OpenWrt – Rev 4

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/*
 *  GPIO latch driver
 *
 *  Copyright (C) 2014 Gabor Juhos <juhosg@openwrt.org>
 *
 *  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/init.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/gpio.h>
#include <linux/slab.h>
#include <linux/platform_device.h>

#include <linux/platform_data/gpio-latch.h>

struct gpio_latch_chip {
        struct gpio_chip gc;

        struct mutex mutex;
        struct mutex latch_mutex;
        bool latch_enabled;
        int le_gpio;
        bool le_active_low;
        int *gpios;
};

static inline struct gpio_latch_chip *to_gpio_latch_chip(struct gpio_chip *gc)
{
        return container_of(gc, struct gpio_latch_chip, gc);
}

static void gpio_latch_lock(struct gpio_latch_chip *glc, bool enable)
{
        mutex_lock(&glc->mutex);

        if (enable)
                glc->latch_enabled = true;

        if (glc->latch_enabled)
                mutex_lock(&glc->latch_mutex);
}

static void gpio_latch_unlock(struct gpio_latch_chip *glc, bool disable)
{
        if (glc->latch_enabled)
                mutex_unlock(&glc->latch_mutex);

        if (disable)
                glc->latch_enabled = true;

        mutex_unlock(&glc->mutex);
}

static int
gpio_latch_get(struct gpio_chip *gc, unsigned offset)
{
        struct gpio_latch_chip *glc = to_gpio_latch_chip(gc);
        int ret;

        gpio_latch_lock(glc, false);
        ret = gpio_get_value(glc->gpios[offset]);
        gpio_latch_unlock(glc, false);

        return ret;
}

static void
gpio_latch_set(struct gpio_chip *gc, unsigned offset, int value)
{
        struct gpio_latch_chip *glc = to_gpio_latch_chip(gc);
        bool enable_latch = false;
        bool disable_latch = false;
        int gpio;

        gpio = glc->gpios[offset];

        if (gpio == glc->le_gpio) {
                enable_latch = value ^ glc->le_active_low;
                disable_latch = !enable_latch;
        }

        gpio_latch_lock(glc, enable_latch);
        gpio_set_value(gpio, value);
        gpio_latch_unlock(glc, disable_latch);
}

static int
gpio_latch_direction_input(struct gpio_chip *gc, unsigned offset)
{
        struct gpio_latch_chip *glc = to_gpio_latch_chip(gc);
        int ret;

        gpio_latch_lock(glc, false);
        ret = gpio_direction_input(glc->gpios[offset]);
        gpio_latch_unlock(glc, false);

        return ret;
}

static int
gpio_latch_direction_output(struct gpio_chip *gc, unsigned offset, int value)
{
        struct gpio_latch_chip *glc = to_gpio_latch_chip(gc);
        bool enable_latch = false;
        bool disable_latch = false;
        int gpio;
        int ret;

        gpio = glc->gpios[offset];

        if (gpio == glc->le_gpio) {
                enable_latch = value ^ glc->le_active_low;
                disable_latch = !enable_latch;
        }

        gpio_latch_lock(glc, enable_latch);
        ret = gpio_direction_output(gpio, value);
        gpio_latch_unlock(glc, disable_latch);

        return ret;
}

static int gpio_latch_probe(struct platform_device *pdev)
{
        struct gpio_latch_chip *glc;
        struct gpio_latch_platform_data *pdata;
        struct gpio_chip *gc;
        int size;
        int ret;
        int i;

        pdata = dev_get_platdata(&pdev->dev);
        if (!pdata)
                return -EINVAL;

        if (pdata->le_gpio_index >= pdata->num_gpios ||
            !pdata->num_gpios ||
            !pdata->gpios)
                return -EINVAL;

        for (i = 0; i < pdata->num_gpios; i++) {
                int gpio = pdata->gpios[i];

                ret = devm_gpio_request(&pdev->dev, gpio,
                                        GPIO_LATCH_DRIVER_NAME);
                if (ret)
                        return ret;
        }

        glc = devm_kzalloc(&pdev->dev, sizeof(*glc), GFP_KERNEL);
        if (!glc)
                return -ENOMEM;

        mutex_init(&glc->mutex);
        mutex_init(&glc->latch_mutex);

        size = pdata->num_gpios * sizeof(glc->gpios[0]);
        glc->gpios = devm_kzalloc(&pdev->dev, size , GFP_KERNEL);
        if (!glc->gpios)
                return -ENOMEM;

        memcpy(glc->gpios, pdata->gpios, size);

        glc->le_gpio = glc->gpios[pdata->le_gpio_index];
        glc->le_active_low = pdata->le_active_low;

        gc = &glc->gc;

        gc->label = GPIO_LATCH_DRIVER_NAME;
        gc->base = pdata->base;
        gc->can_sleep = true;
        gc->ngpio = pdata->num_gpios;
        gc->get = gpio_latch_get;
        gc->set = gpio_latch_set;
        gc->direction_input = gpio_latch_direction_input,
        gc->direction_output = gpio_latch_direction_output;

        platform_set_drvdata(pdev, glc);

        ret = gpiochip_add(&glc->gc);
        if (ret)
                return ret;

        return 0;
}

static int gpio_latch_remove(struct platform_device *pdev)
{
        struct gpio_latch_chip *glc = platform_get_drvdata(pdev);

        gpiochip_remove(&glc->gc);
        return 0;
}


static struct platform_driver gpio_latch_driver = {
        .probe = gpio_latch_probe,
        .remove = gpio_latch_remove,
        .driver = {
                .name = GPIO_LATCH_DRIVER_NAME,
                .owner = THIS_MODULE,
        },
};

static int __init gpio_latch_init(void)
{
        return platform_driver_register(&gpio_latch_driver);
}

postcore_initcall(gpio_latch_init);

MODULE_DESCRIPTION("GPIO latch driver");
MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:" GPIO_LATCH_DRIVER_NAME);