/*
 * Driver for I2C connected EETI EXC3000 multiple touch controller
 *
 * Copyright (C) 2017 Ahmet Inan <inan@distec.de>
 *
 * minimal implementation based on egalax_ts.c and egalax_i2c.c
 *
 * 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/bitops.h>
#include <linux/device.h>
#include <linux/i2c.h>
#include <linux/input.h>
#include <linux/input/mt.h>
#include <linux/input/touchscreen.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/timer.h>
#include <asm/unaligned.h>

#define EXC3000_NUM_SLOTS		10
#define EXC3000_SLOTS_PER_FRAME		5
#define EXC3000_LEN_FRAME		66
#define EXC3000_LEN_POINT		10
#define EXC3000_MT_EVENT		6
#define EXC3000_TIMEOUT_MS		100

struct exc3000_data {
	struct i2c_client *client;
	struct input_dev *input;
	struct touchscreen_properties prop;
	struct timer_list timer;
	u8 buf[2 * EXC3000_LEN_FRAME];
};

static void exc3000_report_slots(struct input_dev *input,
				 struct touchscreen_properties *prop,
				 const u8 *buf, int num)
{
	for (; num--; buf += EXC3000_LEN_POINT) {
		if (buf[0] & BIT(0)) {
			input_mt_slot(input, buf[1]);
			input_mt_report_slot_state(input, MT_TOOL_FINGER, true);
			touchscreen_report_pos(input, prop,
					       get_unaligned_le16(buf + 2),
					       get_unaligned_le16(buf + 4),
					       true);
		}
	}
}

static void exc3000_timer(struct timer_list *t)
{
	struct exc3000_data *data = from_timer(data, t, timer);

	input_mt_sync_frame(data->input);
	input_sync(data->input);
}

static int exc3000_read_frame(struct i2c_client *client, u8 *buf)
{
	int ret;

	ret = i2c_master_send(client, "'", 2);
	if (ret < 0)
		return ret;

	if (ret != 2)
		return -EIO;

	ret = i2c_master_recv(client, buf, EXC3000_LEN_FRAME);
	if (ret < 0)
		return ret;

	if (ret != EXC3000_LEN_FRAME)
		return -EIO;

	if (get_unaligned_le16(buf) != EXC3000_LEN_FRAME ||
			buf[2] != EXC3000_MT_EVENT)
		return -EINVAL;

	return 0;
}

static int exc3000_read_data(struct i2c_client *client,
			     u8 *buf, int *n_slots)
{
	int error;

	error = exc3000_read_frame(client, buf);
	if (error)
		return error;

	*n_slots = buf[3];
	if (!*n_slots || *n_slots > EXC3000_NUM_SLOTS)
		return -EINVAL;

	if (*n_slots > EXC3000_SLOTS_PER_FRAME) {
		/* Read 2nd frame to get the rest of the contacts. */
		error = exc3000_read_frame(client, buf + EXC3000_LEN_FRAME);
		if (error)
			return error;

		/* 2nd chunk must have number of contacts set to 0. */
		if (buf[EXC3000_LEN_FRAME + 3] != 0)
			return -EINVAL;
	}

	return 0;
}

static irqreturn_t exc3000_interrupt(int irq, void *dev_id)
{
	struct exc3000_data *data = dev_id;
	struct input_dev *input = data->input;
	u8 *buf = data->buf;
	int slots, total_slots;
	int error;

	error = exc3000_read_data(data->client, buf, &total_slots);
	if (error) {
		/* Schedule a timer to release "stuck" contacts */
		mod_timer(&data->timer,
			  jiffies + msecs_to_jiffies(EXC3000_TIMEOUT_MS));
		goto out;
	}

	/*
	 * We read full state successfully, no contacts will be "stuck".
	 */
	del_timer_sync(&data->timer);

	while (total_slots > 0) {
		slots = min(total_slots, EXC3000_SLOTS_PER_FRAME);
		exc3000_report_slots(input, &data->prop, buf + 4, slots);
		total_slots -= slots;
		buf += EXC3000_LEN_FRAME;
	}

	input_mt_sync_frame(input);
	input_sync(input);

out:
	return IRQ_HANDLED;
}

static int exc3000_probe(struct i2c_client *client,
			 const struct i2c_device_id *id)
{
	struct exc3000_data *data;
	struct input_dev *input;
	int error;

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

	data->client = client;
	timer_setup(&data->timer, exc3000_timer, 0);

	input = devm_input_allocate_device(&client->dev);
	if (!input)
		return -ENOMEM;

	data->input = input;

	input->name = "EETI EXC3000 Touch Screen";
	input->id.bustype = BUS_I2C;

	input_set_abs_params(input, ABS_MT_POSITION_X, 0, 4095, 0, 0);
	input_set_abs_params(input, ABS_MT_POSITION_Y, 0, 4095, 0, 0);
	touchscreen_parse_properties(input, true, &data->prop);

	error = input_mt_init_slots(input, EXC3000_NUM_SLOTS,
				    INPUT_MT_DIRECT | INPUT_MT_DROP_UNUSED);
	if (error)
		return error;

	error = input_register_device(input);
	if (error)
		return error;

	error = devm_request_threaded_irq(&client->dev, client->irq,
					  NULL, exc3000_interrupt, IRQF_ONESHOT,
					  client->name, data);
	if (error)
		return error;

	return 0;
}

static const struct i2c_device_id exc3000_id[] = {
	{ "exc3000", 0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, exc3000_id);

#ifdef CONFIG_OF
static const struct of_device_id exc3000_of_match[] = {
	{ .compatible = "eeti,exc3000" },
	{ }
};
MODULE_DEVICE_TABLE(of, exc3000_of_match);
#endif

static struct i2c_driver exc3000_driver = {
	.driver = {
		.name	= "exc3000",
		.of_match_table = of_match_ptr(exc3000_of_match),
	},
	.id_table	= exc3000_id,
	.probe		= exc3000_probe,
};

module_i2c_driver(exc3000_driver);

MODULE_AUTHOR("Ahmet Inan <inan@distec.de>");
MODULE_DESCRIPTION("I2C connected EETI EXC3000 multiple touch controller driver");
MODULE_LICENSE("GPL v2");