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#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/buffer.h>
#include <linux/iio/trigger.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/gpio.h>
#include <linux/interrupt.h>

#define SCALE 4882
#define IRQ_TRIGGER_PIN 27
static unsigned int irq_trigger;

struct arduino_adc_data {
    struct i2c_client *client;
    struct mutex lock;
	struct iio_trigger *trigger;
};

static const struct iio_chan_spec arduino_adc_channels[] = {
	{
	    .type = IIO_VOLTAGE,
	    .indexed = 1,
	    .channel = 0,
	    .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
        .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
		.scan_index = 0,
		.scan_type = {
			.sign = 's',
			.realbits = 16,
			.storagebits = 16,
			.shift = 0,
			.endianness = IIO_CPU,
		},
	},
	{
	    .type = IIO_VOLTAGE,
	    .indexed = 1,
	    .channel = 1,
	    .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
        .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
		.scan_index = 1,
		.scan_type = {
			.sign = 's',
			.realbits = 16,
			.storagebits = 16,
			.shift = 0,
			.endianness = IIO_CPU,
		},
	},
};

static const struct iio_trigger_ops arduino_adc_trigger_ops = {
	.owner = THIS_MODULE,
};

static irqreturn_t arduino_adc_trigger_handler(int irq, void *p)
{
	int ret;
	struct iio_poll_func *pf = p;
	struct iio_dev *indio_dev = pf->indio_dev;
	struct arduino_adc_data *data = iio_priv(indio_dev);
	__be16 raw[2];
	int to_buffer[2];

	ret = i2c_master_recv(data->client, (char *)&raw, 4);
	if (ret < 0)
		return ret;

	to_buffer[0] = raw[0];
	to_buffer[1] = raw[1];

	iio_push_to_buffers_with_timestamp(indio_dev, to_buffer,
		pf->timestamp);

	iio_trigger_notify_done(indio_dev->trig);

	return IRQ_HANDLED;
}

static irqreturn_t erpi_gpio_irq_handler(unsigned int irq, void
                                    	 *dev_id, struct pt_regs *regs)
{
	return IRQ_HANDLED;
}

static int arduino_adc_read(struct arduino_adc_data *data, int *val, int channel)
{
	int ret;
	__be16 result[2];

	if(channel & ~1) {
		return -EINVAL;
	}

	ret = i2c_master_recv(data->client, (char *)&result, 4);
	if (ret < 0)
		return ret;

	*val = be16_to_cpu(result[channel]);

	return 0;
}

static int arduino_adc_read_raw(struct iio_dev *indio_dev,
			   struct iio_chan_spec const *chan,
			   int *val, int *val2, long mask)
{
	int ret;
	struct arduino_adc_data *data = iio_priv(indio_dev);

	switch (mask) {
	case IIO_CHAN_INFO_RAW:

		if (iio_buffer_enabled(indio_dev)) {
			return -EBUSY;
		}
		
		switch (chan->type) {
		case IIO_VOLTAGE:
			mutex_lock(&data->lock);
			ret = arduino_adc_read(data, val, chan->channel);
			mutex_unlock(&data->lock);
			if (ret < 0)
				return ret;

			return IIO_VAL_INT;
		default:
			return -EINVAL;
		}
	case IIO_CHAN_INFO_SCALE:
		*val = SCALE / 1000000;
		*val2 = SCALE % 1000000;
		return IIO_VAL_INT_PLUS_MICRO;
	default:
		return -EINVAL;
	}
}

static int arduino_adc_write_raw(struct iio_dev *indio_dev,
			    struct iio_chan_spec const *chan,
			    int val, int val2, long mask)
{
	return 0;
}

static const struct iio_info arduino_adc_info = {
	.read_raw = arduino_adc_read_raw,
	.write_raw = arduino_adc_write_raw,
};

static int arduino_adc_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	int ret;
	struct arduino_adc_data *data;
	struct iio_dev *indio_dev;

	printk(KERN_INFO "arduino_adc_probe called.\n");

	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
	if (!indio_dev)
		return -ENOMEM;

	data = iio_priv(indio_dev);
	i2c_set_clientdata(client, indio_dev);
	data->client = client;

	indio_dev->dev.parent = &client->dev;
	indio_dev->info = &arduino_adc_info;
	indio_dev->name = id->name;
	indio_dev->channels = arduino_adc_channels;
	indio_dev->num_channels = ARRAY_SIZE(arduino_adc_channels);
	indio_dev->modes = INDIO_DIRECT_MODE;

	gpio_request(IRQ_TRIGGER_PIN, "sysfs");
	gpio_direction_input(IRQ_TRIGGER_PIN);
	gpio_export(IRQ_TRIGGER_PIN, false);
	irq_trigger = gpio_to_irq(IRQ_TRIGGER_PIN);

	ret = request_irq(irq_trigger,
				(irq_handler_t) erpi_gpio_irq_handler,
				IRQF_TRIGGER_RISING,
				"rpi_gpio",
				indio_dev);
	if (ret < 0) {
		return ret;
	}

	data->trigger = devm_iio_trigger_alloc(&client->dev, "rpi_gpio");
	if(!data->trigger){
		return -ENOMEM;
	}
	data->trigger->dev.parent = &client->dev;
	data->trigger->ops = &arduino_adc_trigger_ops;
	iio_trigger_set_drvdata(data->trigger, indio_dev);
	indio_dev->trig = data->trigger;
	iio_trigger_get(indio_dev->trig);
	ret = iio_trigger_register(data->trigger);
	if (ret < 0) {
		return ret;
	}

	ret = iio_triggered_buffer_setup(indio_dev, NULL,
					 arduino_adc_trigger_handler, NULL);
	if (ret < 0) {
		return ret;
	}

	return iio_device_register(indio_dev);
}

static int arduino_adc_remove(struct i2c_client *client)
{
	struct iio_dev *indio_dev = i2c_get_clientdata(client);;
	struct arduino_adc_data *data;
	data = iio_priv(indio_dev);

	iio_device_unregister(indio_dev);

	iio_triggered_buffer_cleanup(indio_dev);
	iio_trigger_unregister(data->trigger);

	free_irq(irq_trigger, NULL);
	gpio_unexport(IRQ_TRIGGER_PIN);
	gpio_free(IRQ_TRIGGER_PIN);

	return 0;
}


static const struct i2c_device_id arduino_adc_id[] = {
    { "arduino_adc", 0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, arduino_adc_id);

static struct i2c_driver arduino_adc_driver = {
	.driver = {
		.name = "arduino_adc",
	},
	.probe = arduino_adc_probe,
	.remove = arduino_adc_remove,
	.id_table = arduino_adc_id,
};
module_i2c_driver(arduino_adc_driver);

MODULE_AUTHOR("Hazael dos Santos Batista");
MODULE_DESCRIPTION("Arduino ADC test driver");
MODULE_LICENSE("GPL");