/*
 * lm77.c - Part of lm_sensors, Linux kernel modules for hardware
 *          monitoring
 *
 * Copyright (c) 2004  Andras BALI <drewie@freemail.hu>
 *
 * Heavily based on lm75.c by Frodo Looijaard <frodol@dds.nl>.  The LM77
 * is a temperature sensor and thermal window comparator with 0.5 deg
 * resolution made by National Semiconductor.  Complete datasheet can be
 * obtained at their site:
 *      http://www.national.com/pf/LM/LM77.html
 *
 * 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.
 */

#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>

/* Addresses to scan */
static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b,
                                                I2C_CLIENT_END };

/* The LM77 registers */
#define LM77_REG_TEMP           0x00
#define LM77_REG_CONF           0x01
#define LM77_REG_TEMP_HYST      0x02
#define LM77_REG_TEMP_CRIT      0x03
#define LM77_REG_TEMP_MIN       0x04
#define LM77_REG_TEMP_MAX       0x05

enum temp_index {
        t_input = 0,
        t_crit,
        t_min,
        t_max,
        t_hyst,
        t_num_temp
};

static const u8 temp_regs[t_num_temp] = {
        [t_input] = LM77_REG_TEMP,
        [t_min] = LM77_REG_TEMP_MIN,
        [t_max] = LM77_REG_TEMP_MAX,
        [t_crit] = LM77_REG_TEMP_CRIT,
        [t_hyst] = LM77_REG_TEMP_HYST,
};

/* Each client has this additional data */
struct lm77_data {
        struct i2c_client       *client;
        struct mutex            update_lock;
        char                    valid;
        unsigned long           last_updated;   /* In jiffies */
        int                     temp[t_num_temp]; /* index using temp_index */
        u8                      alarms;
};

/* straight from the datasheet */
#define LM77_TEMP_MIN (-55000)
#define LM77_TEMP_MAX 125000

/*
 * In the temperature registers, the low 3 bits are not part of the
 * temperature values; they are the status bits.
 */
static inline s16 LM77_TEMP_TO_REG(int temp)
{
        return (temp / 500) * 8;
}

static inline int LM77_TEMP_FROM_REG(s16 reg)
{
        return (reg / 8) * 500;
}

/*
 * All registers are word-sized, except for the configuration register.
 * The LM77 uses the high-byte first convention.
 */
static u16 lm77_read_value(struct i2c_client *client, u8 reg)
{
        if (reg == LM77_REG_CONF)
                return i2c_smbus_read_byte_data(client, reg);
        else
                return i2c_smbus_read_word_swapped(client, reg);
}

static int lm77_write_value(struct i2c_client *client, u8 reg, u16 value)
{
        if (reg == LM77_REG_CONF)
                return i2c_smbus_write_byte_data(client, reg, value);
        else
                return i2c_smbus_write_word_swapped(client, reg, value);
}

static struct lm77_data *lm77_update_device(struct device *dev)
{
        struct lm77_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        int i;

        mutex_lock(&data->update_lock);

        if (time_after(jiffies, data->last_updated + HZ + HZ / 2)
            || !data->valid) {
                dev_dbg(&client->dev, "Starting lm77 update\n");
                for (i = 0; i < t_num_temp; i++) {
                        data->temp[i] =
                          LM77_TEMP_FROM_REG(lm77_read_value(client,
                                                             temp_regs[i]));
                }
                data->alarms =
                        lm77_read_value(client, LM77_REG_TEMP) & 0x0007;
                data->last_updated = jiffies;
                data->valid = 1;
        }

        mutex_unlock(&data->update_lock);

        return data;
}

/* sysfs stuff */

static ssize_t show_temp(struct device *dev, struct device_attribute *devattr,
                         char *buf)
{
        struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
        struct lm77_data *data = lm77_update_device(dev);

        return sprintf(buf, "%d\n", data->temp[attr->index]);
}

static ssize_t show_temp_hyst(struct device *dev,
                              struct device_attribute *devattr, char *buf)
{
        struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
        struct lm77_data *data = lm77_update_device(dev);
        int nr = attr->index;
        int temp;

        temp = nr == t_min ? data->temp[nr] + data->temp[t_hyst] :
                             data->temp[nr] - data->temp[t_hyst];

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

static ssize_t set_temp(struct device *dev, struct device_attribute *devattr,
                        const char *buf, size_t count)
{
        struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
        struct lm77_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        int nr = attr->index;
        long val;
        int err;

        err = kstrtol(buf, 10, &val);
        if (err)
                return err;

        val = clamp_val(val, LM77_TEMP_MIN, LM77_TEMP_MAX);
        mutex_lock(&data->update_lock);
        data->temp[nr] = val;
        lm77_write_value(client, temp_regs[nr], LM77_TEMP_TO_REG(val));
        mutex_unlock(&data->update_lock);
        return count;
}

/*
 * hysteresis is stored as a relative value on the chip, so it has to be
 * converted first.
 */
static ssize_t set_temp_hyst(struct device *dev,
                             struct device_attribute *devattr,
                             const char *buf, size_t count)
{
        struct lm77_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        long val;
        int err;

        err = kstrtol(buf, 10, &val);
        if (err)
                return err;

        mutex_lock(&data->update_lock);
        val = clamp_val(data->temp[t_crit] - val, LM77_TEMP_MIN, LM77_TEMP_MAX);
        data->temp[t_hyst] = val;
        lm77_write_value(client, LM77_REG_TEMP_HYST,
                         LM77_TEMP_TO_REG(data->temp[t_hyst]));
        mutex_unlock(&data->update_lock);
        return count;
}

static ssize_t show_alarm(struct device *dev, struct device_attribute *attr,
                          char *buf)
{
        int bitnr = to_sensor_dev_attr(attr)->index;
        struct lm77_data *data = lm77_update_device(dev);
        return sprintf(buf, "%u\n", (data->alarms >> bitnr) & 1);
}

static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, show_temp, NULL, t_input);
static SENSOR_DEVICE_ATTR(temp1_crit, S_IWUSR | S_IRUGO, show_temp, set_temp,
                          t_crit);
static SENSOR_DEVICE_ATTR(temp1_min, S_IWUSR | S_IRUGO, show_temp, set_temp,
                          t_min);
static SENSOR_DEVICE_ATTR(temp1_max, S_IWUSR | S_IRUGO, show_temp, set_temp,
                          t_max);

static SENSOR_DEVICE_ATTR(temp1_crit_hyst, S_IWUSR | S_IRUGO, show_temp_hyst,
                          set_temp_hyst, t_crit);
static SENSOR_DEVICE_ATTR(temp1_min_hyst, S_IRUGO, show_temp_hyst, NULL, t_min);
static SENSOR_DEVICE_ATTR(temp1_max_hyst, S_IRUGO, show_temp_hyst, NULL, t_max);

static SENSOR_DEVICE_ATTR(temp1_crit_alarm, S_IRUGO, show_alarm, NULL, 2);
static SENSOR_DEVICE_ATTR(temp1_min_alarm, S_IRUGO, show_alarm, NULL, 0);
static SENSOR_DEVICE_ATTR(temp1_max_alarm, S_IRUGO, show_alarm, NULL, 1);

static struct attribute *lm77_attrs[] = {
        &sensor_dev_attr_temp1_input.dev_attr.attr,
        &sensor_dev_attr_temp1_crit.dev_attr.attr,
        &sensor_dev_attr_temp1_min.dev_attr.attr,
        &sensor_dev_attr_temp1_max.dev_attr.attr,
        &sensor_dev_attr_temp1_crit_hyst.dev_attr.attr,
        &sensor_dev_attr_temp1_min_hyst.dev_attr.attr,
        &sensor_dev_attr_temp1_max_hyst.dev_attr.attr,
        &sensor_dev_attr_temp1_crit_alarm.dev_attr.attr,
        &sensor_dev_attr_temp1_min_alarm.dev_attr.attr,
        &sensor_dev_attr_temp1_max_alarm.dev_attr.attr,
        NULL
};
ATTRIBUTE_GROUPS(lm77);

/* Return 0 if detection is successful, -ENODEV otherwise */
static int lm77_detect(struct i2c_client *client, struct i2c_board_info *info)
{
        struct i2c_adapter *adapter = client->adapter;
        int i, cur, conf, hyst, crit, min, max;

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
                                     I2C_FUNC_SMBUS_WORD_DATA))
                return -ENODEV;

        /*
         * Here comes the remaining detection.  Since the LM77 has no
         * register dedicated to identification, we have to rely on the
         * following tricks:
         *
         * 1. the high 4 bits represent the sign and thus they should
         *    always be the same
         * 2. the high 3 bits are unused in the configuration register
         * 3. addresses 0x06 and 0x07 return the last read value
         * 4. registers cycling over 8-address boundaries
         *
         * Word-sized registers are high-byte first.
         */

        /* addresses cycling */
        cur = i2c_smbus_read_word_data(client, 0);
        conf = i2c_smbus_read_byte_data(client, 1);
        hyst = i2c_smbus_read_word_data(client, 2);
        crit = i2c_smbus_read_word_data(client, 3);
        min = i2c_smbus_read_word_data(client, 4);
        max = i2c_smbus_read_word_data(client, 5);
        for (i = 8; i <= 0xff; i += 8) {
                if (i2c_smbus_read_byte_data(client, i + 1) != conf
                 || i2c_smbus_read_word_data(client, i + 2) != hyst
                 || i2c_smbus_read_word_data(client, i + 3) != crit
                 || i2c_smbus_read_word_data(client, i + 4) != min
                 || i2c_smbus_read_word_data(client, i + 5) != max)
                        return -ENODEV;
        }

        /* sign bits */
        if (((cur & 0x00f0) != 0xf0 && (cur & 0x00f0) != 0x0)
         || ((hyst & 0x00f0) != 0xf0 && (hyst & 0x00f0) != 0x0)
         || ((crit & 0x00f0) != 0xf0 && (crit & 0x00f0) != 0x0)
         || ((min & 0x00f0) != 0xf0 && (min & 0x00f0) != 0x0)
         || ((max & 0x00f0) != 0xf0 && (max & 0x00f0) != 0x0))
                return -ENODEV;

        /* unused bits */
        if (conf & 0xe0)
                return -ENODEV;

        /* 0x06 and 0x07 return the last read value */
        cur = i2c_smbus_read_word_data(client, 0);
        if (i2c_smbus_read_word_data(client, 6) != cur
         || i2c_smbus_read_word_data(client, 7) != cur)
                return -ENODEV;
        hyst = i2c_smbus_read_word_data(client, 2);
        if (i2c_smbus_read_word_data(client, 6) != hyst
         || i2c_smbus_read_word_data(client, 7) != hyst)
                return -ENODEV;
        min = i2c_smbus_read_word_data(client, 4);
        if (i2c_smbus_read_word_data(client, 6) != min
         || i2c_smbus_read_word_data(client, 7) != min)
                return -ENODEV;

        strlcpy(info->type, "lm77", I2C_NAME_SIZE);

        return 0;
}

static void lm77_init_client(struct i2c_client *client)
{
        /* Initialize the LM77 chip - turn off shutdown mode */
        int conf = lm77_read_value(client, LM77_REG_CONF);
        if (conf & 1)
                lm77_write_value(client, LM77_REG_CONF, conf & 0xfe);
}

static int lm77_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
        struct device *dev = &client->dev;
        struct device *hwmon_dev;
        struct lm77_data *data;

        data = devm_kzalloc(dev, sizeof(struct lm77_data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        data->client = client;
        mutex_init(&data->update_lock);

        /* Initialize the LM77 chip */
        lm77_init_client(client);

        hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
                                                           data, lm77_groups);
        return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct i2c_device_id lm77_id[] = {
        { "lm77", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, lm77_id);

/* This is the driver that will be inserted */
static struct i2c_driver lm77_driver = {
        .class          = I2C_CLASS_HWMON,
        .driver = {
                .name   = "lm77",
        },
        .probe          = lm77_probe,
        .id_table       = lm77_id,
        .detect         = lm77_detect,
        .address_list   = normal_i2c,
};

module_i2c_driver(lm77_driver);

MODULE_AUTHOR("Andras BALI <drewie@freemail.hu>");
MODULE_DESCRIPTION("LM77 driver");
MODULE_LICENSE("GPL");