// SPDX-License-Identifier: GPL-2.0-only
/*
 * rotary_encoder.c
 *
 * (c) 2009 Daniel Mack <daniel@caiaq.de>
 * Copyright (C) 2011 Johan Hovold <jhovold@gmail.com>
 *
 * state machine code inspired by code from Tim Ruetz
 *
 * A generic driver for rotary encoders connected to GPIO lines.
 * See file:Documentation/input/devices/rotary-encoder.rst for more information
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/input.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/gpio/consumer.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/pm.h>
#include <linux/property.h>

#define DRV_NAME "rotary-encoder"

enum rotary_encoder_encoding {
        ROTENC_GRAY,
        ROTENC_BINARY,
};

struct rotary_encoder {
        struct input_dev *input;

        struct mutex access_mutex;

        u32 steps;
        u32 axis;
        bool relative_axis;
        bool rollover;
        enum rotary_encoder_encoding encoding;

        unsigned int pos;

        struct gpio_descs *gpios;

        unsigned int *irq;

        bool armed;
        signed char dir;        /* 1 - clockwise, -1 - CCW */

        unsigned int last_stable;
};

static unsigned int rotary_encoder_get_state(struct rotary_encoder *encoder)
{
        int i;
        unsigned int ret = 0;

        for (i = 0; i < encoder->gpios->ndescs; ++i) {
                int val = gpiod_get_value_cansleep(encoder->gpios->desc[i]);

                /* convert from gray encoding to normal */
                if (encoder->encoding == ROTENC_GRAY && ret & 1)
                        val = !val;

                ret = ret << 1 | val;
        }

        return ret & 3;
}

static void rotary_encoder_report_event(struct rotary_encoder *encoder)
{
        if (encoder->relative_axis) {
                input_report_rel(encoder->input,
                                 encoder->axis, encoder->dir);
        } else {
                unsigned int pos = encoder->pos;

                if (encoder->dir < 0) {
                        /* turning counter-clockwise */
                        if (encoder->rollover)
                                pos += encoder->steps;
                        if (pos)
                                pos--;
                } else {
                        /* turning clockwise */
                        if (encoder->rollover || pos < encoder->steps)
                                pos++;
                }

                if (encoder->rollover)
                        pos %= encoder->steps;

                encoder->pos = pos;
                input_report_abs(encoder->input, encoder->axis, encoder->pos);
        }

        input_sync(encoder->input);
}

static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
{
        struct rotary_encoder *encoder = dev_id;
        unsigned int state;

        guard(mutex)(&encoder->access_mutex);

        state = rotary_encoder_get_state(encoder);

        switch (state) {
        case 0x0:
                if (encoder->armed) {
                        rotary_encoder_report_event(encoder);
                        encoder->armed = false;
                }
                break;

        case 0x1:
        case 0x3:
                if (encoder->armed)
                        encoder->dir = 2 - state;
                break;

        case 0x2:
                encoder->armed = true;
                break;
        }

        return IRQ_HANDLED;
}

static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
{
        struct rotary_encoder *encoder = dev_id;
        unsigned int state;

        guard(mutex)(&encoder->access_mutex);

        state = rotary_encoder_get_state(encoder);

        if (state & 1) {
                encoder->dir = ((encoder->last_stable - state + 1) % 4) - 1;
        } else {
                if (state != encoder->last_stable) {
                        rotary_encoder_report_event(encoder);
                        encoder->last_stable = state;
                }
        }

        return IRQ_HANDLED;
}

static irqreturn_t rotary_encoder_quarter_period_irq(int irq, void *dev_id)
{
        struct rotary_encoder *encoder = dev_id;
        unsigned int state;

        guard(mutex)(&encoder->access_mutex);

        state = rotary_encoder_get_state(encoder);

        if ((encoder->last_stable + 1) % 4 == state) {
                encoder->dir = 1;
                rotary_encoder_report_event(encoder);
        } else if (encoder->last_stable == (state + 1) % 4) {
                encoder->dir = -1;
                rotary_encoder_report_event(encoder);
        }

        encoder->last_stable = state;

        return IRQ_HANDLED;
}

static int rotary_encoder_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct rotary_encoder *encoder;
        struct input_dev *input;
        irq_handler_t handler;
        u32 steps_per_period;
        unsigned int i;
        int err;

        encoder = devm_kzalloc(dev, sizeof(struct rotary_encoder), GFP_KERNEL);
        if (!encoder)
                return -ENOMEM;

        mutex_init(&encoder->access_mutex);

        device_property_read_u32(dev, "rotary-encoder,steps", &encoder->steps);

        err = device_property_read_u32(dev, "rotary-encoder,steps-per-period",
                                       &steps_per_period);
        if (err) {
                /*
                 * The 'half-period' property has been deprecated, you must
                 * use 'steps-per-period' and set an appropriate value, but
                 * we still need to parse it to maintain compatibility. If
                 * neither property is present we fall back to the one step
                 * per period behavior.
                 */
                steps_per_period = device_property_read_bool(dev,
                                        "rotary-encoder,half-period") ? 2 : 1;
        }

        encoder->rollover =
                device_property_read_bool(dev, "rotary-encoder,rollover");

        if (!device_property_present(dev, "rotary-encoder,encoding") ||
            !device_property_match_string(dev, "rotary-encoder,encoding",
                                          "gray")) {
                dev_info(dev, "gray");
                encoder->encoding = ROTENC_GRAY;
        } else if (!device_property_match_string(dev, "rotary-encoder,encoding",
                                                 "binary")) {
                dev_info(dev, "binary");
                encoder->encoding = ROTENC_BINARY;
        } else {
                dev_err(dev, "unknown encoding setting\n");
                return -EINVAL;
        }

        device_property_read_u32(dev, "linux,axis", &encoder->axis);
        encoder->relative_axis =
                device_property_read_bool(dev, "rotary-encoder,relative-axis");

        encoder->gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
        if (IS_ERR(encoder->gpios))
                return dev_err_probe(dev, PTR_ERR(encoder->gpios), "unable to get gpios\n");
        if (encoder->gpios->ndescs < 2) {
                dev_err(dev, "not enough gpios found\n");
                return -EINVAL;
        }

        input = devm_input_allocate_device(dev);
        if (!input)
                return -ENOMEM;

        encoder->input = input;

        input->name = pdev->name;
        input->id.bustype = BUS_HOST;

        if (encoder->relative_axis)
                input_set_capability(input, EV_REL, encoder->axis);
        else
                input_set_abs_params(input,
                                     encoder->axis, 0, encoder->steps, 0, 1);

        switch (steps_per_period >> (encoder->gpios->ndescs - 2)) {
        case 4:
                handler = &rotary_encoder_quarter_period_irq;
                encoder->last_stable = rotary_encoder_get_state(encoder);
                break;
        case 2:
                handler = &rotary_encoder_half_period_irq;
                encoder->last_stable = rotary_encoder_get_state(encoder);
                break;
        case 1:
                handler = &rotary_encoder_irq;
                break;
        default:
                dev_err(dev, "'%d' is not a valid steps-per-period value\n",
                        steps_per_period);
                return -EINVAL;
        }

        encoder->irq =
                devm_kcalloc(dev,
                             encoder->gpios->ndescs, sizeof(*encoder->irq),
                             GFP_KERNEL);
        if (!encoder->irq)
                return -ENOMEM;

        for (i = 0; i < encoder->gpios->ndescs; ++i) {
                encoder->irq[i] = gpiod_to_irq(encoder->gpios->desc[i]);

                err = devm_request_threaded_irq(dev, encoder->irq[i],
                                NULL, handler,
                                IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
                                IRQF_ONESHOT,
                                DRV_NAME, encoder);
                if (err) {
                        dev_err(dev, "unable to request IRQ %d (gpio#%d)\n",
                                encoder->irq[i], i);
                        return err;
                }
        }

        err = input_register_device(input);
        if (err) {
                dev_err(dev, "failed to register input device\n");
                return err;
        }

        device_init_wakeup(dev,
                           device_property_read_bool(dev, "wakeup-source"));

        platform_set_drvdata(pdev, encoder);

        return 0;
}

static int rotary_encoder_suspend(struct device *dev)
{
        struct rotary_encoder *encoder = dev_get_drvdata(dev);
        unsigned int i;

        if (device_may_wakeup(dev)) {
                for (i = 0; i < encoder->gpios->ndescs; ++i)
                        enable_irq_wake(encoder->irq[i]);
        }

        return 0;
}

static int rotary_encoder_resume(struct device *dev)
{
        struct rotary_encoder *encoder = dev_get_drvdata(dev);
        unsigned int i;

        if (device_may_wakeup(dev)) {
                for (i = 0; i < encoder->gpios->ndescs; ++i)
                        disable_irq_wake(encoder->irq[i]);
        }

        return 0;
}

static DEFINE_SIMPLE_DEV_PM_OPS(rotary_encoder_pm_ops,
                                rotary_encoder_suspend, rotary_encoder_resume);

#ifdef CONFIG_OF
static const struct of_device_id rotary_encoder_of_match[] = {
        { .compatible = "rotary-encoder", },
        { },
};
MODULE_DEVICE_TABLE(of, rotary_encoder_of_match);
#endif

static struct platform_driver rotary_encoder_driver = {
        .probe          = rotary_encoder_probe,
        .driver         = {
                .name   = DRV_NAME,
                .pm     = pm_sleep_ptr(&rotary_encoder_pm_ops),
                .of_match_table = of_match_ptr(rotary_encoder_of_match),
        }
};
module_platform_driver(rotary_encoder_driver);

MODULE_ALIAS("platform:" DRV_NAME);
MODULE_DESCRIPTION("GPIO rotary encoder driver");
MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
MODULE_LICENSE("GPL v2");