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

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

Signed-off-by: Phil Reid <preid-qgqNFa1JUf/o2iN0hyhwsIdd74u8MsAO@public.gmane.org>
---
  drivers/iio/potentiometer/Kconfig  |  10 ++
  drivers/iio/potentiometer/Makefile |   1 +
  drivers/iio/potentiometer/ad5272.c | 219 +++++++++++++++++++++++++++++++++++++
  3 files changed, 230 insertions(+)
  create mode 100644 drivers/iio/potentiometer/ad5272.c

diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
index 8bf2825..0b04063 100644
--- a/drivers/iio/potentiometer/Kconfig
+++ b/drivers/iio/potentiometer/Kconfig

@@ -5,6 +5,16 @@
  
  menu "Digital potentiometers"
  
+config AD5272
+	tristate "Analog Devices AD5272 Digital Potentiometer driver"
+	depends on I2C
+	help
+	  Say yes here to build support for the Analog Devices AD5272
+	  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..b9208c2
--- /dev/null
+++ b/drivers/iio/potentiometer/ad5272.c

@@ -0,0 +1,219 @@
+/*
+ * Analog Devices AD5372 digital potentiometer driver
+ * Copyright (C) 2018 Phil Reid <preid-qgqNFa1JUf/o2iN0hyhwsIdd74u8MsAO@public.gmane.org>
+ *
+ * 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
+ *
+ * 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/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_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[] = {
+	/* on-semiconductor parts */
+	[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;
+};
+
+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)
+{
+	u8 buf[2];
+	int ret;
+
+	buf[0] = ((reg & 0xf) << 2) | ((val >> 8) & 0x3);
+	buf[1] = (u8)val;
+
+	mutex_lock(&data->lock);
+	ret = i2c_master_send(data->client, buf, 2);
+	mutex_unlock(&data->lock);
+	return ret < 0 ? ret : 0;
+}
+
+static int ad5272_read(struct ad5272_data *data, int reg, int *val)
+{
+	u8 buf[2];
+	int ret;
+
+	buf[0] = (reg & 0xf) << 2;
+	buf[1] = 0;
+
+	mutex_lock(&data->lock);
+	ret = i2c_master_send(data->client, buf, 2);
+	if (ret < 0)
+		goto error;
+
+	ret = i2c_master_recv(data->client, buf, 2);
+	if (ret < 0)
+		goto error;
+
+	*val = ((buf[0] & 0x3) << 8) | 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)
+		return -EINVAL;
+
+	val = val << data->cfg->shift;
+
+	return ad5272_write(data, AD5272_RDAC_WR, val);
+}
+
+static const struct iio_info ad5272_info = {
+	.read_raw = ad5272_read_raw,
+	.write_raw = ad5272_write_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static int ad5272_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct gpio_desc *reset_gpio;
+	struct iio_dev *indio_dev;
+	struct ad5272_data *data;
+	int ret;
+
+	reset_gpio = devm_gpiod_get_optional(&client->dev, "reset",
+		GPIOD_OUT_LOW);