[PATCH v4 0/2] iio: ad5272: Add support for Analog Devices digital potentiometers

[PATCH v4 0/2] iio: ad5272: Add support for Analog Devices digital potentiometers

[Phil Reid]

Add documentation and driver for the Analog Devices 5272.

Driver currently doesn't support programing the RDAC position to 
non-volatile memory. 

Changes from v3:
- move SPDX-License-Identifier to line 1
- add AD5274 to Kconfig description
- Add missing empty line before return

Changes from v2:
- docs: Fix polarity of reset-gpio example to match driver
- Use a cached aligned buffer for i2c
- remove old invalid comment from c&p

Changes from v1:
- Use spdx license id
- Use sizeof for i2c buffer lens
- Condense code a little when setting up i2c buf
- check val2 in raw write
- Add reset function. Perform a software reset if
  gpio reset pin is not defined
- remove THIS_MODULE assignment
- change of data to use index as per i2c device table


Phil Reid (2):
  dt-bindings: ad5272: Add bindings for Analog Devices digital
    potentiometers
  iio: ad5272: Add support for Analog Devices digital potentiometers

 .../bindings/iio/potentiometer/ad5272.txt          |  27 +++
 drivers/iio/potentiometer/Kconfig                  |  10 +
 drivers/iio/potentiometer/Makefile                 |   1 +
 drivers/iio/potentiometer/ad5272.c                 | 227 +++++++++++++++++++++
 4 files changed, 265 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
 create mode 100644 drivers/iio/potentiometer/ad5272.c

-- 
1.8.3.1

[PATCH v4 1/2] dt-bindings: ad5272: Add bindings for Analog Devices digital potentiometers

[Phil Reid]

Add binding documentation for Analog Devices AD5272 and AD5274 digital
potentiometer devices.

Signed-off-by: Phil Reid <preid@electromag.com.au>
---
 .../bindings/iio/potentiometer/ad5272.txt          | 27 ++++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt

diff --git a/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt b/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
new file mode 100644
index 0000000..11e804c
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
@@ -0,0 +1,27 @@
+* Analog Devices AD5272 digital potentiometer driver
+
+The node for this driver must be a child node of a I2C controller, hence
+all mandatory properties for your controller must be specified. See directory:
+
+        Documentation/devicetree/bindings/i2c
+
+for more details.
+
+Required properties:
+	- compatible:  	Must be one of the following, depending on the model:
+			adi,ad5272-020
+			adi,ad5272-050
+			adi,ad5272-100
+			adi,ad5274-020
+			adi,ad5274-100
+
+Optional properties:
+ - reset-gpios: GPIO specification for the RESET input. This is an
+		active low signal to the PCA953x.
+
+Example:
+ad5272: ad5272@2f {
+	reg = <0x2F>;
+	compatible = "adi,ad5272-020";
+	reset-gpios = <&gpio3 6 GPIO_ACTIVE_HIGH>;
+};
-- 
1.8.3.1

Re: [PATCH v4 1/2] dt-bindings: ad5272: Add bindings for Analog Devices digital potentiometers

[Jonathan Cameron]

On Mon, 29 Jan 2018 21:12:53 +0800
Phil Reid <preid@electromag.com.au> wrote:

> Add binding documentation for Analog Devices AD5272 and AD5274 digital
> potentiometer devices.
> 
> Signed-off-by: Phil Reid <preid@electromag.com.au>
This is simply enough that I doubt Rob or Mark is that bothered about 
reviewing it.  Obviously any reviews are still welcome though as it
will be in a rebaseable tree probably until after the merge window closes.

Applied to the togreg branch of iio.git and pushed out as testing.

Thanks,

Jonathan

> ---
>  .../bindings/iio/potentiometer/ad5272.txt          | 27 ++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
> 
> diff --git a/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt b/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
> new file mode 100644
> index 0000000..11e804c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
> @@ -0,0 +1,27 @@
> +* Analog Devices AD5272 digital potentiometer driver
> +
> +The node for this driver must be a child node of a I2C controller, hence
> +all mandatory properties for your controller must be specified. See directory:
> +
> +        Documentation/devicetree/bindings/i2c
> +
> +for more details.
> +
> +Required properties:
> +	- compatible:  	Must be one of the following, depending on the model:
> +			adi,ad5272-020
> +			adi,ad5272-050
> +			adi,ad5272-100
> +			adi,ad5274-020
> +			adi,ad5274-100
> +
> +Optional properties:
> + - reset-gpios: GPIO specification for the RESET input. This is an
> +		active low signal to the PCA953x.
> +
> +Example:
> +ad5272: ad5272@2f {
> +	reg = <0x2F>;
> +	compatible = "adi,ad5272-020";
> +	reset-gpios = <&gpio3 6 GPIO_ACTIVE_HIGH>;
> +};

Re: [PATCH v4 1/2] dt-bindings: ad5272: Add bindings for Analog Devices digital potentiometers

[Rob Herring]

On Mon, Jan 29, 2018 at 09:12:53PM +0800, Phil Reid wrote:
> Add binding documentation for Analog Devices AD5272 and AD5274 digital
> potentiometer devices.
> 
> Signed-off-by: Phil Reid <preid@electromag.com.au>
> ---
>  .../bindings/iio/potentiometer/ad5272.txt          | 27 ++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
> 
> diff --git a/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt b/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
> new file mode 100644
> index 0000000..11e804c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
> @@ -0,0 +1,27 @@
> +* Analog Devices AD5272 digital potentiometer driver

Bindings describe h/w not drivers.

> +
> +The node for this driver must be a child node of a I2C controller, hence
> +all mandatory properties for your controller must be specified. See directory:
> +
> +        Documentation/devicetree/bindings/i2c
> +
> +for more details.
> +
> +Required properties:
> +	- compatible:  	Must be one of the following, depending on the model:
> +			adi,ad5272-020
> +			adi,ad5272-050
> +			adi,ad5272-100
> +			adi,ad5274-020
> +			adi,ad5274-100
> +
> +Optional properties:
> + - reset-gpios: GPIO specification for the RESET input. This is an
> +		active low signal to the PCA953x.
> +
> +Example:
> +ad5272: ad5272@2f {

potentiometer@2f

Probably a node name we need to add to the spec.

> +	reg = <0x2F>;
> +	compatible = "adi,ad5272-020";
> +	reset-gpios = <&gpio3 6 GPIO_ACTIVE_HIGH>;
> +};
> -- 
> 1.8.3.1
> 

Re: [PATCH v4 1/2] dt-bindings: ad5272: Add bindings for Analog Devices digital potentiometers

[Phil Reid]

On 5/02/2018 14:07, Rob Herring wrote:
> On Mon, Jan 29, 2018 at 09:12:53PM +0800, Phil Reid wrote:
>> Add binding documentation for Analog Devices AD5272 and AD5274 digital
>> potentiometer devices.
>>
>> Signed-off-by: Phil Reid <preid@electromag.com.au>
>> ---
>>   .../bindings/iio/potentiometer/ad5272.txt          | 27 ++++++++++++++++++++++
>>   1 file changed, 27 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
>>
>> diff --git a/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt b/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
>> new file mode 100644
>> index 0000000..11e804c
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
>> @@ -0,0 +1,27 @@
>> +* Analog Devices AD5272 digital potentiometer driver
> 
> Bindings describe h/w not drivers.
ok

> 
>> +
>> +The node for this driver must be a child node of a I2C controller, hence
>> +all mandatory properties for your controller must be specified. See directory:
>> +
>> +        Documentation/devicetree/bindings/i2c
>> +
>> +for more details.
>> +
>> +Required properties:
>> +	- compatible:  	Must be one of the following, depending on the model:
>> +			adi,ad5272-020
>> +			adi,ad5272-050
>> +			adi,ad5272-100
>> +			adi,ad5274-020
>> +			adi,ad5274-100
>> +
>> +Optional properties:
>> + - reset-gpios: GPIO specification for the RESET input. This is an
>> +		active low signal to the PCA953x.
>> +
>> +Example:
>> +ad5272: ad5272@2f {
> 
> potentiometer@2f
ok

> 
> Probably a node name we need to add to the spec.
> 
>> +	reg = <0x2F>;
>> +	compatible = "adi,ad5272-020";
>> +	reset-gpios = <&gpio3 6 GPIO_ACTIVE_HIGH>;
>> +};
>> -- 
>> 1.8.3.1
>>
> 
> 
Jonathan,

How would you like me to fix this as you've applied it to togreg already?
A patch on top of this or a v5.


-- 
Regards
Phil Reid

Re: [PATCH v4 1/2] dt-bindings: ad5272: Add bindings for Analog Devices digital potentiometers

[Jonathan Cameron]

On Mon, 5 Feb 2018 15:25:59 +0800
Phil Reid <preid@electromag.com.au> wrote:

> On 5/02/2018 14:07, Rob Herring wrote:
> > On Mon, Jan 29, 2018 at 09:12:53PM +0800, Phil Reid wrote:  
> >> Add binding documentation for Analog Devices AD5272 and AD5274 digital
> >> potentiometer devices.
> >>
> >> Signed-off-by: Phil Reid <preid@electromag.com.au>
> >> ---
> >>   .../bindings/iio/potentiometer/ad5272.txt          | 27 ++++++++++++++++++++++
> >>   1 file changed, 27 insertions(+)
> >>   create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
> >>
> >> diff --git a/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt b/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
> >> new file mode 100644
> >> index 0000000..11e804c
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/iio/potentiometer/ad5272.txt
> >> @@ -0,0 +1,27 @@
> >> +* Analog Devices AD5272 digital potentiometer driver  
> > 
> > Bindings describe h/w not drivers.  
> ok
> 
> >   
> >> +
> >> +The node for this driver must be a child node of a I2C controller, hence
> >> +all mandatory properties for your controller must be specified. See directory:
> >> +
> >> +        Documentation/devicetree/bindings/i2c
> >> +
> >> +for more details.
> >> +
> >> +Required properties:
> >> +	- compatible:  	Must be one of the following, depending on the model:
> >> +			adi,ad5272-020
> >> +			adi,ad5272-050
> >> +			adi,ad5272-100
> >> +			adi,ad5274-020
> >> +			adi,ad5274-100
> >> +
> >> +Optional properties:
> >> + - reset-gpios: GPIO specification for the RESET input. This is an
> >> +		active low signal to the PCA953x.
> >> +
> >> +Example:
> >> +ad5272: ad5272@2f {  
> > 
> > potentiometer@2f  
> ok
> 
> > 
> > Probably a node name we need to add to the spec.
> >   
> >> +	reg = <0x2F>;
> >> +	compatible = "adi,ad5272-020";
> >> +	reset-gpios = <&gpio3 6 GPIO_ACTIVE_HIGH>;
> >> +};
> >> -- 
> >> 1.8.3.1
> >>  
> > 
> >   
> Jonathan,
> 
> How would you like me to fix this as you've applied it to togreg already?
> A patch on top of this or a v5.
> 
Do a v5, I'll drop v4 and pick it up if Rob is happy.

Jonathan
> 

[PATCH v4 2/2] iio: ad5272: Add support for Analog Devices digital potentiometers

[Phil Reid]

Add implementation for Analog Devices AD5272 and AD5274 digital
potentiometer devices.

Signed-off-by: Phil Reid <preid@electromag.com.au>
---
 drivers/iio/potentiometer/Kconfig  |  10 ++
 drivers/iio/potentiometer/Makefile |   1 +
 drivers/iio/potentiometer/ad5272.c | 231 +++++++++++++++++++++++++++++++++++++
 3 files changed, 242 insertions(+)
 create mode 100644 drivers/iio/potentiometer/ad5272.c

diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
index 8bf2825..8daf6d1 100644
--- a/drivers/iio/potentiometer/Kconfig
+++ b/drivers/iio/potentiometer/Kconfig
@@ -5,6 +5,16 @@
 
 menu "Digital potentiometers"
 
+config AD5272
+	tristate "Analog Devices AD5272 and similar Digital Potentiometer driver"
+	depends on I2C
+	help
+	  Say yes here to build support for the Analog Devices AD5272 and AD5274
+	  digital potentiometer chip.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad5272.
+
 config DS1803
 	tristate "Maxim Integrated DS1803 Digital Potentiometer driver"
 	depends on I2C
diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
index 2260d40..498bbb8 100644
--- a/drivers/iio/potentiometer/Makefile
+++ b/drivers/iio/potentiometer/Makefile
@@ -3,6 +3,7 @@
 #
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_AD5272) += ad5272.o
 obj-$(CONFIG_DS1803) += ds1803.o
 obj-$(CONFIG_MAX5481) += max5481.o
 obj-$(CONFIG_MAX5487) += max5487.o
diff --git a/drivers/iio/potentiometer/ad5272.c b/drivers/iio/potentiometer/ad5272.c
new file mode 100644
index 0000000..0175fd5
--- /dev/null
+++ b/drivers/iio/potentiometer/ad5272.c
@@ -0,0 +1,231 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Analog Devices AD5372 digital potentiometer driver
+ * Copyright (C) 2018 Phil Reid <preid@electromag.com.au>
+ *
+ * Datasheet: http://www.analog.com/media/en/technical-documentation/data-sheets/AD5272_5274.pdf
+ *
+ * DEVID	#Wipers	#Positions	Resistor Opts (kOhm)	i2c address
+ * ad5272	1	1024		20, 50, 100		01011xx
+ * ad5274	1	256		20, 100			01011xx
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+
+#define  AD5272_RDAC_WR  1
+#define  AD5272_RDAC_RD  2
+#define  AD5272_RESET    4
+#define  AD5272_CTL      7
+
+#define  AD5272_RDAC_WR_EN  BIT(1)
+
+struct ad5272_cfg {
+	int max_pos;
+	int kohms;
+	int shift;
+};
+
+enum ad5272_type {
+	AD5272_020,
+	AD5272_050,
+	AD5272_100,
+	AD5274_020,
+	AD5274_100,
+};
+
+static const struct ad5272_cfg ad5272_cfg[] = {
+	[AD5272_020] = { .max_pos = 1024, .kohms = 20 },
+	[AD5272_050] = { .max_pos = 1024, .kohms = 50 },
+	[AD5272_100] = { .max_pos = 1024, .kohms = 100 },
+	[AD5274_020] = { .max_pos = 256,  .kohms = 20,  .shift = 2 },
+	[AD5274_100] = { .max_pos = 256,  .kohms = 100, .shift = 2 },
+};
+
+struct ad5272_data {
+	struct i2c_client       *client;
+	struct mutex            lock;
+	const struct ad5272_cfg *cfg;
+	u8                      buf[2] ____cacheline_aligned;
+};
+
+static const struct iio_chan_spec ad5272_channel = {
+	.type = IIO_RESISTANCE,
+	.output = 1,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+};
+
+static int ad5272_write(struct ad5272_data *data, int reg, int val)
+{
+	int ret;
+
+	data->buf[0] = (reg << 2) | ((val >> 8) & 0x3);
+	data->buf[1] = (u8)val;
+
+	mutex_lock(&data->lock);
+	ret = i2c_master_send(data->client, data->buf, sizeof(data->buf));
+	mutex_unlock(&data->lock);
+	return ret < 0 ? ret : 0;
+}
+
+static int ad5272_read(struct ad5272_data *data, int reg, int *val)
+{
+	int ret;
+
+	data->buf[0] = reg << 2;
+	data->buf[1] = 0;
+
+	mutex_lock(&data->lock);
+	ret = i2c_master_send(data->client, data->buf, sizeof(data->buf));
+	if (ret < 0)
+		goto error;
+
+	ret = i2c_master_recv(data->client, data->buf, sizeof(data->buf));
+	if (ret < 0)
+		goto error;
+
+	*val = ((data->buf[0] & 0x3) << 8) | data->buf[1];
+	ret = 0;
+error:
+	mutex_unlock(&data->lock);
+	return ret;
+}
+
+static int ad5272_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	struct ad5272_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW: {
+		ret = ad5272_read(data, AD5272_RDAC_RD, val);
+		*val = *val >> data->cfg->shift;
+		return ret ? ret : IIO_VAL_INT;
+	}
+	case IIO_CHAN_INFO_SCALE:
+		*val = 1000 * data->cfg->kohms;
+		*val2 = data->cfg->max_pos;
+		return IIO_VAL_FRACTIONAL;
+	}
+
+	return -EINVAL;
+}
+
+static int ad5272_write_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int val, int val2, long mask)
+{
+	struct ad5272_data *data = iio_priv(indio_dev);
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	if (val >= data->cfg->max_pos || val < 0 || val2)
+		return -EINVAL;
+
+	return ad5272_write(data, AD5272_RDAC_WR, val << data->cfg->shift);
+}
+
+static const struct iio_info ad5272_info = {
+	.read_raw = ad5272_read_raw,
+	.write_raw = ad5272_write_raw,
+};
+
+static int ad5272_reset(struct ad5272_data *data)
+{
+	struct gpio_desc *reset_gpio;
+
+	reset_gpio = devm_gpiod_get_optional(&data->client->dev, "reset",
+		GPIOD_OUT_LOW);
+	if (IS_ERR(reset_gpio))
+		return PTR_ERR(reset_gpio);
+
+	if (reset_gpio) {
+		udelay(1);
+		gpiod_set_value(reset_gpio, 1);
+	} else {
+		ad5272_write(data, AD5272_RESET, 0);
+	}
+	usleep_range(1000, 2000);
+
+	return 0;
+}
+
+static int ad5272_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct iio_dev *indio_dev;
+	struct ad5272_data *data;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, indio_dev);
+
+	data = iio_priv(indio_dev);
+	data->client = client;
+	mutex_init(&data->lock);
+	data->cfg = &ad5272_cfg[id->driver_data];
+
+	ret = ad5272_reset(data);
+	if (ret)
+		return ret;
+
+	ret = ad5272_write(data, AD5272_CTL, AD5272_RDAC_WR_EN);
+	if (ret < 0)
+		return -ENODEV;
+
+	indio_dev->dev.parent = dev;
+	indio_dev->info = &ad5272_info;
+	indio_dev->channels = &ad5272_channel;
+	indio_dev->num_channels = 1;
+	indio_dev->name = client->name;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+#if defined(CONFIG_OF)
+static const struct of_device_id ad5272_dt_ids[] = {
+	{ .compatible = "adi,ad5272-020", .data = (void *)AD5272_020 },
+	{ .compatible = "adi,ad5272-050", .data = (void *)AD5272_050 },
+	{ .compatible = "adi,ad5272-100", .data = (void *)AD5272_100 },
+	{ .compatible = "adi,ad5274-020", .data = (void *)AD5274_020 },
+	{ .compatible = "adi,ad5274-100", .data = (void *)AD5274_100 },
+	{}
+};
+MODULE_DEVICE_TABLE(of, ad5272_dt_ids);
+#endif /* CONFIG_OF */
+
+static const struct i2c_device_id ad5272_id[] = {
+	{ "ad5272-020", AD5272_020 },
+	{ "ad5272-050", AD5272_050 },
+	{ "ad5272-100", AD5272_100 },
+	{ "ad5274-020", AD5274_020 },
+	{ "ad5274-100", AD5274_100 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, ad5272_id);
+
+static struct i2c_driver ad5272_driver = {
+	.driver = {
+		.name	= "ad5272",
+		.of_match_table = of_match_ptr(ad5272_dt_ids),
+	},
+	.probe		= ad5272_probe,
+	.id_table	= ad5272_id,
+};
+
+module_i2c_driver(ad5272_driver);
+
+MODULE_AUTHOR("Phil Reid <preid@eletromag.com.au>");
+MODULE_DESCRIPTION("AD5272 digital potentiometer");
+MODULE_LICENSE("GPL v2");
-- 
1.8.3.1

Re: [PATCH v4 2/2] iio: ad5272: Add support for Analog Devices digital potentiometers

[Jonathan Cameron]

On Mon, 29 Jan 2018 21:12:54 +0800
Phil Reid <preid@electromag.com.au> wrote:

> Add implementation for Analog Devices AD5272 and AD5274 digital
> potentiometer devices.
> 
> Signed-off-by: Phil Reid <preid@electromag.com.au>
Nice little driver - thanks.

Applied to the togreg branch of iio.git and pushed out as testing for the
autobuilders to play with it.

Thanks,

Jonathan

> ---
>  drivers/iio/potentiometer/Kconfig  |  10 ++
>  drivers/iio/potentiometer/Makefile |   1 +
>  drivers/iio/potentiometer/ad5272.c | 231 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 242 insertions(+)
>  create mode 100644 drivers/iio/potentiometer/ad5272.c
> 
> diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
> index 8bf2825..8daf6d1 100644
> --- a/drivers/iio/potentiometer/Kconfig
> +++ b/drivers/iio/potentiometer/Kconfig
> @@ -5,6 +5,16 @@
>  
>  menu "Digital potentiometers"
>  
> +config AD5272
> +	tristate "Analog Devices AD5272 and similar Digital Potentiometer driver"
> +	depends on I2C
> +	help
> +	  Say yes here to build support for the Analog Devices AD5272 and AD5274
> +	  digital potentiometer chip.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called ad5272.
> +
>  config DS1803
>  	tristate "Maxim Integrated DS1803 Digital Potentiometer driver"
>  	depends on I2C
> diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
> index 2260d40..498bbb8 100644
> --- a/drivers/iio/potentiometer/Makefile
> +++ b/drivers/iio/potentiometer/Makefile
> @@ -3,6 +3,7 @@
>  #
>  
>  # When adding new entries keep the list in alphabetical order
> +obj-$(CONFIG_AD5272) += ad5272.o
>  obj-$(CONFIG_DS1803) += ds1803.o
>  obj-$(CONFIG_MAX5481) += max5481.o
>  obj-$(CONFIG_MAX5487) += max5487.o
> diff --git a/drivers/iio/potentiometer/ad5272.c b/drivers/iio/potentiometer/ad5272.c
> new file mode 100644
> index 0000000..0175fd5
> --- /dev/null
> +++ b/drivers/iio/potentiometer/ad5272.c
> @@ -0,0 +1,231 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Analog Devices AD5372 digital potentiometer driver
> + * Copyright (C) 2018 Phil Reid <preid@electromag.com.au>
> + *
> + * Datasheet: http://www.analog.com/media/en/technical-documentation/data-sheets/AD5272_5274.pdf
> + *
> + * DEVID	#Wipers	#Positions	Resistor Opts (kOhm)	i2c address
> + * ad5272	1	1024		20, 50, 100		01011xx
> + * ad5274	1	256		20, 100			01011xx
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +#include <linux/module.h>
> +
> +#define  AD5272_RDAC_WR  1
> +#define  AD5272_RDAC_RD  2
> +#define  AD5272_RESET    4
> +#define  AD5272_CTL      7
> +
> +#define  AD5272_RDAC_WR_EN  BIT(1)
> +
> +struct ad5272_cfg {
> +	int max_pos;
> +	int kohms;
> +	int shift;
> +};
> +
> +enum ad5272_type {
> +	AD5272_020,
> +	AD5272_050,
> +	AD5272_100,
> +	AD5274_020,
> +	AD5274_100,
> +};
> +
> +static const struct ad5272_cfg ad5272_cfg[] = {
> +	[AD5272_020] = { .max_pos = 1024, .kohms = 20 },
> +	[AD5272_050] = { .max_pos = 1024, .kohms = 50 },
> +	[AD5272_100] = { .max_pos = 1024, .kohms = 100 },
> +	[AD5274_020] = { .max_pos = 256,  .kohms = 20,  .shift = 2 },
> +	[AD5274_100] = { .max_pos = 256,  .kohms = 100, .shift = 2 },
> +};
> +
> +struct ad5272_data {
> +	struct i2c_client       *client;
> +	struct mutex            lock;
> +	const struct ad5272_cfg *cfg;
> +	u8                      buf[2] ____cacheline_aligned;
> +};
> +
> +static const struct iio_chan_spec ad5272_channel = {
> +	.type = IIO_RESISTANCE,
> +	.output = 1,
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> +};
> +
> +static int ad5272_write(struct ad5272_data *data, int reg, int val)
> +{
> +	int ret;
> +
> +	data->buf[0] = (reg << 2) | ((val >> 8) & 0x3);
> +	data->buf[1] = (u8)val;
> +
> +	mutex_lock(&data->lock);
> +	ret = i2c_master_send(data->client, data->buf, sizeof(data->buf));
> +	mutex_unlock(&data->lock);
> +	return ret < 0 ? ret : 0;
> +}
> +
> +static int ad5272_read(struct ad5272_data *data, int reg, int *val)
> +{
> +	int ret;
> +
> +	data->buf[0] = reg << 2;
> +	data->buf[1] = 0;
> +
> +	mutex_lock(&data->lock);
> +	ret = i2c_master_send(data->client, data->buf, sizeof(data->buf));
> +	if (ret < 0)
> +		goto error;
> +
> +	ret = i2c_master_recv(data->client, data->buf, sizeof(data->buf));
> +	if (ret < 0)
> +		goto error;
> +
> +	*val = ((data->buf[0] & 0x3) << 8) | data->buf[1];
> +	ret = 0;
> +error:
> +	mutex_unlock(&data->lock);
> +	return ret;
> +}
> +
> +static int ad5272_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val, int *val2, long mask)
> +{
> +	struct ad5272_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW: {
> +		ret = ad5272_read(data, AD5272_RDAC_RD, val);
> +		*val = *val >> data->cfg->shift;
> +		return ret ? ret : IIO_VAL_INT;
> +	}
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = 1000 * data->cfg->kohms;
> +		*val2 = data->cfg->max_pos;
> +		return IIO_VAL_FRACTIONAL;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int ad5272_write_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int val, int val2, long mask)
> +{
> +	struct ad5272_data *data = iio_priv(indio_dev);
> +
> +	if (mask != IIO_CHAN_INFO_RAW)
> +		return -EINVAL;
> +
> +	if (val >= data->cfg->max_pos || val < 0 || val2)
> +		return -EINVAL;
> +
> +	return ad5272_write(data, AD5272_RDAC_WR, val << data->cfg->shift);
> +}
> +
> +static const struct iio_info ad5272_info = {
> +	.read_raw = ad5272_read_raw,
> +	.write_raw = ad5272_write_raw,
> +};
> +
> +static int ad5272_reset(struct ad5272_data *data)
> +{
> +	struct gpio_desc *reset_gpio;
> +
> +	reset_gpio = devm_gpiod_get_optional(&data->client->dev, "reset",
> +		GPIOD_OUT_LOW);
> +	if (IS_ERR(reset_gpio))
> +		return PTR_ERR(reset_gpio);
> +
> +	if (reset_gpio) {
> +		udelay(1);
> +		gpiod_set_value(reset_gpio, 1);
> +	} else {
> +		ad5272_write(data, AD5272_RESET, 0);
> +	}
> +	usleep_range(1000, 2000);
> +
> +	return 0;
> +}
> +
> +static int ad5272_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct device *dev = &client->dev;
> +	struct iio_dev *indio_dev;
> +	struct ad5272_data *data;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	i2c_set_clientdata(client, indio_dev);
> +
> +	data = iio_priv(indio_dev);
> +	data->client = client;
> +	mutex_init(&data->lock);
> +	data->cfg = &ad5272_cfg[id->driver_data];
> +
> +	ret = ad5272_reset(data);
> +	if (ret)
> +		return ret;
> +
> +	ret = ad5272_write(data, AD5272_CTL, AD5272_RDAC_WR_EN);
> +	if (ret < 0)
> +		return -ENODEV;
> +
> +	indio_dev->dev.parent = dev;
> +	indio_dev->info = &ad5272_info;
> +	indio_dev->channels = &ad5272_channel;
> +	indio_dev->num_channels = 1;
> +	indio_dev->name = client->name;
> +
> +	return devm_iio_device_register(dev, indio_dev);
> +}
> +
> +#if defined(CONFIG_OF)
> +static const struct of_device_id ad5272_dt_ids[] = {
> +	{ .compatible = "adi,ad5272-020", .data = (void *)AD5272_020 },
> +	{ .compatible = "adi,ad5272-050", .data = (void *)AD5272_050 },
> +	{ .compatible = "adi,ad5272-100", .data = (void *)AD5272_100 },
> +	{ .compatible = "adi,ad5274-020", .data = (void *)AD5274_020 },
> +	{ .compatible = "adi,ad5274-100", .data = (void *)AD5274_100 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, ad5272_dt_ids);
> +#endif /* CONFIG_OF */
> +
> +static const struct i2c_device_id ad5272_id[] = {
> +	{ "ad5272-020", AD5272_020 },
> +	{ "ad5272-050", AD5272_050 },
> +	{ "ad5272-100", AD5272_100 },
> +	{ "ad5274-020", AD5274_020 },
> +	{ "ad5274-100", AD5274_100 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, ad5272_id);
> +
> +static struct i2c_driver ad5272_driver = {
> +	.driver = {
> +		.name	= "ad5272",
> +		.of_match_table = of_match_ptr(ad5272_dt_ids),
> +	},
> +	.probe		= ad5272_probe,
> +	.id_table	= ad5272_id,
> +};
> +
> +module_i2c_driver(ad5272_driver);
> +
> +MODULE_AUTHOR("Phil Reid <preid@eletromag.com.au>");
> +MODULE_DESCRIPTION("AD5272 digital potentiometer");
> +MODULE_LICENSE("GPL v2");