mcp9808: version 2 of the temp calculation

mcp9808-calc-v2.c

/*
 * mcp9808.c - Support for Microchip MCP9808 Digital Temperature Sensor
 *
 * Copyright (C) 2016 Alison Schofield <amsfield22@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/25095A.pdf
 */

#include <linux/i2c.h>
#include <linux/module.h>

#include <linux/iio/iio.h>


#define MCP9808_REG_TAMBIENT		0x05
#define MCP9808_REG_MANUF_ID		0x06
#define MCP9808_REG_DEVICE_ID		0x07


struct mcp9808_data {
	struct i2c_client *client;
};

static int mcp9808_read_raw(struct iio_dev *indio_dev,
			    struct iio_chan_spec const *channel,
			    int *val, int *val2, long mask)

{
	struct mcp9808_data *data = iio_priv(indio_dev);
	int ret;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		if (channel->type == IIO_TEMP) {
			ret = i2c_smbus_read_word_swapped(data->client,
							MCP9808_REG_TAMBIENT);
		if (ret < 0)
			return ret;
		*val = sign_extend32(ret, 12);
		return IIO_VAL_INT;
		}
	case IIO_CHAN_INFO_SCALE:
		*val = 0;
		*val2 = 62500;
		return IIO_VAL_INT_PLUS_MICRO;

	default:
		break;
	}

	return -EINVAL;
}

static const struct iio_chan_spec mcp9808_channels[] = {
	{
		.type = IIO_TEMP,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
			BIT(IIO_CHAN_INFO_SCALE)
	}
};

static const struct iio_info mcp9808_info = {
	.read_raw = mcp9808_read_raw,
	.driver_module = THIS_MODULE,
};

static bool mcp9808_check_id(struct i2c_client *client)
{
	int mid, did;

	mid = i2c_smbus_read_word_swapped(client, MCP9808_REG_MANUF_ID);
	if (mid < 0)
		return false;

	did = i2c_smbus_read_word_swapped(client, MCP9808_REG_DEVICE_ID);
	if (did < 0)
		return false;

	if ((mid == 0x54) && ((did & 0xff00) == 0x0400)) {
		dev_info(&client->dev, "MCP9808 Temperature Sensor\n");
		dev_info(&client->dev,
			"MCP9808 Manuf_id: 0x54 Device_id: 0x04 Rev: 0x%x\n",
			 (did & 0x0f));
		return true;
	}
	return false;
}

static int mcp9808_probe(struct i2c_client *client,
			 const struct i2c_device_id *id)
{
	struct iio_dev *indio_dev;
	struct mcp9808_data *data;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
		return -EOPNOTSUPP;

	if (!mcp9808_check_id(client)) {
		dev_err(&client->dev, "no MCP9808 sensor\n");
		return -ENODEV;
	}

	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
	if (!indio_dev)
		return -ENOMEM;

	data = iio_priv(indio_dev);
	i2c_set_clientdata(client, indio_dev);
	data->client = client;

	indio_dev->dev.parent = &client->dev;
	indio_dev->name = id->name;
	indio_dev->info = &mcp9808_info;

	indio_dev->channels = mcp9808_channels;
	indio_dev->num_channels = ARRAY_SIZE(mcp9808_channels);

	return devm_iio_device_register(&client->dev, indio_dev);
}

static const struct i2c_device_id mcp9808_id[] = {
	{ "mcp9808", 0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, mcp9808_id);

static struct i2c_driver mcp9808_driver = {
	.driver = {
		.name	= "mcp9808",
	},
	.probe = mcp9808_probe,
	.id_table = mcp9808_id,
};
module_i2c_driver(mcp9808_driver);

MODULE_AUTHOR("Alison Schofield <amsfield22@gmail.com>");
MODULE_DESCRIPTION("MCP9808 Temperature Sensor Driver");
MODULE_LICENSE("GPL v2");