// SPDX-License-Identifier: GPL-2.0-only
/*
 * Touch Screen driver for SiS 9200 family I2C Touch panels
 *
 * Copyright (C) 2015 SiS, Inc.
 * Copyright (C) 2016 Nextfour Group
 */

#include <linux/crc-itu-t.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/input.h>
#include <linux/input/mt.h>
#include <linux/interrupt.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/unaligned.h>

#define SIS_I2C_NAME            "sis_i2c_ts"

/*
 * The I2C packet format:
 * le16         byte count
 * u8           Report ID
 * <contact data - variable length>
 * u8           Number of contacts
 * le16         Scan Time (optional)
 * le16         CRC
 *
 * One touch point information consists of 6+ bytes, the order is:
 * u8           contact state
 * u8           finger id
 * le16         x axis
 * le16         y axis
 * u8           contact width (optional)
 * u8           contact height (optional)
 * u8           pressure (optional)
 *
 * Maximum amount of data transmitted in one shot is 64 bytes, if controller
 * needs to report more contacts than fit in one packet it will send true
 * number of contacts in first packet and 0 as number of contacts in second
 * packet.
 */

#define SIS_MAX_PACKET_SIZE             64

#define SIS_PKT_LEN_OFFSET              0
#define SIS_PKT_REPORT_OFFSET           2 /* Report ID/type */
#define SIS_PKT_CONTACT_OFFSET          3 /* First contact */

#define SIS_SCAN_TIME_LEN               2

/* Supported report types */
#define SIS_ALL_IN_ONE_PACKAGE          0x10
#define SIS_PKT_IS_TOUCH(x)             (((x) & 0x0f) == 0x01)
#define SIS_PKT_IS_HIDI2C(x)            (((x) & 0x0f) == 0x06)

/* Contact properties within report */
#define SIS_PKT_HAS_AREA(x)             ((x) & BIT(4))
#define SIS_PKT_HAS_PRESSURE(x)         ((x) & BIT(5))
#define SIS_PKT_HAS_SCANTIME(x)         ((x) & BIT(6))

/* Contact size */
#define SIS_BASE_LEN_PER_CONTACT        6
#define SIS_AREA_LEN_PER_CONTACT        2
#define SIS_PRESSURE_LEN_PER_CONTACT    1

/* Offsets within contact data */
#define SIS_CONTACT_STATUS_OFFSET       0
#define SIS_CONTACT_ID_OFFSET           1 /* Contact ID */
#define SIS_CONTACT_X_OFFSET            2
#define SIS_CONTACT_Y_OFFSET            4
#define SIS_CONTACT_WIDTH_OFFSET        6
#define SIS_CONTACT_HEIGHT_OFFSET       7
#define SIS_CONTACT_PRESSURE_OFFSET(id) (SIS_PKT_HAS_AREA(id) ? 8 : 6)

/* Individual contact state */
#define SIS_STATUS_UP                   0x0
#define SIS_STATUS_DOWN                 0x3

/* Touchscreen parameters */
#define SIS_MAX_FINGERS                 10
#define SIS_MAX_X                       4095
#define SIS_MAX_Y                       4095
#define SIS_MAX_PRESSURE                255

/* Resolution diagonal */
#define SIS_AREA_LENGTH_LONGER          5792
/*((SIS_MAX_X^2) + (SIS_MAX_Y^2))^0.5*/
#define SIS_AREA_LENGTH_SHORT           5792
#define SIS_AREA_UNIT                   (5792 / 32)

struct sis_ts_data {
        struct i2c_client *client;
        struct input_dev *input;

        struct gpio_desc *attn_gpio;
        struct gpio_desc *reset_gpio;

        u8 packet[SIS_MAX_PACKET_SIZE];
};

static int sis_read_packet(struct i2c_client *client, u8 *buf,
                           unsigned int *num_contacts,
                           unsigned int *contact_size)
{
        int count_idx;
        int ret;
        u16 len;
        u16 crc, pkg_crc;
        u8 report_id;

        ret = i2c_master_recv(client, buf, SIS_MAX_PACKET_SIZE);
        if (ret <= 0)
                return -EIO;

        len = get_unaligned_le16(&buf[SIS_PKT_LEN_OFFSET]);
        if (len > SIS_MAX_PACKET_SIZE) {
                dev_err(&client->dev,
                        "%s: invalid packet length (%d vs %d)\n",
                        __func__, len, SIS_MAX_PACKET_SIZE);
                return -E2BIG;
        }

        if (len < 10)
                return -EINVAL;

        report_id = buf[SIS_PKT_REPORT_OFFSET];
        count_idx  = len - 1;
        *contact_size = SIS_BASE_LEN_PER_CONTACT;

        if (report_id != SIS_ALL_IN_ONE_PACKAGE) {
                if (SIS_PKT_IS_TOUCH(report_id)) {
                        /*
                         * Calculate CRC ignoring packet length
                         * in the beginning and CRC transmitted
                         * at the end of the packet.
                         */
                        crc = crc_itu_t(0, buf + 2, len - 2 - 2);
                        pkg_crc = get_unaligned_le16(&buf[len - 2]);

                        if (crc != pkg_crc) {
                                dev_err(&client->dev,
                                        "%s: CRC Error (%d vs %d)\n",
                                        __func__, crc, pkg_crc);
                                return -EINVAL;
                        }

                        count_idx -= 2;

                } else if (!SIS_PKT_IS_HIDI2C(report_id)) {
                        dev_err(&client->dev,
                                "%s: invalid packet ID %#02x\n",
                                __func__, report_id);
                        return -EINVAL;
                }

                if (SIS_PKT_HAS_SCANTIME(report_id))
                        count_idx -= SIS_SCAN_TIME_LEN;

                if (SIS_PKT_HAS_AREA(report_id))
                        *contact_size += SIS_AREA_LEN_PER_CONTACT;
                if (SIS_PKT_HAS_PRESSURE(report_id))
                        *contact_size += SIS_PRESSURE_LEN_PER_CONTACT;
        }

        *num_contacts = buf[count_idx];
        return 0;
}

static int sis_ts_report_contact(struct sis_ts_data *ts, const u8 *data, u8 id)
{
        struct input_dev *input = ts->input;
        int slot;
        u8 status = data[SIS_CONTACT_STATUS_OFFSET];
        u8 pressure;
        u8 height, width;
        u16 x, y;

        if (status != SIS_STATUS_DOWN && status != SIS_STATUS_UP) {
                dev_err(&ts->client->dev, "Unexpected touch status: %#02x\n",
                        data[SIS_CONTACT_STATUS_OFFSET]);
                return -EINVAL;
        }

        slot = input_mt_get_slot_by_key(input, data[SIS_CONTACT_ID_OFFSET]);
        if (slot < 0)
                return -ENOENT;

        input_mt_slot(input, slot);
        input_mt_report_slot_state(input, MT_TOOL_FINGER,
                                   status == SIS_STATUS_DOWN);

        if (status == SIS_STATUS_DOWN) {
                pressure = height = width = 1;
                if (id != SIS_ALL_IN_ONE_PACKAGE) {
                        if (SIS_PKT_HAS_AREA(id)) {
                                width = data[SIS_CONTACT_WIDTH_OFFSET];
                                height = data[SIS_CONTACT_HEIGHT_OFFSET];
                        }

                        if (SIS_PKT_HAS_PRESSURE(id))
                                pressure =
                                        data[SIS_CONTACT_PRESSURE_OFFSET(id)];
                }

                x = get_unaligned_le16(&data[SIS_CONTACT_X_OFFSET]);
                y = get_unaligned_le16(&data[SIS_CONTACT_Y_OFFSET]);

                input_report_abs(input, ABS_MT_TOUCH_MAJOR,
                                 width * SIS_AREA_UNIT);
                input_report_abs(input, ABS_MT_TOUCH_MINOR,
                                 height * SIS_AREA_UNIT);
                input_report_abs(input, ABS_MT_PRESSURE, pressure);
                input_report_abs(input, ABS_MT_POSITION_X, x);
                input_report_abs(input, ABS_MT_POSITION_Y, y);
        }

        return 0;
}

static void sis_ts_handle_packet(struct sis_ts_data *ts)
{
        const u8 *contact;
        unsigned int num_to_report = 0;
        unsigned int num_contacts;
        unsigned int num_reported;
        unsigned int contact_size;
        int error;
        u8 report_id;

        do {
                error = sis_read_packet(ts->client, ts->packet,
                                        &num_contacts, &contact_size);
                if (error)
                        break;

                if (num_to_report == 0) {
                        num_to_report = num_contacts;
                } else if (num_contacts != 0) {
                        dev_err(&ts->client->dev,
                                "%s: nonzero (%d) point count in tail packet\n",
                                __func__, num_contacts);
                        break;
                }

                report_id = ts->packet[SIS_PKT_REPORT_OFFSET];
                contact = &ts->packet[SIS_PKT_CONTACT_OFFSET];
                num_reported = 0;

                while (num_to_report > 0) {
                        error = sis_ts_report_contact(ts, contact, report_id);
                        if (error)
                                break;

                        contact += contact_size;
                        num_to_report--;
                        num_reported++;

                        if (report_id != SIS_ALL_IN_ONE_PACKAGE &&
                            num_reported >= 5) {
                                /*
                                 * The remainder of contacts is sent
                                 * in the 2nd packet.
                                 */
                                break;
                        }
                }
        } while (num_to_report > 0);

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

static irqreturn_t sis_ts_irq_handler(int irq, void *dev_id)
{
        struct sis_ts_data *ts = dev_id;

        do {
                sis_ts_handle_packet(ts);
        } while (ts->attn_gpio && gpiod_get_value_cansleep(ts->attn_gpio));

        return IRQ_HANDLED;
}

static void sis_ts_reset(struct sis_ts_data *ts)
{
        if (ts->reset_gpio) {
                /* Get out of reset */
                usleep_range(1000, 2000);
                gpiod_set_value(ts->reset_gpio, 1);
                usleep_range(1000, 2000);
                gpiod_set_value(ts->reset_gpio, 0);
                msleep(100);
        }
}

static int sis_ts_probe(struct i2c_client *client)
{
        struct sis_ts_data *ts;
        struct input_dev *input;
        int error;

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

        ts->client = client;

        ts->attn_gpio = devm_gpiod_get_optional(&client->dev,
                                                "attn", GPIOD_IN);
        if (IS_ERR(ts->attn_gpio))
                return dev_err_probe(&client->dev, PTR_ERR(ts->attn_gpio),
                                     "Failed to get attention GPIO\n");

        ts->reset_gpio = devm_gpiod_get_optional(&client->dev,
                                                 "reset", GPIOD_OUT_LOW);
        if (IS_ERR(ts->reset_gpio))
                return dev_err_probe(&client->dev, PTR_ERR(ts->reset_gpio),
                                     "Failed to get reset GPIO\n");

        sis_ts_reset(ts);

        ts->input = input = devm_input_allocate_device(&client->dev);
        if (!input) {
                dev_err(&client->dev, "Failed to allocate input device\n");
                return -ENOMEM;
        }

        input->name = "SiS Touchscreen";
        input->id.bustype = BUS_I2C;

        input_set_abs_params(input, ABS_MT_POSITION_X, 0, SIS_MAX_X, 0, 0);
        input_set_abs_params(input, ABS_MT_POSITION_Y, 0, SIS_MAX_Y, 0, 0);
        input_set_abs_params(input, ABS_MT_PRESSURE, 0, SIS_MAX_PRESSURE, 0, 0);
        input_set_abs_params(input, ABS_MT_TOUCH_MAJOR,
                             0, SIS_AREA_LENGTH_LONGER, 0, 0);
        input_set_abs_params(input, ABS_MT_TOUCH_MINOR,
                             0, SIS_AREA_LENGTH_SHORT, 0, 0);

        error = input_mt_init_slots(input, SIS_MAX_FINGERS, INPUT_MT_DIRECT);
        if (error) {
                dev_err(&client->dev,
                        "Failed to initialize MT slots: %d\n", error);
                return error;
        }

        error = devm_request_threaded_irq(&client->dev, client->irq,
                                          NULL, sis_ts_irq_handler,
                                          IRQF_ONESHOT,
                                          client->name, ts);
        if (error) {
                dev_err(&client->dev, "Failed to request IRQ: %d\n", error);
                return error;
        }

        error = input_register_device(ts->input);
        if (error) {
                dev_err(&client->dev,
                        "Failed to register input device: %d\n", error);
                return error;
        }

        return 0;
}

#ifdef CONFIG_OF
static const struct of_device_id sis_ts_dt_ids[] = {
        { .compatible = "sis,9200-ts" },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, sis_ts_dt_ids);
#endif

static const struct i2c_device_id sis_ts_id[] = {
        { .name = SIS_I2C_NAME },
        { .name = "9200-ts" },
        { /* sentinel */  }
};
MODULE_DEVICE_TABLE(i2c, sis_ts_id);

static struct i2c_driver sis_ts_driver = {
        .driver = {
                .name   = SIS_I2C_NAME,
                .of_match_table = of_match_ptr(sis_ts_dt_ids),
        },
        .probe          = sis_ts_probe,
        .id_table       = sis_ts_id,
};
module_i2c_driver(sis_ts_driver);

MODULE_DESCRIPTION("SiS 9200 Family Touchscreen Driver");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Mika Penttilä <mika.penttila@nextfour.com>");