text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * sca3000_core.c -- support VTI sca3000 series accelerometers via SPI
   *
   * Copyright (c) 2009 Jonathan Cameron <jic23@kernel.org>
   *
   * See industrialio/accels/sca3000.h for comments.
   */
  
  #include <linux/interrupt.h>
  #include <linux/fs.h>
  #include <linux/device.h>
  #include <linux/slab.h>
  #include <linux/kernel.h>
  #include <linux/spi/spi.h>
  #include <linux/sysfs.h>
  #include <linux/module.h>
  #include <linux/uaccess.h>
  #include <linux/iio/iio.h>
  #include <linux/iio/sysfs.h>
  #include <linux/iio/events.h>
  #include <linux/iio/buffer.h>
  #include <linux/iio/kfifo_buf.h>
  
  #define SCA3000_WRITE_REG(a) (((a) << 2) | 0x02)
  #define SCA3000_READ_REG(a) ((a) << 2)
  
  #define SCA3000_REG_REVID_ADDR				0x00
  #define   SCA3000_REG_REVID_MAJOR_MASK			GENMASK(8, 4)
  #define   SCA3000_REG_REVID_MINOR_MASK			GENMASK(3, 0)
  
  #define SCA3000_REG_STATUS_ADDR				0x02
  #define   SCA3000_LOCKED				BIT(5)
  #define   SCA3000_EEPROM_CS_ERROR			BIT(1)
  #define   SCA3000_SPI_FRAME_ERROR			BIT(0)
  
  /* All reads done using register decrement so no need to directly access LSBs */
  #define SCA3000_REG_X_MSB_ADDR				0x05
  #define SCA3000_REG_Y_MSB_ADDR				0x07
  #define SCA3000_REG_Z_MSB_ADDR				0x09
  
  #define SCA3000_REG_RING_OUT_ADDR			0x0f
  
  /* Temp read untested - the e05 doesn't have the sensor */
  #define SCA3000_REG_TEMP_MSB_ADDR			0x13
  
  #define SCA3000_REG_MODE_ADDR				0x14
  #define SCA3000_MODE_PROT_MASK				0x28
  #define   SCA3000_REG_MODE_RING_BUF_ENABLE		BIT(7)
  #define   SCA3000_REG_MODE_RING_BUF_8BIT		BIT(6)
  
  /*
   * Free fall detection triggers an interrupt if the acceleration
   * is below a threshold for equivalent of 25cm drop
   */
  #define   SCA3000_REG_MODE_FREE_FALL_DETECT		BIT(4)
  #define   SCA3000_REG_MODE_MEAS_MODE_NORMAL		0x00
  #define   SCA3000_REG_MODE_MEAS_MODE_OP_1		0x01
  #define   SCA3000_REG_MODE_MEAS_MODE_OP_2		0x02
  
  /*
   * In motion detection mode the accelerations are band pass filtered
   * (approx 1 - 25Hz) and then a programmable threshold used to trigger
   * and interrupt.
   */
  #define   SCA3000_REG_MODE_MEAS_MODE_MOT_DET		0x03
  #define   SCA3000_REG_MODE_MODE_MASK			0x03
  
  #define SCA3000_REG_BUF_COUNT_ADDR			0x15
  
  #define SCA3000_REG_INT_STATUS_ADDR			0x16
  #define   SCA3000_REG_INT_STATUS_THREE_QUARTERS		BIT(7)
  #define   SCA3000_REG_INT_STATUS_HALF			BIT(6)
  
  #define SCA3000_INT_STATUS_FREE_FALL			BIT(3)
  #define SCA3000_INT_STATUS_Y_TRIGGER			BIT(2)
  #define SCA3000_INT_STATUS_X_TRIGGER			BIT(1)
  #define SCA3000_INT_STATUS_Z_TRIGGER			BIT(0)
  
  /* Used to allow access to multiplexed registers */
  #define SCA3000_REG_CTRL_SEL_ADDR			0x18
  /* Only available for SCA3000-D03 and SCA3000-D01 */
  #define   SCA3000_REG_CTRL_SEL_I2C_DISABLE		0x01
  #define   SCA3000_REG_CTRL_SEL_MD_CTRL			0x02
  #define   SCA3000_REG_CTRL_SEL_MD_Y_TH			0x03
  #define   SCA3000_REG_CTRL_SEL_MD_X_TH			0x04
  #define   SCA3000_REG_CTRL_SEL_MD_Z_TH			0x05
  /*
   * BE VERY CAREFUL WITH THIS, IF 3 BITS ARE NOT SET the device
   * will not function
   */
  #define   SCA3000_REG_CTRL_SEL_OUT_CTRL			0x0B
  
  #define     SCA3000_REG_OUT_CTRL_PROT_MASK		0xE0
  #define     SCA3000_REG_OUT_CTRL_BUF_X_EN		0x10
  #define     SCA3000_REG_OUT_CTRL_BUF_Y_EN		0x08
  #define     SCA3000_REG_OUT_CTRL_BUF_Z_EN		0x04
  #define     SCA3000_REG_OUT_CTRL_BUF_DIV_MASK		0x03
  #define     SCA3000_REG_OUT_CTRL_BUF_DIV_4		0x02
  #define     SCA3000_REG_OUT_CTRL_BUF_DIV_2		0x01
  
  
  /*
   * Control which motion detector interrupts are on.
   * For now only OR combinations are supported.
   */
  #define SCA3000_MD_CTRL_PROT_MASK			0xC0
  #define SCA3000_MD_CTRL_OR_Y				BIT(0)
  #define SCA3000_MD_CTRL_OR_X				BIT(1)
  #define SCA3000_MD_CTRL_OR_Z				BIT(2)
  /* Currently unsupported */
  #define SCA3000_MD_CTRL_AND_Y				BIT(3)
  #define SCA3000_MD_CTRL_AND_X				BIT(4)
  #define SCA3000_MD_CTRL_AND_Z				BIT(5)
  
  /*
   * Some control registers of complex access methods requiring this register to
   * be used to remove a lock.
   */
  #define SCA3000_REG_UNLOCK_ADDR				0x1e
  
  #define SCA3000_REG_INT_MASK_ADDR			0x21
  #define   SCA3000_REG_INT_MASK_PROT_MASK		0x1C
  
  #define   SCA3000_REG_INT_MASK_RING_THREE_QUARTER	BIT(7)
  #define   SCA3000_REG_INT_MASK_RING_HALF		BIT(6)
  
  #define SCA3000_REG_INT_MASK_ALL_INTS			0x02
  #define SCA3000_REG_INT_MASK_ACTIVE_HIGH		0x01
  #define SCA3000_REG_INT_MASK_ACTIVE_LOW			0x00
  /* Values of multiplexed registers (write to ctrl_data after select) */
  #define SCA3000_REG_CTRL_DATA_ADDR			0x22
  
  /*
   * Measurement modes available on some sca3000 series chips. Code assumes others
   * may become available in the future.
   *
   * Bypass - Bypass the low-pass filter in the signal channel so as to increase
   *          signal bandwidth.
   *
   * Narrow - Narrow low-pass filtering of the signal channel and half output
   *          data rate by decimation.
   *
   * Wide - Widen low-pass filtering of signal channel to increase bandwidth
   */
  #define SCA3000_OP_MODE_BYPASS				0x01
  #define SCA3000_OP_MODE_NARROW				0x02
  #define SCA3000_OP_MODE_WIDE				0x04
  #define SCA3000_MAX_TX 6
  #define SCA3000_MAX_RX 2
  
  /**
   * struct sca3000_state - device instance state information
   * @us:			the associated spi device
   * @info:			chip variant information
   * @last_timestamp:		the timestamp of the last event
   * @mo_det_use_count:		reference counter for the motion detection unit
   * @lock:			lock used to protect elements of sca3000_state
   *				and the underlying device state.
   * @tx:			dma-able transmit buffer
   * @rx:			dma-able receive buffer
   **/
  struct sca3000_state {
  	struct spi_device		*us;
  	const struct sca3000_chip_info	*info;
  	s64				last_timestamp;
  	int				mo_det_use_count;
  	struct mutex			lock;
  	/* Can these share a cacheline ? */
  	u8				rx[384] ____cacheline_aligned;
  	u8				tx[6] ____cacheline_aligned;
  };
  
  /**
   * struct sca3000_chip_info - model dependent parameters
   * @scale:			scale * 10^-6
   * @temp_output:		some devices have temperature sensors.
   * @measurement_mode_freq:	normal mode sampling frequency
   * @measurement_mode_3db_freq:	3db cutoff frequency of the low pass filter for
   * the normal measurement mode.
   * @option_mode_1:		first optional mode. Not all models have one
   * @option_mode_1_freq:		option mode 1 sampling frequency
   * @option_mode_1_3db_freq:	3db cutoff frequency of the low pass filter for
   * the first option mode.
   * @option_mode_2:		second optional mode. Not all chips have one
   * @option_mode_2_freq:		option mode 2 sampling frequency
   * @option_mode_2_3db_freq:	3db cutoff frequency of the low pass filter for
   * the second option mode.
   * @mod_det_mult_xz:		Bit wise multipliers to calculate the threshold
   * for motion detection in the x and z axis.
   * @mod_det_mult_y:		Bit wise multipliers to calculate the threshold
   * for motion detection in the y axis.
   *
   * This structure is used to hold information about the functionality of a given
   * sca3000 variant.
   **/
  struct sca3000_chip_info {
  	unsigned int		scale;
  	bool			temp_output;
  	int			measurement_mode_freq;
  	int			measurement_mode_3db_freq;
  	int			option_mode_1;
  	int			option_mode_1_freq;
  	int			option_mode_1_3db_freq;
  	int			option_mode_2;
  	int			option_mode_2_freq;
  	int			option_mode_2_3db_freq;
  	int			mot_det_mult_xz[6];
  	int			mot_det_mult_y[7];
  };
  
  enum sca3000_variant {
  	d01,
  	e02,
  	e04,
  	e05,
  };
  
  /*
   * Note where option modes are not defined, the chip simply does not
   * support any.
   * Other chips in the sca3000 series use i2c and are not included here.
   *
   * Some of these devices are only listed in the family data sheet and
   * do not actually appear to be available.
   */
  static const struct sca3000_chip_info sca3000_spi_chip_info_tbl[] = {
  	[d01] = {
  		.scale = 7357,
  		.temp_output = true,
  		.measurement_mode_freq = 250,
  		.measurement_mode_3db_freq = 45,
  		.option_mode_1 = SCA3000_OP_MODE_BYPASS,
  		.option_mode_1_freq = 250,
  		.option_mode_1_3db_freq = 70,
  		.mot_det_mult_xz = {50, 100, 200, 350, 650, 1300},
  		.mot_det_mult_y = {50, 100, 150, 250, 450, 850, 1750},
  	},
  	[e02] = {
  		.scale = 9810,
  		.measurement_mode_freq = 125,
  		.measurement_mode_3db_freq = 40,
  		.option_mode_1 = SCA3000_OP_MODE_NARROW,
  		.option_mode_1_freq = 63,
  		.option_mode_1_3db_freq = 11,
  		.mot_det_mult_xz = {100, 150, 300, 550, 1050, 2050},
  		.mot_det_mult_y = {50, 100, 200, 350, 700, 1350, 2700},
  	},
  	[e04] = {
  		.scale = 19620,
  		.measurement_mode_freq = 100,
  		.measurement_mode_3db_freq = 38,
  		.option_mode_1 = SCA3000_OP_MODE_NARROW,
  		.option_mode_1_freq = 50,
  		.option_mode_1_3db_freq = 9,
  		.option_mode_2 = SCA3000_OP_MODE_WIDE,
  		.option_mode_2_freq = 400,
  		.option_mode_2_3db_freq = 70,
  		.mot_det_mult_xz = {200, 300, 600, 1100, 2100, 4100},
  		.mot_det_mult_y = {100, 200, 400, 7000, 1400, 2700, 54000},
  	},
  	[e05] = {
  		.scale = 61313,
  		.measurement_mode_freq = 200,
  		.measurement_mode_3db_freq = 60,
  		.option_mode_1 = SCA3000_OP_MODE_NARROW,
  		.option_mode_1_freq = 50,
  		.option_mode_1_3db_freq = 9,
  		.option_mode_2 = SCA3000_OP_MODE_WIDE,
  		.option_mode_2_freq = 400,
  		.option_mode_2_3db_freq = 75,
  		.mot_det_mult_xz = {600, 900, 1700, 3200, 6100, 11900},
  		.mot_det_mult_y = {300, 600, 1200, 2000, 4100, 7800, 15600},
  	},
  };
  
  static int sca3000_write_reg(struct sca3000_state *st, u8 address, u8 val)
  {
  	st->tx[0] = SCA3000_WRITE_REG(address);
  	st->tx[1] = val;
  	return spi_write(st->us, st->tx, 2);
  }
  
  static int sca3000_read_data_short(struct sca3000_state *st,
  				   u8 reg_address_high,
  				   int len)
  {
  	struct spi_transfer xfer[2] = {
  		{
  			.len = 1,
  			.tx_buf = st->tx,
  		}, {
  			.len = len,
  			.rx_buf = st->rx,
  		}
  	};
  	st->tx[0] = SCA3000_READ_REG(reg_address_high);
  
  	return spi_sync_transfer(st->us, xfer, ARRAY_SIZE(xfer));
  }
  
  /**
   * sca3000_reg_lock_on() - test if the ctrl register lock is on
   * @st: Driver specific device instance data.
   *
   * Lock must be held.
   **/
  static int sca3000_reg_lock_on(struct sca3000_state *st)
  {
  	int ret;
  
  	ret = sca3000_read_data_short(st, SCA3000_REG_STATUS_ADDR, 1);
  	if (ret < 0)
  		return ret;
  
  	return !(st->rx[0] & SCA3000_LOCKED);
  }
  
  /**
   * __sca3000_unlock_reg_lock() - unlock the control registers
   * @st: Driver specific device instance data.
   *
   * Note the device does not appear to support doing this in a single transfer.
   * This should only ever be used as part of ctrl reg read.
   * Lock must be held before calling this
   */
  static int __sca3000_unlock_reg_lock(struct sca3000_state *st)
  {
  	struct spi_transfer xfer[3] = {
  		{
  			.len = 2,
  			.cs_change = 1,
  			.tx_buf = st->tx,
  		}, {
  			.len = 2,
  			.cs_change = 1,
  			.tx_buf = st->tx + 2,
  		}, {
  			.len = 2,
  			.tx_buf = st->tx + 4,
  		},
  	};
  	st->tx[0] = SCA3000_WRITE_REG(SCA3000_REG_UNLOCK_ADDR);
  	st->tx[1] = 0x00;
  	st->tx[2] = SCA3000_WRITE_REG(SCA3000_REG_UNLOCK_ADDR);
  	st->tx[3] = 0x50;
  	st->tx[4] = SCA3000_WRITE_REG(SCA3000_REG_UNLOCK_ADDR);
  	st->tx[5] = 0xA0;
  
  	return spi_sync_transfer(st->us, xfer, ARRAY_SIZE(xfer));
  }
  
  /**
   * sca3000_write_ctrl_reg() write to a lock protect ctrl register
   * @st: Driver specific device instance data.
   * @sel: selects which registers we wish to write to
   * @val: the value to be written
   *
   * Certain control registers are protected against overwriting by the lock
   * register and use a shared write address. This function allows writing of
   * these registers.
   * Lock must be held.
   */
  static int sca3000_write_ctrl_reg(struct sca3000_state *st,
  				  u8 sel,
  				  uint8_t val)
  {
  	int ret;
  
  	ret = sca3000_reg_lock_on(st);
  	if (ret < 0)
  		goto error_ret;
  	if (ret) {
  		ret = __sca3000_unlock_reg_lock(st);
  		if (ret)
  			goto error_ret;
  	}
  
  	/* Set the control select register */
  	ret = sca3000_write_reg(st, SCA3000_REG_CTRL_SEL_ADDR, sel);
  	if (ret)
  		goto error_ret;
  
  	/* Write the actual value into the register */
  	ret = sca3000_write_reg(st, SCA3000_REG_CTRL_DATA_ADDR, val);
  
  error_ret:
  	return ret;
  }
  
  /**
   * sca3000_read_ctrl_reg() read from lock protected control register.
   * @st: Driver specific device instance data.
   * @ctrl_reg: Which ctrl register do we want to read.
   *
   * Lock must be held.
   */
  static int sca3000_read_ctrl_reg(struct sca3000_state *st,
  				 u8 ctrl_reg)
  {
  	int ret;
  
  	ret = sca3000_reg_lock_on(st);
  	if (ret < 0)
  		goto error_ret;
  	if (ret) {
  		ret = __sca3000_unlock_reg_lock(st);
  		if (ret)
  			goto error_ret;
  	}
  	/* Set the control select register */
  	ret = sca3000_write_reg(st, SCA3000_REG_CTRL_SEL_ADDR, ctrl_reg);
  	if (ret)
  		goto error_ret;
  	ret = sca3000_read_data_short(st, SCA3000_REG_CTRL_DATA_ADDR, 1);
  	if (ret)
  		goto error_ret;
  	return st->rx[0];
  error_ret:
  	return ret;
  }
  
  /**
   * sca3000_show_rev() - sysfs interface to read the chip revision number
   * @indio_dev: Device instance specific generic IIO data.
   * Driver specific device instance data can be obtained via
   * via iio_priv(indio_dev)
   */
  static int sca3000_print_rev(struct iio_dev *indio_dev)
  {
  	int ret;
  	struct sca3000_state *st = iio_priv(indio_dev);
  
  	mutex_lock(&st->lock);
  	ret = sca3000_read_data_short(st, SCA3000_REG_REVID_ADDR, 1);
  	if (ret < 0)
  		goto error_ret;
  	dev_info(&indio_dev->dev,
  		 "sca3000 revision major=%lu, minor=%lu\n",
  		 st->rx[0] & SCA3000_REG_REVID_MAJOR_MASK,
  		 st->rx[0] & SCA3000_REG_REVID_MINOR_MASK);
  error_ret:
  	mutex_unlock(&st->lock);
  
  	return ret;
  }
  
  static ssize_t
  sca3000_show_available_3db_freqs(struct device *dev,
  				 struct device_attribute *attr,
  				 char *buf)
  {
  	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
  	struct sca3000_state *st = iio_priv(indio_dev);
  	int len;
  
  	len = sprintf(buf, "%d", st->info->measurement_mode_3db_freq);
  	if (st->info->option_mode_1)
  		len += sprintf(buf + len, " %d",
  			       st->info->option_mode_1_3db_freq);
  	if (st->info->option_mode_2)
  		len += sprintf(buf + len, " %d",
  			       st->info->option_mode_2_3db_freq);
  	len += sprintf(buf + len, "\n");
  
  	return len;
  }
  
  static IIO_DEVICE_ATTR(in_accel_filter_low_pass_3db_frequency_available,
  		       S_IRUGO, sca3000_show_available_3db_freqs,
  		       NULL, 0);
  
  static const struct iio_event_spec sca3000_event = {
  	.type = IIO_EV_TYPE_MAG,
  	.dir = IIO_EV_DIR_RISING,
  	.mask_separate = BIT(IIO_EV_INFO_VALUE) | BIT(IIO_EV_INFO_ENABLE),
  };
  
  /*
   * Note the hack in the number of bits to pretend we have 2 more than
   * we do in the fifo.
   */
  #define SCA3000_CHAN(index, mod)				\
  	{							\
  		.type = IIO_ACCEL,				\
  		.modified = 1,					\
  		.channel2 = mod,				\
  		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
  		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |\
  			BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY),\
  		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),\
  		.address = index,				\
  		.scan_index = index,				\
  		.scan_type = {					\
  			.sign = 's',				\
  			.realbits = 13,				\
  			.storagebits = 16,			\
  			.shift = 3,				\
  			.endianness = IIO_BE,			\
  		},						\
  		.event_spec = &sca3000_event,			\
  		.num_event_specs = 1,				\
  	}
  
  static const struct iio_event_spec sca3000_freefall_event_spec = {
  	.type = IIO_EV_TYPE_MAG,
  	.dir = IIO_EV_DIR_FALLING,
  	.mask_separate = BIT(IIO_EV_INFO_ENABLE) |
  		BIT(IIO_EV_INFO_PERIOD),
  };
  
  static const struct iio_chan_spec sca3000_channels[] = {
  	SCA3000_CHAN(0, IIO_MOD_X),
  	SCA3000_CHAN(1, IIO_MOD_Y),
  	SCA3000_CHAN(2, IIO_MOD_Z),
  	{
  		.type = IIO_ACCEL,
  		.modified = 1,
  		.channel2 = IIO_MOD_X_AND_Y_AND_Z,
  		.scan_index = -1, /* Fake channel */
  		.event_spec = &sca3000_freefall_event_spec,
  		.num_event_specs = 1,
  	},
  };
  
  static const struct iio_chan_spec sca3000_channels_with_temp[] = {
  	SCA3000_CHAN(0, IIO_MOD_X),
  	SCA3000_CHAN(1, IIO_MOD_Y),
  	SCA3000_CHAN(2, IIO_MOD_Z),
  	{
  		.type = IIO_TEMP,
  		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
  		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |
  			BIT(IIO_CHAN_INFO_OFFSET),
  		/* No buffer support */
  		.scan_index = -1,
  	},
  	{
  		.type = IIO_ACCEL,
  		.modified = 1,
  		.channel2 = IIO_MOD_X_AND_Y_AND_Z,
  		.scan_index = -1, /* Fake channel */
  		.event_spec = &sca3000_freefall_event_spec,
  		.num_event_specs = 1,
  	},
  };
  
  static u8 sca3000_addresses[3][3] = {
  	[0] = {SCA3000_REG_X_MSB_ADDR, SCA3000_REG_CTRL_SEL_MD_X_TH,
  	       SCA3000_MD_CTRL_OR_X},
  	[1] = {SCA3000_REG_Y_MSB_ADDR, SCA3000_REG_CTRL_SEL_MD_Y_TH,
  	       SCA3000_MD_CTRL_OR_Y},
  	[2] = {SCA3000_REG_Z_MSB_ADDR, SCA3000_REG_CTRL_SEL_MD_Z_TH,
  	       SCA3000_MD_CTRL_OR_Z},
  };
  
  /**
   * __sca3000_get_base_freq() - obtain mode specific base frequency
   * @st: Private driver specific device instance specific state.
   * @info: chip type specific information.
   * @base_freq: Base frequency for the current measurement mode.
   *
   * lock must be held
   */
  static inline int __sca3000_get_base_freq(struct sca3000_state *st,
  					  const struct sca3000_chip_info *info,
  					  int *base_freq)
  {
  	int ret;
  
  	ret = sca3000_read_data_short(st, SCA3000_REG_MODE_ADDR, 1);
  	if (ret)
  		goto error_ret;
  	switch (SCA3000_REG_MODE_MODE_MASK & st->rx[0]) {
  	case SCA3000_REG_MODE_MEAS_MODE_NORMAL:
  		*base_freq = info->measurement_mode_freq;
  		break;
  	case SCA3000_REG_MODE_MEAS_MODE_OP_1:
  		*base_freq = info->option_mode_1_freq;
  		break;
  	case SCA3000_REG_MODE_MEAS_MODE_OP_2:
  		*base_freq = info->option_mode_2_freq;
  		break;
  	default:
  		ret = -EINVAL;
  	}
  error_ret:
  	return ret;
  }
  
  /**
   * sca3000_read_raw_samp_freq() - read_raw handler for IIO_CHAN_INFO_SAMP_FREQ
   * @st: Private driver specific device instance specific state.
   * @val: The frequency read back.
   *
   * lock must be held
   **/
  static int sca3000_read_raw_samp_freq(struct sca3000_state *st, int *val)
  {
  	int ret;
  
  	ret = __sca3000_get_base_freq(st, st->info, val);
  	if (ret)
  		return ret;
  
  	ret = sca3000_read_ctrl_reg(st, SCA3000_REG_CTRL_SEL_OUT_CTRL);
  	if (ret < 0)
  		return ret;
  
  	if (*val > 0) {
  		ret &= SCA3000_REG_OUT_CTRL_BUF_DIV_MASK;
  		switch (ret) {
  		case SCA3000_REG_OUT_CTRL_BUF_DIV_2:
  			*val /= 2;
  			break;
  		case SCA3000_REG_OUT_CTRL_BUF_DIV_4:
  			*val /= 4;
  			break;
  		}
  	}
  
  	return 0;
  }
  
  /**
   * sca3000_write_raw_samp_freq() - write_raw handler for IIO_CHAN_INFO_SAMP_FREQ
   * @st: Private driver specific device instance specific state.
   * @val: The frequency desired.
   *
   * lock must be held
   */
  static int sca3000_write_raw_samp_freq(struct sca3000_state *st, int val)
  {
  	int ret, base_freq, ctrlval;
  
  	ret = __sca3000_get_base_freq(st, st->info, &base_freq);
  	if (ret)
  		return ret;
  
  	ret = sca3000_read_ctrl_reg(st, SCA3000_REG_CTRL_SEL_OUT_CTRL);
  	if (ret < 0)
  		return ret;
  
  	ctrlval = ret & ~SCA3000_REG_OUT_CTRL_BUF_DIV_MASK;
  
  	if (val == base_freq / 2)
  		ctrlval |= SCA3000_REG_OUT_CTRL_BUF_DIV_2;
  	if (val == base_freq / 4)
  		ctrlval |= SCA3000_REG_OUT_CTRL_BUF_DIV_4;
  	else if (val != base_freq)
  		return -EINVAL;
  
  	return sca3000_write_ctrl_reg(st, SCA3000_REG_CTRL_SEL_OUT_CTRL,
  				     ctrlval);
  }
  
  static int sca3000_read_3db_freq(struct sca3000_state *st, int *val)
  {
  	int ret;
  
  	ret = sca3000_read_data_short(st, SCA3000_REG_MODE_ADDR, 1);
  	if (ret)
  		return ret;
  
  	/* mask bottom 2 bits - only ones that are relevant */
  	st->rx[0] &= SCA3000_REG_MODE_MODE_MASK;
  	switch (st->rx[0]) {
  	case SCA3000_REG_MODE_MEAS_MODE_NORMAL:
  		*val = st->info->measurement_mode_3db_freq;
  		return IIO_VAL_INT;
  	case SCA3000_REG_MODE_MEAS_MODE_MOT_DET:
  		return -EBUSY;
  	case SCA3000_REG_MODE_MEAS_MODE_OP_1:
  		*val = st->info->option_mode_1_3db_freq;
  		return IIO_VAL_INT;
  	case SCA3000_REG_MODE_MEAS_MODE_OP_2:
  		*val = st->info->option_mode_2_3db_freq;
  		return IIO_VAL_INT;
  	default:
  		return -EINVAL;
  	}
  }
  
  static int sca3000_write_3db_freq(struct sca3000_state *st, int val)
  {
  	int ret;
  	int mode;
  
  	if (val == st->info->measurement_mode_3db_freq)
  		mode = SCA3000_REG_MODE_MEAS_MODE_NORMAL;
  	else if (st->info->option_mode_1 &&
  		 (val == st->info->option_mode_1_3db_freq))
  		mode = SCA3000_REG_MODE_MEAS_MODE_OP_1;
  	else if (st->info->option_mode_2 &&
  		 (val == st->info->option_mode_2_3db_freq))
  		mode = SCA3000_REG_MODE_MEAS_MODE_OP_2;
  	else
  		return -EINVAL;
  	ret = sca3000_read_data_short(st, SCA3000_REG_MODE_ADDR, 1);
  	if (ret)
  		return ret;
  
  	st->rx[0] &= ~SCA3000_REG_MODE_MODE_MASK;
  	st->rx[0] |= (mode & SCA3000_REG_MODE_MODE_MASK);
  
  	return sca3000_write_reg(st, SCA3000_REG_MODE_ADDR, st->rx[0]);
  }
  
  static int sca3000_read_raw(struct iio_dev *indio_dev,
  			    struct iio_chan_spec const *chan,
  			    int *val,
  			    int *val2,
  			    long mask)
  {
  	struct sca3000_state *st = iio_priv(indio_dev);
  	int ret;
  	u8 address;
  
  	switch (mask) {
  	case IIO_CHAN_INFO_RAW:
  		mutex_lock(&st->lock);
  		if (chan->type == IIO_ACCEL) {
  			if (st->mo_det_use_count) {
  				mutex_unlock(&st->lock);
  				return -EBUSY;
  			}
  			address = sca3000_addresses[chan->address][0];
  			ret = sca3000_read_data_short(st, address, 2);
  			if (ret < 0) {
  				mutex_unlock(&st->lock);
  				return ret;
  			}
  			*val = (be16_to_cpup((__be16 *)st->rx) >> 3) & 0x1FFF;
  			*val = ((*val) << (sizeof(*val) * 8 - 13)) >>
  				(sizeof(*val) * 8 - 13);
  		} else {
  			/* get the temperature when available */
  			ret = sca3000_read_data_short(st,
  						      SCA3000_REG_TEMP_MSB_ADDR,
  						      2);
  			if (ret < 0) {
  				mutex_unlock(&st->lock);
  				return ret;
  			}
  			*val = ((st->rx[0] & 0x3F) << 3) |
  			       ((st->rx[1] & 0xE0) >> 5);
  		}
  		mutex_unlock(&st->lock);
  		return IIO_VAL_INT;
  	case IIO_CHAN_INFO_SCALE:
  		*val = 0;
  		if (chan->type == IIO_ACCEL)
  			*val2 = st->info->scale;
  		else /* temperature */
  			*val2 = 555556;
  		return IIO_VAL_INT_PLUS_MICRO;
  	case IIO_CHAN_INFO_OFFSET:
  		*val = -214;
  		*val2 = 600000;
  		return IIO_VAL_INT_PLUS_MICRO;
  	case IIO_CHAN_INFO_SAMP_FREQ:
  		mutex_lock(&st->lock);
  		ret = sca3000_read_raw_samp_freq(st, val);
  		mutex_unlock(&st->lock);
  		return ret ? ret : IIO_VAL_INT;
  	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
  		mutex_lock(&st->lock);
  		ret = sca3000_read_3db_freq(st, val);
  		mutex_unlock(&st->lock);
  		return ret;
  	default:
  		return -EINVAL;
  	}
  }
  
  static int sca3000_write_raw(struct iio_dev *indio_dev,
  			     struct iio_chan_spec const *chan,
  			     int val, int val2, long mask)
  {
  	struct sca3000_state *st = iio_priv(indio_dev);
  	int ret;
  
  	switch (mask) {
  	case IIO_CHAN_INFO_SAMP_FREQ:
  		if (val2)
  			return -EINVAL;
  		mutex_lock(&st->lock);
  		ret = sca3000_write_raw_samp_freq(st, val);
  		mutex_unlock(&st->lock);
  		return ret;
  	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
  		if (val2)
  			return -EINVAL;
  		mutex_lock(&st->lock);
  		ret = sca3000_write_3db_freq(st, val);
  		mutex_unlock(&st->lock);
  		return ret;
  	default:
  		return -EINVAL;
  	}
  
  	return ret;
  }
  
  /**
   * sca3000_read_av_freq() - sysfs function to get available frequencies
   * @dev: Device structure for this device.
   * @attr: Description of the attribute.
   * @buf: Incoming string
   *
   * The later modes are only relevant to the ring buffer - and depend on current
   * mode. Note that data sheet gives rather wide tolerances for these so integer
   * division will give good enough answer and not all chips have them specified
   * at all.
   **/
  static ssize_t sca3000_read_av_freq(struct device *dev,
  				    struct device_attribute *attr,
  				    char *buf)
  {
  	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
  	struct sca3000_state *st = iio_priv(indio_dev);
  	int len = 0, ret, val;
  
  	mutex_lock(&st->lock);
  	ret = sca3000_read_data_short(st, SCA3000_REG_MODE_ADDR, 1);
  	val = st->rx[0];
  	mutex_unlock(&st->lock);
  	if (ret)
  		goto error_ret;
  
  	switch (val & SCA3000_REG_MODE_MODE_MASK) {
  	case SCA3000_REG_MODE_MEAS_MODE_NORMAL:
  		len += sprintf(buf + len, "%d %d %d\n",
  			       st->info->measurement_mode_freq,
  			       st->info->measurement_mode_freq / 2,
  			       st->info->measurement_mode_freq / 4);
  		break;
  	case SCA3000_REG_MODE_MEAS_MODE_OP_1:
  		len += sprintf(buf + len, "%d %d %d\n",
  			       st->info->option_mode_1_freq,
  			       st->info->option_mode_1_freq / 2,
  			       st->info->option_mode_1_freq / 4);
  		break;
  	case SCA3000_REG_MODE_MEAS_MODE_OP_2:
  		len += sprintf(buf + len, "%d %d %d\n",
  			       st->info->option_mode_2_freq,
  			       st->info->option_mode_2_freq / 2,
  			       st->info->option_mode_2_freq / 4);
  		break;
  	}
  	return len;
  error_ret:
  	return ret;
  }
  
  /*
   * Should only really be registered if ring buffer support is compiled in.
   * Does no harm however and doing it right would add a fair bit of complexity
   */
  static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(sca3000_read_av_freq);
  
  /**
   * sca3000_read_event_value() - query of a threshold or period
   **/
  static int sca3000_read_event_value(struct iio_dev *indio_dev,
  				    const struct iio_chan_spec *chan,
  				    enum iio_event_type type,
  				    enum iio_event_direction dir,
  				    enum iio_event_info info,
  				    int *val, int *val2)
  {
  	struct sca3000_state *st = iio_priv(indio_dev);
  	long ret;
  	int i;
  
  	switch (info) {
  	case IIO_EV_INFO_VALUE:
  		mutex_lock(&st->lock);
  		ret = sca3000_read_ctrl_reg(st,
  					    sca3000_addresses[chan->address][1]);
  		mutex_unlock(&st->lock);
  		if (ret < 0)
  			return ret;
  		*val = 0;
  		if (chan->channel2 == IIO_MOD_Y)
  			for_each_set_bit(i, &ret,
  					 ARRAY_SIZE(st->info->mot_det_mult_y))
  				*val += st->info->mot_det_mult_y[i];
  		else
  			for_each_set_bit(i, &ret,
  					 ARRAY_SIZE(st->info->mot_det_mult_xz))
  				*val += st->info->mot_det_mult_xz[i];
  
  		return IIO_VAL_INT;
  	case IIO_EV_INFO_PERIOD:
  		*val = 0;
  		*val2 = 226000;
  		return IIO_VAL_INT_PLUS_MICRO;
  	default:
  		return -EINVAL;
  	}
  }
  
  /**
   * sca3000_write_value() - control of threshold and period
   * @indio_dev: Device instance specific IIO information.
   * @chan: Description of the channel for which the event is being
   * configured.
   * @type: The type of event being configured, here magnitude rising
   * as everything else is read only.
   * @dir: Direction of the event (here rising)
   * @info: What information about the event are we configuring.
   * Here the threshold only.
   * @val: Integer part of the value being written..
   * @val2: Non integer part of the value being written. Here always 0.
   */
  static int sca3000_write_event_value(struct iio_dev *indio_dev,
  				     const struct iio_chan_spec *chan,
  				     enum iio_event_type type,
  				     enum iio_event_direction dir,
  				     enum iio_event_info info,
  				     int val, int val2)
  {
  	struct sca3000_state *st = iio_priv(indio_dev);
  	int ret;
  	int i;
  	u8 nonlinear = 0;
  
  	if (chan->channel2 == IIO_MOD_Y) {
  		i = ARRAY_SIZE(st->info->mot_det_mult_y);
  		while (i > 0)
  			if (val >= st->info->mot_det_mult_y[--i]) {
  				nonlinear |= (1 << i);
  				val -= st->info->mot_det_mult_y[i];
  			}
  	} else {
  		i = ARRAY_SIZE(st->info->mot_det_mult_xz);
  		while (i > 0)
  			if (val >= st->info->mot_det_mult_xz[--i]) {
  				nonlinear |= (1 << i);
  				val -= st->info->mot_det_mult_xz[i];
  			}
  	}
  
  	mutex_lock(&st->lock);
  	ret = sca3000_write_ctrl_reg(st,
  				     sca3000_addresses[chan->address][1],
  				     nonlinear);
  	mutex_unlock(&st->lock);
  
  	return ret;
  }
  
  static struct attribute *sca3000_attributes[] = {
  	&iio_dev_attr_in_accel_filter_low_pass_3db_frequency_available.dev_attr.attr,
  	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
  	NULL,
  };
  
  static const struct attribute_group sca3000_attribute_group = {
  	.attrs = sca3000_attributes,
  };
  
  static int sca3000_read_data(struct sca3000_state *st,
  			     u8 reg_address_high,
  			     u8 *rx,
  			     int len)
  {
  	int ret;
  	struct spi_transfer xfer[2] = {
  		{
  			.len = 1,
  			.tx_buf = st->tx,
  		}, {
  			.len = len,
  			.rx_buf = rx,
  		}
  	};
  
  	st->tx[0] = SCA3000_READ_REG(reg_address_high);
  	ret = spi_sync_transfer(st->us, xfer, ARRAY_SIZE(xfer));
  	if (ret) {
  		dev_err(get_device(&st->us->dev), "problem reading register");
  		return ret;
  	}
  
  	return 0;
  }
  
  /**
   * sca3000_ring_int_process() - ring specific interrupt handling.
   * @val: Value of the interrupt status register.
   * @indio_dev: Device instance specific IIO device structure.
   */
  static void sca3000_ring_int_process(u8 val, struct iio_dev *indio_dev)
  {
  	struct sca3000_state *st = iio_priv(indio_dev);
  	int ret, i, num_available;
  
  	mutex_lock(&st->lock);
  
  	if (val & SCA3000_REG_INT_STATUS_HALF) {
  		ret = sca3000_read_data_short(st, SCA3000_REG_BUF_COUNT_ADDR,
  					      1);
  		if (ret)
  			goto error_ret;
  		num_available = st->rx[0];
  		/*
  		 * num_available is the total number of samples available
  		 * i.e. number of time points * number of channels.
  		 */
  		ret = sca3000_read_data(st, SCA3000_REG_RING_OUT_ADDR, st->rx,
  					num_available * 2);
  		if (ret)
  			goto error_ret;
  		for (i = 0; i < num_available / 3; i++) {
  			/*
  			 * Dirty hack to cover for 11 bit in fifo, 13 bit
  			 * direct reading.
  			 *
  			 * In theory the bottom two bits are undefined.
  			 * In reality they appear to always be 0.
  			 */
  			iio_push_to_buffers(indio_dev, st->rx + i * 3 * 2);
  		}
  	}
  error_ret:
  	mutex_unlock(&st->lock);
  }
  
  /**
   * sca3000_event_handler() - handling ring and non ring events
   * @irq: The irq being handled.
   * @private: struct iio_device pointer for the device.
   *
   * Ring related interrupt handler. Depending on event, push to
   * the ring buffer event chrdev or the event one.
   *
   * This function is complicated by the fact that the devices can signify ring
   * and non ring events via the same interrupt line and they can only
   * be distinguished via a read of the relevant status register.
   */
  static irqreturn_t sca3000_event_handler(int irq, void *private)
  {
  	struct iio_dev *indio_dev = private;
  	struct sca3000_state *st = iio_priv(indio_dev);
  	int ret, val;
  	s64 last_timestamp = iio_get_time_ns(indio_dev);
  
  	/*
  	 * Could lead if badly timed to an extra read of status reg,
  	 * but ensures no interrupt is missed.
  	 */
  	mutex_lock(&st->lock);
  	ret = sca3000_read_data_short(st, SCA3000_REG_INT_STATUS_ADDR, 1);
  	val = st->rx[0];
  	mutex_unlock(&st->lock);
  	if (ret)
  		goto done;
  
  	sca3000_ring_int_process(val, indio_dev);
  
  	if (val & SCA3000_INT_STATUS_FREE_FALL)
  		iio_push_event(indio_dev,
  			       IIO_MOD_EVENT_CODE(IIO_ACCEL,
  						  0,
  						  IIO_MOD_X_AND_Y_AND_Z,
  						  IIO_EV_TYPE_MAG,
  						  IIO_EV_DIR_FALLING),
  			       last_timestamp);
  
  	if (val & SCA3000_INT_STATUS_Y_TRIGGER)
  		iio_push_event(indio_dev,
  			       IIO_MOD_EVENT_CODE(IIO_ACCEL,
  						  0,
  						  IIO_MOD_Y,
  						  IIO_EV_TYPE_MAG,
  						  IIO_EV_DIR_RISING),
  			       last_timestamp);
  
  	if (val & SCA3000_INT_STATUS_X_TRIGGER)
  		iio_push_event(indio_dev,
  			       IIO_MOD_EVENT_CODE(IIO_ACCEL,
  						  0,
  						  IIO_MOD_X,
  						  IIO_EV_TYPE_MAG,
  						  IIO_EV_DIR_RISING),
  			       last_timestamp);
  
  	if (val & SCA3000_INT_STATUS_Z_TRIGGER)
  		iio_push_event(indio_dev,
  			       IIO_MOD_EVENT_CODE(IIO_ACCEL,
  						  0,
  						  IIO_MOD_Z,
  						  IIO_EV_TYPE_MAG,
  						  IIO_EV_DIR_RISING),
  			       last_timestamp);
  
  done:
  	return IRQ_HANDLED;
  }
  
  /**
   * sca3000_read_event_config() what events are enabled
   **/
  static int sca3000_read_event_config(struct iio_dev *indio_dev,
  				     const struct iio_chan_spec *chan,
  				     enum iio_event_type type,
  				     enum iio_event_direction dir)
  {
  	struct sca3000_state *st = iio_priv(indio_dev);
  	int ret;
  	/* read current value of mode register */
  	mutex_lock(&st->lock);
  
  	ret = sca3000_read_data_short(st, SCA3000_REG_MODE_ADDR, 1);
  	if (ret)
  		goto error_ret;
  
  	switch (chan->channel2) {
  	case IIO_MOD_X_AND_Y_AND_Z:
  		ret = !!(st->rx[0] & SCA3000_REG_MODE_FREE_FALL_DETECT);
  		break;
  	case IIO_MOD_X:
  	case IIO_MOD_Y:
  	case IIO_MOD_Z:
  		/*
  		 * Motion detection mode cannot run at the same time as
  		 * acceleration data being read.
  		 */
  		if ((st->rx[0] & SCA3000_REG_MODE_MODE_MASK)
  		    != SCA3000_REG_MODE_MEAS_MODE_MOT_DET) {
  			ret = 0;
  		} else {
  			ret = sca3000_read_ctrl_reg(st,
  						SCA3000_REG_CTRL_SEL_MD_CTRL);
  			if (ret < 0)
  				goto error_ret;
  			/* only supporting logical or's for now */
  			ret = !!(ret & sca3000_addresses[chan->address][2]);
  		}
  		break;
  	default:
  		ret = -EINVAL;
  	}
  
  error_ret:
  	mutex_unlock(&st->lock);
  
  	return ret;
  }
  
  static int sca3000_freefall_set_state(struct iio_dev *indio_dev, int state)
  {
  	struct sca3000_state *st = iio_priv(indio_dev);
  	int ret;
  
  	/* read current value of mode register */
  	ret = sca3000_read_data_short(st, SCA3000_REG_MODE_ADDR, 1);
  	if (ret)
  		return ret;
  
  	/* if off and should be on */
  	if (state && !(st->rx[0] & SCA3000_REG_MODE_FREE_FALL_DETECT))
  		return sca3000_write_reg(st, SCA3000_REG_MODE_ADDR,
  					 st->rx[0] | SCA3000_REG_MODE_FREE_FALL_DETECT);
  	/* if on and should be off */
  	else if (!state && (st->rx[0] & SCA3000_REG_MODE_FREE_FALL_DETECT))
  		return sca3000_write_reg(st, SCA3000_REG_MODE_ADDR,
  					 st->rx[0] & ~SCA3000_REG_MODE_FREE_FALL_DETECT);
  	else
  		return 0;
  }
  
  static int sca3000_motion_detect_set_state(struct iio_dev *indio_dev, int axis,
  					   int state)
  {
  	struct sca3000_state *st = iio_priv(indio_dev);
  	int ret, ctrlval;
  
  	/*
  	 * First read the motion detector config to find out if
  	 * this axis is on
  	 */
  	ret = sca3000_read_ctrl_reg(st, SCA3000_REG_CTRL_SEL_MD_CTRL);
  	if (ret < 0)
  		return ret;
  	ctrlval = ret;
  	/* if off and should be on */
  	if (state && !(ctrlval & sca3000_addresses[axis][2])) {
  		ret = sca3000_write_ctrl_reg(st,
  					     SCA3000_REG_CTRL_SEL_MD_CTRL,
  					     ctrlval |
  					     sca3000_addresses[axis][2]);
  		if (ret)
  			return ret;
  		st->mo_det_use_count++;
  	} else if (!state && (ctrlval & sca3000_addresses[axis][2])) {
  		ret = sca3000_write_ctrl_reg(st,
  					     SCA3000_REG_CTRL_SEL_MD_CTRL,
  					     ctrlval &
  					     ~(sca3000_addresses[axis][2]));
  		if (ret)
  			return ret;
  		st->mo_det_use_count--;
  	}
  
  	/* read current value of mode register */
  	ret = sca3000_read_data_short(st, SCA3000_REG_MODE_ADDR, 1);
  	if (ret)
  		return ret;
  	/* if off and should be on */
  	if ((st->mo_det_use_count) &&
  	    ((st->rx[0] & SCA3000_REG_MODE_MODE_MASK)
  	     != SCA3000_REG_MODE_MEAS_MODE_MOT_DET))
  		return sca3000_write_reg(st, SCA3000_REG_MODE_ADDR,
  			(st->rx[0] & ~SCA3000_REG_MODE_MODE_MASK)
  			| SCA3000_REG_MODE_MEAS_MODE_MOT_DET);
  	/* if on and should be off */
  	else if (!(st->mo_det_use_count) &&
  		 ((st->rx[0] & SCA3000_REG_MODE_MODE_MASK)
  		  == SCA3000_REG_MODE_MEAS_MODE_MOT_DET))
  		return sca3000_write_reg(st, SCA3000_REG_MODE_ADDR,
  			st->rx[0] & SCA3000_REG_MODE_MODE_MASK);
  	else
  		return 0;
  }
  
  /**
   * sca3000_write_event_config() - simple on off control for motion detector
   * @indio_dev: IIO device instance specific structure. Data specific to this
   * particular driver may be accessed via iio_priv(indio_dev).
   * @chan: Description of the channel whose event we are configuring.
   * @type: The type of event.
   * @dir: The direction of the event.
   * @state: Desired state of event being configured.
   *
   * This is a per axis control, but enabling any will result in the
   * motion detector unit being enabled.
   * N.B. enabling motion detector stops normal data acquisition.
   * There is a complexity in knowing which mode to return to when
   * this mode is disabled.  Currently normal mode is assumed.
   **/
  static int sca3000_write_event_config(struct iio_dev *indio_dev,
  				      const struct iio_chan_spec *chan,
  				      enum iio_event_type type,
  				      enum iio_event_direction dir,
  				      int state)
  {
  	struct sca3000_state *st = iio_priv(indio_dev);
  	int ret;
  
  	mutex_lock(&st->lock);
  	switch (chan->channel2) {
  	case IIO_MOD_X_AND_Y_AND_Z:
  		ret = sca3000_freefall_set_state(indio_dev, state);
  		break;
  
  	case IIO_MOD_X:
  	case IIO_MOD_Y:
  	case IIO_MOD_Z:
  		ret = sca3000_motion_detect_set_state(indio_dev,
  						      chan->address,
  						      state);
  		break;
  	default:
  		ret = -EINVAL;
  		break;
  	}
  	mutex_unlock(&st->lock);
  
  	return ret;
  }
  
  static int sca3000_configure_ring(struct iio_dev *indio_dev)
  {
  	struct iio_buffer *buffer;
  
  	buffer = devm_iio_kfifo_allocate(&indio_dev->dev);
  	if (!buffer)
  		return -ENOMEM;
  
  	iio_device_attach_buffer(indio_dev, buffer);
  	indio_dev->modes |= INDIO_BUFFER_SOFTWARE;
  
  	return 0;
  }
  
  static inline
  int __sca3000_hw_ring_state_set(struct iio_dev *indio_dev, bool state)
  {
  	struct sca3000_state *st = iio_priv(indio_dev);
  	int ret;
  
  	mutex_lock(&st->lock);
  	ret = sca3000_read_data_short(st, SCA3000_REG_MODE_ADDR, 1);
  	if (ret)
  		goto error_ret;
  	if (state) {
  		dev_info(&indio_dev->dev, "supposedly enabling ring buffer\n");
  		ret = sca3000_write_reg(st,
  			SCA3000_REG_MODE_ADDR,
  			(st->rx[0] | SCA3000_REG_MODE_RING_BUF_ENABLE));
  	} else
  		ret = sca3000_write_reg(st,
  			SCA3000_REG_MODE_ADDR,
  			(st->rx[0] & ~SCA3000_REG_MODE_RING_BUF_ENABLE));
  error_ret:
  	mutex_unlock(&st->lock);
  
  	return ret;
  }
  
  /**
   * sca3000_hw_ring_preenable() - hw ring buffer preenable function
   * @indio_dev: structure representing the IIO device. Device instance
   * specific state can be accessed via iio_priv(indio_dev).
   *
   * Very simple enable function as the chip will allows normal reads
   * during ring buffer operation so as long as it is indeed running
   * before we notify the core, the precise ordering does not matter.
   */
  static int sca3000_hw_ring_preenable(struct iio_dev *indio_dev)
  {
  	int ret;
  	struct sca3000_state *st = iio_priv(indio_dev);
  
  	mutex_lock(&st->lock);
  
  	/* Enable the 50% full interrupt */
  	ret = sca3000_read_data_short(st, SCA3000_REG_INT_MASK_ADDR, 1);
  	if (ret)
  		goto error_unlock;
  	ret = sca3000_write_reg(st,
  				SCA3000_REG_INT_MASK_ADDR,
  				st->rx[0] | SCA3000_REG_INT_MASK_RING_HALF);
  	if (ret)
  		goto error_unlock;
  
  	mutex_unlock(&st->lock);
  
  	return __sca3000_hw_ring_state_set(indio_dev, 1);
  
  error_unlock:
  	mutex_unlock(&st->lock);
  
  	return ret;
  }
  
  static int sca3000_hw_ring_postdisable(struct iio_dev *indio_dev)
  {
  	int ret;
  	struct sca3000_state *st = iio_priv(indio_dev);
  
  	ret = __sca3000_hw_ring_state_set(indio_dev, 0);
  	if (ret)
  		return ret;
  
  	/* Disable the 50% full interrupt */
  	mutex_lock(&st->lock);
  
  	ret = sca3000_read_data_short(st, SCA3000_REG_INT_MASK_ADDR, 1);
  	if (ret)
  		goto unlock;
  	ret = sca3000_write_reg(st,
  				SCA3000_REG_INT_MASK_ADDR,
  				st->rx[0] & ~SCA3000_REG_INT_MASK_RING_HALF);
  unlock:
  	mutex_unlock(&st->lock);
  	return ret;
  }
  
  static const struct iio_buffer_setup_ops sca3000_ring_setup_ops = {
  	.preenable = &sca3000_hw_ring_preenable,
  	.postdisable = &sca3000_hw_ring_postdisable,
  };
  
  /**
   * sca3000_clean_setup() - get the device into a predictable state
   * @st: Device instance specific private data structure
   *
   * Devices use flash memory to store many of the register values
   * and hence can come up in somewhat unpredictable states.
   * Hence reset everything on driver load.
   */
  static int sca3000_clean_setup(struct sca3000_state *st)
  {
  	int ret;
  
  	mutex_lock(&st->lock);
  	/* Ensure all interrupts have been acknowledged */
  	ret = sca3000_read_data_short(st, SCA3000_REG_INT_STATUS_ADDR, 1);
  	if (ret)
  		goto error_ret;
  
  	/* Turn off all motion detection channels */
  	ret = sca3000_read_ctrl_reg(st, SCA3000_REG_CTRL_SEL_MD_CTRL);
  	if (ret < 0)
  		goto error_ret;
  	ret = sca3000_write_ctrl_reg(st, SCA3000_REG_CTRL_SEL_MD_CTRL,
  				     ret & SCA3000_MD_CTRL_PROT_MASK);
  	if (ret)
  		goto error_ret;
  
  	/* Disable ring buffer */
  	ret = sca3000_read_ctrl_reg(st, SCA3000_REG_CTRL_SEL_OUT_CTRL);
  	if (ret < 0)
  		goto error_ret;
  	ret = sca3000_write_ctrl_reg(st, SCA3000_REG_CTRL_SEL_OUT_CTRL,
  				     (ret & SCA3000_REG_OUT_CTRL_PROT_MASK)
  				     | SCA3000_REG_OUT_CTRL_BUF_X_EN
  				     | SCA3000_REG_OUT_CTRL_BUF_Y_EN
  				     | SCA3000_REG_OUT_CTRL_BUF_Z_EN
  				     | SCA3000_REG_OUT_CTRL_BUF_DIV_4);
  	if (ret)
  		goto error_ret;
  	/* Enable interrupts, relevant to mode and set up as active low */
  	ret = sca3000_read_data_short(st, SCA3000_REG_INT_MASK_ADDR, 1);
  	if (ret)
  		goto error_ret;
  	ret = sca3000_write_reg(st,
  				SCA3000_REG_INT_MASK_ADDR,
  				(ret & SCA3000_REG_INT_MASK_PROT_MASK)
  				| SCA3000_REG_INT_MASK_ACTIVE_LOW);
  	if (ret)
  		goto error_ret;
  	/*
  	 * Select normal measurement mode, free fall off, ring off
  	 * Ring in 12 bit mode - it is fine to overwrite reserved bits 3,5
  	 * as that occurs in one of the example on the datasheet
  	 */
  	ret = sca3000_read_data_short(st, SCA3000_REG_MODE_ADDR, 1);
  	if (ret)
  		goto error_ret;
  	ret = sca3000_write_reg(st, SCA3000_REG_MODE_ADDR,
  				(st->rx[0] & SCA3000_MODE_PROT_MASK));
  
  error_ret:
  	mutex_unlock(&st->lock);
  	return ret;
  }
  
  static const struct iio_info sca3000_info = {
  	.attrs = &sca3000_attribute_group,
  	.read_raw = &sca3000_read_raw,
  	.write_raw = &sca3000_write_raw,
  	.read_event_value = &sca3000_read_event_value,
  	.write_event_value = &sca3000_write_event_value,
  	.read_event_config = &sca3000_read_event_config,
  	.write_event_config = &sca3000_write_event_config,
  };
  
  static int sca3000_probe(struct spi_device *spi)
  {
  	int ret;
  	struct sca3000_state *st;
  	struct iio_dev *indio_dev;
  
  	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
  	if (!indio_dev)
  		return -ENOMEM;
  
  	st = iio_priv(indio_dev);
  	spi_set_drvdata(spi, indio_dev);
  	st->us = spi;
  	mutex_init(&st->lock);
  	st->info = &sca3000_spi_chip_info_tbl[spi_get_device_id(spi)
  					      ->driver_data];
  
  	indio_dev->dev.parent = &spi->dev;
  	indio_dev->name = spi_get_device_id(spi)->name;
  	indio_dev->info = &sca3000_info;
  	if (st->info->temp_output) {
  		indio_dev->channels = sca3000_channels_with_temp;
  		indio_dev->num_channels =
  			ARRAY_SIZE(sca3000_channels_with_temp);
  	} else {
  		indio_dev->channels = sca3000_channels;
  		indio_dev->num_channels = ARRAY_SIZE(sca3000_channels);
  	}
  	indio_dev->modes = INDIO_DIRECT_MODE;
  
  	ret = sca3000_configure_ring(indio_dev);
  	if (ret)
  		return ret;
  
  	if (spi->irq) {
  		ret = request_threaded_irq(spi->irq,
  					   NULL,
  					   &sca3000_event_handler,
  					   IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
  					   "sca3000",
  					   indio_dev);
  		if (ret)
  			return ret;
  	}
  	indio_dev->setup_ops = &sca3000_ring_setup_ops;
  	ret = sca3000_clean_setup(st);
  	if (ret)
  		goto error_free_irq;
  
  	ret = sca3000_print_rev(indio_dev);
  	if (ret)
  		goto error_free_irq;
  
  	return iio_device_register(indio_dev);
  
  error_free_irq:
  	if (spi->irq)
  		free_irq(spi->irq, indio_dev);
  
  	return ret;
  }
  
  static int sca3000_stop_all_interrupts(struct sca3000_state *st)
  {
  	int ret;
  
  	mutex_lock(&st->lock);
  	ret = sca3000_read_data_short(st, SCA3000_REG_INT_MASK_ADDR, 1);
  	if (ret)
  		goto error_ret;
  	ret = sca3000_write_reg(st, SCA3000_REG_INT_MASK_ADDR,
  				(st->rx[0] &
  				 ~(SCA3000_REG_INT_MASK_RING_THREE_QUARTER |
  				   SCA3000_REG_INT_MASK_RING_HALF |
  				   SCA3000_REG_INT_MASK_ALL_INTS)));
  error_ret:
  	mutex_unlock(&st->lock);
  	return ret;
  }
  
  static int sca3000_remove(struct spi_device *spi)
  {
  	struct iio_dev *indio_dev = spi_get_drvdata(spi);
  	struct sca3000_state *st = iio_priv(indio_dev);
  
  	iio_device_unregister(indio_dev);
  
  	/* Must ensure no interrupts can be generated after this! */
  	sca3000_stop_all_interrupts(st);
  	if (spi->irq)
  		free_irq(spi->irq, indio_dev);
  
  	return 0;
  }
  
  static const struct spi_device_id sca3000_id[] = {
  	{"sca3000_d01", d01},
  	{"sca3000_e02", e02},
  	{"sca3000_e04", e04},
  	{"sca3000_e05", e05},
  	{}
  };
  MODULE_DEVICE_TABLE(spi, sca3000_id);
  
  static struct spi_driver sca3000_driver = {
  	.driver = {
  		.name = "sca3000",
  	},
  	.probe = sca3000_probe,
  	.remove = sca3000_remove,
  	.id_table = sca3000_id,
  };
  module_spi_driver(sca3000_driver);
  
  MODULE_AUTHOR("Jonathan Cameron <jic23@kernel.org>");
  MODULE_DESCRIPTION("VTI SCA3000 Series Accelerometers SPI driver");
  MODULE_LICENSE("GPL v2");
  