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Date:   Sat, 16 Mar 2019 19:00:53 +0000
From:   Jonathan Cameron <jic23@kernel.org>
To:     Marcelo Schmitt <marcelo.schmitt1@gmail.com>
Cc:     lars@metafoo.de, Michael.Hennerich@analog.com, knaack.h@gmx.de,
        pmeerw@pmeerw.net, linux-iio@vger.kernel.org,
        linux-kernel@vger.kernel.org, kernel-usp@googlegroups.com
Subject: Re: [PATCH v4 7/7] staging: iio: ad5933: move out of staging
Message-ID: <20190316190053.4f3c7b08@archlinux>
In-Reply-To: <20190316150811.hlwvltiplloywkng@smtp.gmail.com>
References: <20190316150811.hlwvltiplloywkng@smtp.gmail.com>
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On Sat, 16 Mar 2019 12:08:11 -0300
Marcelo Schmitt <marcelo.schmitt1@gmail.com> wrote:

> Move ad5933 impedance-analyzer driver from staging to mainline.
> The ad5933 is a high precision impedance converter system solution
> that combines an on-board frequency generator with an
> analog-to-digital converter (ADC). This driver was designed to be
> compatible with both ad5933 and ad5934 chips.
> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
Hi Marcelo,

A few new bits I spotted whilst looking at this again.
Obviously the issues with the renames in the previous patch still
apply.  

I'd like to get a few more sets of eyes on the driver before moving
it.  It's complex and quite different from most others so needs
more consideration than a more 'standard' driver!
Anyhow, upshot is that even if I thought it was perfect I'd still
want to give it a week or two on the list before concluding
everyone is happy with it.

Thanks,

Jonathan


> ---
>  drivers/iio/impedance-analyzer/Kconfig        |  18 +
>  drivers/iio/impedance-analyzer/Makefile       |   5 +
>  drivers/iio/impedance-analyzer/ad5933.c       | 811 ++++++++++++++++++
>  .../staging/iio/impedance-analyzer/Kconfig    |  18 -
>  .../staging/iio/impedance-analyzer/Makefile   |   5 -
>  .../staging/iio/impedance-analyzer/ad5933.c   | 811 ------------------
>  6 files changed, 834 insertions(+), 834 deletions(-)
>  create mode 100644 drivers/iio/impedance-analyzer/Kconfig
>  create mode 100644 drivers/iio/impedance-analyzer/Makefile
>  create mode 100644 drivers/iio/impedance-analyzer/ad5933.c
>  delete mode 100644 drivers/staging/iio/impedance-analyzer/Kconfig
>  delete mode 100644 drivers/staging/iio/impedance-analyzer/Makefile
>  delete mode 100644 drivers/staging/iio/impedance-analyzer/ad5933.c
> 
> diff --git a/drivers/iio/impedance-analyzer/Kconfig b/drivers/iio/impedance-analyzer/Kconfig
> new file mode 100644
> index 000000000000..b9a679cdd146
> --- /dev/null
> +++ b/drivers/iio/impedance-analyzer/Kconfig
> @@ -0,0 +1,18 @@
> +#
> +# Impedance Converter, Network Analyzer drivers
> +#
> +menu "Network Analyzer, Impedance Converters"
> +
> +config AD5933
> +	tristate "Analog Devices AD5933, AD5934 driver"
> +	depends on I2C
> +	select IIO_BUFFER
> +	select IIO_KFIFO_BUF
> +	help
> +	  Say yes here to build support for Analog Devices Impedance Converter,
> +	  Network Analyzer, AD5933/4.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called ad5933.
> +
> +endmenu
> diff --git a/drivers/iio/impedance-analyzer/Makefile b/drivers/iio/impedance-analyzer/Makefile
> new file mode 100644
> index 000000000000..7604d786583e
> --- /dev/null
> +++ b/drivers/iio/impedance-analyzer/Makefile
> @@ -0,0 +1,5 @@
> +#
> +# Makefile for Impedance Converter, Network Analyzer drivers
> +#
> +
> +obj-$(CONFIG_AD5933) += ad5933.o
> diff --git a/drivers/iio/impedance-analyzer/ad5933.c b/drivers/iio/impedance-analyzer/ad5933.c
> new file mode 100644
> index 000000000000..262415bc659d
> --- /dev/null
> +++ b/drivers/iio/impedance-analyzer/ad5933.c
> @@ -0,0 +1,811 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * AD5933 AD5934 Impedance Converter, Network Analyzer
> + *
> + * Copyright 2011 Analog Devices Inc.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/interrupt.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/sysfs.h>
> +#include <linux/types.h>
> +
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/kfifo_buf.h>
> +#include <linux/iio/sysfs.h>
> +
> +/* AD5933/AD5934 Registers */
> +#define AD5933_REG_CONTROL_HB		0x80	/* R/W, 1 byte */
> +#define AD5933_REG_CONTROL_LB		0x81	/* R/W, 1 byte */
> +#define AD5933_REG_FREQ_START		0x82	/* R/W, 3 bytes */
> +#define AD5933_REG_FREQ_INC		0x85	/* R/W, 3 bytes */
> +#define AD5933_REG_INC_NUM		0x88	/* R/W, 2 bytes, 9 bit */
> +#define AD5933_REG_SETTLING_CYCLES	0x8A	/* R/W, 2 bytes */
> +#define AD5933_REG_STATUS		0x8F	/* R, 1 byte */
> +#define AD5933_REG_TEMP_DATA		0x92	/* R, 2 bytes*/
> +#define AD5933_REG_REAL_DATA		0x94	/* R, 2 bytes*/
> +#define AD5933_REG_IMAG_DATA		0x96	/* R, 2 bytes*/
> +
> +/* AD5933_REG_CONTROL_HB Bits */
> +#define AD5933_CTRL_INIT_START_FREQ	(0x1 << 4)
> +#define AD5933_CTRL_START_SWEEP		(0x2 << 4)
> +#define AD5933_CTRL_INC_FREQ		(0x3 << 4)
> +#define AD5933_CTRL_REPEAT_FREQ		(0x4 << 4)
> +#define AD5933_CTRL_MEASURE_TEMP	(0x9 << 4)
> +#define AD5933_CTRL_POWER_DOWN		(0xA << 4)
> +#define AD5933_CTRL_STANDBY		(0xB << 4)
> +
> +#define AD5933_CTRL_RANGE_2000mVpp	(0x0 << 1)
> +#define AD5933_CTRL_RANGE_200mVpp	(0x1 << 1)
> +#define AD5933_CTRL_RANGE_400mVpp	(0x2 << 1)
> +#define AD5933_CTRL_RANGE_1000mVpp	(0x3 << 1)
These defines are never actually used...
Would be better to have an values passed into the macro
below even if they were.

> +#define AD5933_CTRL_RANGE(x)		((x) << 1)
> +
> +#define AD5933_CTRL_PGA_GAIN_1		(0x1 << 0)
> +#define AD5933_CTRL_PGA_GAIN_5		(0x0 << 0)
> +
> +/* AD5933_REG_CONTROL_LB Bits */
> +#define AD5933_CTRL_RESET		(0x1 << 4)
> +#define AD5933_CTRL_INT_SYSCLK		(0x0 << 3)
> +#define AD5933_CTRL_EXT_SYSCLK		(0x1 << 3)
> +
> +/* AD5933_REG_STATUS Bits */
> +#define AD5933_STAT_TEMP_VALID		(0x1 << 0)
> +#define AD5933_STAT_DATA_VALID		(0x1 << 1)
> +#define AD5933_STAT_SWEEP_DONE		(0x1 << 2)
BIT()

> +
> +/* I2C Block Commands */
> +#define AD5933_I2C_BLOCK_WRITE		0xA0
> +#define AD5933_I2C_BLOCK_READ		0xA1
> +#define AD5933_I2C_ADDR_POINTER		0xB0
> +
> +/* Device Specs */
> +#define AD5933_INT_OSC_FREQ_Hz		16776000
> +#define AD5933_MAX_OUTPUT_FREQ_Hz	100000
> +#define AD5933_MAX_RETRIES		100
> +

I think this next lot are being used as an enum
rather than because there values have specific meaning.
If so, just use an enum.

> +#define AD5933_OUT_RANGE		1
> +#define AD5933_OUT_RANGE_AVAIL		2
> +#define AD5933_OUT_SETTLING_CYCLES	3
> +#define AD5933_IN_PGA_GAIN		4
> +#define AD5933_IN_PGA_GAIN_AVAIL	5
> +#define AD5933_FREQ_POINTS		6
> +
> +#define AD5933_POLL_TIME_ms		10
> +#define AD5933_INIT_EXCITATION_TIME_ms	100
> +
> +struct ad5933_state {
> +	struct i2c_client		*client;
> +	struct regulator		*reg;
> +	struct clk			*mclk;
> +	struct delayed_work		work;
> +	struct mutex			lock; /* Protect sensor state */
> +	unsigned long			mclk_hz;
> +	unsigned char			ctrl_hb;
> +	unsigned char			ctrl_lb;
> +	unsigned int			range_avail[4];
> +	unsigned short			vref_mv;
> +	unsigned short			settling_cycles;
> +	unsigned short			freq_points;
> +	unsigned int			freq_start;
> +	unsigned int			freq_inc;
> +	unsigned int			state;
> +	unsigned int			poll_time_jiffies;
> +};
> +
> +#define AD5933_CHANNEL(_type, _extend_name, _info_mask_separate, _address, \
> +		_scan_index, _realbits) { \
> +	.type = (_type), \
> +	.extend_name = (_extend_name), \
> +	.info_mask_separate = (_info_mask_separate), \
> +	.address = (_address), \
> +	.scan_index = (_scan_index), \
> +	.scan_type = { \
> +		.sign = 's', \
> +		.realbits = (_realbits), \
> +		.storagebits = 16, \
> +	}, \
> +}
> +
> +static const struct iio_chan_spec ad5933_channels[] = {
> +	AD5933_CHANNEL(IIO_TEMP, NULL, BIT(IIO_CHAN_INFO_RAW) |
> +		BIT(IIO_CHAN_INFO_SCALE), AD5933_REG_TEMP_DATA, -1, 14),
> +	/* Ring Channels */
> +	AD5933_CHANNEL(IIO_VOLTAGE, "real", 0, AD5933_REG_REAL_DATA, 0, 16),
> +	AD5933_CHANNEL(IIO_VOLTAGE, "imag", 0, AD5933_REG_IMAG_DATA, 1, 16),
> +};
> +
> +static int ad5933_i2c_write(struct i2c_client *client, u8 reg, u8 len, u8 *data)
> +{
> +	int ret;
> +
> +	while (len--) {
> +		ret = i2c_smbus_write_byte_data(client, reg++, *data++);
> +		if (ret < 0) {
> +			dev_err(&client->dev, "I2C write error\n");
> +			return ret;
> +		}
> +	}
> +	return 0;
> +}
> +
> +static int ad5933_i2c_read(struct i2c_client *client, u8 reg, u8 len, u8 *data)
> +{
> +	int ret;
> +
> +	while (len--) {
> +		ret = i2c_smbus_read_byte_data(client, reg++);
> +		if (ret < 0) {
> +			dev_err(&client->dev, "I2C read error\n");
> +			return ret;
> +		}
> +		*data++ = ret;
> +	}
> +	return 0;
> +}
> +
> +static int ad5933_cmd(struct ad5933_state *st, unsigned char cmd)
> +{
> +	unsigned char dat = st->ctrl_hb | cmd;
> +
> +	return ad5933_i2c_write(st->client,
> +			AD5933_REG_CONTROL_HB, 1, &dat);
> +}
> +
> +static int ad5933_reset(struct ad5933_state *st)
> +{
> +	unsigned char dat = st->ctrl_lb | AD5933_CTRL_RESET;
> +
> +	return ad5933_i2c_write(st->client,
> +			AD5933_REG_CONTROL_LB, 1, &dat);
> +}
> +
> +static int ad5933_wait_busy(struct ad5933_state *st, unsigned char event)
> +{
> +	unsigned char val, timeout = AD5933_MAX_RETRIES;
> +	int ret;
> +
> +	while (timeout--) {
> +		ret =  ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &val);
> +		if (ret < 0)
> +			return ret;
> +		if (val & event)
> +			return val;
> +		cpu_relax();
> +		mdelay(1);
> +	}
> +
> +	return -EAGAIN;
> +}
> +
> +static int ad5933_set_freq(struct ad5933_state *st,
> +			   unsigned int reg, unsigned long freq)
> +{
> +	unsigned long long freqreg;
> +	union {
> +		__be32 d32;
> +		u8 d8[4];
> +	} dat;
> +
> +	freqreg = (u64)freq * (u64)(1 << 27);
> +	do_div(freqreg, st->mclk_hz / 4);
> +
> +	switch (reg) {
> +	case AD5933_REG_FREQ_START:
> +		st->freq_start = freq;
> +		break;
> +	case AD5933_REG_FREQ_INC:
> +		st->freq_inc = freq;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	dat.d32 = cpu_to_be32(freqreg);
> +	return ad5933_i2c_write(st->client, reg, 3, &dat.d8[1]);
> +}
> +
> +static int ad5933_setup(struct ad5933_state *st)
> +{
> +	__be16 dat;
> +	int ret;
> +
> +	ret = ad5933_reset(st);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = ad5933_set_freq(st, AD5933_REG_FREQ_START, 10000);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = ad5933_set_freq(st, AD5933_REG_FREQ_INC, 200);
> +	if (ret < 0)
> +		return ret;
> +
> +	st->settling_cycles = 10;
> +	dat = cpu_to_be16(st->settling_cycles);
> +
> +	ret = ad5933_i2c_write(st->client,
> +			       AD5933_REG_SETTLING_CYCLES,
> +			       2, (u8 *)&dat);
> +	if (ret < 0)
> +		return ret;
> +
> +	st->freq_points = 100;
> +	dat = cpu_to_be16(st->freq_points);
> +
> +	return ad5933_i2c_write(st->client, AD5933_REG_INC_NUM, 2, (u8 *)&dat);
> +}
> +
> +static void ad5933_calc_out_ranges(struct ad5933_state *st)
> +{
> +	int i;
> +	unsigned int normalized_3v3[4] = {1980, 198, 383, 970};
> +
> +	for (i = 0; i < 4; i++)
> +		st->range_avail[i] = normalized_3v3[i] * st->vref_mv / 3300;
> +}
> +
> +/*
> + * handles: AD5933_REG_FREQ_START and AD5933_REG_FREQ_INC
> + */
> +
> +static ssize_t ad5933_show_frequency(struct device *dev,
> +				     struct device_attribute *attr,
> +				     char *buf)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	struct ad5933_state *st = iio_priv(indio_dev);
> +	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> +	int ret;
> +	unsigned long long freqreg;
> +	union {
> +		__be32 d32;
> +		u8 d8[4];
> +	} dat;
> +
> +	ret = iio_device_claim_direct_mode(indio_dev);
> +	if (ret)
> +		return ret;
> +	ret = ad5933_i2c_read(st->client, this_attr->address, 3, &dat.d8[1]);
> +	iio_device_release_direct_mode(indio_dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	freqreg = be32_to_cpu(dat.d32) & 0xFFFFFF;
> +
> +	freqreg = (u64)freqreg * (u64)(st->mclk_hz / 4);
> +	do_div(freqreg, 1 << 27);
> +
> +	return sprintf(buf, "%d\n", (int)freqreg);
> +}
> +
> +static ssize_t ad5933_store_frequency(struct device *dev,
> +				      struct device_attribute *attr,
> +				      const char *buf,
> +				      size_t len)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	struct ad5933_state *st = iio_priv(indio_dev);
> +	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> +	unsigned long val;
> +	int ret;
> +
> +	ret = kstrtoul(buf, 10, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val > AD5933_MAX_OUTPUT_FREQ_Hz)
> +		return -EINVAL;
> +
> +	ret = iio_device_claim_direct_mode(indio_dev);
> +	if (ret)
> +		return ret;
> +	ret = ad5933_set_freq(st, this_attr->address, val);
> +	iio_device_release_direct_mode(indio_dev);
> +
> +	return ret ? ret : len;
> +}
> +
> +static IIO_DEVICE_ATTR(out_altvoltage0_frequency_start, 0644,
> +			ad5933_show_frequency,
> +			ad5933_store_frequency,
> +			AD5933_REG_FREQ_START);
> +
> +static IIO_DEVICE_ATTR(out_altvoltage0_frequency_increment, 0644,
> +			ad5933_show_frequency,
> +			ad5933_store_frequency,
> +			AD5933_REG_FREQ_INC);
> +
> +static ssize_t ad5933_show(struct device *dev,
> +			   struct device_attribute *attr,
> +			   char *buf)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	struct ad5933_state *st = iio_priv(indio_dev);
> +	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> +	int ret = 0, len = 0;
> +
> +	mutex_lock(&st->lock);
> +	switch ((u32)this_attr->address) {
> +	case AD5933_OUT_RANGE:
> +		len = sprintf(buf, "%u\n",
> +			      st->range_avail[(st->ctrl_hb >> 1) & 0x3]);
> +		break;
> +	case AD5933_OUT_RANGE_AVAIL:
> +		len = sprintf(buf, "%u %u %u %u\n", st->range_avail[0],
> +			      st->range_avail[3], st->range_avail[2],
> +			      st->range_avail[1]);
> +		break;
> +	case AD5933_OUT_SETTLING_CYCLES:
> +		len = sprintf(buf, "%d\n", st->settling_cycles);
> +		break;
> +	case AD5933_IN_PGA_GAIN:
> +		len = sprintf(buf, "%s\n",
> +			      (st->ctrl_hb & AD5933_CTRL_PGA_GAIN_1) ?
> +			      "1" : "0.2");
> +		break;
> +	case AD5933_IN_PGA_GAIN_AVAIL:
> +		len = sprintf(buf, "1 0.2\n");
> +		break;
> +	case AD5933_FREQ_POINTS:
> +		len = sprintf(buf, "%d\n", st->freq_points);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +	}
> +
> +	mutex_unlock(&st->lock);
> +	return ret ? ret : len;
> +}
> +
> +static ssize_t ad5933_store(struct device *dev,
> +			    struct device_attribute *attr,
> +			    const char *buf,
> +			    size_t len)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	struct ad5933_state *st = iio_priv(indio_dev);
> +	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> +	u16 val;
> +	int i, ret = 0;
> +	__be16 dat;
> +
> +	if (this_attr->address != AD5933_IN_PGA_GAIN) {
> +		ret = kstrtou16(buf, 10, &val);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	ret = iio_device_claim_direct_mode(indio_dev);
> +	if (ret)
> +		return ret;
> +	mutex_lock(&st->lock);
> +	switch ((u32)this_attr->address) {
> +	case AD5933_OUT_RANGE:
> +		ret = -EINVAL;
> +		for (i = 0; i < 4; i++)
> +			if (val == st->range_avail[i]) {
> +				st->ctrl_hb &= ~AD5933_CTRL_RANGE(0x3);
Use a proper mask, not the max value in the field.

> +				st->ctrl_hb |= AD5933_CTRL_RANGE(i);
> +				ret = ad5933_cmd(st, 0);
> +				break;
> +			}
> +		break;
> +	case AD5933_IN_PGA_GAIN:
> +		if (sysfs_streq(buf, "1")) {
> +			st->ctrl_hb |= AD5933_CTRL_PGA_GAIN_1;
> +		} else if (sysfs_streq(buf, "0.2")) {
> +			st->ctrl_hb &= ~AD5933_CTRL_PGA_GAIN_1;
> +		} else {
> +			ret = -EINVAL;
> +			break;
> +		}
> +		ret = ad5933_cmd(st, 0);
> +		break;
> +	case AD5933_OUT_SETTLING_CYCLES:
> +		val = clamp(val, (u16)0, (u16)0x7FF);
> +		st->settling_cycles = val;
> +
> +		/* 2x, 4x handling, see datasheet */
> +		if (val > 1022)
> +			val = (val >> 2) | (3 << 9);
> +		else if (val > 511)
> +			val = (val >> 1) | (1 << 9);
> +
> +		dat = cpu_to_be16(val);
> +		ret = ad5933_i2c_write(st->client,
> +				       AD5933_REG_SETTLING_CYCLES,
> +				       2, (u8 *)&dat);
> +		break;
> +	case AD5933_FREQ_POINTS:
> +		val = clamp(val, (u16)0, (u16)511);
> +		st->freq_points = val;
> +
> +		dat = cpu_to_be16(val);
> +		ret = ad5933_i2c_write(st->client, AD5933_REG_INC_NUM, 2,
> +				       (u8 *)&dat);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +	}
> +
> +	mutex_unlock(&st->lock);
> +	iio_device_release_direct_mode(indio_dev);
> +	return ret ? ret : len;
> +}
> +
> +static IIO_DEVICE_ATTR(out_voltage0_scale, 0644,
> +			ad5933_show,
> +			ad5933_store,
> +			AD5933_OUT_RANGE);
> +
> +static IIO_DEVICE_ATTR(out_voltage0_scale_available, 0444,
> +			ad5933_show,
> +			NULL,
> +			AD5933_OUT_RANGE_AVAIL);
> +
> +static IIO_DEVICE_ATTR(in_voltage0_scale, 0644,
> +			ad5933_show,
> +			ad5933_store,
> +			AD5933_IN_PGA_GAIN);
> +
> +static IIO_DEVICE_ATTR(in_voltage0_scale_available, 0444,
> +			ad5933_show,
> +			NULL,
> +			AD5933_IN_PGA_GAIN_AVAIL);
> +
> +static IIO_DEVICE_ATTR(out_altvoltage0_frequency_points, 0644,
> +			ad5933_show,
> +			ad5933_store,
> +			AD5933_FREQ_POINTS);
> +
> +static IIO_DEVICE_ATTR(out_altvoltage0_settling_cycles, 0644,
> +			ad5933_show,
> +			ad5933_store,
> +			AD5933_OUT_SETTLING_CYCLES);
> +
> +/*
> + * note:
> + * ideally we would handle the scale attributes via the iio_info
> + * (read|write)_raw methods, however this part is a untypical since we
> + * don't create dedicated sysfs channel attributes for out0 and in0.
> + */
> +static struct attribute *ad5933_attributes[] = {
> +	&iio_dev_attr_out_altvoltage0_raw.dev_attr.attr,
> +	&iio_dev_attr_out_altvoltage0_scale_available.dev_attr.attr,
> +	&iio_dev_attr_out_altvoltage0_frequency_start.dev_attr.attr,
> +	&iio_dev_attr_out_altvoltage0_frequency_increment.dev_attr.attr,
> +	&iio_dev_attr_out_altvoltage0_frequency_points.dev_attr.attr,
> +	&iio_dev_attr_out_altvoltage0_settling_cycles.dev_attr.attr,
> +	&iio_dev_attr_in_voltage0_scale.dev_attr.attr,
> +	&iio_dev_attr_in_voltage0_scale_available.dev_attr.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group ad5933_attribute_group = {
> +	.attrs = ad5933_attributes,
> +};
> +
> +static int ad5933_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val,
> +			   int *val2,
> +			   long m)
> +{
> +	struct ad5933_state *st = iio_priv(indio_dev);
> +	__be16 dat;
> +	int ret;
> +
> +	switch (m) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = iio_device_claim_direct_mode(indio_dev);
> +		if (ret)
> +			return ret;
> +		ret = ad5933_cmd(st, AD5933_CTRL_MEASURE_TEMP);
> +		if (ret < 0)
> +			goto out;
> +		ret = ad5933_wait_busy(st, AD5933_STAT_TEMP_VALID);
> +		if (ret < 0)
> +			goto out;
> +
> +		ret = ad5933_i2c_read(st->client,
> +				      AD5933_REG_TEMP_DATA,
> +				      2, (u8 *)&dat);
> +		if (ret < 0)
> +			goto out;
> +		iio_device_release_direct_mode(indio_dev);
> +		*val = sign_extend32(be16_to_cpu(dat), 13);
> +
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = 1000;
> +		*val2 = 5;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	}
> +
> +	return -EINVAL;
> +out:
> +	iio_device_release_direct_mode(indio_dev);
> +	return ret;
> +}
> +
> +static const struct iio_info ad5933_info = {
> +	.read_raw = ad5933_read_raw,
> +	.attrs = &ad5933_attribute_group,
> +};
> +
> +static int ad5933_ring_preenable(struct iio_dev *indio_dev)
> +{
> +	struct ad5933_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	if (bitmap_empty(indio_dev->active_scan_mask, indio_dev->masklength))
> +		return -EINVAL;
> +
> +	ret = ad5933_reset(st);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = ad5933_cmd(st, AD5933_CTRL_STANDBY);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = ad5933_cmd(st, AD5933_CTRL_INIT_START_FREQ);
> +	if (ret < 0)
> +		return ret;
> +
> +	st->state = AD5933_CTRL_INIT_START_FREQ;
> +
> +	return 0;
> +}
> +
> +static int ad5933_ring_postenable(struct iio_dev *indio_dev)
> +{
> +	struct ad5933_state *st = iio_priv(indio_dev);
> +
> +	/*
> +	 * AD5933_CTRL_INIT_START_FREQ:
> +	 * High Q complex circuits require a long time to reach steady state.
> +	 * To facilitate the measurement of such impedances, this mode allows
> +	 * the user full control of the settling time requirement before
> +	 * entering start frequency sweep mode where the impedance measurement
> +	 * takes place. In this mode the impedance is excited with the
> +	 * programmed start frequency (ad5933_ring_preenable),
> +	 * but no measurement takes place.
> +	 */
> +
> +	schedule_delayed_work(&st->work,
> +			      msecs_to_jiffies(AD5933_INIT_EXCITATION_TIME_ms));
> +	return 0;
> +}
> +
> +static int ad5933_ring_postdisable(struct iio_dev *indio_dev)
> +{
> +	struct ad5933_state *st = iio_priv(indio_dev);
> +
> +	cancel_delayed_work_sync(&st->work);
> +	return ad5933_cmd(st, AD5933_CTRL_POWER_DOWN);
> +}
> +
> +static const struct iio_buffer_setup_ops ad5933_ring_setup_ops = {
> +	.preenable = ad5933_ring_preenable,
> +	.postenable = ad5933_ring_postenable,
> +	.postdisable = ad5933_ring_postdisable,
> +};
> +
> +static int ad5933_register_ring_funcs_and_init(struct iio_dev *indio_dev)
> +{
> +	struct iio_buffer *buffer;
> +
> +	buffer = iio_kfifo_allocate();
> +	if (!buffer)
> +		return -ENOMEM;
> +
> +	iio_device_attach_buffer(indio_dev, buffer);
> +
> +	/* Ring buffer functions - here trigger setup related */
> +	indio_dev->setup_ops = &ad5933_ring_setup_ops;
> +
> +	return 0;
> +}
> +
> +static void ad5933_work(struct work_struct *work)
> +{
> +	struct ad5933_state *st = container_of(work,
> +		struct ad5933_state, work.work);
> +	struct iio_dev *indio_dev = i2c_get_clientdata(st->client);
> +	__be16 buf[2];
> +	int val[2];
> +	unsigned char status;
> +	int ret;
> +
> +	if (st->state == AD5933_CTRL_INIT_START_FREQ) {
> +		/* start sweep */
> +		ad5933_cmd(st, AD5933_CTRL_START_SWEEP);
> +		st->state = AD5933_CTRL_START_SWEEP;
> +		schedule_delayed_work(&st->work, st->poll_time_jiffies);
> +		return;
> +	}
> +
> +	ret = ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
> +	if (ret)
> +		return;
> +
> +	if (status & AD5933_STAT_DATA_VALID) {
> +		int scan_count = bitmap_weight(indio_dev->active_scan_mask,
> +					       indio_dev->masklength);
> +		ret = ad5933_i2c_read(st->client,
> +				test_bit(1, indio_dev->active_scan_mask) ?
> +				AD5933_REG_REAL_DATA : AD5933_REG_IMAG_DATA,
> +				scan_count * 2, (u8 *)buf);
> +		if (ret)
> +			return;
> +
> +		if (scan_count == 2) {
> +			val[0] = be16_to_cpu(buf[0]);
> +			val[1] = be16_to_cpu(buf[1]);
> +		} else {
> +			val[0] = be16_to_cpu(buf[0]);
> +		}
> +		iio_push_to_buffers(indio_dev, val);
> +	} else {
> +		/* no data available - try again later */
> +		schedule_delayed_work(&st->work, st->poll_time_jiffies);
> +		return;
> +	}
> +
> +	if (status & AD5933_STAT_SWEEP_DONE) {
> +		/*
> +		 * last sample received - power down do
> +		 * nothing until the ring enable is toggled
> +		 */
> +		ad5933_cmd(st, AD5933_CTRL_POWER_DOWN);
> +	} else {
> +		/* we just received a valid datum, move on to the next */
> +		ad5933_cmd(st, AD5933_CTRL_INC_FREQ);
> +		schedule_delayed_work(&st->work, st->poll_time_jiffies);
> +	}
> +}
> +
> +static int ad5933_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	int ret;
> +	struct ad5933_state *st;
> +	struct iio_dev *indio_dev;
> +	unsigned long ext_clk_hz = 0;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	st = iio_priv(indio_dev);
> +	i2c_set_clientdata(client, indio_dev);
> +	st->client = client;
> +
> +	mutex_init(&st->lock);
> +
> +	st->reg = devm_regulator_get(&client->dev, "vdd");
> +	if (IS_ERR(st->reg))
> +		return PTR_ERR(st->reg);
> +
> +	ret = regulator_enable(st->reg);
> +	if (ret) {
> +		dev_err(&client->dev, "Failed to enable specified VDD supply\n");
> +		return ret;
> +	}
> +	ret = regulator_get_voltage(st->reg);
> +
> +	if (ret < 0)
> +		goto error_disable_reg;
> +
> +	st->vref_mv = ret / 1000;
> +
> +	st->mclk = devm_clk_get(&client->dev, "mclk");
> +	if (IS_ERR(st->mclk) && PTR_ERR(st->mclk) != -ENOENT) {
> +		ret = PTR_ERR(st->mclk);
> +		goto error_disable_reg;
> +	}
> +
> +	if (!IS_ERR(st->mclk)) {
> +		ret = clk_prepare_enable(st->mclk);
> +		if (ret < 0)
> +			goto error_disable_reg;
> +		ext_clk_hz = clk_get_rate(st->mclk);
> +	}
> +
> +	if (ext_clk_hz) {
> +		st->mclk_hz = ext_clk_hz;
> +		st->ctrl_lb = AD5933_CTRL_EXT_SYSCLK;
> +	} else {
> +		st->mclk_hz = AD5933_INT_OSC_FREQ_Hz;
> +		st->ctrl_lb = AD5933_CTRL_INT_SYSCLK;
> +	}
> +
> +	ad5933_calc_out_ranges(st);
> +	INIT_DELAYED_WORK(&st->work, ad5933_work);
> +	st->poll_time_jiffies = msecs_to_jiffies(AD5933_POLL_TIME_ms);
> +
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->info = &ad5933_info;
> +	indio_dev->name = id->name;
> +	indio_dev->modes = (INDIO_BUFFER_SOFTWARE | INDIO_DIRECT_MODE);
> +	indio_dev->channels = ad5933_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(ad5933_channels);
> +
> +	ret = ad5933_register_ring_funcs_and_init(indio_dev);
> +	if (ret)
> +		goto error_disable_mclk;
> +
> +	ret = ad5933_setup(st);
> +	if (ret)
> +		goto error_unreg_ring;
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret)
> +		goto error_unreg_ring;
> +
> +	return 0;
> +
> +error_unreg_ring:
> +	iio_kfifo_free(indio_dev->buffer);
> +error_disable_mclk:
> +	clk_disable_unprepare(st->mclk);
> +error_disable_reg:
> +	regulator_disable(st->reg);
> +
> +	return ret;
> +}
> +
> +static int ad5933_remove(struct i2c_client *client)
> +{
> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +	struct ad5933_state *st = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
> +	iio_kfifo_free(indio_dev->buffer);
> +	regulator_disable(st->reg);
> +	clk_disable_unprepare(st->mclk);

Why is this in a different order to the error handling above?
(and I assume probe but that's off the top of my screen)

> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id ad5933_id[] = {
> +	{ "ad5933", 0 },
> +	{ "ad5934", 0 },
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, ad5933_id);
> +
> +static const struct of_device_id ad5933_of_match[] = {
> +	{ .compatible = "adi,ad5933" },
> +	{ .compatible = "adi,ad5934" },
> +	{ },
> +};
> +
> +MODULE_DEVICE_TABLE(of, ad5933_of_match);
> +
> +static struct i2c_driver ad5933_driver = {
> +	.driver = {
> +		.name = "ad5933",
> +		.of_match_table = ad5933_of_match,
> +	},
> +	.probe = ad5933_probe,
> +	.remove = ad5933_remove,
> +	.id_table = ad5933_id,
> +};
> +module_i2c_driver(ad5933_driver);
> +
> +MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
> +MODULE_DESCRIPTION("Analog Devices AD5933 Impedance Conv. Network Analyzer");
> +MODULE_LICENSE("GPL v2");