[PATCH v2] iio: mcp4xxx_dpot: Driver for Microchip digital potentiometers

[Peter Rosin <peda@lysator.liu.se>]

From: Peter Rosin <peda@axentia.se>

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

These are either single (45xx) or dual (46xx) wipers with either
129 (4x3x) or 257 (4x5x) steps, and configured either as
potentiometers (4xx1) or rheostats (4xx2).

Signed-off-by: Peter Rosin <peda@axentia.se>
---
 MAINTAINERS                    |    5 +
 drivers/iio/Kconfig            |    1 +
 drivers/iio/Makefile           |    1 +
 drivers/iio/pot/Kconfig        |   20 ++++
 drivers/iio/pot/Makefile       |    6 ++
 drivers/iio/pot/mcp4xxx_dpot.c |  218 ++++++++++++++++++++++++++++++++++++++++
 6 files changed, 251 insertions(+)
 create mode 100644 drivers/iio/pot/Kconfig
 create mode 100644 drivers/iio/pot/Makefile
 create mode 100644 drivers/iio/pot/mcp4xxx_dpot.c

diff --git a/MAINTAINERS b/MAINTAINERS
index b60e2b2369d2..2a34b75b3034 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6600,6 +6600,11 @@ W:	http://linuxtv.org
 S:	Maintained
 F:	drivers/media/radio/radio-maxiradio*
 
+MCP4XXX MICROCHIP DIGITAL POTENTIOMETER DRIVER
+M:	Peter Rosin <peda@axentia.se>
+S:	Maintained
+F:	drivers/iio/pot/mcp4xxx_dpot.*
+
 MEDIA DRIVERS FOR RENESAS - VSP1
 M:	Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 L:	linux-media@vger.kernel.org
diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 4011effe4c05..837aabad4b9a 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -73,6 +73,7 @@ source "drivers/iio/orientation/Kconfig"
 if IIO_TRIGGER
    source "drivers/iio/trigger/Kconfig"
 endif #IIO_TRIGGER
+source "drivers/iio/pot/Kconfig"
 source "drivers/iio/pressure/Kconfig"
 source "drivers/iio/proximity/Kconfig"
 source "drivers/iio/temperature/Kconfig"
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index 698afc2d17ce..df026289309f 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -23,6 +23,7 @@ obj-y += imu/
 obj-y += light/
 obj-y += magnetometer/
 obj-y += orientation/
+obj-y += pot/
 obj-y += pressure/
 obj-y += proximity/
 obj-y += temperature/
diff --git a/drivers/iio/pot/Kconfig b/drivers/iio/pot/Kconfig
new file mode 100644
index 000000000000..48ebc7ef6b6b
--- /dev/null
+++ b/drivers/iio/pot/Kconfig
@@ -0,0 +1,20 @@
+#
+# Potentiometer drivers
+#
+# When adding new entries keep the list in alphabetical order
+
+menu "Digital potentiometers"
+
+config MCP4XXX_DPOT
+	tristate "Microchip MCP45xx/MCP46xx Digital Potentiometer driver"
+	depends on I2C
+	help
+	  Say yes here to build support for the Microship
+	  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 mcp4xxx_dpot.
+
+endmenu
diff --git a/drivers/iio/pot/Makefile b/drivers/iio/pot/Makefile
new file mode 100644
index 000000000000..763628ed649a
--- /dev/null
+++ b/drivers/iio/pot/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for industrial I/O potentiometer drivers
+#
+
+# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_MCP4XXX_DPOT) += mcp4xxx_dpot.o
diff --git a/drivers/iio/pot/mcp4xxx_dpot.c b/drivers/iio/pot/mcp4xxx_dpot.c
new file mode 100644
index 000000000000..30a1fb8fa46d
--- /dev/null
+++ b/drivers/iio/pot/mcp4xxx_dpot.c
@@ -0,0 +1,218 @@
+/*
+ * Industrial I/O driver for Microchip digital potentiometers
+ * Copyright (c) 2015  Axentia Technologies AB
+ * Author: Peter Rosin <peda@axentia.se>
+ *
+ * DEVID		#Wipers		#Positions	Resistor Options (kOhm)
+ * mcp4531		1		129		5, 10, 50, 100
+ * mcp4532		1		129		5, 10, 50, 100
+ * mcp4551		1		257		5, 10, 50, 100
+ * mcp4552		1		257		5, 10, 50, 100
+ * mcp4631		2		129		5, 10, 50, 100
+ * mcp4632		2		129		5, 10, 50, 100
+ * mcp4651		2		257		5, 10, 50, 100
+ * mcp4652		2		257		5, 10, 50, 100
+ *
+ * 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>
+
+
+#define DPOT_CONF(wipers, max_pos, uid) \
+	((((wipers) & 0xf) << 10) | \
+	 (((max_pos) & 0xf) << 6) | \
+	 ((uid) & 0x3f))
+
+#define DPOT_UID(conf)     ((conf) & 0x3f)
+#define DPOT_MAX_POS(conf) (((conf) >> 6) & 0xf)
+#define DPOT_WIPERS(conf)  (((conf) >> 10) & 0xf)
+
+enum mcp4xxx_dpot_devid {
+	MCP4531_ID = DPOT_CONF(1, 7, 0),
+	MCP4532_ID = DPOT_CONF(1, 7, 1),
+	MCP4551_ID = DPOT_CONF(1, 8, 2),
+	MCP4552_ID = DPOT_CONF(1, 8, 3),
+	MCP4631_ID = DPOT_CONF(2, 7, 4),
+	MCP4632_ID = DPOT_CONF(2, 7, 5),
+	MCP4651_ID = DPOT_CONF(2, 8, 6),
+	MCP4652_ID = DPOT_CONF(2, 8, 7),
+};
+
+struct mcp4xxx_dpot_data {
+	struct i2c_client *client;
+	unsigned int max_pos;
+	unsigned long devid;
+	int cache[2];
+};
+
+static const struct iio_chan_spec mcp4xxx_dpot_channels[] = {
+	{
+		.type = IIO_STEPS,
+		.indexed = 1,
+		.output = 1,
+		.channel = 0,
+		.address = 0 << 4,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+	}, {
+		.type = IIO_STEPS,
+		.indexed = 1,
+		.output = 1,
+		.channel = 1,
+		.address = 1 << 4,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+	}
+};
+
+static int mcp4xxx_dpot_get_value(struct iio_dev *indio_dev,
+				  int address, int *val)
+{
+	struct mcp4xxx_dpot_data *data = iio_priv(indio_dev);
+	s32 value;
+
+	value = i2c_smbus_read_word_data(data->client,  address | 0xc);
+	if (value < 0)
+		return value;
+	*val = ((value >> 8) & 0xff) | ((value & 0xff) << 8);
+	return 0;
+}
+
+static int mcp4xxx_dpot_set_value(struct iio_dev *indio_dev,
+				  int address, int val)
+{
+	struct mcp4xxx_dpot_data *data = iio_priv(indio_dev);
+
+	if (val >= data->max_pos || val < 0)
+		return -EINVAL;
+
+	return i2c_smbus_write_byte_data(data->client,
+					 address | (val >> 8),
+					 val & 0xff);
+}
+
+static int mcp4xxx_dpot_read_raw(struct iio_dev *indio_dev,
+				 struct iio_chan_spec const *chan,
+				 int *val, int *val2, long mask)
+{
+	struct mcp4xxx_dpot_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		*val = data->cache[chan->channel];
+		return IIO_VAL_INT;
+	}
+
+	return -EINVAL;
+}
+
+static int mcp4xxx_dpot_write_raw(struct iio_dev *indio_dev,
+				  struct iio_chan_spec const *chan,
+				  int val, int val2, long mask)
+{
+	struct mcp4xxx_dpot_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = mcp4xxx_dpot_set_value(indio_dev, chan->address, val);
+		if (ret >= 0)
+			data->cache[chan->channel] = val;
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
+static const struct iio_info mcp4xxx_dpot_info = {
+	.read_raw = mcp4xxx_dpot_read_raw,
+	.write_raw = mcp4xxx_dpot_write_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static int mcp4xxx_dpot_probe(struct i2c_client *client,
+			      const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	unsigned long devid = id->driver_data;
+	struct mcp4xxx_dpot_data *data;
+	struct iio_dev *indio_dev;
+	int ch;
+	int err;
+
+	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(&client->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;
+
+	data->max_pos = (1 << DPOT_MAX_POS(devid)) + 1;
+
+	indio_dev->dev.parent = dev;
+	indio_dev->info = &mcp4xxx_dpot_info;
+	indio_dev->channels = mcp4xxx_dpot_channels;
+	indio_dev->num_channels = DPOT_WIPERS(devid);
+	indio_dev->name = client->name;
+
+	for (i = 0; i < indio_dev->num_channels; ++i) {
+		err = mcp4xxx_dpot_get_value(indio_dev,
+					     indio_dev->channels[i].address,
+					     &data->cache[i]);
+		if (err) {
+			dev_err(dev, "failed to read potentiometer value\n");
+			return err;
+		}
+	}
+
+	return iio_device_register(indio_dev);
+}
+
+static int mcp4xxx_dpot_remove(struct i2c_client *client)
+{
+	iio_device_unregister(i2c_get_clientdata(client));
+	return 0;
+}
+
+static const struct i2c_device_id mcp4xxx_dpot_id[] = {
+	{ "mcp4531", MCP4531_ID },
+	{ "mcp4532", MCP4532_ID },
+	{ "mcp4551", MCP4551_ID },
+	{ "mcp4552", MCP4552_ID },
+	{ "mcp4631", MCP4631_ID },
+	{ "mcp4632", MCP4632_ID },
+	{ "mcp4651", MCP4651_ID },
+	{ "mcp4652", MCP4652_ID },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, mcp4xxx_dpot_id);
+
+static struct i2c_driver mcp4xxx_dpot_driver = {
+	.driver = {
+		.name	= "mcp4xxx_dpot",
+	},
+	.probe		= mcp4xxx_dpot_probe,
+	.remove		= mcp4xxx_dpot_remove,
+	.id_table	= mcp4xxx_dpot_id,
+};
+
+module_i2c_driver(mcp4xxx_dpot_driver);
+
+MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
+MODULE_DESCRIPTION("MCP4XXX digital potentiometer");
+MODULE_LICENSE("GPL");
-- 
1.7.10.4