mcp3021.c

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/*
 * mcp3021.c - driver for Microchip MCP3021 and MCP3221
 *
 * Copyright (C) 2008-2009, 2012 Freescale Semiconductor, Inc.
 * Author: Mingkai Hu <[email protected]>
 * Reworked by Sven Schuchmann <[email protected]>
 *
 * This driver export the value of analog input voltage to sysfs, the
 * voltage unit is mV. Through the sysfs interface, lm-sensors tool
 * can also display the input voltage.
 *
 * 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.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/hwmon.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/err.h>
#include <linux/device.h>

/* Vdd info */
#define MCP3021_VDD_MAX     5500
#define MCP3021_VDD_MIN     2700
#define MCP3021_VDD_REF     3300

/* output format */
#define MCP3021_SAR_SHIFT   2
#define MCP3021_SAR_MASK    0x3ff

#define MCP3021_OUTPUT_RES  10  /* 10-bit resolution */
#define MCP3021_OUTPUT_SCALE    4

#define MCP3221_SAR_SHIFT   0
#define MCP3221_SAR_MASK    0xfff
#define MCP3221_OUTPUT_RES  12  /* 12-bit resolution */
#define MCP3221_OUTPUT_SCALE    1

enum chips {
    mcp3021,
    mcp3221
};

/*
 * Client data (each client gets its own)
 */
struct mcp3021_data {
    struct device *hwmon_dev;
    u32 vdd;    /* device power supply */
    u16 sar_shift;
    u16 sar_mask;
    u8 output_res;
    u8 output_scale;
};

static int mcp3021_read16(struct i2c_client *client)
{
    struct mcp3021_data *data = i2c_get_clientdata(client);
    int ret;
    u16 reg;
    __be16 buf;

    ret = i2c_master_recv(client, (char *)&buf, 2);
    if (ret < 0)
        return ret;
    if (ret != 2)
        return -EIO;

    /* The output code of the MCP3021 is transmitted with MSB first. */
    reg = be16_to_cpu(buf);

    /*
     * The ten-bit output code is composed of the lower 4-bit of the
     * first byte and the upper 6-bit of the second byte.
     */
    reg = (reg >> data->sar_shift) & data->sar_mask;

    return reg;
}

static inline u16 volts_from_reg(struct mcp3021_data *data, u16 val)
{
    if (val == 0)
        return 0;

    val = val * data->output_scale - data->output_scale / 2;

    return val * DIV_ROUND_CLOSEST(data->vdd,
            (1 << data->output_res) * data->output_scale);
}

static ssize_t show_in_input(struct device *dev, struct device_attribute *attr,
        char *buf)
{
    struct i2c_client *client = to_i2c_client(dev);
    struct mcp3021_data *data = i2c_get_clientdata(client);
    int reg, in_input;

    reg = mcp3021_read16(client);
    if (reg < 0)
        return reg;

    in_input = volts_from_reg(data, reg);

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

static DEVICE_ATTR(in0_input, S_IRUGO, show_in_input, NULL);

static int mcp3021_probe(struct i2c_client *client,
                const struct i2c_device_id *id)
{
    int err;
    struct mcp3021_data *data = NULL;

    if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
        return -ENODEV;

    data = devm_kzalloc(&client->dev, sizeof(struct mcp3021_data),
                GFP_KERNEL);
    if (!data)
        return -ENOMEM;

    i2c_set_clientdata(client, data);

    switch (id->driver_data) {
    case mcp3021:
        data->sar_shift = MCP3021_SAR_SHIFT;
        data->sar_mask = MCP3021_SAR_MASK;
        data->output_res = MCP3021_OUTPUT_RES;
        data->output_scale = MCP3021_OUTPUT_SCALE;
        break;

    case mcp3221:
        data->sar_shift = MCP3221_SAR_SHIFT;
        data->sar_mask = MCP3221_SAR_MASK;
        data->output_res = MCP3221_OUTPUT_RES;
        data->output_scale = MCP3221_OUTPUT_SCALE;
        break;
    }

    if (client->dev.platform_data) {
        data->vdd = *(u32 *)client->dev.platform_data;
        if (data->vdd > MCP3021_VDD_MAX || data->vdd < MCP3021_VDD_MIN)
            return -EINVAL;
    } else
        data->vdd = MCP3021_VDD_REF;

    err = sysfs_create_file(&client->dev.kobj, &dev_attr_in0_input.attr);
    if (err)
        return err;

    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_file(&client->dev.kobj, &dev_attr_in0_input.attr);
    return err;
}

static int mcp3021_remove(struct i2c_client *client)
{
    struct mcp3021_data *data = i2c_get_clientdata(client);

    hwmon_device_unregister(data->hwmon_dev);
    sysfs_remove_file(&client->dev.kobj, &dev_attr_in0_input.attr);

    return 0;
}

static const struct i2c_device_id mcp3021_id[] = {
    { "mcp3021", mcp3021 },
    { "mcp3221", mcp3221 },
    { }
};
MODULE_DEVICE_TABLE(i2c, mcp3021_id);

static struct i2c_driver mcp3021_driver = {
    .driver = {
        .name = "mcp3021",
    },
    .probe = mcp3021_probe,
    .remove = mcp3021_remove,
    .id_table = mcp3021_id,
};

module_i2c_driver(mcp3021_driver);

MODULE_AUTHOR("Mingkai Hu <[email protected]>");
MODULE_DESCRIPTION("Microchip MCP3021/MCP3221 driver");
MODULE_LICENSE("GPL");