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tsl2550.c

/*
 *  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>
#include <linux/delay.h>

#define TSL2550_DRV_NAME      "tsl2550"
#define DRIVER_VERSION        "1.1.1"

/*
 * 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)
{
      unsigned long end;
      int loop = 0, ret = 0;

      /*
       * Read ADC channel waiting at most 400ms (see data sheet for further
       * info).
       * To avoid long busy wait we spin for few milliseconds then
       * start sleeping.
       */
      end = jiffies + msecs_to_jiffies(400);
      while (time_before(jiffies, end)) {
            i2c_smbus_write_byte(client, cmd);

            if (loop++ < 5)
                  mdelay(1);
            else
                  msleep(1);

            ret = i2c_smbus_read_byte(client);
            if (ret < 0)
                  return ret;
            else if (ret & 0x0080)
                  break;
      }
      if (!(ret & 0x80))
            return -EIO;
      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 (c0 && (c1 <= c0))
            r = c1 * 128 / c0;
      else
            return -1;

      /* Calculate LUX */
      lux = ((c0 - c1) * ratio_lut[r]) / 256;

      /* 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)
{
      u8 ch0, ch1;
      int ret;

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

      mdelay(1);

      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;

      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_write_byte(client, TSL2550_POWER_UP);
      if (err < 0)
            return err;
      mdelay(1);
      if (i2c_smbus_read_byte(client) != 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)
{
      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_BYTE)) {
            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;
}

static struct i2c_driver tsl2550_driver = {
      .driver = {
            .name = TSL2550_DRV_NAME,
            .owner      = THIS_MODULE,
      },
      .probe      = tsl2550_probe,
      .remove     = __devexit_p(tsl2550_remove),
};

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);

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