Re: [PATCH v2 2/3] iio: adc: ltc2497: split protocol independent part in a separate module

[Jonathan Cameron <jic23@kernel.org>]

On Sat, 16 Nov 2019 15:58:08 +0000
Jonathan Cameron <jic23@kernel.org> wrote:

> On Thu, 14 Nov 2019 11:51:58 +0100
> Uwe Kleine-König <u.kleine-koenig@pengutronix.de> wrote:
> 
> > This allows to share most of this driver for the ltc2496 driver added in
> > the next commit that is an SPI variant of the ltc2497.
> > 
> > Also generalize the entry in MAINTAINER to cover the newly introduced
> > files.
> > 
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>  
> I'm fairly sure there is no way of easily enforcing data being it's own
> cacheline whilst on the stack.  I would just put that back in the generic
> structure and add a note saying it's only used for the SPI users of
> the core structure.
Which is odd given this is an i2c driver (so far).  Whilst wolfram
has added the option to do direct DMA on i2c devices, I don't think this
driver is using it anyway.  Hence that ___cacheline_aligned magic
probably wasn't needed here in the first place.

The SPI driver however definitely needs those guarantees. Comments in patch 3.

Jonathan

> 
> Jonathan
> 
> > ---
> >  MAINTAINERS               |   2 +-
> >  drivers/iio/adc/Makefile  |   2 +-
> >  drivers/iio/adc/ltc2497.c | 237 +++++-------------------------------
> >  drivers/iio/adc/ltc249x.c | 244 ++++++++++++++++++++++++++++++++++++++
> >  drivers/iio/adc/ltc249x.h |  18 +++
> >  5 files changed, 292 insertions(+), 211 deletions(-)
> >  create mode 100644 drivers/iio/adc/ltc249x.c
> >  create mode 100644 drivers/iio/adc/ltc249x.h
> > 
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index eb19fad370d7..8b1211038617 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -1029,7 +1029,7 @@ S:	Supported
> >  F:	Documentation/ABI/testing/sysfs-bus-iio-frequency-ad9523
> >  F:	Documentation/ABI/testing/sysfs-bus-iio-frequency-adf4350
> >  F:	drivers/iio/*/ad*
> > -F:	drivers/iio/adc/ltc2497*
> > +F:	drivers/iio/adc/ltc249*
> >  X:	drivers/iio/*/adjd*
> >  F:	drivers/staging/iio/*/ad*
> >  
> > diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> > index ef9cc485fb67..660242c2cca7 100644
> > --- a/drivers/iio/adc/Makefile
> > +++ b/drivers/iio/adc/Makefile
> > @@ -47,7 +47,7 @@ obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
> >  obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o
> >  obj-$(CONFIG_LTC2471) += ltc2471.o
> >  obj-$(CONFIG_LTC2485) += ltc2485.o
> > -obj-$(CONFIG_LTC2497) += ltc2497.o
> > +obj-$(CONFIG_LTC2497) += ltc2497.o ltc249x.o
> >  obj-$(CONFIG_MAX1027) += max1027.o
> >  obj-$(CONFIG_MAX11100) += max11100.o
> >  obj-$(CONFIG_MAX1118) += max1118.o
> > diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c
> > index 470406032720..640c512c5090 100644
> > --- a/drivers/iio/adc/ltc2497.c
> > +++ b/drivers/iio/adc/ltc2497.c
> > @@ -7,260 +7,79 @@
> >   * Datasheet: http://cds.linear.com/docs/en/datasheet/2497fd.pdf
> >   */
> >  
> > -#include <linux/delay.h>
> >  #include <linux/i2c.h>
> >  #include <linux/iio/iio.h>
> >  #include <linux/iio/driver.h>
> > -#include <linux/iio/sysfs.h>
> >  #include <linux/module.h>
> >  #include <linux/of.h>
> > -#include <linux/regulator/consumer.h>
> >  
> > -#define LTC2497_ENABLE			0xA0
> > -#define LTC2497_SGL			BIT(4)
> > -#define LTC2497_DIFF			0
> > -#define LTC2497_SIGN			BIT(3)
> > -#define LTC2497_CONFIG_DEFAULT		LTC2497_ENABLE
> > -#define LTC2497_CONVERSION_TIME_MS	150ULL
> > +#include "ltc249x.h"
> >  
> >  struct ltc2497_st {
> > +	/* this must be the first member */
> > +	struct ltc249x_driverdata common_ddata;
> >  	struct i2c_client *client;
> > -	struct regulator *ref;
> > -	ktime_t	time_prev;
> > -	u8 addr_prev;
> > -	/*
> > -	 * DMA (thus cache coherency maintenance) requires the
> > -	 * transfer buffers to live in their own cache lines.
> > -	 */
> > -	__be32 buf ____cacheline_aligned;
> >  };
> >  
> > -static int ltc2497_wait_conv(struct ltc2497_st *st)
> > -{
> > -	s64 time_elapsed;
> > -
> > -	time_elapsed = ktime_ms_delta(ktime_get(), st->time_prev);
> > -
> > -	if (time_elapsed < LTC2497_CONVERSION_TIME_MS) {
> > -		/* delay if conversion time not passed
> > -		 * since last read or write
> > -		 */
> > -		if (msleep_interruptible(
> > -		    LTC2497_CONVERSION_TIME_MS - time_elapsed))
> > -			return -ERESTARTSYS;
> > -
> > -		return 0;
> > -	}
> > -
> > -	if (time_elapsed - LTC2497_CONVERSION_TIME_MS <= 0) {
> > -		/* We're in automatic mode -
> > -		 * so the last reading is stil not outdated
> > -		 */
> > -		return 0;
> > -	}
> > -
> > -	return 1;
> > -}
> > -
> > -static int ltc2497_read(struct ltc2497_st *st, u8 address, int *val)
> > +static int ltc2497_result_and_measure(struct ltc249x_driverdata *ddata,
> > +				      u8 address, int *val)
> >  {
> > -	struct i2c_client *client = st->client;
> > -	int ret;
> > -
> > -	ret = ltc2497_wait_conv(st);
> > -	if (ret < 0)
> > -		return ret;
> > -
> > -	if (ret || st->addr_prev != address) {
> > -		ret = i2c_smbus_write_byte(st->client,
> > -					   LTC2497_ENABLE | address);
> > -		if (ret < 0)
> > -			return ret;
> > -		st->addr_prev = address;
> > -		if (msleep_interruptible(LTC2497_CONVERSION_TIME_MS))
> > -			return -ERESTARTSYS;
> > -	}
> > -	ret = i2c_master_recv(client, (char *)&st->buf, 3);
> > -	if (ret < 0)  {
> > -		dev_err(&client->dev, "i2c_master_recv failed\n");
> > -		return ret;
> > -	}
> > -	st->time_prev = ktime_get();
> > +	struct ltc2497_st *st =
> > +		container_of(ddata, struct ltc2497_st, common_ddata);
> >  
> > -	/* convert and shift the result,
> > -	 * and finally convert from offset binary to signed integer
> > +	/*
> > +	 * DMA (thus cache coherency maintenance) requires the
> > +	 * transfer buffers to live in their own cache lines.
> >  	 */
> > -	*val = (be32_to_cpu(st->buf) >> 14) - (1 << 17);
> > -
> > -	return ret;
> > -}
> > -
> > -static int ltc2497_read_raw(struct iio_dev *indio_dev,
> > -			    struct iio_chan_spec const *chan,
> > -			    int *val, int *val2, long mask)
> > -{
> > -	struct ltc2497_st *st = iio_priv(indio_dev);
> > +	__be32 buf ____cacheline_aligned;  
> 
> From what I recall that has no useful affect on the stack.
> Can only be used to enforce padding within a structure on the
> heap.  Directly allocating from the heap here would also
> provide relevant guarantees.
> 
> >  	int ret;
> >  
> > -	switch (mask) {
> > -	case IIO_CHAN_INFO_RAW:
> > -		mutex_lock(&indio_dev->mlock);
> > -		ret = ltc2497_read(st, chan->address, val);
> > -		mutex_unlock(&indio_dev->mlock);
> > -		if (ret < 0)
> > +	if (val) {
> > +		ret = i2c_master_recv(st->client, (char *)&buf, 3);
> > +		if (ret < 0) {
> > +			dev_err(&st->client->dev, "i2c_master_recv failed\n");
> >  			return ret;
> > +		}
> >  
> > -		return IIO_VAL_INT;
> > -
> > -	case IIO_CHAN_INFO_SCALE:
> > -		ret = regulator_get_voltage(st->ref);
> > -		if (ret < 0)
> > -			return ret;
> > -
> > -		*val = ret / 1000;
> > -		*val2 = 17;
> > -
> > -		return IIO_VAL_FRACTIONAL_LOG2;
> > -
> > -	default:
> > -		return -EINVAL;
> > +		*val = (be32_to_cpu(buf) >> 14) - (1 << 17);
> >  	}
> > -}
> >  
> > -#define LTC2497_CHAN(_chan, _addr, _ds_name) { \
> > -	.type = IIO_VOLTAGE, \
> > -	.indexed = 1, \
> > -	.channel = (_chan), \
> > -	.address = (_addr | (_chan / 2) | ((_chan & 1) ? LTC2497_SIGN : 0)), \
> > -	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> > -	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> > -	.datasheet_name = (_ds_name), \
> > -}
> > -
> > -#define LTC2497_CHAN_DIFF(_chan, _addr) { \
> > -	.type = IIO_VOLTAGE, \
> > -	.indexed = 1, \
> > -	.channel = (_chan) * 2 + ((_addr) & LTC2497_SIGN ? 1 : 0), \
> > -	.channel2 = (_chan) * 2 + ((_addr) & LTC2497_SIGN ? 0 : 1),\
> > -	.address = (_addr | _chan), \
> > -	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> > -	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> > -	.differential = 1, \
> > +	ret = i2c_smbus_write_byte(st->client,
> > +				   LTC249X_ENABLE | address);
> > +	if (ret)
> > +		dev_err(&st->client->dev, "i2c transfer failed: %pe\n",
> > +			ERR_PTR(ret));
> > +	return ret;
> >  }
> >  
> > -static const struct iio_chan_spec ltc2497_channel[] = {
> > -	LTC2497_CHAN(0, LTC2497_SGL, "CH0"),
> > -	LTC2497_CHAN(1, LTC2497_SGL, "CH1"),
> > -	LTC2497_CHAN(2, LTC2497_SGL, "CH2"),
> > -	LTC2497_CHAN(3, LTC2497_SGL, "CH3"),
> > -	LTC2497_CHAN(4, LTC2497_SGL, "CH4"),
> > -	LTC2497_CHAN(5, LTC2497_SGL, "CH5"),
> > -	LTC2497_CHAN(6, LTC2497_SGL, "CH6"),
> > -	LTC2497_CHAN(7, LTC2497_SGL, "CH7"),
> > -	LTC2497_CHAN(8, LTC2497_SGL, "CH8"),
> > -	LTC2497_CHAN(9, LTC2497_SGL, "CH9"),
> > -	LTC2497_CHAN(10, LTC2497_SGL, "CH10"),
> > -	LTC2497_CHAN(11, LTC2497_SGL, "CH11"),
> > -	LTC2497_CHAN(12, LTC2497_SGL, "CH12"),
> > -	LTC2497_CHAN(13, LTC2497_SGL, "CH13"),
> > -	LTC2497_CHAN(14, LTC2497_SGL, "CH14"),
> > -	LTC2497_CHAN(15, LTC2497_SGL, "CH15"),
> > -	LTC2497_CHAN_DIFF(0, LTC2497_DIFF),
> > -	LTC2497_CHAN_DIFF(1, LTC2497_DIFF),
> > -	LTC2497_CHAN_DIFF(2, LTC2497_DIFF),
> > -	LTC2497_CHAN_DIFF(3, LTC2497_DIFF),
> > -	LTC2497_CHAN_DIFF(4, LTC2497_DIFF),
> > -	LTC2497_CHAN_DIFF(5, LTC2497_DIFF),
> > -	LTC2497_CHAN_DIFF(6, LTC2497_DIFF),
> > -	LTC2497_CHAN_DIFF(7, LTC2497_DIFF),
> > -	LTC2497_CHAN_DIFF(0, LTC2497_DIFF | LTC2497_SIGN),
> > -	LTC2497_CHAN_DIFF(1, LTC2497_DIFF | LTC2497_SIGN),
> > -	LTC2497_CHAN_DIFF(2, LTC2497_DIFF | LTC2497_SIGN),
> > -	LTC2497_CHAN_DIFF(3, LTC2497_DIFF | LTC2497_SIGN),
> > -	LTC2497_CHAN_DIFF(4, LTC2497_DIFF | LTC2497_SIGN),
> > -	LTC2497_CHAN_DIFF(5, LTC2497_DIFF | LTC2497_SIGN),
> > -	LTC2497_CHAN_DIFF(6, LTC2497_DIFF | LTC2497_SIGN),
> > -	LTC2497_CHAN_DIFF(7, LTC2497_DIFF | LTC2497_SIGN),
> > -};
> > -
> > -static const struct iio_info ltc2497_info = {
> > -	.read_raw = ltc2497_read_raw,
> > -};
> > -
> >  static int ltc2497_probe(struct i2c_client *client,
> >  			 const struct i2c_device_id *id)
> >  {
> >  	struct iio_dev *indio_dev;
> >  	struct ltc2497_st *st;
> > -	struct iio_map *plat_data;
> > -	int ret;
> > +	struct device *dev = &client->dev;
> >  
> >  	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
> >  				     I2C_FUNC_SMBUS_WRITE_BYTE))
> >  		return -EOPNOTSUPP;
> >  
> > -	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*st));
> > +	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
> >  	if (!indio_dev)
> >  		return -ENOMEM;
> >  
> >  	st = iio_priv(indio_dev);
> >  	i2c_set_clientdata(client, indio_dev);
> >  	st->client = client;
> > +	st->common_ddata.result_and_measure = ltc2497_result_and_measure;
> >  
> > -	indio_dev->dev.parent = &client->dev;
> > -	indio_dev->name = id->name;
> > -	indio_dev->info = &ltc2497_info;
> > -	indio_dev->modes = INDIO_DIRECT_MODE;
> > -	indio_dev->channels = ltc2497_channel;
> > -	indio_dev->num_channels = ARRAY_SIZE(ltc2497_channel);
> > -
> > -	st->ref = devm_regulator_get(&client->dev, "vref");
> > -	if (IS_ERR(st->ref))
> > -		return PTR_ERR(st->ref);
> > -
> > -	ret = regulator_enable(st->ref);
> > -	if (ret < 0)
> > -		return ret;
> > -
> > -	if (client->dev.platform_data) {
> > -		plat_data = ((struct iio_map *)client->dev.platform_data);
> > -		ret = iio_map_array_register(indio_dev, plat_data);
> > -		if (ret) {
> > -			dev_err(&indio_dev->dev, "iio map err: %d\n", ret);
> > -			goto err_regulator_disable;
> > -		}
> > -	}
> > -
> > -	ret = i2c_smbus_write_byte(st->client, LTC2497_CONFIG_DEFAULT);
> > -	if (ret < 0)
> > -		goto err_array_unregister;
> > -
> > -	st->addr_prev = LTC2497_CONFIG_DEFAULT;
> > -	st->time_prev = ktime_get();
> > -
> > -	ret = iio_device_register(indio_dev);
> > -	if (ret < 0)
> > -		goto err_array_unregister;
> > -
> > -	return 0;
> > -
> > -err_array_unregister:
> > -	iio_map_array_unregister(indio_dev);
> > -
> > -err_regulator_disable:
> > -	regulator_disable(st->ref);
> > -
> > -	return ret;
> > +	return ltc249x_probe(dev, indio_dev);
> >  }
> >  
> >  static int ltc2497_remove(struct i2c_client *client)
> >  {
> >  	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> > -	struct ltc2497_st *st = iio_priv(indio_dev);
> >  
> > -	iio_map_array_unregister(indio_dev);
> > -	iio_device_unregister(indio_dev);
> > -	regulator_disable(st->ref);
> > +	ltc249x_remove(indio_dev);
> >  
> >  	return 0;
> >  }
> > diff --git a/drivers/iio/adc/ltc249x.c b/drivers/iio/adc/ltc249x.c
> > new file mode 100644
> > index 000000000000..7af1086236c0
> > --- /dev/null
> > +++ b/drivers/iio/adc/ltc249x.c
> > @@ -0,0 +1,244 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * ltc249x.c - Common code for Analog Devices/Linear Technology
> > + * LTC2496 and LTC2497 ADCs
> > + *
> > + * Copyright (C) 2017 Analog Devices Inc.
> > + */
> > +
> > +#include <linux/delay.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/iio/driver.h>
> > +#include <linux/module.h>
> > +#include <linux/regulator/consumer.h>
> > +
> > +#include "ltc249x.h"
> > +
> > +#define LTC249X_SGL			BIT(4)
> > +#define LTC249X_DIFF			0
> > +#define LTC249X_SIGN			BIT(3)
> > +
> > +static int ltc249x_wait_conv(struct ltc249x_driverdata *ddata)
> > +{
> > +	s64 time_elapsed;
> > +
> > +	time_elapsed = ktime_ms_delta(ktime_get(), ddata->time_prev);
> > +
> > +	if (time_elapsed < LTC249X_CONVERSION_TIME_MS) {
> > +		/* delay if conversion time not passed
> > +		 * since last read or write
> > +		 */
> > +		if (msleep_interruptible(
> > +		    LTC249X_CONVERSION_TIME_MS - time_elapsed))
> > +			return -ERESTARTSYS;
> > +
> > +		return 0;
> > +	}
> > +
> > +	if (time_elapsed - LTC249X_CONVERSION_TIME_MS <= 0) {
> > +		/* We're in automatic mode -
> > +		 * so the last reading is still not outdated
> > +		 */
> > +		return 0;
> > +	}
> > +
> > +	return 1;
> > +}
> > +
> > +static int ltc249x_read(struct ltc249x_driverdata *ddata, u8 address, int *val)
> > +{
> > +	int ret;
> > +
> > +	ret = ltc249x_wait_conv(ddata);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	if (ret || ddata->addr_prev != address) {
> > +		ret = ddata->result_and_measure(ddata, address, NULL);
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		ddata->addr_prev = address;
> > +
> > +		if (msleep_interruptible(LTC249X_CONVERSION_TIME_MS))
> > +			return -ERESTARTSYS;
> > +	}
> > +
> > +	ret = ddata->result_and_measure(ddata, address, val);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	ddata->time_prev = ktime_get();
> > +
> > +	return ret;
> > +}
> > +
> > +static int ltc249x_read_raw(struct iio_dev *indio_dev,
> > +			    struct iio_chan_spec const *chan,
> > +			    int *val, int *val2, long mask)
> > +{
> > +	struct ltc249x_driverdata *ddata = iio_priv(indio_dev);
> > +	int ret;
> > +
> > +	switch (mask) {
> > +	case IIO_CHAN_INFO_RAW:
> > +		mutex_lock(&indio_dev->mlock);
> > +		ret = ltc249x_read(ddata, chan->address, val);
> > +		mutex_unlock(&indio_dev->mlock);
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		return IIO_VAL_INT;
> > +
> > +	case IIO_CHAN_INFO_SCALE:
> > +		ret = regulator_get_voltage(ddata->ref);
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		*val = ret / 1000;
> > +		*val2 = 17;
> > +
> > +		return IIO_VAL_FRACTIONAL_LOG2;
> > +
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}
> > +
> > +#define LTC249X_CHAN(_chan, _addr, _ds_name) { \
> > +	.type = IIO_VOLTAGE, \
> > +	.indexed = 1, \
> > +	.channel = (_chan), \
> > +	.address = (_addr | (_chan / 2) | ((_chan & 1) ? LTC249X_SIGN : 0)), \
> > +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> > +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> > +	.datasheet_name = (_ds_name), \
> > +}
> > +
> > +#define LTC249X_CHAN_DIFF(_chan, _addr) { \
> > +	.type = IIO_VOLTAGE, \
> > +	.indexed = 1, \
> > +	.channel = (_chan) * 2 + ((_addr) & LTC249X_SIGN ? 1 : 0), \
> > +	.channel2 = (_chan) * 2 + ((_addr) & LTC249X_SIGN ? 0 : 1),\
> > +	.address = (_addr | _chan), \
> > +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> > +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> > +	.differential = 1, \
> > +}
> > +
> > +static const struct iio_chan_spec ltc249x_channel[] = {
> > +	LTC249X_CHAN(0, LTC249X_SGL, "CH0"),
> > +	LTC249X_CHAN(1, LTC249X_SGL, "CH1"),
> > +	LTC249X_CHAN(2, LTC249X_SGL, "CH2"),
> > +	LTC249X_CHAN(3, LTC249X_SGL, "CH3"),
> > +	LTC249X_CHAN(4, LTC249X_SGL, "CH4"),
> > +	LTC249X_CHAN(5, LTC249X_SGL, "CH5"),
> > +	LTC249X_CHAN(6, LTC249X_SGL, "CH6"),
> > +	LTC249X_CHAN(7, LTC249X_SGL, "CH7"),
> > +	LTC249X_CHAN(8, LTC249X_SGL, "CH8"),
> > +	LTC249X_CHAN(9, LTC249X_SGL, "CH9"),
> > +	LTC249X_CHAN(10, LTC249X_SGL, "CH10"),
> > +	LTC249X_CHAN(11, LTC249X_SGL, "CH11"),
> > +	LTC249X_CHAN(12, LTC249X_SGL, "CH12"),
> > +	LTC249X_CHAN(13, LTC249X_SGL, "CH13"),
> > +	LTC249X_CHAN(14, LTC249X_SGL, "CH14"),
> > +	LTC249X_CHAN(15, LTC249X_SGL, "CH15"),
> > +	LTC249X_CHAN_DIFF(0, LTC249X_DIFF),
> > +	LTC249X_CHAN_DIFF(1, LTC249X_DIFF),
> > +	LTC249X_CHAN_DIFF(2, LTC249X_DIFF),
> > +	LTC249X_CHAN_DIFF(3, LTC249X_DIFF),
> > +	LTC249X_CHAN_DIFF(4, LTC249X_DIFF),
> > +	LTC249X_CHAN_DIFF(5, LTC249X_DIFF),
> > +	LTC249X_CHAN_DIFF(6, LTC249X_DIFF),
> > +	LTC249X_CHAN_DIFF(7, LTC249X_DIFF),
> > +	LTC249X_CHAN_DIFF(0, LTC249X_DIFF | LTC249X_SIGN),
> > +	LTC249X_CHAN_DIFF(1, LTC249X_DIFF | LTC249X_SIGN),
> > +	LTC249X_CHAN_DIFF(2, LTC249X_DIFF | LTC249X_SIGN),
> > +	LTC249X_CHAN_DIFF(3, LTC249X_DIFF | LTC249X_SIGN),
> > +	LTC249X_CHAN_DIFF(4, LTC249X_DIFF | LTC249X_SIGN),
> > +	LTC249X_CHAN_DIFF(5, LTC249X_DIFF | LTC249X_SIGN),
> > +	LTC249X_CHAN_DIFF(6, LTC249X_DIFF | LTC249X_SIGN),
> > +	LTC249X_CHAN_DIFF(7, LTC249X_DIFF | LTC249X_SIGN),
> > +};
> > +
> > +static const struct iio_info ltc249x_info = {
> > +	.read_raw = ltc249x_read_raw,
> > +};
> > +
> > +int ltc249x_probe(struct device *dev, struct iio_dev *indio_dev)
> > +{
> > +	struct ltc249x_driverdata *ddata = iio_priv(indio_dev);
> > +	int ret;
> > +
> > +	indio_dev->dev.parent = dev;
> > +	indio_dev->name = dev_name(dev);
> > +	indio_dev->info = &ltc249x_info;
> > +	indio_dev->modes = INDIO_DIRECT_MODE;
> > +	indio_dev->channels = ltc249x_channel;
> > +	indio_dev->num_channels = ARRAY_SIZE(ltc249x_channel);
> > +
> > +	ret = ddata->result_and_measure(ddata, LTC249X_CONFIG_DEFAULT, NULL);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	ddata->ref = devm_regulator_get(dev, "vref");
> > +	if (IS_ERR(ddata->ref)) {
> > +		if (PTR_ERR(ddata->ref) != -EPROBE_DEFER)
> > +			dev_err(dev, "Failed to get vref regulator: %pe\n",
> > +				ddata->ref);
> > +
> > +		return PTR_ERR(ddata->ref);
> > +	}
> > +
> > +	ret = regulator_enable(ddata->ref);
> > +	if (ret < 0) {
> > +		dev_err(dev, "Failed to enable vref regulator: %pe\n",
> > +			ERR_PTR(ret));
> > +		return ret;
> > +	}
> > +
> > +	if (dev->platform_data) {
> > +		struct iio_map *plat_data;
> > +
> > +		plat_data = (struct iio_map *)dev->platform_data;
> > +
> > +		ret = iio_map_array_register(indio_dev, plat_data);
> > +		if (ret) {
> > +			dev_err(&indio_dev->dev, "iio map err: %d\n", ret);
> > +			goto err_regulator_disable;
> > +		}
> > +	}
> > +
> > +	ddata->addr_prev = LTC249X_CONFIG_DEFAULT;
> > +	ddata->time_prev = ktime_get();
> > +
> > +	ret = iio_device_register(indio_dev);
> > +	if (ret < 0)
> > +		goto err_array_unregister;
> > +
> > +	return 0;
> > +
> > +err_array_unregister:
> > +	iio_map_array_unregister(indio_dev);
> > +
> > +err_regulator_disable:
> > +	regulator_disable(ddata->ref);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_NS(ltc249x_probe, LTC249X);
> > +
> > +void ltc249x_remove(struct iio_dev *indio_dev)
> > +{
> > +	struct ltc249x_driverdata *ddata = iio_priv(indio_dev);
> > +
> > +	iio_device_unregister(indio_dev);
> > +
> > +	iio_map_array_unregister(indio_dev);
> > +
> > +	regulator_disable(ddata->ref);
> > +}
> > +EXPORT_SYMBOL_NS(ltc249x_remove, LTC249X);
> > +
> > +MODULE_DESCRIPTION("common code for LTC2496/LTC2497 drivers");
> > +MODULE_LICENSE("GPL v2");
> > diff --git a/drivers/iio/adc/ltc249x.h b/drivers/iio/adc/ltc249x.h
> > new file mode 100644
> > index 000000000000..b272a3f96d03
> > --- /dev/null
> > +++ b/drivers/iio/adc/ltc249x.h
> > @@ -0,0 +1,18 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +
> > +#define LTC249X_ENABLE			0xA0
> > +#define LTC249X_CONFIG_DEFAULT		LTC249X_ENABLE
> > +#define LTC249X_CONVERSION_TIME_MS	150ULL
> > +
> > +struct ltc249x_driverdata {
> > +	struct regulator *ref;
> > +	ktime_t	time_prev;
> > +	u8 addr_prev;
> > +	int (*result_and_measure)(struct ltc249x_driverdata *ddata,
> > +				  u8 address, int *val);
> > +};
> > +
> > +int ltc249x_probe(struct device *dev, struct iio_dev *indio_dev);
> > +void ltc249x_remove(struct iio_dev *indio_dev);
> > +
> > +MODULE_IMPORT_NS(LTC249X);  
>