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[PATCH] iio: max5487: Add support for Maxim digital potentiometers

Started byCristina Moraru <cristina.moraru09@gmail.com>
First post2016-03-24 12:30 +0100
Last post2016-04-01 10:40 +0200
Articles 6 — 3 participants

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Contents

  [PATCH] iio: max5487: Add support for Maxim digital potentiometers Cristina Moraru <cristina.moraru09@gmail.com> - 2016-03-24 12:30 +0100
    Re: [PATCH] iio: max5487: Add support for Maxim digital potentiometers Daniel Baluta <daniel.baluta@intel.com> - 2016-03-24 12:50 +0100
    RE: [PATCH] iio: max5487: Add support for Maxim digital  potentiometers Peter Rosin <peda@axentia.se> - 2016-03-24 22:50 +0100
      Re: [PATCH] iio: max5487: Add support for Maxim digital potentiometers Daniel Baluta <daniel.baluta@intel.com> - 2016-04-01 10:30 +0200
    RE: [PATCH] iio: max5487: Add support for Maxim digital  potentiometers Peter Rosin <peda@axentia.se> - 2016-03-25 11:30 +0100
      Re: [PATCH] iio: max5487: Add support for Maxim digital potentiometers Daniel Baluta <daniel.baluta@intel.com> - 2016-04-01 10:40 +0200

#1364090 — [PATCH] iio: max5487: Add support for Maxim digital potentiometers

FromCristina Moraru <cristina.moraru09@gmail.com>
Date2016-03-24 12:30 +0100
Subject[PATCH] iio: max5487: Add support for Maxim digital potentiometers
Message-ID<rgbCG-1Mm-1@gated-at.bofh.it>
Add implementation for Maxim MAX5487, MAX5488, MAX5489
digital potentiometers.

Signed-off-by: Cristina Moraru <cristina.moraru09@gmail.com>
CC: Daniel Baluta <daniel.baluta@intel.com>
---
 drivers/iio/potentiometer/Kconfig   |  11 +++
 drivers/iio/potentiometer/Makefile  |   1 +
 drivers/iio/potentiometer/max5487.c | 185 ++++++++++++++++++++++++++++++++++++
 3 files changed, 197 insertions(+)
 create mode 100644 drivers/iio/potentiometer/max5487.c

diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
index ffc735c..3046c79 100644
--- a/drivers/iio/potentiometer/Kconfig
+++ b/drivers/iio/potentiometer/Kconfig
@@ -5,6 +5,17 @@
 
 menu "Digital potentiometers"
 
+config MAX5487
+        tristate "Maxim MAX5487/MAX5488/MAX5489  Digital Potentiometer driver"
+        depends on SPI
+        help
+          Say yes here to build support for the Maxim
+          MAX5487, MAX5488, MAX5489 digital potentiomenter
+	  chips.
+
+          To compile this driver as a module, choose M here: the
+          module will be called max5487.
+
 config MCP4531
 	tristate "Microchip MCP45xx/MCP46xx Digital Potentiometer driver"
 	depends on I2C
diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
index b563b49..dcc791a 100644
--- a/drivers/iio/potentiometer/Makefile
+++ b/drivers/iio/potentiometer/Makefile
@@ -3,5 +3,6 @@
 #
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_MAX5487) += max5487.o
 obj-$(CONFIG_MCP4531) += mcp4531.o
 obj-$(CONFIG_TPL0102) += tpl0102.o
diff --git a/drivers/iio/potentiometer/max5487.c b/drivers/iio/potentiometer/max5487.c
new file mode 100644
index 0000000..69db979
--- /dev/null
+++ b/drivers/iio/potentiometer/max5487.c
@@ -0,0 +1,185 @@
+/*
+ * max5487.c - Support for MAX5487, MAX5488, MAX5489 digital potentiometers
+ *
+ * Copyright (C) Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/acpi.h>
+#include <linux/regmap.h>
+
+#include <linux/iio/sysfs.h>
+#include <linux/iio/iio.h>
+
+#define MAX5487_DRV_NAME "max5487"
+
+#define MAX5487_WRITE_WIPER_A	0x01
+#define MAX5487_WRITE_WIPER_B	0x02
+
+/* copy both wiper regs to NV regs */
+#define MAX5487_COPY_AB_TO_NV	0x23
+/* copy both NV regs to wiper regs */
+#define MAX5487_COPY_NV_TO_AB	0x33
+
+enum {
+	MAX5487,
+	MAX5488,
+	MAX5489,
+};
+
+struct max5487_cfg {
+	int wipers;
+	int max_pos;
+	int kohms;
+};
+
+static const struct max5487_cfg max5487_cfg[] = {
+	[MAX5487] = { .wipers = 2, .max_pos = 256, .kohms =  10,},
+	[MAX5488] = { .wipers = 2, .max_pos = 256, .kohms =  50,},
+	[MAX5489] = { .wipers = 2, .max_pos = 256, .kohms =  100,}
+};
+
+struct max5487_data {
+	struct regmap *regmap;
+	int chip_id;
+};
+
+#define MAX5487_CHANNEL(ch, addr) {				\
+	.type = IIO_RESISTANCE,					\
+	.indexed = 1,						\
+	.output = 1,						\
+	.channel = ch,						\
+	.address = addr,					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+}
+
+static const struct iio_chan_spec max5487_channels[] = {
+	MAX5487_CHANNEL(0, MAX5487_WRITE_WIPER_A),
+	MAX5487_CHANNEL(1, MAX5487_WRITE_WIPER_B),
+};
+
+static int max5487_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct max5487_data *data = iio_priv(indio_dev);
+
+	if (mask != IIO_CHAN_INFO_SCALE)
+		return -EINVAL;
+
+	*val = 1000 * max5487_cfg[data->chip_id].kohms;
+	*val2 = max5487_cfg[data->chip_id].max_pos;
+	return IIO_VAL_FRACTIONAL;
+}
+
+static int max5487_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int val, int val2, long mask)
+{
+	struct max5487_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (val < 0 || val >= max5487_cfg[data->chip_id].max_pos)
+			return -EINVAL;
+		return regmap_write(data->regmap, chan->address, val);
+	default:
+		return -EINVAL;
+	}
+	return -EINVAL;
+}
+
+static const struct iio_info max5487_info = {
+	.read_raw = &max5487_read_raw,
+	.write_raw = &max5487_write_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static const struct regmap_config max5487_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+
+	.max_register = MAX5487_COPY_NV_TO_AB,
+};
+
+static int max5487_spi_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct max5487_data *data;
+	const struct spi_device_id *id = spi_get_device_id(spi);
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	dev_set_drvdata(&spi->dev, indio_dev);
+	data = iio_priv(indio_dev);
+
+	data->regmap = devm_regmap_init_spi(spi, &max5487_regmap_config);
+	if (IS_ERR(data->regmap))
+		return PTR_ERR(data->regmap);
+
+	data->chip_id = id->driver_data;
+
+	indio_dev->info = &max5487_info;
+	indio_dev->name = id->name;
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = max5487_channels;
+	indio_dev->num_channels = ARRAY_SIZE(max5487_channels);
+
+	/* restore both wiper regs from NV regs */
+	ret = regmap_write(data->regmap, MAX5487_COPY_NV_TO_AB, 0);
+	if (ret < 0)
+		return ret;
+
+	return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+static int max5487_spi_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(&spi->dev);
+	struct max5487_data *data = iio_priv(indio_dev);
+
+	/* save both wiper regs to NV regs */
+	return regmap_write(data->regmap, MAX5487_COPY_AB_TO_NV, 0);
+}
+
+static const struct spi_device_id max5487_id[] = {
+	{ "MAX5487", MAX5487 },
+	{ "MAX5488", MAX5488 },
+	{ "MAX5489", MAX5489 },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, max5487_id);
+
+static const struct acpi_device_id max5487_acpi_match[] = {
+	{ "MAX5487", MAX5487 },
+	{ "MAX5488", MAX5488 },
+	{ "MAX5489", MAX5489 },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, max5487_acpi_match);
+
+static struct spi_driver max5487_driver = {
+	.driver = {
+		.name = MAX5487_DRV_NAME,
+		.owner = THIS_MODULE,
+		.acpi_match_table = ACPI_PTR(max5487_acpi_match),
+	},
+	.id_table = max5487_id,
+	.probe = max5487_spi_probe,
+	.remove = max5487_spi_remove
+};
+module_spi_driver(max5487_driver);
+
+MODULE_AUTHOR("Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>");
+MODULE_DESCRIPTION("max5487 SPI driver");
+MODULE_LICENSE("GPL v2");
-- 
2.5.0

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#1364103

FromDaniel Baluta <daniel.baluta@intel.com>
Date2016-03-24 12:50 +0100
Message-ID<rgbW2-25h-9@gated-at.bofh.it>
In reply to#1364090
On Thu, Mar 24, 2016 at 1:21 PM, Cristina Moraru
<cristina.moraru09@gmail.com> wrote:
> Add implementation for Maxim MAX5487, MAX5488, MAX5489
> digital potentiometers.

Datasheet: http://datasheets.maximintegrated.com/en/ds/MAX5487-MAX5489.pdf
>
> Signed-off-by: Cristina Moraru <cristina.moraru09@gmail.com>
> CC: Daniel Baluta <daniel.baluta@intel.com>

Tested-by: Daniel Baluta <daniel.baluta@intel.com>

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#1364465 — RE: [PATCH] iio: max5487: Add support for Maxim digital potentiometers

FromPeter Rosin <peda@axentia.se>
Date2016-03-24 22:50 +0100
SubjectRE: [PATCH] iio: max5487: Add support for Maxim digital potentiometers
Message-ID<rgliF-fL-1@gated-at.bofh.it>
In reply to#1364090
Hi Cristina,

Some comments inline...

Cheers,
Peter

Cristina Moraru wrote:
> Add implementation for Maxim MAX5487, MAX5488, MAX5489
> digital potentiometers.
> 
> Signed-off-by: Cristina Moraru <cristina.moraru09@gmail.com>
> CC: Daniel Baluta <daniel.baluta@intel.com>
> ---
>  drivers/iio/potentiometer/Kconfig   |  11 +++
>  drivers/iio/potentiometer/Makefile  |   1 +
>  drivers/iio/potentiometer/max5487.c | 185 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 197 insertions(+)
>  create mode 100644 drivers/iio/potentiometer/max5487.c
> 
> diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
> index ffc735c..3046c79 100644
> --- a/drivers/iio/potentiometer/Kconfig
> +++ b/drivers/iio/potentiometer/Kconfig
> @@ -5,6 +5,17 @@
>  
>  menu "Digital potentiometers"
>  
> +config MAX5487
> +        tristate "Maxim MAX5487/MAX5488/MAX5489  Digital Potentiometer driver"
> +        depends on SPI
> +        help
> +          Say yes here to build support for the Maxim
> +          MAX5487, MAX5488, MAX5489 digital potentiomenter
> +	  chips.

The whitespace on this line is different.

> +
> +          To compile this driver as a module, choose M here: the
> +          module will be called max5487.
> +
>  config MCP4531
>  	tristate "Microchip MCP45xx/MCP46xx Digital Potentiometer driver"
>  	depends on I2C
> diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
> index b563b49..dcc791a 100644
> --- a/drivers/iio/potentiometer/Makefile
> +++ b/drivers/iio/potentiometer/Makefile
> @@ -3,5 +3,6 @@
>  #
>  
>  # When adding new entries keep the list in alphabetical order
> +obj-$(CONFIG_MAX5487) += max5487.o
>  obj-$(CONFIG_MCP4531) += mcp4531.o
>  obj-$(CONFIG_TPL0102) += tpl0102.o
> diff --git a/drivers/iio/potentiometer/max5487.c b/drivers/iio/potentiometer/max5487.c
> new file mode 100644
> index 0000000..69db979
> --- /dev/null
> +++ b/drivers/iio/potentiometer/max5487.c
> @@ -0,0 +1,185 @@
> +/*
> + * max5487.c - Support for MAX5487, MAX5488, MAX5489 digital potentiometers
> + *
> + * Copyright (C) Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + */
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +#include <linux/acpi.h>
> +#include <linux/regmap.h>
> +
> +#include <linux/iio/sysfs.h>
> +#include <linux/iio/iio.h>
> +
> +#define MAX5487_DRV_NAME "max5487"
> +
> +#define MAX5487_WRITE_WIPER_A	0x01
> +#define MAX5487_WRITE_WIPER_B	0x02
> +
> +/* copy both wiper regs to NV regs */
> +#define MAX5487_COPY_AB_TO_NV	0x23
> +/* copy both NV regs to wiper regs */
> +#define MAX5487_COPY_NV_TO_AB	0x33
> +
> +enum {
> +	MAX5487,
> +	MAX5488,
> +	MAX5489,
> +};
> +
> +struct max5487_cfg {
> +	int wipers;
> +	int max_pos;
> +	int kohms;
> +};
> +
> +static const struct max5487_cfg max5487_cfg[] = {
> +	[MAX5487] = { .wipers = 2, .max_pos = 256, .kohms =  10,},
> +	[MAX5488] = { .wipers = 2, .max_pos = 256, .kohms =  50,},
> +	[MAX5489] = { .wipers = 2, .max_pos = 256, .kohms =  100,}
> +};

.wipers and .max_pos need not be in max5487_cfg, they are common.
.wipers isn't even used. Which means that if you like, you can
use the ohms reading as the driver_data directly instead of going
via the MAX548x enumeration, see below. Or is there some reason
not doing so?

> +
> +struct max5487_data {
> +	struct regmap *regmap;
> +	int chip_id;

I.e., change chip_id to kohms.

> +};
> +
> +#define MAX5487_CHANNEL(ch, addr) {				\
> +	.type = IIO_RESISTANCE,					\
> +	.indexed = 1,						\
> +	.output = 1,						\
> +	.channel = ch,						\
> +	.address = addr,					\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> +}
> +
> +static const struct iio_chan_spec max5487_channels[] = {
> +	MAX5487_CHANNEL(0, MAX5487_WRITE_WIPER_A),
> +	MAX5487_CHANNEL(1, MAX5487_WRITE_WIPER_B),
> +};
> +
> +static int max5487_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val, int *val2, long mask)
> +{
> +	struct max5487_data *data = iio_priv(indio_dev);
> +
> +	if (mask != IIO_CHAN_INFO_SCALE)
> +		return -EINVAL;
> +
> +	*val = 1000 * max5487_cfg[data->chip_id].kohms;

Use data->kohms here.

> +	*val2 = max5487_cfg[data->chip_id].max_pos;

Hardcode this to 256 (using a define).

> +	return IIO_VAL_FRACTIONAL;
> +}
> +
> +static int max5487_write_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int val, int val2, long mask)
> +{
> +	struct max5487_data *data = iio_priv(indio_dev);
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		if (val < 0 || val >= max5487_cfg[data->chip_id].max_pos)

Hardcode to 256.

> +			return -EINVAL;
> +		return regmap_write(data->regmap, chan->address, val);
> +	default:
> +		return -EINVAL;
> +	}
> +	return -EINVAL;
> +}
> +
> +static const struct iio_info max5487_info = {
> +	.read_raw = &max5487_read_raw,
> +	.write_raw = &max5487_write_raw,
> +	.driver_module = THIS_MODULE,
> +};
> +
> +static const struct regmap_config max5487_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +
> +	.max_register = MAX5487_COPY_NV_TO_AB,
> +};
> +
> +static int max5487_spi_probe(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev;
> +	struct max5487_data *data;
> +	const struct spi_device_id *id = spi_get_device_id(spi);
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(&spi->dev, indio_dev);
> +	data = iio_priv(indio_dev);
> +
> +	data->regmap = devm_regmap_init_spi(spi, &max5487_regmap_config);
> +	if (IS_ERR(data->regmap))
> +		return PTR_ERR(data->regmap);
> +
> +	data->chip_id = id->driver_data;

Use data->kohms = id->driver_data

> +
> +	indio_dev->info = &max5487_info;
> +	indio_dev->name = id->name;
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = max5487_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(max5487_channels);
> +
> +	/* restore both wiper regs from NV regs */
> +	ret = regmap_write(data->regmap, MAX5487_COPY_NV_TO_AB, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	return devm_iio_device_register(&spi->dev, indio_dev);
> +}
> +
> +static int max5487_spi_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = dev_get_drvdata(&spi->dev);
> +	struct max5487_data *data = iio_priv(indio_dev);
> +
> +	/* save both wiper regs to NV regs */
> +	return regmap_write(data->regmap, MAX5487_COPY_AB_TO_NV, 0);
> +}
> +
> +static const struct spi_device_id max5487_id[] = {
> +	{ "MAX5487", MAX5487 },
> +	{ "MAX5488", MAX5488 },
> +	{ "MAX5489", MAX5489 },

Use 10, 50, and 100 instead of the MAX548x enums.

> +	{ }
> +};
> +MODULE_DEVICE_TABLE(spi, max5487_id);
> +
> +static const struct acpi_device_id max5487_acpi_match[] = {
> +	{ "MAX5487", MAX5487 },
> +	{ "MAX5488", MAX5488 },
> +	{ "MAX5489", MAX5489 },

Dito.

> +	{ },
> +};
> +MODULE_DEVICE_TABLE(acpi, max5487_acpi_match);
> +
> +static struct spi_driver max5487_driver = {
> +	.driver = {
> +		.name = MAX5487_DRV_NAME,
> +		.owner = THIS_MODULE,
> +		.acpi_match_table = ACPI_PTR(max5487_acpi_match),
> +	},
> +	.id_table = max5487_id,
> +	.probe = max5487_spi_probe,
> +	.remove = max5487_spi_remove
> +};
> +module_spi_driver(max5487_driver);
> +
> +MODULE_AUTHOR("Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>");
> +MODULE_DESCRIPTION("max5487 SPI driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.5.0
> 
>

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#1369098

FromDaniel Baluta <daniel.baluta@intel.com>
Date2016-04-01 10:30 +0200
Message-ID<rj2CS-1CC-3@gated-at.bofh.it>
In reply to#1364465
> .wipers and .max_pos need not be in max5487_cfg, they are common.
> .wipers isn't even used. Which means that if you like, you can
> use the ohms reading as the driver_data directly instead of going
> via the MAX548x enumeration, see below. Or is there some reason
> not doing so?

You make a good point. Anyhow we thought of a generic approach. In the future
this chip family could support more wipers with different positions.

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#1364630 — RE: [PATCH] iio: max5487: Add support for Maxim digital potentiometers

FromPeter Rosin <peda@axentia.se>
Date2016-03-25 11:30 +0100
SubjectRE: [PATCH] iio: max5487: Add support for Maxim digital potentiometers
Message-ID<rgxaa-ei-9@gated-at.bofh.it>
In reply to#1364090
Hi again,

Cristina Moraru wrote:
> Add implementation for Maxim MAX5487, MAX5488, MAX5489
> digital potentiometers.
> 
> Signed-off-by: Cristina Moraru <cristina.moraru09@gmail.com>
> CC: Daniel Baluta <daniel.baluta@intel.com>

Some more comments, the mcp4531 chips have n**2 + 1 positions,
therefore .max_pos in that driver isn't the number of wiper positions, it's
the actual maximum value. So, in this driver, the corrent number for
.max_pos would be 255, otherwise the reported scale is wrong (and then
you also need to adjust the EINVAL check in max5487_write_raw to use >
instead of >=).

Further comparison with the mcp4531 driver reveals that this driver does
not support IIO_CHAN_INFO_RAW in max5487_read_raw. I assume the SPI
interface does not support reading back the current value?

Cheers,
Peter

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#1369106

FromDaniel Baluta <daniel.baluta@intel.com>
Date2016-04-01 10:40 +0200
Message-ID<rj2My-1GR-11@gated-at.bofh.it>
In reply to#1364630
On Fri, Mar 25, 2016 at 12:20 PM, Peter Rosin <peda@axentia.se> wrote:
> Hi again,
>
> Cristina Moraru wrote:
>> Add implementation for Maxim MAX5487, MAX5488, MAX5489
>> digital potentiometers.
>>
>> Signed-off-by: Cristina Moraru <cristina.moraru09@gmail.com>
>> CC: Daniel Baluta <daniel.baluta@intel.com>
>
> Some more comments, the mcp4531 chips have n**2 + 1 positions,
> therefore .max_pos in that driver isn't the number of wiper positions, it's
> the actual maximum value. So, in this driver, the corrent number for
> .max_pos would be 255, otherwise the reported scale is wrong (and then
> you also need to adjust the EINVAL check in max5487_write_raw to use >
> instead of >=).
>
> Further comparison with the mcp4531 driver reveals that this driver does
> not support IIO_CHAN_INFO_RAW in max5487_read_raw. I assume the SPI
> interface does not support reading back the current value?

Yes. The registers are write only. We could have used the caching
facility of regmap with default values.

The problem is when using the non volatile (NV) mem there is no way to know
the previous wiper position.

Daniel.

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