mcp4725.c

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/*
 * mcp4725.c - Support for Microchip MCP4725
 *
 * Copyright (C) 2012 Peter Meerwald <[email protected]>
 *
 * Based on max517 by Roland Stigge <[email protected]>
 *
 * This file is subject to the terms and conditions of version 2 of
 * the GNU General Public License.  See the file COPYING in the main
 * directory of this archive for more details.
 *
 * driver for the Microchip I2C 12-bit digital-to-analog converter (DAC)
 * (7-bit I2C slave address 0x60, the three LSBs can be configured in
 * hardware)
 *
 * writing the DAC value to EEPROM is not supported
 */

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

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>

#include <linux/iio/dac/mcp4725.h>

#define MCP4725_DRV_NAME "mcp4725"

struct mcp4725_data {
    struct i2c_client *client;
    u16 vref_mv;
    u16 dac_value;
};

#ifdef CONFIG_PM_SLEEP
static int mcp4725_suspend(struct device *dev)
{
    u8 outbuf[2];

    outbuf[0] = 0x3 << 4; /* power-down bits, 500 kOhm resistor */
    outbuf[1] = 0;

    return i2c_master_send(to_i2c_client(dev), outbuf, 2);
}

static int mcp4725_resume(struct device *dev)
{
    struct iio_dev *indio_dev = dev_to_iio_dev(dev);
    struct mcp4725_data *data = iio_priv(indio_dev);
    u8 outbuf[2];

    /* restore previous DAC value */
    outbuf[0] = (data->dac_value >> 8) & 0xf;
    outbuf[1] = data->dac_value & 0xff;

    return i2c_master_send(to_i2c_client(dev), outbuf, 2);
}

static SIMPLE_DEV_PM_OPS(mcp4725_pm_ops, mcp4725_suspend, mcp4725_resume);
#define MCP4725_PM_OPS (&mcp4725_pm_ops)
#else
#define MCP4725_PM_OPS NULL
#endif

static const struct iio_chan_spec mcp4725_channel = {
    .type       = IIO_VOLTAGE,
    .indexed    = 1,
    .output     = 1,
    .channel    = 0,
    .info_mask  = IIO_CHAN_INFO_RAW_SEPARATE_BIT |
              IIO_CHAN_INFO_SCALE_SHARED_BIT,
    .scan_type  = IIO_ST('u', 12, 16, 0),
};

static int mcp4725_set_value(struct iio_dev *indio_dev, int val)
{
    struct mcp4725_data *data = iio_priv(indio_dev);
    u8 outbuf[2];
    int ret;

    if (val >= (1 << 12) || val < 0)
        return -EINVAL;

    outbuf[0] = (val >> 8) & 0xf;
    outbuf[1] = val & 0xff;

    ret = i2c_master_send(data->client, outbuf, 2);
    if (ret < 0)
        return ret;
    else if (ret != 2)
        return -EIO;
    else
        return 0;
}

static int mcp4725_read_raw(struct iio_dev *indio_dev,
               struct iio_chan_spec const *chan,
               int *val, int *val2, long mask)
{
    struct mcp4725_data *data = iio_priv(indio_dev);
    unsigned long scale_uv;

    switch (mask) {
    case IIO_CHAN_INFO_RAW:
        *val = data->dac_value;
        return IIO_VAL_INT;
    case IIO_CHAN_INFO_SCALE:
        scale_uv = (data->vref_mv * 1000) >> 12;
        *val =  scale_uv / 1000000;
        *val2 = scale_uv % 1000000;
        return IIO_VAL_INT_PLUS_MICRO;
    }
    return -EINVAL;
}

static int mcp4725_write_raw(struct iio_dev *indio_dev,
                   struct iio_chan_spec const *chan,
                   int val, int val2, long mask)
{
    struct mcp4725_data *data = iio_priv(indio_dev);
    int ret;

    switch (mask) {
    case IIO_CHAN_INFO_RAW:
        ret = mcp4725_set_value(indio_dev, val);
        data->dac_value = val;
        break;
    default:
        ret = -EINVAL;
        break;
    }

    return ret;
}

static const struct iio_info mcp4725_info = {
    .read_raw = mcp4725_read_raw,
    .write_raw = mcp4725_write_raw,
    .driver_module = THIS_MODULE,
};

static int __devinit mcp4725_probe(struct i2c_client *client,
            const struct i2c_device_id *id)
{
    struct mcp4725_data *data;
    struct iio_dev *indio_dev;
    struct mcp4725_platform_data *platform_data = client->dev.platform_data;
    u8 inbuf[3];
    int err;

    if (!platform_data || !platform_data->vref_mv) {
        dev_err(&client->dev, "invalid platform data");
        err = -EINVAL;
        goto exit;
    }

    indio_dev = iio_device_alloc(sizeof(*data));
    if (indio_dev == NULL) {
        err = -ENOMEM;
        goto exit;
    }
    data = iio_priv(indio_dev);
    i2c_set_clientdata(client, indio_dev);
    data->client = client;

    indio_dev->dev.parent = &client->dev;
    indio_dev->info = &mcp4725_info;
    indio_dev->channels = &mcp4725_channel;
    indio_dev->num_channels = 1;
    indio_dev->modes = INDIO_DIRECT_MODE;

    data->vref_mv = platform_data->vref_mv;

    /* read current DAC value */
    err = i2c_master_recv(client, inbuf, 3);
    if (err < 0) {
        dev_err(&client->dev, "failed to read DAC value");
        goto exit_free_device;
    }
    data->dac_value = (inbuf[1] << 4) | (inbuf[2] >> 4);

    err = iio_device_register(indio_dev);
    if (err)
        goto exit_free_device;

    dev_info(&client->dev, "MCP4725 DAC registered\n");

    return 0;

exit_free_device:
    iio_device_free(indio_dev);
exit:
    return err;
}

static int __devexit mcp4725_remove(struct i2c_client *client)
{
    struct iio_dev *indio_dev = i2c_get_clientdata(client);

    iio_device_unregister(indio_dev);
    iio_device_free(indio_dev);

    return 0;
}

static const struct i2c_device_id mcp4725_id[] = {
    { "mcp4725", 0 },
    { }
};
MODULE_DEVICE_TABLE(i2c, mcp4725_id);

static struct i2c_driver mcp4725_driver = {
    .driver = {
        .name   = MCP4725_DRV_NAME,
        .pm = MCP4725_PM_OPS,
    },
    .probe      = mcp4725_probe,
    .remove     = __devexit_p(mcp4725_remove),
    .id_table   = mcp4725_id,
};
module_i2c_driver(mcp4725_driver);

MODULE_AUTHOR("Peter Meerwald <[email protected]>");
MODULE_DESCRIPTION("MCP4725 12-bit DAC");
MODULE_LICENSE("GPL");