ledtrig-gpio.c

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/*
 * ledtrig-gio.c - LED Trigger Based on GPIO events
 *
 * Copyright 2009 Felipe Balbi <[email protected]>
 *
 * 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/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/gpio.h>
#include <linux/interrupt.h>
#include <linux/workqueue.h>
#include <linux/leds.h>
#include <linux/slab.h>
#include "leds.h"

struct gpio_trig_data {
    struct led_classdev *led;
    struct work_struct work;

    unsigned desired_brightness;    /* desired brightness when led is on */
    unsigned inverted;      /* true when gpio is inverted */
    unsigned gpio;          /* gpio that triggers the leds */
};

static irqreturn_t gpio_trig_irq(int irq, void *_led)
{
    struct led_classdev *led = _led;
    struct gpio_trig_data *gpio_data = led->trigger_data;

    /* just schedule_work since gpio_get_value can sleep */
    schedule_work(&gpio_data->work);

    return IRQ_HANDLED;
};

static void gpio_trig_work(struct work_struct *work)
{
    struct gpio_trig_data *gpio_data = container_of(work,
            struct gpio_trig_data, work);
    int tmp;

    if (!gpio_data->gpio)
        return;

    tmp = gpio_get_value(gpio_data->gpio);
    if (gpio_data->inverted)
        tmp = !tmp;

    if (tmp) {
        if (gpio_data->desired_brightness)
            __led_set_brightness(gpio_data->led,
                       gpio_data->desired_brightness);
        else
            __led_set_brightness(gpio_data->led, LED_FULL);
    } else {
        __led_set_brightness(gpio_data->led, LED_OFF);
    }
}

static ssize_t gpio_trig_brightness_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct led_classdev *led = dev_get_drvdata(dev);
    struct gpio_trig_data *gpio_data = led->trigger_data;

    return sprintf(buf, "%u\n", gpio_data->desired_brightness);
}

static ssize_t gpio_trig_brightness_store(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t n)
{
    struct led_classdev *led = dev_get_drvdata(dev);
    struct gpio_trig_data *gpio_data = led->trigger_data;
    unsigned desired_brightness;
    int ret;

    ret = sscanf(buf, "%u", &desired_brightness);
    if (ret < 1 || desired_brightness > 255) {
        dev_err(dev, "invalid value\n");
        return -EINVAL;
    }

    gpio_data->desired_brightness = desired_brightness;

    return n;
}
static DEVICE_ATTR(desired_brightness, 0644, gpio_trig_brightness_show,
        gpio_trig_brightness_store);

static ssize_t gpio_trig_inverted_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct led_classdev *led = dev_get_drvdata(dev);
    struct gpio_trig_data *gpio_data = led->trigger_data;

    return sprintf(buf, "%u\n", gpio_data->inverted);
}

static ssize_t gpio_trig_inverted_store(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t n)
{
    struct led_classdev *led = dev_get_drvdata(dev);
    struct gpio_trig_data *gpio_data = led->trigger_data;
    unsigned long inverted;
    int ret;

    ret = strict_strtoul(buf, 10, &inverted);
    if (ret < 0)
        return ret;

    if (inverted > 1)
        return -EINVAL;

    gpio_data->inverted = inverted;

    /* After inverting, we need to update the LED. */
    schedule_work(&gpio_data->work);

    return n;
}
static DEVICE_ATTR(inverted, 0644, gpio_trig_inverted_show,
        gpio_trig_inverted_store);

static ssize_t gpio_trig_gpio_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct led_classdev *led = dev_get_drvdata(dev);
    struct gpio_trig_data *gpio_data = led->trigger_data;

    return sprintf(buf, "%u\n", gpio_data->gpio);
}

static ssize_t gpio_trig_gpio_store(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t n)
{
    struct led_classdev *led = dev_get_drvdata(dev);
    struct gpio_trig_data *gpio_data = led->trigger_data;
    unsigned gpio;
    int ret;

    ret = sscanf(buf, "%u", &gpio);
    if (ret < 1) {
        dev_err(dev, "couldn't read gpio number\n");
        flush_work(&gpio_data->work);
        return -EINVAL;
    }

    if (gpio_data->gpio == gpio)
        return n;

    if (!gpio) {
        if (gpio_data->gpio != 0)
            free_irq(gpio_to_irq(gpio_data->gpio), led);
        gpio_data->gpio = 0;
        return n;
    }

    ret = request_irq(gpio_to_irq(gpio), gpio_trig_irq,
            IRQF_SHARED | IRQF_TRIGGER_RISING
            | IRQF_TRIGGER_FALLING, "ledtrig-gpio", led);
    if (ret) {
        dev_err(dev, "request_irq failed with error %d\n", ret);
    } else {
        if (gpio_data->gpio != 0)
            free_irq(gpio_to_irq(gpio_data->gpio), led);
        gpio_data->gpio = gpio;
    }

    return ret ? ret : n;
}
static DEVICE_ATTR(gpio, 0644, gpio_trig_gpio_show, gpio_trig_gpio_store);

static void gpio_trig_activate(struct led_classdev *led)
{
    struct gpio_trig_data *gpio_data;
    int ret;

    gpio_data = kzalloc(sizeof(*gpio_data), GFP_KERNEL);
    if (!gpio_data)
        return;

    ret = device_create_file(led->dev, &dev_attr_gpio);
    if (ret)
        goto err_gpio;

    ret = device_create_file(led->dev, &dev_attr_inverted);
    if (ret)
        goto err_inverted;

    ret = device_create_file(led->dev, &dev_attr_desired_brightness);
    if (ret)
        goto err_brightness;

    gpio_data->led = led;
    led->trigger_data = gpio_data;
    INIT_WORK(&gpio_data->work, gpio_trig_work);
    led->activated = true;

    return;

err_brightness:
    device_remove_file(led->dev, &dev_attr_inverted);

err_inverted:
    device_remove_file(led->dev, &dev_attr_gpio);

err_gpio:
    kfree(gpio_data);
}

static void gpio_trig_deactivate(struct led_classdev *led)
{
    struct gpio_trig_data *gpio_data = led->trigger_data;

    if (led->activated) {
        device_remove_file(led->dev, &dev_attr_gpio);
        device_remove_file(led->dev, &dev_attr_inverted);
        device_remove_file(led->dev, &dev_attr_desired_brightness);
        flush_work(&gpio_data->work);
        if (gpio_data->gpio != 0)
            free_irq(gpio_to_irq(gpio_data->gpio), led);
        kfree(gpio_data);
        led->activated = false;
    }
}

static struct led_trigger gpio_led_trigger = {
    .name       = "gpio",
    .activate   = gpio_trig_activate,
    .deactivate = gpio_trig_deactivate,
};

static int __init gpio_trig_init(void)
{
    return led_trigger_register(&gpio_led_trigger);
}
module_init(gpio_trig_init);

static void __exit gpio_trig_exit(void)
{
    led_trigger_unregister(&gpio_led_trigger);
}
module_exit(gpio_trig_exit);

MODULE_AUTHOR("Felipe Balbi <[email protected]>");
MODULE_DESCRIPTION("GPIO LED trigger");
MODULE_LICENSE("GPL");