rotary_encoder.c

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/*
 * rotary_encoder.c
 *
 * (c) 2009 Daniel Mack <[email protected]>
 * Copyright (C) 2011 Johan Hovold <[email protected]>
 *
 * state machine code inspired by code from Tim Ruetz
 *
 * A generic driver for rotary encoders connected to GPIO lines.
 * See file:Documentation/input/rotary-encoder.txt for more information
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/input.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/gpio.h>
#include <linux/rotary_encoder.h>
#include <linux/slab.h>
#include <linux/of_platform.h>
#include <linux/of_gpio.h>

#define DRV_NAME "rotary-encoder"

struct rotary_encoder {
    struct input_dev *input;
    const struct rotary_encoder_platform_data *pdata;

    unsigned int axis;
    unsigned int pos;

    unsigned int irq_a;
    unsigned int irq_b;

    bool armed;
    unsigned char dir;  /* 0 - clockwise, 1 - CCW */

    char last_stable;
};

static int rotary_encoder_get_state(const struct rotary_encoder_platform_data *pdata)
{
    int a = !!gpio_get_value(pdata->gpio_a);
    int b = !!gpio_get_value(pdata->gpio_b);

    a ^= pdata->inverted_a;
    b ^= pdata->inverted_b;

    return ((a << 1) | b);
}

static void rotary_encoder_report_event(struct rotary_encoder *encoder)
{
    const struct rotary_encoder_platform_data *pdata = encoder->pdata;

    if (pdata->relative_axis) {
        input_report_rel(encoder->input,
                 pdata->axis, encoder->dir ? -1 : 1);
    } else {
        unsigned int pos = encoder->pos;

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

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

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

    input_sync(encoder->input);
}

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

    state = rotary_encoder_get_state(encoder->pdata);

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

    case 0x1:
    case 0x2:
        if (encoder->armed)
            encoder->dir = state - 1;
        break;

    case 0x3:
        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;
    int state;

    state = rotary_encoder_get_state(encoder->pdata);

    switch (state) {
    case 0x00:
    case 0x03:
        if (state != encoder->last_stable) {
            rotary_encoder_report_event(encoder);
            encoder->last_stable = state;
        }
        break;

    case 0x01:
    case 0x02:
        encoder->dir = (encoder->last_stable + state) & 0x01;
        break;
    }

    return IRQ_HANDLED;
}

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

static struct rotary_encoder_platform_data * __devinit
rotary_encoder_parse_dt(struct device *dev)
{
    const struct of_device_id *of_id =
                of_match_device(rotary_encoder_of_match, dev);
    struct device_node *np = dev->of_node;
    struct rotary_encoder_platform_data *pdata;
    enum of_gpio_flags flags;

    if (!of_id || !np)
        return NULL;

    pdata = kzalloc(sizeof(struct rotary_encoder_platform_data),
            GFP_KERNEL);
    if (!pdata)
        return ERR_PTR(-ENOMEM);

    of_property_read_u32(np, "rotary-encoder,steps", &pdata->steps);
    of_property_read_u32(np, "linux,axis", &pdata->axis);

    pdata->gpio_a = of_get_gpio_flags(np, 0, &flags);
    pdata->inverted_a = flags & OF_GPIO_ACTIVE_LOW;

    pdata->gpio_b = of_get_gpio_flags(np, 1, &flags);
    pdata->inverted_b = flags & OF_GPIO_ACTIVE_LOW;

    pdata->relative_axis = !!of_get_property(np,
                    "rotary-encoder,relative-axis", NULL);
    pdata->rollover = !!of_get_property(np,
                    "rotary-encoder,rollover", NULL);
    pdata->half_period = !!of_get_property(np,
                    "rotary-encoder,half-period", NULL);

    return pdata;
}
#else
static inline struct rotary_encoder_platform_data *
rotary_encoder_parse_dt(struct device *dev)
{
    return NULL;
}
#endif

static int __devinit rotary_encoder_probe(struct platform_device *pdev)
{
    struct device *dev = &pdev->dev;
    const struct rotary_encoder_platform_data *pdata = dev_get_platdata(dev);
    struct rotary_encoder *encoder;
    struct input_dev *input;
    irq_handler_t handler;
    int err;

    if (!pdata) {
        pdata = rotary_encoder_parse_dt(dev);
        if (IS_ERR(pdata))
            return PTR_ERR(pdata);

        if (!pdata) {
            dev_err(dev, "missing platform data\n");
            return -EINVAL;
        }
    }

    encoder = kzalloc(sizeof(struct rotary_encoder), GFP_KERNEL);
    input = input_allocate_device();
    if (!encoder || !input) {
        err = -ENOMEM;
        goto exit_free_mem;
    }

    encoder->input = input;
    encoder->pdata = pdata;

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

    if (pdata->relative_axis) {
        input->evbit[0] = BIT_MASK(EV_REL);
        input->relbit[0] = BIT_MASK(pdata->axis);
    } else {
        input->evbit[0] = BIT_MASK(EV_ABS);
        input_set_abs_params(encoder->input,
                     pdata->axis, 0, pdata->steps, 0, 1);
    }

    /* request the GPIOs */
    err = gpio_request_one(pdata->gpio_a, GPIOF_IN, dev_name(dev));
    if (err) {
        dev_err(dev, "unable to request GPIO %d\n", pdata->gpio_a);
        goto exit_free_mem;
    }

    err = gpio_request_one(pdata->gpio_b, GPIOF_IN, dev_name(dev));
    if (err) {
        dev_err(dev, "unable to request GPIO %d\n", pdata->gpio_b);
        goto exit_free_gpio_a;
    }

    encoder->irq_a = gpio_to_irq(pdata->gpio_a);
    encoder->irq_b = gpio_to_irq(pdata->gpio_b);

    /* request the IRQs */
    if (pdata->half_period) {
        handler = &rotary_encoder_half_period_irq;
        encoder->last_stable = rotary_encoder_get_state(pdata);
    } else {
        handler = &rotary_encoder_irq;
    }

    err = request_irq(encoder->irq_a, handler,
              IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
              DRV_NAME, encoder);
    if (err) {
        dev_err(dev, "unable to request IRQ %d\n", encoder->irq_a);
        goto exit_free_gpio_b;
    }

    err = request_irq(encoder->irq_b, handler,
              IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
              DRV_NAME, encoder);
    if (err) {
        dev_err(dev, "unable to request IRQ %d\n", encoder->irq_b);
        goto exit_free_irq_a;
    }

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

    platform_set_drvdata(pdev, encoder);

    return 0;

exit_free_irq_b:
    free_irq(encoder->irq_b, encoder);
exit_free_irq_a:
    free_irq(encoder->irq_a, encoder);
exit_free_gpio_b:
    gpio_free(pdata->gpio_b);
exit_free_gpio_a:
    gpio_free(pdata->gpio_a);
exit_free_mem:
    input_free_device(input);
    kfree(encoder);
    if (!dev_get_platdata(&pdev->dev))
        kfree(pdata);

    return err;
}

static int __devexit rotary_encoder_remove(struct platform_device *pdev)
{
    struct rotary_encoder *encoder = platform_get_drvdata(pdev);
    const struct rotary_encoder_platform_data *pdata = encoder->pdata;

    free_irq(encoder->irq_a, encoder);
    free_irq(encoder->irq_b, encoder);
    gpio_free(pdata->gpio_a);
    gpio_free(pdata->gpio_b);

    input_unregister_device(encoder->input);
    kfree(encoder);

    if (!dev_get_platdata(&pdev->dev))
        kfree(pdata);

    platform_set_drvdata(pdev, NULL);

    return 0;
}

static struct platform_driver rotary_encoder_driver = {
    .probe      = rotary_encoder_probe,
    .remove     = __devexit_p(rotary_encoder_remove),
    .driver     = {
        .name   = DRV_NAME,
        .owner  = THIS_MODULE,
        .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 <[email protected]>, Johan Hovold");
MODULE_LICENSE("GPL v2");