/*
 * D-Link DIR-685 router I2C-based Touchkeys input driver
 * Copyright (C) 2017 Linus Walleij <linus.walleij@linaro.org>
 *
 * This is a one-off touchkey controller based on the Cypress Semiconductor
 * CY8C214 MCU with some firmware in its internal 8KB flash. The circuit
 * board inside the router is named E119921
 */

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/input.h>
#include <linux/slab.h>
#include <linux/bitops.h>

struct dir685_touchkeys {
	struct device		*dev;
	struct i2c_client	*client;
	struct input_dev	*input;
	unsigned long		cur_key;
	u16			codes[7];
};

static irqreturn_t dir685_tk_irq_thread(int irq, void *data)
{
	struct dir685_touchkeys *tk = data;
	const int num_bits = min_t(int, ARRAY_SIZE(tk->codes), 16);
	unsigned long changed;
	u8 buf[6];
	unsigned long key;
	int i;
	int err;

	memset(buf, 0, sizeof(buf));
	err = i2c_master_recv(tk->client, buf, sizeof(buf));
	if (err != sizeof(buf)) {
		dev_err(tk->dev, "short read %d\n", err);
		return IRQ_HANDLED;
	}

	dev_dbg(tk->dev, "IN: %*ph\n", (int)sizeof(buf), buf);
	key = be16_to_cpup((__be16 *) &buf[4]);

	/* Figure out if any bits went high or low since last message */
	changed = tk->cur_key ^ key;
	for_each_set_bit(i, &changed, num_bits) {
		dev_dbg(tk->dev, "key %d is %s\n", i,
			test_bit(i, &key) ? "down" : "up");
		input_report_key(tk->input, tk->codes[i], test_bit(i, &key));
	}

	/* Store currently down keys */
	tk->cur_key = key;
	input_sync(tk->input);

	return IRQ_HANDLED;
}

static int dir685_tk_probe(struct i2c_client *client,
			   const struct i2c_device_id *id)
{
	struct dir685_touchkeys *tk;
	struct device *dev = &client->dev;
	u8 bl_data[] = { 0xa7, 0x40 };
	int err;
	int i;

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

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

	tk->client = client;
	tk->dev = dev;

	tk->input->keycodesize = sizeof(u16);
	tk->input->keycodemax = ARRAY_SIZE(tk->codes);
	tk->input->keycode = tk->codes;
	tk->codes[0] = KEY_UP;
	tk->codes[1] = KEY_DOWN;
	tk->codes[2] = KEY_LEFT;
	tk->codes[3] = KEY_RIGHT;
	tk->codes[4] = KEY_ENTER;
	tk->codes[5] = KEY_WPS_BUTTON;
	/*
	 * This key appears in the vendor driver, but I have
	 * not been able to activate it.
	 */
	tk->codes[6] = KEY_RESERVED;

	__set_bit(EV_KEY, tk->input->evbit);
	for (i = 0; i < ARRAY_SIZE(tk->codes); i++)
		__set_bit(tk->codes[i], tk->input->keybit);
	__clear_bit(KEY_RESERVED, tk->input->keybit);

	tk->input->name = "D-Link DIR-685 touchkeys";
	tk->input->id.bustype = BUS_I2C;

	err = input_register_device(tk->input);
	if (err)
		return err;

	/* Set the brightness to max level */
	err = i2c_master_send(client, bl_data, sizeof(bl_data));
	if (err != sizeof(bl_data))
		dev_warn(tk->dev, "error setting brightness level\n");

	if (!client->irq) {
		dev_err(dev, "no IRQ on the I2C device\n");
		return -ENODEV;
	}
	err = devm_request_threaded_irq(dev, client->irq,
					NULL, dir685_tk_irq_thread,
					IRQF_ONESHOT,
					"dir685-tk", tk);
	if (err) {
		dev_err(dev, "can't request IRQ\n");
		return err;
	}

	return 0;
}

static const struct i2c_device_id dir685_tk_id[] = {
	{ "dir685tk", 0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, dir685_tk_id);

#ifdef CONFIG_OF
static const struct of_device_id dir685_tk_of_match[] = {
	{ .compatible = "dlink,dir685-touchkeys" },
	{},
};
MODULE_DEVICE_TABLE(of, dir685_tk_of_match);
#endif

static struct i2c_driver dir685_tk_i2c_driver = {
	.driver = {
		.name	= "dlin-dir685-touchkeys",
		.of_match_table = of_match_ptr(dir685_tk_of_match),
	},
	.probe		= dir685_tk_probe,
	.id_table	= dir685_tk_id,
};
module_i2c_driver(dir685_tk_i2c_driver);

MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
MODULE_DESCRIPTION("D-Link DIR-685 touchkeys driver");
MODULE_LICENSE("GPL");