Input: add support for Flipper One haptic LRA

Flipper One has a haptic LRA (linear resonant actuator) exposed via its
MCU interconnect interface.

Add a driver to expose the haptic actuator as a force feedback device.

Signed-off-by: Alexey Charkov <alchark@flipper.net>

Author: alchark

drivers/input/misc/Kconfig

@@ -184,11 +184,23 @@ config INPUT_FLIPPER_ONE
 	help
 	  Say Y here to enable support for human-machine interfacing
 	  functions on the Flipper One networking multitool, including its
-	  builtin buttons, touchpad, haptic feedback and headset inputs.
+	  builtin buttons, touchpad and headset inputs.
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called flipper-one-input.
 
+config INPUT_FLIPPER_ONE_HAPTIC
+	tristate "Flipper One haptic feedback support"
+	depends on MFD_FLIPPER_ONE
+	help
+	  Say Y here to enable support for the haptic feedback actuator
+	  on the Flipper One networking multitool. Effects are played from
+	  the controller's built-in waveform library through the force
+	  feedback interface.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called flipper-one-haptic.
+
 config INPUT_PCSPKR
 	tristate "PC Speaker support"
 	depends on PCSPKR_PLATFORM

drivers/input/misc/Makefile

@@ -37,6 +37,7 @@ obj-$(CONFIG_INPUT_DA9055_ONKEY)	+= da9055_onkey.o
 obj-$(CONFIG_INPUT_DA9063_ONKEY)	+= da9063_onkey.o
 obj-$(CONFIG_INPUT_E3X0_BUTTON)		+= e3x0-button.o
 obj-$(CONFIG_INPUT_FLIPPER_ONE)		+= flipper-one-input.o
+obj-$(CONFIG_INPUT_FLIPPER_ONE_HAPTIC)	+= flipper-one-haptic.o
 obj-$(CONFIG_INPUT_DRV260X_HAPTICS)	+= drv260x.o
 obj-$(CONFIG_INPUT_DRV2665_HAPTICS)	+= drv2665.o
 obj-$(CONFIG_INPUT_DRV2667_HAPTICS)	+= drv2667.o

drivers/input/misc/flipper-one-haptic.c

@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Flipper One haptic feedback driver
+ * Copyright (C) 2026 Flipper FZCO
+ */
+
+#include <linux/bitfield.h>
+#include <linux/input.h>
+#include <linux/minmax.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/uaccess.h>
+#include <linux/workqueue.h>
+
+#include <linux/mfd/flipper-one-mcu.h>
+
+/* Highest effect index in the controller's built-in waveform library */
+#define FO_HAPTIC_EFFECT_MAX	123
+
+/* Number of effects userspace may keep uploaded at once */
+#define FO_HAPTIC_MAX_EFFECTS	16
+
+struct fo_haptic {
+	struct fomcu_device *fomcu;
+	struct device *dev;
+	struct work_struct play_work;
+	u16 effect_val[FO_HAPTIC_MAX_EFFECTS];
+	u16 play_val;
+};
+
+static void fo_haptic_play_work(struct work_struct *work)
+{
+	struct fo_haptic *haptic = container_of(work, struct fo_haptic,
+						play_work);
+	int err;
+
+	err = regmap_write(haptic->fomcu->regmap, FOMCU_REG_HAPTIC,
+			   READ_ONCE(haptic->play_val));
+	if (err)
+		dev_err(haptic->dev, "Failed to write haptic register: %d\n",
+			err);
+}
+
+static int fo_haptic_upload(struct input_dev *idev, struct ff_effect *effect,
+			    struct ff_effect *old)
+{
+	struct fo_haptic *haptic = input_get_drvdata(idev);
+	unsigned int duration;
+	s16 id;
+
+	if (effect->type != FF_PERIODIC ||
+	    effect->u.periodic.waveform != FF_CUSTOM)
+		return -EINVAL;
+
+	/* custom_data holds a single s16: the library effect index */
+	if (effect->u.periodic.custom_len != 1)
+		return -EINVAL;
+
+	if (copy_from_user(&id, effect->u.periodic.custom_data, sizeof(id)))
+		return -EFAULT;
+
+	if (id < 0 || id > FO_HAPTIC_EFFECT_MAX)
+		return -EINVAL;
+
+	/*
+	 * Durations 0 and 1 are reserved to mean "play the full
+	 * library waveform", other values are in milliseconds
+	 */
+	duration = min_t(unsigned int, effect->replay.length,
+			 FIELD_MAX(FOMCU_HAPTIC_DURATION));
+
+	haptic->effect_val[effect->id] = FOMCU_HAPTIC_PLAY |
+		FIELD_PREP(FOMCU_HAPTIC_EFFECT, id) |
+		FIELD_PREP(FOMCU_HAPTIC_DURATION, duration);
+
+	return 0;
+}
+
+static int fo_haptic_playback(struct input_dev *idev, int effect_id, int value)
+{
+	struct fo_haptic *haptic = input_get_drvdata(idev);
+
+	WRITE_ONCE(haptic->play_val,
+		   value ? haptic->effect_val[effect_id] : 0);
+	schedule_work(&haptic->play_work);
+
+	return 0;
+}
+
+static void fo_haptic_close(struct input_dev *idev)
+{
+	struct fo_haptic *haptic = input_get_drvdata(idev);
+
+	cancel_work_sync(&haptic->play_work);
+	regmap_write(haptic->fomcu->regmap, FOMCU_REG_HAPTIC, 0);
+}
+
+static int fo_haptic_probe(struct platform_device *pdev)
+{
+	struct fomcu_device *fomcu = dev_get_drvdata(pdev->dev.parent);
+	struct device *dev = &pdev->dev;
+	struct fo_haptic *haptic;
+	struct input_dev *idev;
+	int err;
+
+	haptic = devm_kzalloc(dev, sizeof(*haptic), GFP_KERNEL);
+	if (!haptic)
+		return -ENOMEM;
+
+	haptic->fomcu = fomcu;
+	haptic->dev = dev;
+	INIT_WORK(&haptic->play_work, fo_haptic_play_work);
+
+	idev = devm_input_allocate_device(dev);
+	if (!idev)
+		return -ENOMEM;
+
+	idev->name = "Flipper One Haptic";
+	idev->phys = "flipper-one-haptic/input0";
+	idev->id.bustype = BUS_I2C;
+	idev->close = fo_haptic_close;
+	input_set_drvdata(idev, haptic);
+
+	input_set_capability(idev, EV_FF, FF_PERIODIC);
+	input_set_capability(idev, EV_FF, FF_CUSTOM);
+
+	err = input_ff_create(idev, FO_HAPTIC_MAX_EFFECTS);
+	if (err)
+		return dev_err_probe(dev, err, "Failed to create FF device\n");
+
+	idev->ff->upload = fo_haptic_upload;
+	idev->ff->playback = fo_haptic_playback;
+
+	err = input_register_device(idev);
+	if (err)
+		return dev_err_probe(dev, err,
+				     "Failed to register input device\n");
+
+	return 0;
+}
+
+static const struct platform_device_id fo_haptic_id_table[] = {
+	{ "flipper-one-haptic", },
+	{ }
+};
+MODULE_DEVICE_TABLE(platform, fo_haptic_id_table);
+
+static struct platform_driver fo_haptic_driver = {
+	.driver = {
+		.name = "flipper-one-haptic",
+	},
+	.probe = fo_haptic_probe,
+	.id_table = fo_haptic_id_table,
+};
+module_platform_driver(fo_haptic_driver);
+
+MODULE_DESCRIPTION("Flipper One haptic feedback driver");
+MODULE_AUTHOR("Alexey Charkov <alchark@flipper.net>");
+MODULE_LICENSE("GPL");