/*
 *  tsl2550.c - Linux kernel modules for ambient light sensor
 *
 *  Copyright (C) 2007 Rodolfo Giometti <giometti@linux.it>
 *  Copyright (C) 2007 Eurotech S.p.A. <info@eurotech.it>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/mutex.h>

#define TSL2550_DRV_NAME        "tsl2550"
#define DRIVER_VERSION          "1.2"

/*
 * Defines
 */

#define TSL2550_POWER_DOWN              0x00
#define TSL2550_POWER_UP                0x03
#define TSL2550_STANDARD_RANGE          0x18
#define TSL2550_EXTENDED_RANGE          0x1d
#define TSL2550_READ_ADC0               0x43
#define TSL2550_READ_ADC1               0x83

/*
 * Structs
 */

struct tsl2550_data {
        struct i2c_client *client;
        struct mutex update_lock;

        unsigned int power_state : 1;
        unsigned int operating_mode : 1;
};

/*
 * Global data
 */

static const u8 TSL2550_MODE_RANGE[2] = {
        TSL2550_STANDARD_RANGE, TSL2550_EXTENDED_RANGE,
};

/*
 * Management functions
 */

static int tsl2550_set_operating_mode(struct i2c_client *client, int mode)
{
        struct tsl2550_data *data = i2c_get_clientdata(client);

        int ret = i2c_smbus_write_byte(client, TSL2550_MODE_RANGE[mode]);

        data->operating_mode = mode;

        return ret;
}

static int tsl2550_set_power_state(struct i2c_client *client, int state)
{
        struct tsl2550_data *data = i2c_get_clientdata(client);
        int ret;

        if (state == 0)
                ret = i2c_smbus_write_byte(client, TSL2550_POWER_DOWN);
        else {
                ret = i2c_smbus_write_byte(client, TSL2550_POWER_UP);

                /* On power up we should reset operating mode also... */
                tsl2550_set_operating_mode(client, data->operating_mode);
        }

        data->power_state = state;

        return ret;
}

static int tsl2550_get_adc_value(struct i2c_client *client, u8 cmd)
{
        int ret;

        ret = i2c_smbus_read_byte_data(client, cmd);
        if (ret < 0)
                return ret;
        if (!(ret & 0x80))
                return -EAGAIN;
        return ret & 0x7f;      /* remove the "valid" bit */
}

/*
 * LUX calculation
 */

#define TSL2550_MAX_LUX         1846

static const u8 ratio_lut[] = {
        100, 100, 100, 100, 100, 100, 100, 100,
        100, 100, 100, 100, 100, 100, 99, 99,
        99, 99, 99, 99, 99, 99, 99, 99,
        99, 99, 99, 98, 98, 98, 98, 98,
        98, 98, 97, 97, 97, 97, 97, 96,
        96, 96, 96, 95, 95, 95, 94, 94,
        93, 93, 93, 92, 92, 91, 91, 90,
        89, 89, 88, 87, 87, 86, 85, 84,
        83, 82, 81, 80, 79, 78, 77, 75,
        74, 73, 71, 69, 68, 66, 64, 62,
        60, 58, 56, 54, 52, 49, 47, 44,
        42, 41, 40, 40, 39, 39, 38, 38,
        37, 37, 37, 36, 36, 36, 35, 35,
        35, 35, 34, 34, 34, 34, 33, 33,
        33, 33, 32, 32, 32, 32, 32, 31,
        31, 31, 31, 31, 30, 30, 30, 30,
        30,
};

static const u16 count_lut[] = {
        0, 1, 2, 3, 4, 5, 6, 7,
        8, 9, 10, 11, 12, 13, 14, 15,
        16, 18, 20, 22, 24, 26, 28, 30,
        32, 34, 36, 38, 40, 42, 44, 46,
        49, 53, 57, 61, 65, 69, 73, 77,
        81, 85, 89, 93, 97, 101, 105, 109,
        115, 123, 131, 139, 147, 155, 163, 171,
        179, 187, 195, 203, 211, 219, 227, 235,
        247, 263, 279, 295, 311, 327, 343, 359,
        375, 391, 407, 423, 439, 455, 471, 487,
        511, 543, 575, 607, 639, 671, 703, 735,
        767, 799, 831, 863, 895, 927, 959, 991,
        1039, 1103, 1167, 1231, 1295, 1359, 1423, 1487,
        1551, 1615, 1679, 1743, 1807, 1871, 1935, 1999,
        2095, 2223, 2351, 2479, 2607, 2735, 2863, 2991,
        3119, 3247, 3375, 3503, 3631, 3759, 3887, 4015,
};

/*
 * This function is described into Taos TSL2550 Designer's Notebook
 * pages 2, 3.
 */
static int tsl2550_calculate_lux(u8 ch0, u8 ch1)
{
        unsigned int lux;

        /* Look up count from channel values */
        u16 c0 = count_lut[ch0];
        u16 c1 = count_lut[ch1];

        /*
         * Calculate ratio.
         * Note: the "128" is a scaling factor
         */
        u8 r = 128;

        /* Avoid division by 0 and count 1 cannot be greater than count 0 */
        if (c1 <= c0)
                if (c0) {
                        r = c1 * 128 / c0;

                        /* Calculate LUX */
                        lux = ((c0 - c1) * ratio_lut[r]) / 256;
                } else
                        lux = 0;
        else
                return -EAGAIN;

        /* LUX range check */
        return lux > TSL2550_MAX_LUX ? TSL2550_MAX_LUX : lux;
}

/*
 * SysFS support
 */

static ssize_t tsl2550_show_power_state(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct tsl2550_data *data = i2c_get_clientdata(to_i2c_client(dev));

        return sprintf(buf, "%u\n", data->power_state);
}

static ssize_t tsl2550_store_power_state(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct tsl2550_data *data = i2c_get_clientdata(client);
        unsigned long val = simple_strtoul(buf, NULL, 10);
        int ret;

        if (val < 0 || val > 1)
                return -EINVAL;

        mutex_lock(&data->update_lock);
        ret = tsl2550_set_power_state(client, val);
        mutex_unlock(&data->update_lock);

        if (ret < 0)
                return ret;

        return count;
}

static DEVICE_ATTR(power_state, S_IWUSR | S_IRUGO,
                   tsl2550_show_power_state, tsl2550_store_power_state);

static ssize_t tsl2550_show_operating_mode(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct tsl2550_data *data = i2c_get_clientdata(to_i2c_client(dev));

        return sprintf(buf, "%u\n", data->operating_mode);
}

static ssize_t tsl2550_store_operating_mode(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct tsl2550_data *data = i2c_get_clientdata(client);
        unsigned long val = simple_strtoul(buf, NULL, 10);
        int ret;

        if (val < 0 || val > 1)
                return -EINVAL;

        if (data->power_state == 0)
                return -EBUSY;

        mutex_lock(&data->update_lock);
        ret = tsl2550_set_operating_mode(client, val);
        mutex_unlock(&data->update_lock);

        if (ret < 0)
                return ret;

        return count;
}

static DEVICE_ATTR(operating_mode, S_IWUSR | S_IRUGO,
                   tsl2550_show_operating_mode, tsl2550_store_operating_mode);

static ssize_t __tsl2550_show_lux(struct i2c_client *client, char *buf)
{
        struct tsl2550_data *data = i2c_get_clientdata(client);
        u8 ch0, ch1;
        int ret;

        ret = tsl2550_get_adc_value(client, TSL2550_READ_ADC0);
        if (ret < 0)
                return ret;
        ch0 = ret;

        ret = tsl2550_get_adc_value(client, TSL2550_READ_ADC1);
        if (ret < 0)
                return ret;
        ch1 = ret;

        /* Do the job */
        ret = tsl2550_calculate_lux(ch0, ch1);
        if (ret < 0)
                return ret;
        if (data->operating_mode == 1)
                ret *= 5;

        return sprintf(buf, "%d\n", ret);
}

static ssize_t tsl2550_show_lux1_input(struct device *dev,
                        struct device_attribute *attr, char *buf)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct tsl2550_data *data = i2c_get_clientdata(client);
        int ret;

        /* No LUX data if not operational */
        if (!data->power_state)
                return -EBUSY;

        mutex_lock(&data->update_lock);
        ret = __tsl2550_show_lux(client, buf);
        mutex_unlock(&data->update_lock);

        return ret;
}

static DEVICE_ATTR(lux1_input, S_IRUGO,
                   tsl2550_show_lux1_input, NULL);

static struct attribute *tsl2550_attributes[] = {
        &dev_attr_power_state.attr,
        &dev_attr_operating_mode.attr,
        &dev_attr_lux1_input.attr,
        NULL
};

static const struct attribute_group tsl2550_attr_group = {
        .attrs = tsl2550_attributes,
};

/*
 * Initialization function
 */

static int tsl2550_init_client(struct i2c_client *client)
{
        struct tsl2550_data *data = i2c_get_clientdata(client);
        int err;

        /*
         * Probe the chip. To do so we try to power up the device and then to
         * read back the 0x03 code
         */
        err = i2c_smbus_read_byte_data(client, TSL2550_POWER_UP);
        if (err < 0)
                return err;
        if (err != TSL2550_POWER_UP)
                return -ENODEV;
        data->power_state = 1;

        /* Set the default operating mode */
        err = i2c_smbus_write_byte(client,
                                   TSL2550_MODE_RANGE[data->operating_mode]);
        if (err < 0)
                return err;

        return 0;
}

/*
 * I2C init/probing/exit functions
 */

static struct i2c_driver tsl2550_driver;
static int __devinit tsl2550_probe(struct i2c_client *client,
                                   const struct i2c_device_id *id)
{
        struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
        struct tsl2550_data *data;
        int *opmode, err = 0;

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE
                                            | I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
                err = -EIO;
                goto exit;
        }

        data = kzalloc(sizeof(struct tsl2550_data), GFP_KERNEL);
        if (!data) {
                err = -ENOMEM;
                goto exit;
        }
        data->client = client;
        i2c_set_clientdata(client, data);

        /* Check platform data */
        opmode = client->dev.platform_data;
        if (opmode) {
                if (*opmode < 0 || *opmode > 1) {
                        dev_err(&client->dev, "invalid operating_mode (%d)\n",
                                        *opmode);
                        err = -EINVAL;
                        goto exit_kfree;
                }
                data->operating_mode = *opmode;
        } else
                data->operating_mode = 0;       /* default mode is standard */
        dev_info(&client->dev, "%s operating mode\n",
                        data->operating_mode ? "extended" : "standard");

        mutex_init(&data->update_lock);

        /* Initialize the TSL2550 chip */
        err = tsl2550_init_client(client);
        if (err)
                goto exit_kfree;

        /* Register sysfs hooks */
        err = sysfs_create_group(&client->dev.kobj, &tsl2550_attr_group);
        if (err)
                goto exit_kfree;

        dev_info(&client->dev, "support ver. %s enabled\n", DRIVER_VERSION);

        return 0;

exit_kfree:
        kfree(data);
exit:
        return err;
}

static int __devexit tsl2550_remove(struct i2c_client *client)
{
        sysfs_remove_group(&client->dev.kobj, &tsl2550_attr_group);

        /* Power down the device */
        tsl2550_set_power_state(client, 0);

        kfree(i2c_get_clientdata(client));

        return 0;
}

#ifdef CONFIG_PM

static int tsl2550_suspend(struct i2c_client *client, pm_message_t mesg)
{
        return tsl2550_set_power_state(client, 0);
}

static int tsl2550_resume(struct i2c_client *client)
{
        return tsl2550_set_power_state(client, 1);
}

#else

#define tsl2550_suspend         NULL
#define tsl2550_resume          NULL

#endif /* CONFIG_PM */

static const struct i2c_device_id tsl2550_id[] = {
        { "tsl2550", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, tsl2550_id);

static struct i2c_driver tsl2550_driver = {
        .driver = {
                .name   = TSL2550_DRV_NAME,
                .owner  = THIS_MODULE,
        },
        .suspend = tsl2550_suspend,
        .resume = tsl2550_resume,
        .probe  = tsl2550_probe,
        .remove = __devexit_p(tsl2550_remove),
        .id_table = tsl2550_id,
};

static int __init tsl2550_init(void)
{
        return i2c_add_driver(&tsl2550_driver);
}

static void __exit tsl2550_exit(void)
{
        i2c_del_driver(&tsl2550_driver);
}

MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
MODULE_DESCRIPTION("TSL2550 ambient light sensor driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRIVER_VERSION);

module_init(tsl2550_init);
module_exit(tsl2550_exit);