/*
   * 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_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN),\
  }
  
  static const struct iio_chan_spec ad8366_channels[] = {
  	AD8366_CHAN(0),
  	AD8366_CHAN(1),
  };
  
  static int ad8366_probe(struct spi_device *spi)
  {
  	struct iio_dev *indio_dev;
  	struct ad8366_state *st;
  	int ret;
  
  	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
  	if (indio_dev == NULL)
  		return -ENOMEM;
  
  	st = iio_priv(indio_dev);
  
  	st->reg = devm_regulator_get(&spi->dev, "vcc");
  	if (!IS_ERR(st->reg)) {
  		ret = regulator_enable(st->reg);
  		if (ret)
  			return ret;
  	}
  
  	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);
  
  	return ret;
  }
  
  static int 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);
  
  	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		= ad8366_remove,
  	.id_table	= ad8366_id,
  };
  
  module_spi_driver(ad8366_driver);
  
  MODULE_AUTHOR("Michael Hennerich <hennerich@blackfin.uclinux.org>");
  MODULE_DESCRIPTION("Analog Devices AD8366 VGA");
  MODULE_LICENSE("GPL v2");