mcp9808: misc cleanups

mcp9808-cleanup.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>
#include <linux/iio/sysfs.h>

#define MCP9808_REG_TAMBIENT		0x05
#define MCP9808_REG_MANUF_ID		0x06
#define MCP9808_REG_DEVICE_ID		0x07
#define MCP9808_REG_RESOLUTION		0x08

#define MCP9808_MANUF_ID		0x54
#define MCP9808_DEVICE_ID		0x0400
#define MCP9808_DEVICE_ID_MASK		0xff00

struct mcp9808_data {
	struct i2c_client *client;
	struct mutex	   lock;	/* protect int_time change */
	int		   int_time;	/* sensor integration time */
};

/* Integration time in microseconds, MCP9808_REG_RESOLUTION bits */
static const int mcp9808_int_time[][2] = {
	{500000, 0},
	{250000, 1},
	{125000, 2},
	{ 62500, 3},
};

static IIO_CONST_ATTR(temp_integration_time_available,
		"0.5 0.25 0.125 0.0625");

static struct attribute *mcp9808_attributes[] = {
		&iio_const_attr_temp_integration_time_available.dev_attr.attr,
		NULL
};

static struct attribute_group mcp9808_attribute_group = {
		.attrs = mcp9808_attributes,
};

static int mcp9808_set_it_time(struct mcp9808_data *data, int val2)
{
	int ret = -EINVAL;
	int i;

	for (i = 0; i < ARRAY_SIZE(mcp9808_int_time); i++) {
		if (val2 == mcp9808_int_time[i][0]) {
			mutex_lock(&data->lock);
			ret = i2c_smbus_write_byte_data(data->client,
							MCP9808_REG_RESOLUTION,
							mcp9808_int_time[i][1]);
			data->int_time = val2;
			mutex_unlock(&data->lock);

			break;
		}
	}
	return ret;
}

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:
		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;

	case IIO_CHAN_INFO_INT_TIME:
		*val = 0;
		*val2 = data->int_time;
		return IIO_VAL_INT_PLUS_MICRO;

	default:
		break;
	}

	return -EINVAL;
}

static int mcp9808_write_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 = -EINVAL;

	if (mask == IIO_CHAN_INFO_INT_TIME) {
		if (!val)
			ret = mcp9808_set_it_time(data, val2);
	}
	return ret;
}

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

static const struct iio_info mcp9808_info = {
	.read_raw = mcp9808_read_raw,
	.write_raw = mcp9808_write_raw,
	.attrs = &mcp9808_attribute_group,
	.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;

	return ((mid == MCP9808_MANUF_ID) &&
		((did & MCP9808_DEVICE_ID_MASK) == MCP9808_DEVICE_ID));
}

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;
	mutex_init(&data->lock);
	data->int_time = 62500;  /* power-on default integration time */

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

	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");