mlnxdev, mlnxeff);
+			}
+			mlnx_clr_started(mlnxeff);
+		} else {
+			pr_debug("Effect ID %d already stopped\n", effect_id);
+			return 0;
+		}
+	}
+	mlnx_play_effects(mlnxdev);
+
+	return 0;
+}
+
+static void mlnx_timer_fired(unsigned long data)
+{
+	struct input_dev *dev = (struct input_dev *)data;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->event_lock, flags);
+	mlnx_play_effects(dev->ff->private);
+	spin_unlock_irqrestore(&dev->event_lock, flags);
+}
+
+static int mlnx_upload(struct input_dev *dev, struct ff_effect *effect,
+		       struct ff_effect *old)
+{
+	struct mlnx_device *mlnxdev = dev->ff->private;
+	struct mlnx_effect *mlnxeff = &mlnxdev->effects[effect->id];
+	const u16 length = effect->replay.length;
+	const u16 delay = effect->replay.delay;
+	int ret, fade_from;
+
+	/* Effect's timing is below kernel timer resolution */
+	if (length && length < FF_MIN_EFFECT_LENGTH)
+		effect->replay.length = FF_MIN_EFFECT_LENGTH;
+	if (delay && delay < FF_MIN_EFFECT_LENGTH)
+		effect->replay.delay = FF_MIN_EFFECT_LENGTH;
+
+	/* Periodic effects must have a non-zero period */
+	if (effect->type == FF_PERIODIC) {
+		if (!effect->u.periodic.period)
+			return -EINVAL;
+	}
+	/* Ramp effects cannot be infinite */
+	if (effect->type == FF_RAMP && !length)
+		return -EINVAL;
+
+	if (mlnx_is_combinable(effect)) {
+		const struct ff_envelope *envelope = mlnx_get_envelope(effect);
+
+		/* Infinite effects cannot fade */
+		if (!length && envelope->fade_length > 0)
+			return -EINVAL;
+		/* Fade length cannot be greater than effect duration */
+		fade_from = (int)length - (int)envelope->fade_length;
+		if (fade_from < 0)
+			return -EINVAL;
+		/* Envelope cannot start fading before it finishes attacking */
+		if (fade_from < envelope->attack_length && fade_from > 0)
+			return -EINVAL;
+	}
+
+
+	spin_lock_irq(&dev->event_lock);
+	mlnxeff->effect = *effect; /* Keep internal copy of the effect */
+	/* Check if the effect being modified is playing */
+	if (mlnx_is_started(mlnxeff)) {
+		if (mlnx_is_playing(mlnxeff)) {
+			mlnx_clr_playing(mlnxeff);
+			ret = mlnx_restart_effect(mlnxdev, mlnxeff);
+
+			if (ret) {
+				/* Restore the original effect */
+				if (old)
+					mlnxeff->effect = *old;
+				spin_unlock_irq(&dev->event_lock);
+				return ret;
+			}
+		}
+
+		mlnx_schedule_playback(mlnxdev);
+		spin_unlock_irq(&dev->event_lock);
+		return 0;
+	}
+
+	if (mlnx_is_conditional(effect)) {
+		ret = mlnx_upload_conditional(mlnxdev, &mlnxeff->effect);
+		if (ret) {
+			/* Restore the original effect */
+			if (old)
+				mlnxeff->effect = *old;
+			spin_unlock_irq(&dev->event_lock);
+			return ret;
+		}
+	}
+
+	spin_unlock_irq(&dev->event_lock);
+
+	return 0;
+}
+
+int input_ff_create_mlnx(struct input_dev *dev, void *data,
+			 int(*control_effect)(struct input_dev *, void *, const struct mlnx_effect_command *),
+			 const u16 update_rate)
+{
+	struct mlnx_device *mlnxdev;
+	int ret;
+
+	mlnxdev = kzalloc(sizeof(*mlnxdev), GFP_KERNEL);
+	if (!mlnxdev)
+		return -ENOMEM;
+
+	mlnxdev->dev = dev;
+	mlnxdev->private = data;
+	mlnxdev->control_effect = control_effect;
+	mlnxdev->gain = 0xffff;
+	mlnxdev->update_rate_jiffies = update_rate < FF_MIN_EFFECT_LENGTH ?
+				       FF_MIN_EFFECT_LENGTH : update_rate;
+	setup_timer(&mlnxdev->timer, mlnx_timer_fired, (unsigned long)dev);
+
+	ret = input_ff_create(dev, FF_MAX_EFFECTS);
+	if (ret) {
+		kfree(mlnxdev);
+		return ret;
+	}
+
+	dev->ff->private = mlnxdev;
+	dev->ff->upload = mlnx_upload;
+	dev->ff->set_gain = mlnx_set_gain;
+	dev->ff->destroy = mlnx_destroy;
+	dev->ff->playback = mlnx_startstop;
+
+	pr_debug("Device successfully registered.\n");
+	return 0;
+}
+EXPORT_SYMBOL_GPL(input_ff_create_mlnx);
diff --git a/include/linux/input/ff-memless-next.h b/include/linux/input/ff-memless-next.h
new file mode 100644
index 0000000..f2fb080
--- /dev/null
+++ b/include/linux/input/ff-memless-next.h
@@ -0,0 +1,31 @@
+#include <linux/input.h>
+
+enum mlnx_commands {
+	MLNX_START_COMBINED,
+	MLNX_STOP_COMBINED,
+	MLNX_START_UNCOMB,
+	MLNX_STOP_UNCOMB,
+	MLNX_UPLOAD_UNCOMB
+};
+
+struct mlnx_simple_force {
+	const s32 x;
+	const s32 y;
+};
+
+struct mlnx_uncomb_effect {
+	const int id;
+	const struct ff_effect *effect;
+};
+
+struct mlnx_effect_command {
+	const enum mlnx_commands cmd;
+	union {
+		const struct mlnx_simple_force simple_force;
+		const struct mlnx_uncomb_effect uncomb;
+	} u;
+};
+
+int input_ff_create_mlnx(struct input_dev *dev, void *data,
+			 int(*control_effect)(struct input_dev *, void *, const struct mlnx_effect_command *),
+			 const u16 update_rate);
-- 
1.8.5.3


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[PATCH 2/5] Port hid-lg4ff to ff-memless-next

[Michal Malý]

Port hid-lg4ff to ff-memless-next.

---
 drivers/hid/Kconfig     |  2 +-
 drivers/hid/hid-lg4ff.c | 86 +++++++++++++++++++++++++++++--------------------
 2 files changed, 52 insertions(+), 36 deletions(-)

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 34e2d39..31c4b43 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -389,7 +389,7 @@ config LOGIG940_FF
 config LOGIWHEELS_FF
 	bool "Logitech wheels configuration and force feedback support"
 	depends on HID_LOGITECH
-	select INPUT_FF_MEMLESS
+	select INPUT_FF_MEMLESS_NEXT
 	default LOGITECH_FF
 	help
 	  Say Y here if you want to enable force feedback and range setting
diff --git a/drivers/hid/hid-lg4ff.c b/drivers/hid/hid-lg4ff.c
index befe0e3..f236b9f 100644
--- a/drivers/hid/hid-lg4ff.c
+++ b/drivers/hid/hid-lg4ff.c
@@ -25,6 +25,7 @@
 
 
 #include <linux/input.h>
+#include <linux/input/ff-memless-next.h>
 #include <linux/usb.h>
 #include <linux/hid.h>
 
@@ -44,6 +45,8 @@
 #define G27_REV_MAJ 0x12
 #define G27_REV_MIN 0x38
 
+#define FF_UPDATE_RATE 8
+
 #define to_hid_device(pdev) container_of(pdev, struct hid_device, dev)
 
 static void hid_lg4ff_set_range_dfp(struct hid_device *hid, u16 range);
@@ -182,47 +185,60 @@ int lg4ff_adjust_input_event(struct hid_device *hid, struct hid_field *field,
 	}
 }
 
-static int hid_lg4ff_play(struct input_dev *dev, void *data, struct ff_effect *effect)
+static int hid_lg4ff_start_combined(struct hid_device *hid, struct hid_report *report,
+				    const struct mlnx_simple_force *force)
+{
+	__s32 *value = report->field[0]->value;
+	int scaled_x;
+
+	/* Scale down from MLNX range */
+	scaled_x = 0x80 - (force->x * 0xff / 0xffff);
+
+	value[0] = 0x11;	/* Slot 1 */
+	value[1] = 0x08;
+	value[2] = scaled_x;
+	value[3] = 0x80;
+	value[4] = 0x00;
+	value[5] = 0x00;
+	value[6] = 0x00;
+
+	hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+	return 0;
+}
+
+static int hid_lg4ff_stop_combined(struct hid_device *hid, struct hid_report *report)
+{
+	__s32 *value = report->field[0]->value;
+
+	value[0] = 0x11;	/* Slot 1 */
+	value[1] = 0x08;
+	value[2] = 0x80;
+	value[3] = 0x80;
+	value[4] = 0x00;
+	value[5] = 0x00;
+	value[6] = 0x00;
+
+	hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+	return 0;
+}
+
+static int hid_lg4ff_control(struct input_dev *dev, void *data, const struct mlnx_effect_command *command)
 {
 	struct hid_device *hid = input_get_drvdata(dev);
 	struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
 	struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
-	__s32 *value = report->field[0]->value;
-	int x;
-
-#define CLAMP(x) do { if (x < 0) x = 0; else if (x > 0xff) x = 0xff; } while (0)
-
-	switch (effect->type) {
-	case FF_CONSTANT:
-		x = effect->u.ramp.start_level + 0x80;	/* 0x80 is no force */
-		CLAMP(x);
-
-		if (x == 0x80) {
-			/* De-activate force in slot-1*/
-			value[0] = 0x13;
-			value[1] = 0x00;
-			value[2] = 0x00;
-			value[3] = 0x00;
-			value[4] = 0x00;
-			value[5] = 0x00;
-			value[6] = 0x00;
-
-			hid_hw_request(hid, report, HID_REQ_SET_REPORT);
-			return 0;
-		}
 
-		value[0] = 0x11;	/* Slot 1 */
-		value[1] = 0x08;
-		value[2] = x;
-		value[3] = 0x80;
-		value[4] = 0x00;
-		value[5] = 0x00;
-		value[6] = 0x00;
-
-		hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+	switch (command->cmd) {
+	case MLNX_START_COMBINED:
+		return hid_lg4ff_start_combined(hid, report, &command->u.simple_force);
+		break;
+	case MLNX_STOP_COMBINED:
+		return hid_lg4ff_stop_combined(hid, report);
 		break;
+	default:
+		dbg_hid("Unsupported effect command");
+		return -EINVAL;
 	}
-	return 0;
 }
 
 /* Sends default autocentering command compatible with
@@ -608,7 +624,7 @@ int lg4ff_init(struct hid_device *hid)
 	for (j = 0; lg4ff_devices[i].ff_effects[j] >= 0; j++)
 		set_bit(lg4ff_devices[i].ff_effects[j], dev->ffbit);
 
-	error = input_ff_create_memless(dev, NULL, hid_lg4ff_play);
+	error = input_ff_create_mlnx(dev, (void *)NULL, hid_lg4ff_control, FF_UPDATE_RATE);
 
 	if (error)
 		return error;
-- 
1.8.5.3

[PATCH 3/5] Add support for periodic effects in hid-lg4ff

[Michal Malý]

Add support for periodic effects in hid-lg4ff

Signed-off-by: Michal Malý <madcatxster@prifuk.cz>
---
 drivers/hid/hid-lg4ff.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/hid/hid-lg4ff.c b/drivers/hid/hid-lg4ff.c
index f236b9f..c82b02c 100644
--- a/drivers/hid/hid-lg4ff.c
+++ b/drivers/hid/hid-lg4ff.c
@@ -71,6 +71,12 @@ struct lg4ff_device_entry {
 
 static const signed short lg4ff_wheel_effects[] = {
 	FF_CONSTANT,
+	FF_PERIODIC,
+	FF_SQUARE,
+	FF_TRIANGLE,
+	FF_SINE,
+	FF_SAW_UP,
+	FF_SAW_DOWN,
 	FF_AUTOCENTER,
 	-1
 };
-- 
1.8.5.3


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[PATCH 4/5] Add support for ramp effect in hid-lg4ff

[Michal Malý]

Add support for ramp effect in hid-lg4ff

Signed-off-by: Michal Malý <madcatxster@prifuk.cz>
---
 drivers/hid/hid-lg4ff.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/hid/hid-lg4ff.c b/drivers/hid/hid-lg4ff.c
index c82b02c..75245cc 100644
--- a/drivers/hid/hid-lg4ff.c
+++ b/drivers/hid/hid-lg4ff.c
@@ -71,6 +71,7 @@ struct lg4ff_device_entry {
 
 static const signed short lg4ff_wheel_effects[] = {
 	FF_CONSTANT,
+	FF_RAMP,
 	FF_PERIODIC,
 	FF_SQUARE,
 	FF_TRIANGLE,
-- 
1.8.5.3


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[PATCH 5/5] Remove the note that no driver currently uses ff-memless-next

[Michal Malý]

Remove the note that no driver currently uses ff-memless-next

Signed-off-by: Michal Malý <madcatxster@prifuk.cz>
---
 drivers/input/Kconfig | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/input/Kconfig b/drivers/input/Kconfig
index 4371a12..ba05100 100644
--- a/drivers/input/Kconfig
+++ b/drivers/input/Kconfig
@@ -81,8 +81,7 @@ config INPUT_FF_MEMLESS_NEXT
 	tristate "New version of support for memoryless force feedback devices"
 	help
 	  Say Y here if you want to enable support for various memoryless
-	  force feedback devices (as of now there is no hardware-specific
-	  driver that supports this).
+	  force feedback devices.
 
 	  If unsure, say N.
 
-- 
1.8.5.3


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Re: [PATCH 2/5] Port hid-lg4ff to ff-memless-next

[Michal Malý]

Hi,

I have simply taken what we have right now and ported it over to ff-mlnx.
I believe that any improvements based on the previous investigation should
go into another series because we most certainly don't want to introduce any
regressions.

Michal

Re: [PATCH 2/5] Port hid-lg4ff to ff-memless-next

[Michal Malý]

On Wednesday 05 of February 2014 00:54:45 Michal Malý wrote:
> Hi,
> 
> I have simply taken what we have right now and ported it over to ff-mlnx.
> I believe that any improvements based on the previous investigation should
> go into another series because we most certainly don't want to introduce any
> regressions.
> 
> Michal

Ahh... please disregard this. 2/5 should have the same fix for zero force as 
we have right now - it should effectively stop the effect when the force is 
zero.

Michal
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Re: [PATCH 2/5] Port hid-lg4ff to ff-memless-next

[simon]

> Ahh... please disregard this. 2/5 should have the same fix for zero force
> as
> we have right now - it should effectively stop the effect when the force
> is zero.

Hi,
We need to think carefully on this as a '+10' combined with '-10' force
will result in '0'; however we do not want to deactivate the wheel
(no-resistance mode) as this will result in 'ticking' on the wheel as
force transitions through 0.... ideally we'd need to know that there are
no forces set.

I'll attempt to build these patches this week and give them a test,
Simon.

Re: [PATCH 2/5] Port hid-lg4ff to ff-memless-next

[Michal Malý]

On Wednesday 05 of February 2014 09:41:16 you wrote:
> On Wed, Feb 5, 2014 at 1:08 AM, <simon@mungewell.org> wrote:
> > > Ahh... please disregard this. 2/5 should have the same fix for zero
> > > force
> > > as
> > > we have right now - it should effectively stop the effect when the force
> > > is zero.
> > 
> > Hi,
> > We need to think carefully on this as a '+10' combined with '-10' force
> > will result in '0'; however we do not want to deactivate the wheel
> > (no-resistance mode) as this will result in 'ticking' on the wheel as
> > force transitions through 0.... ideally we'd need to know that there are
> > no forces set.
> 
> No problem Simon, this is thought about:
> If forces are active, and they cancel out, hid_lg4ff_start_combined is
> called with 0 force (scaled_x = 0x80), instead of hid_lg4ff_stop_combined
> as you assumed.

Okay, so to set things straight: I should modify to patch to send 0x13 when 
the effect is fully stopped and use 0x11 0x80 to only zeroize the force when 
the overall force is zero? My DFP doesn't differentiate between these states 
so I cannot tell what is the right thing to do.

Michal

Re: [PATCH 2/5] Port hid-lg4ff to ff-memless-next

[Jiri Kosina]

On Wed, 5 Feb 2014, Michal Malý wrote:

> > > We need to think carefully on this as a '+10' combined with '-10' force
> > > will result in '0'; however we do not want to deactivate the wheel
> > > (no-resistance mode) as this will result in 'ticking' on the wheel as
> > > force transitions through 0.... ideally we'd need to know that there are
> > > no forces set.
> > 
> > No problem Simon, this is thought about:
> > If forces are active, and they cancel out, hid_lg4ff_start_combined is
> > called with 0 force (scaled_x = 0x80), instead of hid_lg4ff_stop_combined
> > as you assumed.
> 
> Okay, so to set things straight: I should modify to patch to send 0x13 when 
> the effect is fully stopped and use 0x11 0x80 to only zeroize the force when 
> the overall force is zero? My DFP doesn't differentiate between these states 
> so I cannot tell what is the right thing to do.

Has there been any conclusion to this, please?

-- 
Jiri Kosina
SUSE Labs
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Re: [PATCH 2/5] Port hid-lg4ff to ff-memless-next

[Michal Malý]

On Thursday 20 of February 2014 16:16:52 Jiri Kosina wrote:
> On Wed, 5 Feb 2014, Michal Malý wrote:
> > > > We need to think carefully on this as a '+10' combined with '-10'
> > > > force
> > > > will result in '0'; however we do not want to deactivate the wheel
> > > > (no-resistance mode) as this will result in 'ticking' on the wheel as
> > > > force transitions through 0.... ideally we'd need to know that there
> > > > are
> > > > no forces set.
> > > 
> > > No problem Simon, this is thought about:
> > > If forces are active, and they cancel out, hid_lg4ff_start_combined is
> > > called with 0 force (scaled_x = 0x80), instead of
> > > hid_lg4ff_stop_combined
> > > as you assumed.
> > 
> > Okay, so to set things straight: I should modify to patch to send 0x13
> > when
> > the effect is fully stopped and use 0x11 0x80 to only zeroize the force
> > when the overall force is zero? My DFP doesn't differentiate between
> > these states so I cannot tell what is the right thing to do.
> 
> Has there been any conclusion to this, please?

Yes the has and the necessary fix is already in place in my working copy along 
with another few fixed to the ff-memless-next. Do you consider our approach 
sane and viable for mainlining? I've already explained to Joe Perches why I 
propose ff-memless-next as a separate module rather than a patch to ff-memless 
we have now. Unless anybody has any objections I'll check in with the rest of 
the guys and submit a hopefully final version within a day or two.

Michal
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