ad8366.c

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/*
 * AD8366 SPI Dual-Digital Variable Gain Amplifier (VGA)
 *
 * Copyright 2012 Analog Devices Inc.
 *
 * Licensed under the GPL-2.
 */

#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/sysfs.h>
#include <linux/spi/spi.h>
#include <linux/regulator/consumer.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/bitrev.h>

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

struct ad8366_state {
    struct spi_device   *spi;
    struct regulator    *reg;
    unsigned char       ch[2];
    /*
     * DMA (thus cache coherency maintenance) requires the
     * transfer buffers to live in their own cache lines.
     */
    unsigned char       data[2] ____cacheline_aligned;
};

static int ad8366_write(struct iio_dev *indio_dev,
            unsigned char ch_a, char unsigned ch_b)
{
    struct ad8366_state *st = iio_priv(indio_dev);
    int ret;

    ch_a = bitrev8(ch_a & 0x3F);
    ch_b = bitrev8(ch_b & 0x3F);

    st->data[0] = ch_b >> 4;
    st->data[1] = (ch_b << 4) | (ch_a >> 2);

    ret = spi_write(st->spi, st->data, ARRAY_SIZE(st->data));
    if (ret < 0)
        dev_err(&indio_dev->dev, "write failed (%d)", ret);

    return ret;
}

static int ad8366_read_raw(struct iio_dev *indio_dev,
               struct iio_chan_spec const *chan,
               int *val,
               int *val2,
               long m)
{
    struct ad8366_state *st = iio_priv(indio_dev);
    int ret;
    unsigned code;

    mutex_lock(&indio_dev->mlock);
    switch (m) {
    case IIO_CHAN_INFO_HARDWAREGAIN:
        code = st->ch[chan->channel];

        /* Values in dB */
        code = code * 253 + 4500;
        *val = code / 1000;
        *val2 = (code % 1000) * 1000;

        ret = IIO_VAL_INT_PLUS_MICRO_DB;
        break;
    default:
        ret = -EINVAL;
    }
    mutex_unlock(&indio_dev->mlock);

    return ret;
};

static int ad8366_write_raw(struct iio_dev *indio_dev,
                struct iio_chan_spec const *chan,
                int val,
                int val2,
                long mask)
{
    struct ad8366_state *st = iio_priv(indio_dev);
    unsigned code;
    int ret;

    if (val < 0 || val2 < 0)
        return -EINVAL;

    /* Values in dB */
    code = (((u8)val * 1000) + ((u32)val2 / 1000));

    if (code > 20500 || code < 4500)
        return -EINVAL;

    code = (code - 4500) / 253;

    mutex_lock(&indio_dev->mlock);
    switch (mask) {
    case IIO_CHAN_INFO_HARDWAREGAIN:
        st->ch[chan->channel] = code;
        ret = ad8366_write(indio_dev, st->ch[0], st->ch[1]);
        break;
    default:
        ret = -EINVAL;
    }
    mutex_unlock(&indio_dev->mlock);

    return ret;
}

static const struct iio_info ad8366_info = {
    .read_raw = &ad8366_read_raw,
    .write_raw = &ad8366_write_raw,
    .driver_module = THIS_MODULE,
};

#define AD8366_CHAN(_channel) {             \
    .type = IIO_VOLTAGE,                \
    .output = 1,                    \
    .indexed = 1,                   \
    .channel = _channel,                \
    .info_mask = IIO_CHAN_INFO_HARDWAREGAIN_SEPARATE_BIT,\
}

static const struct iio_chan_spec ad8366_channels[] = {
    AD8366_CHAN(0),
    AD8366_CHAN(1),
};

static int __devinit ad8366_probe(struct spi_device *spi)
{
    struct iio_dev *indio_dev;
    struct ad8366_state *st;
    int ret;

    indio_dev = iio_device_alloc(sizeof(*st));
    if (indio_dev == NULL)
        return -ENOMEM;

    st = iio_priv(indio_dev);

    st->reg = regulator_get(&spi->dev, "vcc");
    if (!IS_ERR(st->reg)) {
        ret = regulator_enable(st->reg);
        if (ret)
            goto error_put_reg;
    }

    spi_set_drvdata(spi, indio_dev);
    st->spi = spi;

    indio_dev->dev.parent = &spi->dev;
    indio_dev->name = spi_get_device_id(spi)->name;
    indio_dev->info = &ad8366_info;
    indio_dev->modes = INDIO_DIRECT_MODE;
    indio_dev->channels = ad8366_channels;
    indio_dev->num_channels = ARRAY_SIZE(ad8366_channels);

    ret = iio_device_register(indio_dev);
    if (ret)
        goto error_disable_reg;

    ad8366_write(indio_dev, 0 , 0);

    return 0;

error_disable_reg:
    if (!IS_ERR(st->reg))
        regulator_disable(st->reg);
error_put_reg:
    if (!IS_ERR(st->reg))
        regulator_put(st->reg);

    iio_device_free(indio_dev);

    return ret;
}

static int __devexit ad8366_remove(struct spi_device *spi)
{
    struct iio_dev *indio_dev = spi_get_drvdata(spi);
    struct ad8366_state *st = iio_priv(indio_dev);
    struct regulator *reg = st->reg;

    iio_device_unregister(indio_dev);

    if (!IS_ERR(reg)) {
        regulator_disable(reg);
        regulator_put(reg);
    }

    iio_device_free(indio_dev);

    return 0;
}

static const struct spi_device_id ad8366_id[] = {
    {"ad8366", 0},
    {}
};

static struct spi_driver ad8366_driver = {
    .driver = {
        .name   = KBUILD_MODNAME,
        .owner  = THIS_MODULE,
    },
    .probe      = ad8366_probe,
    .remove     = __devexit_p(ad8366_remove),
    .id_table   = ad8366_id,
};

module_spi_driver(ad8366_driver);

MODULE_AUTHOR("Michael Hennerich <[email protected]>");
MODULE_DESCRIPTION("Analog Devices AD8366 VGA");
MODULE_LICENSE("GPL v2");