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/*
* 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");
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