/*
 * Nest driver for keys on GPIO lines
 *
 * Copyright 2017 Dmitry Yatsushkevich <dmitryya@google.com>
 *
 * 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/init.h>
#include <linux/fs.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/input.h>
#include <linux/gpio_keys.h>
#include <linux/gpio.h>
#include <linux/of_platform.h>
#include <linux/of_gpio.h>
#include <linux/spinlock.h>
#include <linux/hrtimer.h>
#include <linux/delay.h>
#include <linux/ktime.h>
#include <linux/nest_gpio_keys.h>

struct gpio_button_data {
	const struct gpio_keys_button *button;
	struct input_dev *input;
	unsigned int irq;
	struct hrtimer debounce_timer;
	atomic_t debounce_ongoing;
};

struct gpio_keys_drvdata {
	const struct gpio_keys_platform_data *pdata;
	struct input_dev *input;
	struct gpio_button_data data[0];
};

static void gpio_keys_gpio_report_event(struct gpio_button_data *bdata)
{
	const struct gpio_keys_button *button = bdata->button;
	struct input_dev *input = bdata->input;
	int state = (gpio_get_value_cansleep(button->gpio) ? 1 : 0) ^ button->active_low;

	input_event(input, button->type, button->code, !!state);
	input_sync(input);
}

#define KEY_DEBOUNCE_TIMEOUT_MS 40
static irqreturn_t gpio_keys_gpio_isr(int irq, void *dev_id)
{
	struct gpio_button_data *bdata = dev_id;

	if (!atomic_xchg(&bdata->debounce_ongoing, 1)) {
		ktime_t kt;

		BUG_ON(irq != bdata->irq);

		kt = ktime_set(KEY_DEBOUNCE_TIMEOUT_MS / 1000 /* sec */ ,
				(KEY_DEBOUNCE_TIMEOUT_MS % 1000) * 1000000 /* nsec */ );
		hrtimer_start(&bdata->debounce_timer, kt, HRTIMER_MODE_REL);
	}

	return IRQ_HANDLED;
}

static enum hrtimer_restart debounce_timer_handler(struct hrtimer *handle)
{
	struct gpio_button_data *pdata =
	    container_of(handle, struct gpio_button_data, debounce_timer);
	const struct gpio_keys_button *button = pdata->button;
	struct input_dev *input = pdata->input;
	int state;

	state = (gpio_get_value(button->gpio) ? 1 : 0) ^ button->active_low;

	input_event(input, button->type, button->code, !!state);
	input_sync(input);

	atomic_set(&pdata->debounce_ongoing, 0);
	return HRTIMER_NORESTART;
}

static int gpio_keys_setup_key(struct platform_device *pdev,
			       struct input_dev *input,
			       struct gpio_button_data *bdata,
			       const struct gpio_keys_button *button)
{
	const char *desc = button->desc ? button->desc : "nest_gpio_keys";
	struct device *dev = &pdev->dev;
	unsigned long irqflags;
	int irq, error;

	bdata->input = input;
	bdata->button = button;

	if (!gpio_is_valid(button->gpio)) {
		dev_err(dev, "No valid GPIO specified\n");
		return -EINVAL;
	}

	error = gpio_request_one(button->gpio, GPIOF_IN, desc);
	if (error < 0) {
		dev_err(dev, "Failed to request GPIO %d, error %d\n",
			button->gpio, error);
		return error;
	}

	irq = gpio_to_irq(button->gpio);
	if (irq < 0) {
		error = irq;
		dev_err(dev, "Unable to get irq number for GPIO %d, error %d\n",
			button->gpio, error);
		goto fail;
	}
	bdata->irq = irq;
	hrtimer_init(&bdata->debounce_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	bdata->debounce_timer.function = debounce_timer_handler;
	atomic_set(&bdata->debounce_ongoing, 0);

	irqflags = IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING;

	input_set_capability(input, button->type, button->code);

	/*
	 * If platform has specified that the button can be disabled,
	 * we don't want it to share the interrupt line.
	 */
	if (!button->can_disable)
		irqflags |= IRQF_SHARED;

	error = request_any_context_irq(bdata->irq, gpio_keys_gpio_isr, irqflags, desc, bdata);
	if (error < 0) {
		dev_err(dev, "Unable to claim irq %d; error %d\n", bdata->irq, error);
		goto fail;
	}

	return 0;

 fail:
	if (gpio_is_valid(button->gpio))
		gpio_free(button->gpio);

	return error;
}

static void gpio_keys_report_state(struct gpio_keys_drvdata *ddata)
{
	struct input_dev *input = ddata->input;
	int i;

	for (i = 0; i < ddata->pdata->nbuttons; i++) {
		struct gpio_button_data *bdata = &ddata->data[i];
		if (gpio_is_valid(bdata->button->gpio))
			gpio_keys_gpio_report_event(bdata);
	}
	input_sync(input);
}

static int gpio_keys_open(struct input_dev *input)
{
	struct gpio_keys_drvdata *ddata = input_get_drvdata(input);
	const struct gpio_keys_platform_data *pdata = ddata->pdata;
	int error;

	if (pdata->enable) {
		error = pdata->enable(input->dev.parent);
		if (error)
			return error;
	}

	/* Report current state of buttons that are connected to GPIOs */
	gpio_keys_report_state(ddata);

	return 0;
}

static void gpio_keys_close(struct input_dev *input)
{
	struct gpio_keys_drvdata *ddata = input_get_drvdata(input);
	const struct gpio_keys_platform_data *pdata = ddata->pdata;

	if (pdata->disable)
		pdata->disable(input->dev.parent);
}

/*
 * Handlers for alternative sources of platform_data
 */

#ifdef CONFIG_OF
/*
 * Translate OpenFirmware node properties into platform_data
 */
static struct gpio_keys_platform_data *gpio_keys_get_devtree_pdata(struct device *dev)
{
	struct device_node *node, *pp;
	struct gpio_keys_platform_data *pdata;
	struct gpio_keys_button *button;
	int error;
	int nbuttons;
	int i;

	node = dev->of_node;
	if (!node) {
		error = -ENODEV;
		goto err_out;
	}

	nbuttons = of_get_child_count(node);
	if (nbuttons == 0) {
		error = -ENODEV;
		goto err_out;
	}

	pdata = kzalloc(sizeof(*pdata) + nbuttons * (sizeof *button),
			GFP_KERNEL);
	if (!pdata) {
		error = -ENOMEM;
		goto err_out;
	}

	pdata->buttons = (struct gpio_keys_button *)(pdata + 1);
	pdata->nbuttons = nbuttons;

	pdata->rep = ! !of_get_property(node, "autorepeat", NULL);

	i = 0;
	for_each_child_of_node(node, pp) {
		int gpio;
		enum of_gpio_flags flags;

		if (!of_find_property(pp, "gpios", NULL)) {
			pdata->nbuttons--;
			dev_warn(dev, "Found button without gpios\n");
			continue;
		}

		gpio = of_get_gpio_flags(pp, 0, &flags);
		if (gpio < 0) {
			error = gpio;
			if (error != -EPROBE_DEFER)
				dev_err(dev, "Failed to get gpio flags, error: %d\n",
					error);
			goto err_free_pdata;
		}

		button = &pdata->buttons[i++];

		button->gpio = gpio;
		button->active_low = flags & OF_GPIO_ACTIVE_LOW;

		if (of_property_read_u32(pp, "linux,code", &button->code)) {
			dev_err(dev, "Button without keycode: 0x%x\n",
				button->gpio);
			error = -EINVAL;
			goto err_free_pdata;
		}

		button->desc = of_get_property(pp, "label", NULL);
		button->type = EV_KEY;
	}

	if (pdata->nbuttons == 0) {
		error = -EINVAL;
		goto err_free_pdata;
	}

	return pdata;

 err_free_pdata:
	kfree(pdata);
 err_out:
	return ERR_PTR(error);
}

static struct of_device_id gpio_keys_of_match[] = {
	{.compatible = "nest-gpio-keys",},
	{},
};

MODULE_DEVICE_TABLE(of, gpio_keys_of_match);

#else

static inline struct gpio_keys_platform_data *gpio_keys_get_devtree_pdata(struct device *dev)
{
	return ERR_PTR(-ENODEV);
}

#endif

static void gpio_remove_key(struct gpio_button_data *bdata)
{
	hrtimer_cancel(&bdata->debounce_timer);
	atomic_set(&bdata->debounce_ongoing, 0);
	free_irq(bdata->irq, bdata);
	if (gpio_is_valid(bdata->button->gpio))
		gpio_free(bdata->button->gpio);
}

static int gpio_keys_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	const struct gpio_keys_platform_data *pdata = dev_get_platdata(dev);
	struct gpio_keys_drvdata *ddata;
	struct input_dev *input;
	int i, error;

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

	ddata = kzalloc(sizeof(struct gpio_keys_drvdata) +
			pdata->nbuttons * sizeof(struct gpio_button_data),
			GFP_KERNEL);
	input = input_allocate_device();
	if (!ddata || !input) {
		dev_err(dev, "failed to allocate state\n");
		error = -ENOMEM;
		goto fail1;
	}

	ddata->pdata = pdata;
	ddata->input = input;

	platform_set_drvdata(pdev, ddata);
	input_set_drvdata(input, ddata);

	input->name = pdata->name ? : pdev->name;
	input->phys = "gpio-keys/input0";
	input->dev.parent = &pdev->dev;
	input->open = gpio_keys_open;
	input->close = gpio_keys_close;

	input->id.bustype = BUS_HOST;
	input->id.vendor = NEST_ID;
	input->id.product = 0x0001;
	input->id.version = 0x0100;

	/* Enable auto repeat feature of Linux input subsystem */
	if (pdata->rep)
		__set_bit(EV_REP, input->evbit);

	for (i = 0; i < pdata->nbuttons; i++) {
		const struct gpio_keys_button *button = &pdata->buttons[i];
		struct gpio_button_data *bdata = &ddata->data[i];

		error = gpio_keys_setup_key(pdev, input, bdata, button);
		if (error)
			goto fail2;
	}

	error = input_register_device(input);
	if (error) {
		dev_err(dev, "Unable to register input device, error: %d\n",
			error);
		goto fail2;
	}

	return 0;

 fail2:
	while (--i >= 0)
		gpio_remove_key(&ddata->data[i]);

	platform_set_drvdata(pdev, NULL);
 fail1:
	input_free_device(input);
	kfree(ddata);
	/* If we have no platform data, we allocated pdata dynamically. */
	if (!dev_get_platdata(&pdev->dev))
		kfree(pdata);

	return error;
}

static int gpio_keys_remove(struct platform_device *pdev)
{
	struct gpio_keys_drvdata *ddata = platform_get_drvdata(pdev);
	struct input_dev *input = ddata->input;
	int i;

	for (i = 0; i < ddata->pdata->nbuttons; i++)
		gpio_remove_key(&ddata->data[i]);

	input_unregister_device(input);

	/* If we have no platform data, we allocated pdata dynamically. */
	if (!dev_get_platdata(&pdev->dev))
		kfree(ddata->pdata);

	kfree(ddata);

	return 0;
}

static struct platform_driver gpio_keys_device_driver = {
	.probe = gpio_keys_probe,
	.remove = gpio_keys_remove,
	.driver = {
		   .name = "nest-gpio-keys",
		   .owner = THIS_MODULE,
		   .of_match_table = of_match_ptr(gpio_keys_of_match),
		   }
};

static int __init gpio_keys_init(void)
{
	return platform_driver_register(&gpio_keys_device_driver);
}

static void __exit gpio_keys_exit(void)
{
	platform_driver_unregister(&gpio_keys_device_driver);
}

late_initcall(gpio_keys_init);
module_exit(gpio_keys_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Dmitry Yatsushkevich <dmitryya@google.com>");
MODULE_DESCRIPTION("Nest GPIOs keyboard driver. Based on gpio-keys driver.");
MODULE_ALIAS("platform:nest-gpio-keys");