// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * lm75.c - Part of lm_sensors, Linux kernel modules for hardware
 *       monitoring
 * Copyright (c) 1998, 1999  Frodo Looijaard <frodol@dds.nl>
 */

#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/of_device.h>
#include <linux/of.h>
#include <linux/regmap.h>
#include <linux/util_macros.h>
#include <linux/regulator/consumer.h>
#include "lm75.h"

/*
 * This driver handles the LM75 and compatible digital temperature sensors.
 */

enum lm75_type {                /* keep sorted in alphabetical order */
        adt75,
        ds1775,
        ds75,
        ds7505,
        g751,
        lm75,
        lm75a,
        lm75b,
        max6625,
        max6626,
        max31725,
        mcp980x,
        pct2075,
        stds75,
        stlm75,
        tcn75,
        tmp100,
        tmp101,
        tmp105,
        tmp112,
        tmp175,
        tmp275,
        tmp75,
        tmp75b,
        tmp75c,
        tmp1075,
};

/**
 * struct lm75_params - lm75 configuration parameters.
 * @set_mask:           Bits to set in configuration register when configuring
 *                      the chip.
 * @clr_mask:           Bits to clear in configuration register when configuring
 *                      the chip.
 * @default_resolution: Default number of bits to represent the temperature
 *                      value.
 * @resolution_limits:  Limit register resolution. Optional. Should be set if
 *                      the resolution of limit registers does not match the
 *                      resolution of the temperature register.
 * @resolutions:        List of resolutions associated with sample times.
 *                      Optional. Should be set if num_sample_times is larger
 *                      than 1, and if the resolution changes with sample times.
 *                      If set, number of entries must match num_sample_times.
 * @default_sample_time:Sample time to be set by default.
 * @num_sample_times:   Number of possible sample times to be set. Optional.
 *                      Should be set if the number of sample times is larger
 *                      than one.
 * @sample_times:       All the possible sample times to be set. Mandatory if
 *                      num_sample_times is larger than 1. If set, number of
 *                      entries must match num_sample_times.
 */

struct lm75_params {
        u8                      set_mask;
        u8                      clr_mask;
        u8                      default_resolution;
        u8                      resolution_limits;
        const u8                *resolutions;
        unsigned int            default_sample_time;
        u8                      num_sample_times;
        const unsigned int      *sample_times;
};

/* Addresses scanned */
static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b, 0x4c,
                                        0x4d, 0x4e, 0x4f, I2C_CLIENT_END };

/* The LM75 registers */
#define LM75_REG_TEMP           0x00
#define LM75_REG_CONF           0x01
#define LM75_REG_HYST           0x02
#define LM75_REG_MAX            0x03
#define PCT2075_REG_IDLE        0x04

/* Each client has this additional data */
struct lm75_data {
        struct i2c_client               *client;
        struct regmap                   *regmap;
        struct regulator                *vs;
        u8                              orig_conf;
        u8                              current_conf;
        u8                              resolution;     /* In bits, 9 to 16 */
        unsigned int                    sample_time;    /* In ms */
        enum lm75_type                  kind;
        const struct lm75_params        *params;
};

/*-----------------------------------------------------------------------*/

static const u8 lm75_sample_set_masks[] = { 0 << 5, 1 << 5, 2 << 5, 3 << 5 };

#define LM75_SAMPLE_CLEAR_MASK  (3 << 5)

/* The structure below stores the configuration values of the supported devices.
 * In case of being supported multiple configurations, the default one must
 * always be the first element of the array
 */
static const struct lm75_params device_params[] = {
        [adt75] = {
                .clr_mask = 1 << 5,     /* not one-shot mode */
                .default_resolution = 12,
                .default_sample_time = MSEC_PER_SEC / 10,
        },
        [ds1775] = {
                .clr_mask = 3 << 5,
                .set_mask = 2 << 5,     /* 11-bit mode */
                .default_resolution = 11,
                .default_sample_time = 500,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 125, 250, 500, 1000 },
                .resolutions = (u8 []) {9, 10, 11, 12 },
        },
        [ds75] = {
                .clr_mask = 3 << 5,
                .set_mask = 2 << 5,     /* 11-bit mode */
                .default_resolution = 11,
                .default_sample_time = 600,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 150, 300, 600, 1200 },
                .resolutions = (u8 []) {9, 10, 11, 12 },
        },
        [stds75] = {
                .clr_mask = 3 << 5,
                .set_mask = 2 << 5,     /* 11-bit mode */
                .default_resolution = 11,
                .default_sample_time = 600,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 150, 300, 600, 1200 },
                .resolutions = (u8 []) {9, 10, 11, 12 },
        },
        [stlm75] = {
                .default_resolution = 9,
                .default_sample_time = MSEC_PER_SEC / 6,
        },
        [ds7505] = {
                .set_mask = 3 << 5,     /* 12-bit mode*/
                .default_resolution = 12,
                .default_sample_time = 200,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 25, 50, 100, 200 },
                .resolutions = (u8 []) {9, 10, 11, 12 },
        },
        [g751] = {
                .default_resolution = 9,
                .default_sample_time = MSEC_PER_SEC / 10,
        },
        [lm75] = {
                .default_resolution = 9,
                .default_sample_time = MSEC_PER_SEC / 10,
        },
        [lm75a] = {
                .default_resolution = 9,
                .default_sample_time = MSEC_PER_SEC / 10,
        },
        [lm75b] = {
                .default_resolution = 11,
                .default_sample_time = MSEC_PER_SEC / 10,
        },
        [max6625] = {
                .default_resolution = 9,
                .default_sample_time = MSEC_PER_SEC / 7,
        },
        [max6626] = {
                .default_resolution = 12,
                .default_sample_time = MSEC_PER_SEC / 7,
                .resolution_limits = 9,
        },
        [max31725] = {
                .default_resolution = 16,
                .default_sample_time = MSEC_PER_SEC / 20,
        },
        [tcn75] = {
                .default_resolution = 9,
                .default_sample_time = MSEC_PER_SEC / 18,
        },
        [pct2075] = {
                .default_resolution = 11,
                .default_sample_time = MSEC_PER_SEC / 10,
                .num_sample_times = 31,
                .sample_times = (unsigned int []){ 100, 200, 300, 400, 500, 600,
                700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700,
                1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700,
                2800, 2900, 3000, 3100 },
        },
        [mcp980x] = {
                .set_mask = 3 << 5,     /* 12-bit mode */
                .clr_mask = 1 << 7,     /* not one-shot mode */
                .default_resolution = 12,
                .resolution_limits = 9,
                .default_sample_time = 240,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 30, 60, 120, 240 },
                .resolutions = (u8 []) {9, 10, 11, 12 },
        },
        [tmp100] = {
                .set_mask = 3 << 5,     /* 12-bit mode */
                .clr_mask = 1 << 7,     /* not one-shot mode */
                .default_resolution = 12,
                .default_sample_time = 320,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 40, 80, 160, 320 },
                .resolutions = (u8 []) {9, 10, 11, 12 },
        },
        [tmp101] = {
                .set_mask = 3 << 5,     /* 12-bit mode */
                .clr_mask = 1 << 7,     /* not one-shot mode */
                .default_resolution = 12,
                .default_sample_time = 320,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 40, 80, 160, 320 },
                .resolutions = (u8 []) {9, 10, 11, 12 },
        },
        [tmp105] = {
                .set_mask = 3 << 5,     /* 12-bit mode */
                .clr_mask = 1 << 7,     /* not one-shot mode*/
                .default_resolution = 12,
                .default_sample_time = 220,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 28, 55, 110, 220 },
                .resolutions = (u8 []) {9, 10, 11, 12 },
        },
        [tmp112] = {
                .set_mask = 3 << 5,     /* 8 samples / second */
                .clr_mask = 1 << 7,     /* no one-shot mode*/
                .default_resolution = 12,
                .default_sample_time = 125,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 125, 250, 1000, 4000 },
        },
        [tmp175] = {
                .set_mask = 3 << 5,     /* 12-bit mode */
                .clr_mask = 1 << 7,     /* not one-shot mode*/
                .default_resolution = 12,
                .default_sample_time = 220,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 28, 55, 110, 220 },
                .resolutions = (u8 []) {9, 10, 11, 12 },
        },
        [tmp275] = {
                .set_mask = 3 << 5,     /* 12-bit mode */
                .clr_mask = 1 << 7,     /* not one-shot mode*/
                .default_resolution = 12,
                .default_sample_time = 220,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 28, 55, 110, 220 },
                .resolutions = (u8 []) {9, 10, 11, 12 },
        },
        [tmp75] = {
                .set_mask = 3 << 5,     /* 12-bit mode */
                .clr_mask = 1 << 7,     /* not one-shot mode*/
                .default_resolution = 12,
                .default_sample_time = 220,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 28, 55, 110, 220 },
                .resolutions = (u8 []) {9, 10, 11, 12 },
        },
        [tmp75b] = { /* not one-shot mode, Conversion rate 37Hz */
                .clr_mask = 1 << 7 | 3 << 5,
                .default_resolution = 12,
                .default_sample_time = MSEC_PER_SEC / 37,
                .sample_times = (unsigned int []){ MSEC_PER_SEC / 37,
                        MSEC_PER_SEC / 18,
                        MSEC_PER_SEC / 9, MSEC_PER_SEC / 4 },
                .num_sample_times = 4,
        },
        [tmp75c] = {
                .clr_mask = 1 << 5,     /*not one-shot mode*/
                .default_resolution = 12,
                .default_sample_time = MSEC_PER_SEC / 12,
        },
        [tmp1075] = { /* not one-shot mode, 27.5 ms sample rate */
                .clr_mask = 1 << 5 | 1 << 6 | 1 << 7,
                .default_resolution = 12,
                .default_sample_time = 28,
                .num_sample_times = 4,
                .sample_times = (unsigned int []){ 28, 55, 110, 220 },
        }
};

static inline long lm75_reg_to_mc(s16 temp, u8 resolution)
{
        return ((temp >> (16 - resolution)) * 1000) >> (resolution - 8);
}

static int lm75_write_config(struct lm75_data *data, u8 set_mask,
                             u8 clr_mask)
{
        u8 value;

        clr_mask |= LM75_SHUTDOWN;
        value = data->current_conf & ~clr_mask;
        value |= set_mask;

        if (data->current_conf != value) {
                s32 err;

                err = i2c_smbus_write_byte_data(data->client, LM75_REG_CONF,
                                                value);
                if (err)
                        return err;
                data->current_conf = value;
        }
        return 0;
}

static int lm75_read(struct device *dev, enum hwmon_sensor_types type,
                     u32 attr, int channel, long *val)
{
        struct lm75_data *data = dev_get_drvdata(dev);
        unsigned int regval;
        int err, reg;

        switch (type) {
        case hwmon_chip:
                switch (attr) {
                case hwmon_chip_update_interval:
                        *val = data->sample_time;
                        break;
                default:
                        return -EINVAL;
                }
                break;
        case hwmon_temp:
                switch (attr) {
                case hwmon_temp_input:
                        reg = LM75_REG_TEMP;
                        break;
                case hwmon_temp_max:
                        reg = LM75_REG_MAX;
                        break;
                case hwmon_temp_max_hyst:
                        reg = LM75_REG_HYST;
                        break;
                default:
                        return -EINVAL;
                }
                err = regmap_read(data->regmap, reg, &regval);
                if (err < 0)
                        return err;

                *val = lm75_reg_to_mc(regval, data->resolution);
                break;
        default:
                return -EINVAL;
        }
        return 0;
}

static int lm75_write_temp(struct device *dev, u32 attr, long temp)
{
        struct lm75_data *data = dev_get_drvdata(dev);
        u8 resolution;
        int reg;

        switch (attr) {
        case hwmon_temp_max:
                reg = LM75_REG_MAX;
                break;
        case hwmon_temp_max_hyst:
                reg = LM75_REG_HYST;
                break;
        default:
                return -EINVAL;
        }

        /*
         * Resolution of limit registers is assumed to be the same as the
         * temperature input register resolution unless given explicitly.
         */
        if (data->params->resolution_limits)
                resolution = data->params->resolution_limits;
        else
                resolution = data->resolution;

        temp = clamp_val(temp, LM75_TEMP_MIN, LM75_TEMP_MAX);
        temp = DIV_ROUND_CLOSEST(temp  << (resolution - 8),
                                 1000) << (16 - resolution);

        return regmap_write(data->regmap, reg, (u16)temp);
}

static int lm75_update_interval(struct device *dev, long val)
{
        struct lm75_data *data = dev_get_drvdata(dev);
        unsigned int reg;
        u8 index;
        s32 err;

        index = find_closest(val, data->params->sample_times,
                             (int)data->params->num_sample_times);

        switch (data->kind) {
        default:
                err = lm75_write_config(data, lm75_sample_set_masks[index],
                                        LM75_SAMPLE_CLEAR_MASK);
                if (err)
                        return err;

                data->sample_time = data->params->sample_times[index];
                if (data->params->resolutions)
                        data->resolution = data->params->resolutions[index];
                break;
        case tmp112:
                err = regmap_read(data->regmap, LM75_REG_CONF, &reg);
                if (err < 0)
                        return err;
                reg &= ~0x00c0;
                reg |= (3 - index) << 6;
                err = regmap_write(data->regmap, LM75_REG_CONF, reg);
                if (err < 0)
                        return err;
                data->sample_time = data->params->sample_times[index];
                break;
        case pct2075:
                err = i2c_smbus_write_byte_data(data->client, PCT2075_REG_IDLE,
                                                index + 1);
                if (err)
                        return err;
                data->sample_time = data->params->sample_times[index];
                break;
        }
        return 0;
}

static int lm75_write_chip(struct device *dev, u32 attr, long val)
{
        switch (attr) {
        case hwmon_chip_update_interval:
                return lm75_update_interval(dev, val);
        default:
                return -EINVAL;
        }
        return 0;
}

static int lm75_write(struct device *dev, enum hwmon_sensor_types type,
                      u32 attr, int channel, long val)
{
        switch (type) {
        case hwmon_chip:
                return lm75_write_chip(dev, attr, val);
        case hwmon_temp:
                return lm75_write_temp(dev, attr, val);
        default:
                return -EINVAL;
        }
        return 0;
}

static umode_t lm75_is_visible(const void *data, enum hwmon_sensor_types type,
                               u32 attr, int channel)
{
        const struct lm75_data *config_data = data;

        switch (type) {
        case hwmon_chip:
                switch (attr) {
                case hwmon_chip_update_interval:
                        if (config_data->params->num_sample_times > 1)
                                return 0644;
                        return 0444;
                }
                break;
        case hwmon_temp:
                switch (attr) {
                case hwmon_temp_input:
                        return 0444;
                case hwmon_temp_max:
                case hwmon_temp_max_hyst:
                        return 0644;
                }
                break;
        default:
                break;
        }
        return 0;
}

static const struct hwmon_channel_info *lm75_info[] = {
        HWMON_CHANNEL_INFO(chip,
                           HWMON_C_REGISTER_TZ | HWMON_C_UPDATE_INTERVAL),
        HWMON_CHANNEL_INFO(temp,
                           HWMON_T_INPUT | HWMON_T_MAX | HWMON_T_MAX_HYST),
        NULL
};

static const struct hwmon_ops lm75_hwmon_ops = {
        .is_visible = lm75_is_visible,
        .read = lm75_read,
        .write = lm75_write,
};

static const struct hwmon_chip_info lm75_chip_info = {
        .ops = &lm75_hwmon_ops,
        .info = lm75_info,
};

static bool lm75_is_writeable_reg(struct device *dev, unsigned int reg)
{
        return reg != LM75_REG_TEMP;
}

static bool lm75_is_volatile_reg(struct device *dev, unsigned int reg)
{
        return reg == LM75_REG_TEMP || reg == LM75_REG_CONF;
}

static const struct regmap_config lm75_regmap_config = {
        .reg_bits = 8,
        .val_bits = 16,
        .max_register = PCT2075_REG_IDLE,
        .writeable_reg = lm75_is_writeable_reg,
        .volatile_reg = lm75_is_volatile_reg,
        .val_format_endian = REGMAP_ENDIAN_BIG,
        .cache_type = REGCACHE_RBTREE,
        .use_single_read = true,
        .use_single_write = true,
};

static void lm75_disable_regulator(void *data)
{
        struct lm75_data *lm75 = data;

        regulator_disable(lm75->vs);
}

static void lm75_remove(void *data)
{
        struct lm75_data *lm75 = data;
        struct i2c_client *client = lm75->client;

        i2c_smbus_write_byte_data(client, LM75_REG_CONF, lm75->orig_conf);
}

static const struct i2c_device_id lm75_ids[];

static int lm75_probe(struct i2c_client *client)
{
        struct device *dev = &client->dev;
        struct device *hwmon_dev;
        struct lm75_data *data;
        int status, err;
        enum lm75_type kind;

        if (client->dev.of_node)
                kind = (enum lm75_type)of_device_get_match_data(&client->dev);
        else
                kind = i2c_match_id(lm75_ids, client)->driver_data;

        if (!i2c_check_functionality(client->adapter,
                        I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA))
                return -EIO;

        data = devm_kzalloc(dev, sizeof(struct lm75_data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        data->client = client;
        data->kind = kind;

        data->vs = devm_regulator_get(dev, "vs");
        if (IS_ERR(data->vs))
                return PTR_ERR(data->vs);

        data->regmap = devm_regmap_init_i2c(client, &lm75_regmap_config);
        if (IS_ERR(data->regmap))
                return PTR_ERR(data->regmap);

        /* Set to LM75 resolution (9 bits, 1/2 degree C) and range.
         * Then tweak to be more precise when appropriate.
         */

        data->params = &device_params[data->kind];

        /* Save default sample time and resolution*/
        data->sample_time = data->params->default_sample_time;
        data->resolution = data->params->default_resolution;

        /* Enable the power */
        err = regulator_enable(data->vs);
        if (err) {
                dev_err(dev, "failed to enable regulator: %d\n", err);
                return err;
        }

        err = devm_add_action_or_reset(dev, lm75_disable_regulator, data);
        if (err)
                return err;

        /* Cache original configuration */
        status = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
        if (status < 0) {
                dev_dbg(dev, "Can't read config? %d\n", status);
                return status;
        }
        data->orig_conf = status;
        data->current_conf = status;

        err = lm75_write_config(data, data->params->set_mask,
                                data->params->clr_mask);
        if (err)
                return err;

        err = devm_add_action_or_reset(dev, lm75_remove, data);
        if (err)
                return err;

        hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
                                                         data, &lm75_chip_info,
                                                         NULL);
        if (IS_ERR(hwmon_dev))
                return PTR_ERR(hwmon_dev);

        dev_info(dev, "%s: sensor '%s'\n", dev_name(hwmon_dev), client->name);

        return 0;
}

static const struct i2c_device_id lm75_ids[] = {
        { "adt75", adt75, },
        { "ds1775", ds1775, },
        { "ds75", ds75, },
        { "ds7505", ds7505, },
        { "g751", g751, },
        { "lm75", lm75, },
        { "lm75a", lm75a, },
        { "lm75b", lm75b, },
        { "max6625", max6625, },
        { "max6626", max6626, },
        { "max31725", max31725, },
        { "max31726", max31725, },
        { "mcp980x", mcp980x, },
        { "pct2075", pct2075, },
        { "stds75", stds75, },
        { "stlm75", stlm75, },
        { "tcn75", tcn75, },
        { "tmp100", tmp100, },
        { "tmp101", tmp101, },
        { "tmp105", tmp105, },
        { "tmp112", tmp112, },
        { "tmp175", tmp175, },
        { "tmp275", tmp275, },
        { "tmp75", tmp75, },
        { "tmp75b", tmp75b, },
        { "tmp75c", tmp75c, },
        { "tmp1075", tmp1075, },
        { /* LIST END */ }
};
MODULE_DEVICE_TABLE(i2c, lm75_ids);

static const struct of_device_id __maybe_unused lm75_of_match[] = {
        {
                .compatible = "adi,adt75",
                .data = (void *)adt75
        },
        {
                .compatible = "dallas,ds1775",
                .data = (void *)ds1775
        },
        {
                .compatible = "dallas,ds75",
                .data = (void *)ds75
        },
        {
                .compatible = "dallas,ds7505",
                .data = (void *)ds7505
        },
        {
                .compatible = "gmt,g751",
                .data = (void *)g751
        },
        {
                .compatible = "national,lm75",
                .data = (void *)lm75
        },
        {
                .compatible = "national,lm75a",
                .data = (void *)lm75a
        },
        {
                .compatible = "national,lm75b",
                .data = (void *)lm75b
        },
        {
                .compatible = "maxim,max6625",
                .data = (void *)max6625
        },
        {
                .compatible = "maxim,max6626",
                .data = (void *)max6626
        },
        {
                .compatible = "maxim,max31725",
                .data = (void *)max31725
        },
        {
                .compatible = "maxim,max31726",
                .data = (void *)max31725
        },
        {
                .compatible = "maxim,mcp980x",
                .data = (void *)mcp980x
        },
        {
                .compatible = "nxp,pct2075",
                .data = (void *)pct2075
        },
        {
                .compatible = "st,stds75",
                .data = (void *)stds75
        },
        {
                .compatible = "st,stlm75",
                .data = (void *)stlm75
        },
        {
                .compatible = "microchip,tcn75",
                .data = (void *)tcn75
        },
        {
                .compatible = "ti,tmp100",
                .data = (void *)tmp100
        },
        {
                .compatible = "ti,tmp101",
                .data = (void *)tmp101
        },
        {
                .compatible = "ti,tmp105",
                .data = (void *)tmp105
        },
        {
                .compatible = "ti,tmp112",
                .data = (void *)tmp112
        },
        {
                .compatible = "ti,tmp175",
                .data = (void *)tmp175
        },
        {
                .compatible = "ti,tmp275",
                .data = (void *)tmp275
        },
        {
                .compatible = "ti,tmp75",
                .data = (void *)tmp75
        },
        {
                .compatible = "ti,tmp75b",
                .data = (void *)tmp75b
        },
        {
                .compatible = "ti,tmp75c",
                .data = (void *)tmp75c
        },
        {
                .compatible = "ti,tmp1075",
                .data = (void *)tmp1075
        },
        { },
};
MODULE_DEVICE_TABLE(of, lm75_of_match);

#define LM75A_ID 0xA1

/* Return 0 if detection is successful, -ENODEV otherwise */
static int lm75_detect(struct i2c_client *new_client,
                       struct i2c_board_info *info)
{
        struct i2c_adapter *adapter = new_client->adapter;
        int i;
        int conf, hyst, os;
        bool is_lm75a = 0;

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

        /*
         * Now, we do the remaining detection. There is no identification-
         * dedicated register so we have to rely on several tricks:
         * unused bits, registers cycling over 8-address boundaries,
         * addresses 0x04-0x07 returning the last read value.
         * The cycling+unused addresses combination is not tested,
         * since it would significantly slow the detection down and would
         * hardly add any value.
         *
         * The National Semiconductor LM75A is different than earlier
         * LM75s.  It has an ID byte of 0xaX (where X is the chip
         * revision, with 1 being the only revision in existence) in
         * register 7, and unused registers return 0xff rather than the
         * last read value.
         *
         * Note that this function only detects the original National
         * Semiconductor LM75 and the LM75A. Clones from other vendors
         * aren't detected, on purpose, because they are typically never
         * found on PC hardware. They are found on embedded designs where
         * they can be instantiated explicitly so detection is not needed.
         * The absence of identification registers on all these clones
         * would make their exhaustive detection very difficult and weak,
         * and odds are that the driver would bind to unsupported devices.
         */

        /* Unused bits */
        conf = i2c_smbus_read_byte_data(new_client, 1);
        if (conf & 0xe0)
                return -ENODEV;

        /* First check for LM75A */
        if (i2c_smbus_read_byte_data(new_client, 7) == LM75A_ID) {
                /*
                 * LM75A returns 0xff on unused registers so
                 * just to be sure we check for that too.
                 */
                if (i2c_smbus_read_byte_data(new_client, 4) != 0xff
                 || i2c_smbus_read_byte_data(new_client, 5) != 0xff
                 || i2c_smbus_read_byte_data(new_client, 6) != 0xff)
                        return -ENODEV;
                is_lm75a = 1;
                hyst = i2c_smbus_read_byte_data(new_client, 2);
                os = i2c_smbus_read_byte_data(new_client, 3);
        } else { /* Traditional style LM75 detection */
                /* Unused addresses */
                hyst = i2c_smbus_read_byte_data(new_client, 2);
                if (i2c_smbus_read_byte_data(new_client, 4) != hyst
                 || i2c_smbus_read_byte_data(new_client, 5) != hyst
                 || i2c_smbus_read_byte_data(new_client, 6) != hyst
                 || i2c_smbus_read_byte_data(new_client, 7) != hyst)
                        return -ENODEV;
                os = i2c_smbus_read_byte_data(new_client, 3);
                if (i2c_smbus_read_byte_data(new_client, 4) != os
                 || i2c_smbus_read_byte_data(new_client, 5) != os
                 || i2c_smbus_read_byte_data(new_client, 6) != os
                 || i2c_smbus_read_byte_data(new_client, 7) != os)
                        return -ENODEV;
        }
        /*
         * It is very unlikely that this is a LM75 if both
         * hysteresis and temperature limit registers are 0.
         */
        if (hyst == 0 && os == 0)
                return -ENODEV;

        /* Addresses cycling */
        for (i = 8; i <= 248; i += 40) {
                if (i2c_smbus_read_byte_data(new_client, i + 1) != conf
                 || i2c_smbus_read_byte_data(new_client, i + 2) != hyst
                 || i2c_smbus_read_byte_data(new_client, i + 3) != os)
                        return -ENODEV;
                if (is_lm75a && i2c_smbus_read_byte_data(new_client, i + 7)
                                != LM75A_ID)
                        return -ENODEV;
        }

        strlcpy(info->type, is_lm75a ? "lm75a" : "lm75", I2C_NAME_SIZE);

        return 0;
}

#ifdef CONFIG_PM
static int lm75_suspend(struct device *dev)
{
        int status;
        struct i2c_client *client = to_i2c_client(dev);

        status = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
        if (status < 0) {
                dev_dbg(&client->dev, "Can't read config? %d\n", status);
                return status;
        }
        status = status | LM75_SHUTDOWN;
        i2c_smbus_write_byte_data(client, LM75_REG_CONF, status);
        return 0;
}

static int lm75_resume(struct device *dev)
{
        int status;
        struct i2c_client *client = to_i2c_client(dev);

        status = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
        if (status < 0) {
                dev_dbg(&client->dev, "Can't read config? %d\n", status);
                return status;
        }
        status = status & ~LM75_SHUTDOWN;
        i2c_smbus_write_byte_data(client, LM75_REG_CONF, status);
        return 0;
}

static const struct dev_pm_ops lm75_dev_pm_ops = {
        .suspend        = lm75_suspend,
        .resume         = lm75_resume,
};
#define LM75_DEV_PM_OPS (&lm75_dev_pm_ops)
#else
#define LM75_DEV_PM_OPS NULL
#endif /* CONFIG_PM */

static struct i2c_driver lm75_driver = {
        .class          = I2C_CLASS_HWMON,
        .driver = {
                .name   = "lm75",
                .of_match_table = of_match_ptr(lm75_of_match),
                .pm     = LM75_DEV_PM_OPS,
        },
        .probe_new      = lm75_probe,
        .id_table       = lm75_ids,
        .detect         = lm75_detect,
        .address_list   = normal_i2c,
};

module_i2c_driver(lm75_driver);

MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl>");
MODULE_DESCRIPTION("LM75 driver");
MODULE_LICENSE("GPL");