iio: mcp4531: Driver for Microchip digital potentiometers

Add support for Microchip digital potentiometers and rheostats
	MCP4531, MCP4532, MCP4551, MCP4552
	MCP4631, MCP4632, MCP4651, MCP4652

DEVICE   Wipers  Steps  Resistor Opts (kOhm)  i2c address
MCP4531  1       129    5, 10, 50, 100        010111x
MCP4532  1       129    5, 10, 50, 100        01011xx
MCP4551  1       257    5, 10, 50, 100        010111x
MCP4552  1       257    5, 10, 50, 100        01011xx
MCP4631  2       129    5, 10, 50, 100        0101xxx
MCP4632  2       129    5, 10, 50, 100        01011xx
MCP4651  2       257    5, 10, 50, 100        0101xxx
MCP4652  2       257    5, 10, 50, 100        01011xx

Datasheet: http://www.microchip.com/downloads/en/DeviceDoc/22096b.pdfSigned-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

MAINTAINERS

@@ -6682,6 +6682,12 @@ W:	http://linuxtv.org
 S:	Maintained
 F:	drivers/media/radio/radio-maxiradio*
 
+MCP4531 MICROCHIP DIGITAL POTENTIOMETER DRIVER
+M:	Peter Rosin <peda@axentia.se>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	drivers/iio/potentiometer/mcp4531.c
+
 MEDIA DRIVERS FOR RENESAS - VSP1
 M:	Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 L:	linux-media@vger.kernel.org

drivers/iio/Kconfig

@@ -60,6 +60,7 @@ source "drivers/iio/orientation/Kconfig"
 if IIO_TRIGGER
    source "drivers/iio/trigger/Kconfig"
 endif #IIO_TRIGGER
+source "drivers/iio/potentiometer/Kconfig"
 source "drivers/iio/pressure/Kconfig"
 source "drivers/iio/proximity/Kconfig"
 source "drivers/iio/temperature/Kconfig"

drivers/iio/Makefile

@@ -23,6 +23,7 @@ obj-y += imu/
 obj-y += light/
 obj-y += magnetometer/
 obj-y += orientation/
+obj-y += potentiometer/
 obj-y += pressure/
 obj-y += proximity/
 obj-y += temperature/

drivers/iio/potentiometer/Kconfig

+#
+# Potentiometer drivers
+#
+# When adding new entries keep the list in alphabetical order
+
+menu "Digital potentiometers"
+
+config MCP4531
+	tristate "Microchip MCP45xx/MCP46xx Digital Potentiometer driver"
+	depends on I2C
+	help
+	  Say yes here to build support for the Microchip
+	  MCP4531, MCP4532, MCP4551, MCP4552,
+	  MCP4631, MCP4632, MCP4651, MCP4652
+	  digital potentiomenter chips.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called mcp4531.
+
+endmenu

drivers/iio/potentiometer/Makefile

+#
+# Makefile for industrial I/O potentiometer drivers
+#
+
+# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_MCP4531) += mcp4531.o

drivers/iio/potentiometer/mcp4531.c

+/*
+ * Industrial I/O driver for Microchip digital potentiometers
+ * Copyright (c) 2015  Axentia Technologies AB
+ * Author: Peter Rosin <peda@axentia.se>
+ *
+ * Datasheet: http://www.microchip.com/downloads/en/DeviceDoc/22096b.pdf
+ *
+ * DEVID	#Wipers	#Positions	Resistor Opts (kOhm)	i2c address
+ * mcp4531	1	129		5, 10, 50, 100          010111x
+ * mcp4532	1	129		5, 10, 50, 100          01011xx
+ * mcp4551	1	257		5, 10, 50, 100          010111x
+ * mcp4552	1	257		5, 10, 50, 100          01011xx
+ * mcp4631	2	129		5, 10, 50, 100          0101xxx
+ * mcp4632	2	129		5, 10, 50, 100          01011xx
+ * mcp4651	2	257		5, 10, 50, 100          0101xxx
+ * mcp4652	2	257		5, 10, 50, 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/module.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+
+#include <linux/iio/iio.h>
+
+struct mcp4531_cfg {
+	int wipers;
+	int max_pos;
+	int kohms;
+};
+
+enum mcp4531_type {
+	MCP453x_502,
+	MCP453x_103,
+	MCP453x_503,
+	MCP453x_104,
+	MCP455x_502,
+	MCP455x_103,
+	MCP455x_503,
+	MCP455x_104,
+	MCP463x_502,
+	MCP463x_103,
+	MCP463x_503,
+	MCP463x_104,
+	MCP465x_502,
+	MCP465x_103,
+	MCP465x_503,
+	MCP465x_104,
+};
+
+static const struct mcp4531_cfg mcp4531_cfg[] = {
+	[MCP453x_502] = { .wipers = 1, .max_pos = 128, .kohms =   5, },
+	[MCP453x_103] = { .wipers = 1, .max_pos = 128, .kohms =  10, },
+	[MCP453x_503] = { .wipers = 1, .max_pos = 128, .kohms =  50, },
+	[MCP453x_104] = { .wipers = 1, .max_pos = 128, .kohms = 100, },
+	[MCP455x_502] = { .wipers = 1, .max_pos = 256, .kohms =   5, },
+	[MCP455x_103] = { .wipers = 1, .max_pos = 256, .kohms =  10, },
+	[MCP455x_503] = { .wipers = 1, .max_pos = 256, .kohms =  50, },
+	[MCP455x_104] = { .wipers = 1, .max_pos = 256, .kohms = 100, },
+	[MCP463x_502] = { .wipers = 2, .max_pos = 128, .kohms =   5, },
+	[MCP463x_103] = { .wipers = 2, .max_pos = 128, .kohms =  10, },
+	[MCP463x_503] = { .wipers = 2, .max_pos = 128, .kohms =  50, },
+	[MCP463x_104] = { .wipers = 2, .max_pos = 128, .kohms = 100, },
+	[MCP465x_502] = { .wipers = 2, .max_pos = 256, .kohms =   5, },
+	[MCP465x_103] = { .wipers = 2, .max_pos = 256, .kohms =  10, },
+	[MCP465x_503] = { .wipers = 2, .max_pos = 256, .kohms =  50, },
+	[MCP465x_104] = { .wipers = 2, .max_pos = 256, .kohms = 100, },
+};
+
+#define MCP4531_WRITE (0 << 2)
+#define MCP4531_INCR  (1 << 2)
+#define MCP4531_DECR  (2 << 2)
+#define MCP4531_READ  (3 << 2)
+
+#define MCP4531_WIPER_SHIFT (4)
+
+struct mcp4531_data {
+	struct i2c_client *client;
+	unsigned long devid;
+};
+
+#define MCP4531_CHANNEL(ch) {					\
+	.type = IIO_RESISTANCE,					\
+	.indexed = 1,						\
+	.output = 1,						\
+	.channel = (ch),					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+}
+
+static const struct iio_chan_spec mcp4531_channels[] = {
+	MCP4531_CHANNEL(0),
+	MCP4531_CHANNEL(1),
+};
+
+static int mcp4531_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct mcp4531_data *data = iio_priv(indio_dev);
+	int address = chan->channel << MCP4531_WIPER_SHIFT;
+	s32 ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = i2c_smbus_read_word_swapped(data->client,
+						  MCP4531_READ | address);
+		if (ret < 0)
+			return ret;
+		*val = ret;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 1000 * mcp4531_cfg[data->devid].kohms;
+		*val2 = mcp4531_cfg[data->devid].max_pos;
+		return IIO_VAL_FRACTIONAL;
+	}
+
+	return -EINVAL;
+}
+
+static int mcp4531_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int val, int val2, long mask)
+{
+	struct mcp4531_data *data = iio_priv(indio_dev);
+	int address = chan->channel << MCP4531_WIPER_SHIFT;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (val > mcp4531_cfg[data->devid].max_pos || val < 0)
+			return -EINVAL;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return i2c_smbus_write_byte_data(data->client,
+					 MCP4531_WRITE | address | (val >> 8),
+					 val & 0xff);
+}
+
+static const struct iio_info mcp4531_info = {
+	.read_raw = mcp4531_read_raw,
+	.write_raw = mcp4531_write_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static int mcp4531_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	unsigned long devid = id->driver_data;
+	struct mcp4531_data *data;
+	struct iio_dev *indio_dev;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_WORD_DATA)) {
+		dev_err(dev, "SMBUS Word Data not supported\n");
+		return -EIO;
+	}
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+	data = iio_priv(indio_dev);
+	i2c_set_clientdata(client, indio_dev);
+	data->client = client;
+	data->devid = devid;
+
+	indio_dev->dev.parent = dev;
+	indio_dev->info = &mcp4531_info;
+	indio_dev->channels = mcp4531_channels;
+	indio_dev->num_channels = mcp4531_cfg[devid].wipers;
+	indio_dev->name = client->name;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct i2c_device_id mcp4531_id[] = {
+	{ "mcp4531-502", MCP453x_502 },
+	{ "mcp4531-103", MCP453x_103 },
+	{ "mcp4531-503", MCP453x_503 },
+	{ "mcp4531-104", MCP453x_104 },
+	{ "mcp4532-502", MCP453x_502 },
+	{ "mcp4532-103", MCP453x_103 },
+	{ "mcp4532-503", MCP453x_503 },
+	{ "mcp4532-104", MCP453x_104 },
+	{ "mcp4551-502", MCP455x_502 },
+	{ "mcp4551-103", MCP455x_103 },
+	{ "mcp4551-503", MCP455x_503 },
+	{ "mcp4551-104", MCP455x_104 },
+	{ "mcp4552-502", MCP455x_502 },
+	{ "mcp4552-103", MCP455x_103 },
+	{ "mcp4552-503", MCP455x_503 },
+	{ "mcp4552-104", MCP455x_104 },
+	{ "mcp4631-502", MCP463x_502 },
+	{ "mcp4631-103", MCP463x_103 },
+	{ "mcp4631-503", MCP463x_503 },
+	{ "mcp4631-104", MCP463x_104 },
+	{ "mcp4632-502", MCP463x_502 },
+	{ "mcp4632-103", MCP463x_103 },
+	{ "mcp4632-503", MCP463x_503 },
+	{ "mcp4632-104", MCP463x_104 },
+	{ "mcp4651-502", MCP465x_502 },
+	{ "mcp4651-103", MCP465x_103 },
+	{ "mcp4651-503", MCP465x_503 },
+	{ "mcp4651-104", MCP465x_104 },
+	{ "mcp4652-502", MCP465x_502 },
+	{ "mcp4652-103", MCP465x_103 },
+	{ "mcp4652-503", MCP465x_503 },
+	{ "mcp4652-104", MCP465x_104 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, mcp4531_id);
+
+static struct i2c_driver mcp4531_driver = {
+	.driver = {
+		.name	= "mcp4531",
+	},
+	.probe		= mcp4531_probe,
+	.id_table	= mcp4531_id,
+};
+
+module_i2c_driver(mcp4531_driver);
+
+MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
+MODULE_DESCRIPTION("MCP4531 digital potentiometer");
+MODULE_LICENSE("GPL");