hwmon: Add MCP3021 ADC driver

Kernel driver MCP3021

======================

Supported chips:

  * Microchip Technology MCP3021

    Prefix: 'mcp3021'

    Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/21805a.pdf

Author: Mingkai Hu

Description

-----------

This driver implements support for the Microchip Technology MCP3021 chip.

The Microchip Technology Inc. MCP3021 is a successive approximation A/D

converter (ADC) with 10-bit resolution.

This device provides one single-ended input with very low power consumption.

Communication to the MCP3021 is performed using a 2-wire I2C compatible

interface. Standard (100 kHz) and Fast (400 kHz) I2C modes are available.

The default I2C device address is 0x4d (contact the Microchip factory for

additional address options).

	  This driver can also be built as a module.  If so, the module

	  will be called max6650.

config SENSORS_MCP3021

	tristate "Microchip MCP3021"

	depends on I2C && EXPERIMENTAL

	help

	  If you say yes here you get support for the MCP3021 chip

	  that is a A/D converter (ADC) with 10-bit resolution.

	  This driver can also be built as a module.  If so, the module

	  will be called mcp3021.

config SENSORS_NTC_THERMISTOR

	tristate "NTC thermistor support"

	depends on EXPERIMENTAL

obj-$(CONFIG_SENSORS_MAX6642)	+= max6642.o

obj-$(CONFIG_SENSORS_MAX6650)	+= max6650.o

obj-$(CONFIG_SENSORS_MC13783_ADC)+= mc13783-adc.o

obj-$(CONFIG_SENSORS_MCP3021)	+= mcp3021.o

obj-$(CONFIG_SENSORS_NTC_THERMISTOR)	+= ntc_thermistor.o

obj-$(CONFIG_SENSORS_PC87360)	+= pc87360.o

obj-$(CONFIG_SENSORS_PC87427)	+= pc87427.o

/*

 * mcp3021.c - driver for the Microchip MCP3021 chip

 *

 * Copyright (C) 2008-2009, 2012 Freescale Semiconductor, Inc.

 * Author: Mingkai Hu <Mingkai.hu@freescale.com>

 *

 * 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

/*

 * Client data (each client gets its own)

 */

struct mcp3021_data {

	struct device *hwmon_dev;

	u32 vdd;	/* device power supply */

};

static int mcp3021_read16(struct i2c_client *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 >> MCP3021_SAR_SHIFT) & MCP3021_SAR_MASK;

	return reg;

}

static inline u16 volts_from_reg(u16 vdd, u16 val)

{

	if (val == 0)

		return 0;

	val = val * MCP3021_OUTPUT_SCALE - MCP3021_OUTPUT_SCALE / 2;

	return val * DIV_ROUND_CLOSEST(vdd,

			(1 << MCP3021_OUTPUT_RES) * MCP3021_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->vdd, 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 = kzalloc(sizeof(struct mcp3021_data), GFP_KERNEL);

	if (!data)

		return -ENOMEM;

	i2c_set_clientdata(client, data);

	if (client->dev.platform_data) {

		data->vdd = *(u32 *)client->dev.platform_data;

		if (data->vdd > MCP3021_VDD_MAX ||

				data->vdd < MCP3021_VDD_MIN) {

			err = -EINVAL;

			goto exit_free;

		}

	} else

		data->vdd = MCP3021_VDD_REF;

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

	if (err)

		goto exit_free;

	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);

exit_free:

	kfree(data);

	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);

	kfree(data);

	return 0;

}

static const struct i2c_device_id mcp3021_id[] = {

	{ "mcp3021", 0 },

	{ }

};

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 <Mingkai.hu@freescale.com>");

MODULE_DESCRIPTION("Microchip MCP3021 driver");

MODULE_LICENSE("GPL");