/*
  	ads7828.c - lm_sensors driver for ads7828 12-bit 8-channel ADC
  	(C) 2007 EADS Astrium
  
  	This driver is based on the lm75 and other lm_sensors/hwmon drivers

  	Written by Steve Hardy <shardy@redhat.com>

  
  	Datasheet available at: http://focus.ti.com/lit/ds/symlink/ads7828.pdf
  
  	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/jiffies.h>
  #include <linux/i2c.h>
  #include <linux/hwmon.h>
  #include <linux/hwmon-sysfs.h>
  #include <linux/err.h>
  #include <linux/mutex.h>
  
  /* The ADS7828 registers */
  #define ADS7828_NCH 8 /* 8 channels of 12-bit A-D supported */
  #define ADS7828_CMD_SD_SE 0x80 /* Single ended inputs */
  #define ADS7828_CMD_SD_DIFF 0x00 /* Differential inputs */
  #define ADS7828_CMD_PD0 0x0 /* Power Down between A-D conversions */
  #define ADS7828_CMD_PD1 0x04 /* Internal ref OFF && A-D ON */
  #define ADS7828_CMD_PD2 0x08 /* Internal ref ON && A-D OFF */
  #define ADS7828_CMD_PD3 0x0C /* Internal ref ON && A-D ON */
  #define ADS7828_INT_VREF_MV 2500 /* Internal vref is 2.5V, 2500mV */
  
  /* Addresses to scan */

  static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b,

  	I2C_CLIENT_END };

  /* Module parameters */

  static bool se_input = 1; /* Default is SE, 0 == diff */
  static bool int_vref = 1; /* Default is internal ref ON */

  static int vref_mv = ADS7828_INT_VREF_MV; /* set if vref != 2.5V */
  module_param(se_input, bool, S_IRUGO);
  module_param(int_vref, bool, S_IRUGO);
  module_param(vref_mv, int, S_IRUGO);
  
  /* Global Variables */
  static u8 ads7828_cmd_byte; /* cmd byte without channel bits */
  static unsigned int ads7828_lsb_resol; /* resolution of the ADC sample lsb */
  
  /* Each client has this additional data */
  struct ads7828_data {

  	struct device *hwmon_dev;
  	struct mutex update_lock; /* mutex protect updates */
  	char valid; /* !=0 if following fields are valid */
  	unsigned long last_updated; /* In jiffies */
  	u16 adc_input[ADS7828_NCH]; /* ADS7828_NCH 12-bit samples */
  };
  
  /* Function declaration - necessary due to function dependencies */

  static int ads7828_detect(struct i2c_client *client,

  			  struct i2c_board_info *info);
  static int ads7828_probe(struct i2c_client *client,
  			 const struct i2c_device_id *id);

  static inline u8 channel_cmd_byte(int ch)
  {
  	/* cmd byte C2,C1,C0 - see datasheet */
  	u8 cmd = (((ch>>1) | (ch&0x01)<<2)<<4);
  	cmd |= ads7828_cmd_byte;
  	return cmd;
  }
  
  /* Update data for the device (all 8 channels) */
  static struct ads7828_data *ads7828_update_device(struct device *dev)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct ads7828_data *data = i2c_get_clientdata(client);
  
  	mutex_lock(&data->update_lock);
  
  	if (time_after(jiffies, data->last_updated + HZ + HZ / 2)
  			|| !data->valid) {
  		unsigned int ch;
  		dev_dbg(&client->dev, "Starting ads7828 update
  ");
  
  		for (ch = 0; ch < ADS7828_NCH; ch++) {
  			u8 cmd = channel_cmd_byte(ch);

  			data->adc_input[ch] =
  				i2c_smbus_read_word_swapped(client, cmd);

  		}
  		data->last_updated = jiffies;
  		data->valid = 1;
  	}
  
  	mutex_unlock(&data->update_lock);
  
  	return data;
  }
  
  /* sysfs callback function */
  static ssize_t show_in(struct device *dev, struct device_attribute *da,
  	char *buf)
  {
  	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
  	struct ads7828_data *data = ads7828_update_device(dev);
  	/* Print value (in mV as specified in sysfs-interface documentation) */
  	return sprintf(buf, "%d
  ", (data->adc_input[attr->index] *
  		ads7828_lsb_resol)/1000);
  }
  
  #define in_reg(offset)\
  static SENSOR_DEVICE_ATTR(in##offset##_input, S_IRUGO, show_in,\
  	NULL, offset)
  
  in_reg(0);
  in_reg(1);
  in_reg(2);
  in_reg(3);
  in_reg(4);
  in_reg(5);
  in_reg(6);
  in_reg(7);
  
  static struct attribute *ads7828_attributes[] = {
  	&sensor_dev_attr_in0_input.dev_attr.attr,
  	&sensor_dev_attr_in1_input.dev_attr.attr,
  	&sensor_dev_attr_in2_input.dev_attr.attr,
  	&sensor_dev_attr_in3_input.dev_attr.attr,
  	&sensor_dev_attr_in4_input.dev_attr.attr,
  	&sensor_dev_attr_in5_input.dev_attr.attr,
  	&sensor_dev_attr_in6_input.dev_attr.attr,
  	&sensor_dev_attr_in7_input.dev_attr.attr,
  	NULL
  };
  
  static const struct attribute_group ads7828_group = {
  	.attrs = ads7828_attributes,
  };

  static int ads7828_remove(struct i2c_client *client)

  {
  	struct ads7828_data *data = i2c_get_clientdata(client);
  	hwmon_device_unregister(data->hwmon_dev);
  	sysfs_remove_group(&client->dev.kobj, &ads7828_group);

  	kfree(i2c_get_clientdata(client));
  	return 0;
  }

  static const struct i2c_device_id ads7828_id[] = {

  	{ "ads7828", 0 },

  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, ads7828_id);

  /* This is the driver that will be inserted */
  static struct i2c_driver ads7828_driver = {

  	.class = I2C_CLASS_HWMON,

  	.driver = {
  		.name = "ads7828",
  	},

  	.probe = ads7828_probe,
  	.remove = ads7828_remove,
  	.id_table = ads7828_id,
  	.detect = ads7828_detect,

  	.address_list = normal_i2c,

  };

  /* Return 0 if detection is successful, -ENODEV otherwise */

  static int ads7828_detect(struct i2c_client *client,

  			  struct i2c_board_info *info)

  {

  	struct i2c_adapter *adapter = client->adapter;

  	int ch;

  
  	/* Check we have a valid client */
  	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA))

  		return -ENODEV;

  
  	/* Now, we do the remaining detection. There is no identification
  	dedicated register so attempt to sanity check using knowledge of
  	the chip
  	- Read from the 8 channel addresses
  	- Check the top 4 bits of each result are not set (12 data bits)
  	*/

  	for (ch = 0; ch < ADS7828_NCH; ch++) {
  		u16 in_data;
  		u8 cmd = channel_cmd_byte(ch);

  		in_data = i2c_smbus_read_word_swapped(client, cmd);

  		if (in_data & 0xF000) {
  			pr_debug("%s : Doesn't look like an ads7828 device
  ",
  				 __func__);
  			return -ENODEV;

  		}
  	}

  	strlcpy(info->type, "ads7828", I2C_NAME_SIZE);

  	return 0;
  }

  static int ads7828_probe(struct i2c_client *client,
  			 const struct i2c_device_id *id)
  {
  	struct ads7828_data *data;
  	int err;

  	data = kzalloc(sizeof(struct ads7828_data), GFP_KERNEL);
  	if (!data) {
  		err = -ENOMEM;
  		goto exit;
  	}

  	i2c_set_clientdata(client, data);

  	mutex_init(&data->update_lock);

  	/* Register sysfs hooks */
  	err = sysfs_create_group(&client->dev.kobj, &ads7828_group);
  	if (err)

  		goto exit_free;

  
  	data->hwmon_dev = hwmon_device_register(&client->dev);
  	if (IS_ERR(data->hwmon_dev)) {
  		err = PTR_ERR(data->hwmon_dev);
  		goto exit_remove;
  	}
  
  	return 0;
  
  exit_remove:
  	sysfs_remove_group(&client->dev.kobj, &ads7828_group);

  exit_free:
  	kfree(data);
  exit:
  	return err;
  }
  
  static int __init sensors_ads7828_init(void)
  {
  	/* Initialize the command byte according to module parameters */
  	ads7828_cmd_byte = se_input ?
  		ADS7828_CMD_SD_SE : ADS7828_CMD_SD_DIFF;
  	ads7828_cmd_byte |= int_vref ?
  		ADS7828_CMD_PD3 : ADS7828_CMD_PD1;
  
  	/* Calculate the LSB resolution */
  	ads7828_lsb_resol = (vref_mv*1000)/4096;
  
  	return i2c_add_driver(&ads7828_driver);
  }
  
  static void __exit sensors_ads7828_exit(void)
  {
  	i2c_del_driver(&ads7828_driver);
  }

  MODULE_AUTHOR("Steve Hardy <shardy@redhat.com>");

  MODULE_DESCRIPTION("ADS7828 driver");
  MODULE_LICENSE("GPL");
  
  module_init(sensors_ads7828_init);
  module_exit(sensors_ads7828_exit);