Date:	Wed, 16 Mar 2016 12:37:38 +0100
From:	Slawomir Stepien <sst@...zta.fm>
To:	jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
	pmeerw@...erw.net
Cc:	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iio: add driver for Microchip MCP414X/416X/424X/426X

The following functionalities are supported:
 - write, read from volatile and non volatile memory
 - increase and decrease commands
 - read from status register
 - write and read to tcon register

Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/22059b.pdf

Signed-off-by: Slawomir Stepien <sst@...zta.fm>
---
 .../bindings/iio/potentiometer/mcp41xx.txt         |  51 ++
 Documentation/iio/mcp41xx.txt                      |  86 +++
 drivers/iio/potentiometer/Kconfig                  |  18 +
 drivers/iio/potentiometer/Makefile                 |   1 +
 drivers/iio/potentiometer/mcp41xx.c                | 709 +++++++++++++++++++++
 5 files changed, 865 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/mcp41xx.txt
 create mode 100644 Documentation/iio/mcp41xx.txt
 create mode 100644 drivers/iio/potentiometer/mcp41xx.c

diff --git a/Documentation/devicetree/bindings/iio/potentiometer/mcp41xx.txt b/Documentation/devicetree/bindings/iio/potentiometer/mcp41xx.txt
new file mode 100644
index 0000000..6031142
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/potentiometer/mcp41xx.txt
@@ -0,0 +1,51 @@
+* Microchip MCP414X/416X/424X/426X Digital Potentiometer driver
+
+The node for this driver must be a child node of a SPI controller, hence
+all mandatory properties described in
+
+        Documentation/devicetree/bindings/spi/spi-bus.txt
+
+must be specified.
+
+Required properties:
+	- compatible:  	Must be one of the following, depending on the
+			model:
+			"microchip,mcp4113x-502"
+			"microchip,mcp4113x-103"
+			"microchip,mcp4113x-503"
+			"microchip,mcp4113x-104"
+			"microchip,mcp4114x-502"
+			"microchip,mcp4114x-103"
+			"microchip,mcp4114x-503"
+			"microchip,mcp4114x-104"
+			"microchip,mcp4115x-502"
+			"microchip,mcp4115x-103"
+			"microchip,mcp4115x-503"
+			"microchip,mcp4115x-104"
+			"microchip,mcp4116x-502"
+			"microchip,mcp4116x-103"
+			"microchip,mcp4116x-503"
+			"microchip,mcp4116x-104"
+			"microchip,mcp4123x-502"
+			"microchip,mcp4123x-103"
+			"microchip,mcp4123x-503"
+			"microchip,mcp4123x-104"
+			"microchip,mcp4124x-502"
+			"microchip,mcp4124x-103"
+			"microchip,mcp4124x-503"
+			"microchip,mcp4124x-104"
+			"microchip,mcp4125x-502"
+			"microchip,mcp4125x-103"
+			"microchip,mcp4125x-503"
+			"microchip,mcp4125x-104"
+			"microchip,mcp4126x-502"
+			"microchip,mcp4126x-103"
+			"microchip,mcp4126x-503"
+			"microchip,mcp4126x-104"
+
+Example:
+mcp41xx: mcp41xx@0 {
+	compatible = "mcp416x-502";
+	reg = <0>;
+	spi-max-frequency = <500000>;
+};
diff --git a/Documentation/iio/mcp41xx.txt b/Documentation/iio/mcp41xx.txt
new file mode 100644
index 0000000..57dc889
--- /dev/null
+++ b/Documentation/iio/mcp41xx.txt
@@ -0,0 +1,86 @@
+Industrial I/O driver for MCP414X/416X/424X/426X Digital POTs
+-------------------------------------------------------------
+
+Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/22059a.pdf
+
+sysfs interface
+---------------
+N is the wiper number (0 = first wiper, 1 = second wiper)
+
+File:	/sys/bus/iio/devices/../decr_wiperN
+Mode:	Write
+Description:
+	Write anything to this file to decrease wiper N position by one step.
+Example:
+	echo > decr_wiper0
+
+
+File:	/sys/bus/iio/devices/../incr_wiperN
+Mode:	Write
+Description:
+	Write anything to this file to increase wiper N position by one step.
+Example:
+	echo > incr_wiper0
+
+
+File:	/sys/bus/iio/devices/../memory_map
+Mode:	Read/Write
+Description:
+	Read the whole memory or write value to given memory address.
+	Read outputs two columns. First column is address and second column is
+	value at that address.
+	For write use hex values with leading 0x. First hex is address second
+	hex is the value.
+Example:
+	cat memory_map
+	echo "0x00 0x80" > memory_map
+
+
+File:	/sys/bus/iio/devices/../nv_wiperN
+Mode:	Read/Write
+Description:
+	Read or write to non volatile memory of wiper N.
+	Read outputs decimal value that corresponds to wiper position.
+	For write use decimal value that corresponds to wiper position.
+Example:
+	cat nv_wiper0
+	echo "128" > nv_wiper0
+
+
+File:	/sys/bus/iio/devices/../out_resistance_scale
+Mode:	Read
+Description:
+	Read the resistance scale of one step (in ohms).
+Example:
+	cat out_resistance_scale
+
+
+File:	/sys/bus/iio/devices/../out_resistanceN_raw
+Mode:	Read/Write
+Description:
+	Read or write to volatile memory of wiper N.
+	Read outputs decimal value that corresponds to wiper position.
+	For write use decimal value that corresponds to wiper position.
+Example:
+	cat out_resistance0_raw
+	echo "128" > out_resistance0_raw
+
+
+File:	/sys/bus/iio/devices/../status_register
+Mode:	Read
+Description:
+	Read status register.
+	Read outputs content in binary format.
+Example:
+	cat status_register
+
+
+File:	/sys/bus/iio/devices/../tcon_register
+Mode:	ead/Write
+Description:
+	Read or write to tcon register.
+	Read outputs content in binary format.
+	For write use binary format string.
+Example:
+	cat tcon_register
+	echo "111111100" > tcon_register
diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
index fd75db7..4540367 100644
--- a/drivers/iio/potentiometer/Kconfig
+++ b/drivers/iio/potentiometer/Kconfig
@@ -5,6 +5,24 @@
 
 menu "Digital potentiometers"
 
+config MCP41XX
+	tristate "Microchip MCP414X/416X/424X/426X Digital Potentiometer driver"
+	depends on SPI
+	help
+	  Say yes here to build support for the Microchip
+	  MCP4131, MCP4132,
+	  MCP4141, MCP4142,
+	  MCP4151, MCP4152,
+	  MCP4161, MCP4162,
+	  MCP4231, MCP4232,
+	  MCP4241, MCP4242,
+	  MCP4251, MCP4252,
+	  MCP4261, MCP4262,
+	  digital potentiomenter chips.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called mcp41xx.
+
 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 8afe492..1266ebf 100644
--- a/drivers/iio/potentiometer/Makefile
+++ b/drivers/iio/potentiometer/Makefile
@@ -3,4 +3,5 @@
 #
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_MCP41XX) += mcp41xx.o
 obj-$(CONFIG_MCP4531) += mcp4531.o
diff --git a/drivers/iio/potentiometer/mcp41xx.c b/drivers/iio/potentiometer/mcp41xx.c
new file mode 100644
index 0000000..654965b
--- /dev/null
+++ b/drivers/iio/potentiometer/mcp41xx.c
@@ -0,0 +1,709 @@
+/*
+ * Industrial I/O driver for MCP414X/416X/424X/426X Digital POTs
+ *
+ * Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/22059a.pdf
+ *
+ * Copyright (c) 2016 Slawomir Stepien
+ *
+ * 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/err.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+#define MCP41XX_WRITE		(0x00 << 2)
+#define MCP41XX_INCR		(0x01 << 2)
+#define MCP41XX_DECR		(0x02 << 2)
+#define MCP41XX_READ		(0x03 << 2)
+
+#define MCP41XX_FULL_SCALE(t)	(t[0] == 0xFF ? 256 : t[1])
+#define MCP41XX_9BIT_VALUE(t)	((t[1] + (t[0] << 8)) & 0x1FF)
+
+#define MCP41XX_MIN_ADDR	0x00
+#define MCP41XX_MAX_ADDR	0x0F
+
+#define MCP41XX_NV_OFFSET	0x02
+
+#define MCP41XX_TCON_ADDR	0x04
+#define MCP41XX_STATUS_ADDR	0x05
+
+struct mcp41xx_cfg {
+	unsigned long int devid;
+	unsigned int wipers;
+	unsigned int num_pos;
+	unsigned int kohms;
+};
+
+enum mcp41xx_type {
+	MCP413x_502,
+	MCP413x_103,
+	MCP413x_503,
+	MCP413x_104,
+	MCP414x_502,
+	MCP414x_103,
+	MCP414x_503,
+	MCP414x_104,
+	MCP415x_502,
+	MCP415x_103,
+	MCP415x_503,
+	MCP415x_104,
+	MCP416x_502,
+	MCP416x_103,
+	MCP416x_503,
+	MCP416x_104,
+	MCP423x_502,
+	MCP423x_103,
+	MCP423x_503,
+	MCP423x_104,
+	MCP424x_502,
+	MCP424x_103,
+	MCP424x_503,
+	MCP424x_104,
+	MCP425x_502,
+	MCP425x_103,
+	MCP425x_503,
+	MCP425x_104,
+	MCP426x_502,
+	MCP426x_103,
+	MCP426x_503,
+	MCP426x_104,
+};
+
+static const struct mcp41xx_cfg mcp41xx_cfg[] = {
+	[MCP413x_502] =	{ .wipers = 1, .num_pos = 129, .kohms =   5 },
+	[MCP413x_103] = { .wipers = 1, .num_pos = 129, .kohms =  10 },
+	[MCP413x_503] =	{ .wipers = 1, .num_pos = 129, .kohms =  50 },
+	[MCP413x_104] =	{ .wipers = 1, .num_pos = 129, .kohms = 100 },
+	[MCP414x_502] =	{ .wipers = 1, .num_pos = 129, .kohms =   5 },
+	[MCP414x_103] =	{ .wipers = 1, .num_pos = 129, .kohms =  10 },
+	[MCP414x_503] =	{ .wipers = 1, .num_pos = 129, .kohms =  50 },
+	[MCP414x_104] =	{ .wipers = 1, .num_pos = 129, .kohms = 100 },
+	[MCP415x_502] =	{ .wipers = 1, .num_pos = 257, .kohms =   5 },
+	[MCP415x_103] =	{ .wipers = 1, .num_pos = 257, .kohms =  10 },
+	[MCP415x_503] =	{ .wipers = 1, .num_pos = 257, .kohms =  50 },
+	[MCP415x_104] =	{ .wipers = 1, .num_pos = 257, .kohms = 100 },
+	[MCP416x_502] =	{ .wipers = 1, .num_pos = 257, .kohms =   5 },
+	[MCP416x_103] =	{ .wipers = 1, .num_pos = 257, .kohms =  10 },
+	[MCP416x_503] =	{ .wipers = 1, .num_pos = 257, .kohms =  50 },
+	[MCP416x_104] =	{ .wipers = 1, .num_pos = 257, .kohms = 100 },
+	[MCP423x_502] =	{ .wipers = 2, .num_pos = 129, .kohms =   5 },
+	[MCP423x_103] =	{ .wipers = 2, .num_pos = 129, .kohms =  10 },
+	[MCP423x_503] =	{ .wipers = 2, .num_pos = 129, .kohms =  50 },
+	[MCP423x_104] =	{ .wipers = 2, .num_pos = 129, .kohms = 100 },
+	[MCP424x_502] =	{ .wipers = 2, .num_pos = 129, .kohms =   5 },
+	[MCP424x_103] =	{ .wipers = 2, .num_pos = 129, .kohms =  10 },
+	[MCP424x_503] =	{ .wipers = 2, .num_pos = 129, .kohms =  50 },
+	[MCP424x_104] =	{ .wipers = 2, .num_pos = 129, .kohms = 100 },
+	[MCP425x_502] =	{ .wipers = 2, .num_pos = 257, .kohms =   5 },
+	[MCP425x_103] =	{ .wipers = 2, .num_pos = 257, .kohms =  10 },
+	[MCP425x_503] =	{ .wipers = 2, .num_pos = 257, .kohms =  50 },
+	[MCP425x_104] =	{ .wipers = 2, .num_pos = 257, .kohms = 100 },
+	[MCP426x_502] =	{ .wipers = 2, .num_pos = 257, .kohms =   5 },
+	[MCP426x_103] =	{ .wipers = 2, .num_pos = 257, .kohms =  10 },
+	[MCP426x_503] =	{ .wipers = 2, .num_pos = 257, .kohms =  50 },
+	[MCP426x_104] =	{ .wipers = 2, .num_pos = 257, .kohms = 100 },
+};
+
+struct mcp41xx_data {
+	struct spi_device *spi;
+	struct mutex lock;
+	unsigned long devid;
+	u8 tx[2], rx[2];
+	struct spi_transfer xfer;
+	struct spi_message msg;
+};
+
+#define MCP41XX_CHANNEL(ch) {					\
+	.type = IIO_RESISTANCE,					\
+	.output = 1,						\
+	.indexed = 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 mcp41xx_channels[] = {
+	MCP41XX_CHANNEL(0),
+	MCP41XX_CHANNEL(1),
+};
+
+/* Function based on: arch/parisc/kernel/traps.c */
+static int printbinary(char *buf, unsigned long x, int nbits)
+{
+	unsigned long mask = 1UL << (nbits - 2);
+
+	while (mask != 0) {
+		*buf++ = (mask & x ? '1' : '0');
+		mask >>= 1;
+	}
+	*buf++ = '\n';
+	*buf = '\0';
+
+	return nbits;
+}
+
+static int mcp41xx_exec(struct mcp41xx_data *data,
+		u8 addr, u8 cmd,
+		int *trans, size_t n)
+{
+	int err;
+	struct spi_device *spi = data->spi;
+
+	/* Two bytes are needed for the response */
+	if (n != 2)
+		return -EINVAL;
+
+	switch (cmd) {
+	case MCP41XX_READ:
+		data->xfer.len = 2; /* Two bytes transfer for this command */
+		data->tx[0] = (addr << 4) | MCP41XX_READ;
+		data->tx[1] = 0;
+		break;
+
+	case MCP41XX_WRITE:
+		data->xfer.len = 2;
+		/* Shift trans[0] to see if this is full scale value write */
+		data->tx[0] = (addr << 4) | MCP41XX_WRITE | (trans[0] >> 8);
+		data->tx[1] = (trans[0]) & 0xFF; /* 8 bits here */
+		break;
+
+	case MCP41XX_INCR:
+		data->xfer.len = 1; /* One byte transfer for this command */
+		data->tx[0] = (addr << 4) | MCP41XX_INCR;
+		break;
+
+	case MCP41XX_DECR:
+		data->xfer.len = 1;
+		data->tx[0] = (addr << 4) | MCP41XX_DECR;
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	dev_dbg(&spi->dev, "mcp41xx_exec: tx0: 0x%x tx1: 0x%x\n",
+			data->tx[0], data->tx[1]);
+
+	mutex_lock(&data->lock);
+	spi_message_init(&data->msg);
+	spi_message_add_tail(&data->xfer, &data->msg);
+
+	err = spi_sync(spi, &data->msg);
+	if (err) {
+		dev_err(&spi->dev, "spi_sync(): %d\n", err);
+		mutex_unlock(&data->lock);
+		return err;
+	}
+	mutex_unlock(&data->lock);
+
+	dev_dbg(&spi->dev, "mcp41xx_exec: rx0: 0x%x rx1: 0x%x\n",
+			data->rx[0], data->rx[1]);
+
+	/* Copy back the response */
+	trans[0] = data->rx[0];
+	trans[1] = data->rx[1];
+
+	return 0;
+}
+
+static ssize_t mcp41xx_show_memory_map(struct device *dev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	ssize_t i = 0;
+	int err;
+	int addr;
+	int trans[2];
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mcp41xx_data *data = iio_priv(indio_dev);
+
+	/* Read the whole memory */
+	for (addr = MCP41XX_MIN_ADDR; addr <= MCP41XX_MAX_ADDR; addr++) {
+		err = mcp41xx_exec(data,
+				addr, MCP41XX_READ,
+				trans, ARRAY_SIZE(trans));
+		if (err)
+			return i;
+
+		/* First column is address, second is value */
+		i += scnprintf(&buf[i],
+				12, "0x%02x 0x%03x\n",
+				addr, MCP41XX_9BIT_VALUE(trans));
+	}
+
+	return i;
+}
+
+static ssize_t mcp41xx_store_memory_map(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf, size_t len)
+{
+	int err;
+	int addr;
+	int trans[2];
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mcp41xx_data *data = iio_priv(indio_dev);
+
+	err = sscanf(buf, "0x%x 0x%x\n", &addr, &trans[0]);
+	if (err != 2)
+		return err;
+
+	err = mcp41xx_exec(data, addr, MCP41XX_WRITE, trans, ARRAY_SIZE(trans));
+	if (err)
+		return err;
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR(memory_map, S_IRUGO | S_IWUSR,
+		mcp41xx_show_memory_map,
+		mcp41xx_store_memory_map,
+		0);
+
+static ssize_t mcp41xx_show_nv_wiper(struct device *dev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	int err;
+	int trans[2];
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mcp41xx_data *data = iio_priv(indio_dev);
+	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
+
+	err = mcp41xx_exec(data,
+			this_attr->address + MCP41XX_NV_OFFSET, MCP41XX_READ,
+			trans, ARRAY_SIZE(trans));
+	if (err)
+		return -EINVAL;
+
+	return sprintf(buf, "%d\n", MCP41XX_FULL_SCALE(trans));
+}
+
+static ssize_t mcp41xx_store_nv_wiper(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf, size_t len)
+{
+	int err;
+	int trans[2];
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mcp41xx_data *data = iio_priv(indio_dev);
+	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
+
+	err = kstrtoint(buf, 10, &trans[0]);
+	if (err)
+		return -EINVAL;
+
+	err = mcp41xx_exec(data,
+			this_attr->address + MCP41XX_NV_OFFSET, MCP41XX_WRITE,
+			trans, ARRAY_SIZE(trans));
+	if (err)
+		return -EINVAL;
+
+	return len;
+}
+
+#define MCP41XX_NV_WIPER(n) IIO_DEVICE_ATTR(nv_wiper##n, S_IRUGO | S_IWUSR, \
+		mcp41xx_show_nv_wiper, mcp41xx_store_nv_wiper, n)
+
+MCP41XX_NV_WIPER(0);
+MCP41XX_NV_WIPER(1);
+
+static ssize_t mcp41xx_store_incr_wiper(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf, size_t len)
+{
+	int err;
+	int trans[2];
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mcp41xx_data *data = iio_priv(indio_dev);
+	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
+
+	err = mcp41xx_exec(data,
+			this_attr->address, MCP41XX_INCR,
+			trans, ARRAY_SIZE(trans));
+	if (err)
+		return -EINVAL;
+
+	return len;
+}
+
+static ssize_t mcp41xx_store_decr_wiper(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf, size_t len)
+{
+	int err;
+	int trans[2];
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mcp41xx_data *data = iio_priv(indio_dev);
+	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
+
+	err = mcp41xx_exec(data,
+			this_attr->address, MCP41XX_DECR,
+			trans, ARRAY_SIZE(trans));
+	if (err)
+		return -EINVAL;
+
+	return len;
+}
+
+#define MCP41XX_INCR_ATTR(n) IIO_DEVICE_ATTR(incr_wiper##n, S_IWUSR,	\
+		NULL, mcp41xx_store_incr_wiper, n)
+
+MCP41XX_INCR_ATTR(0);
+MCP41XX_INCR_ATTR(1);
+
+#define MCP41XX_DECR_ATTR(n) IIO_DEVICE_ATTR(decr_wiper##n, S_IWUSR,	\
+		NULL, mcp41xx_store_decr_wiper, n)
+
+MCP41XX_DECR_ATTR(0);
+MCP41XX_DECR_ATTR(1);
+
+static ssize_t mcp41xx_show_status_register(struct device *dev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	int err;
+	int trans[2];
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mcp41xx_data *data = iio_priv(indio_dev);
+	unsigned long val;
+
+	err = mcp41xx_exec(data,
+			MCP41XX_STATUS_ADDR, MCP41XX_READ,
+			trans, ARRAY_SIZE(trans));
+	if (err)
+		return -EINVAL;
+
+	val = MCP41XX_9BIT_VALUE(trans);
+	return printbinary(buf, val, 10); /* One extra for new line */
+}
+
+static IIO_DEVICE_ATTR(status_register, S_IRUGO,
+		mcp41xx_show_status_register,
+		NULL,
+		0);
+
+static ssize_t mcp41xx_show_tcon_register(struct device *dev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	int err;
+	int trans[2];
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mcp41xx_data *data = iio_priv(indio_dev);
+	unsigned long val;
+
+	err = mcp41xx_exec(data,
+			MCP41XX_TCON_ADDR, MCP41XX_READ,
+			trans, ARRAY_SIZE(trans));
+	if (err)
+		return -EINVAL;
+
+	val = MCP41XX_9BIT_VALUE(trans);
+	return printbinary(buf, val, 10); /* One extra for new line */
+}
+
+static ssize_t mcp41xx_store_tcon_register(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf, size_t len)
+{
+	int err;
+	int trans[2];
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mcp41xx_data *data = iio_priv(indio_dev);
+
+	err = kstrtoint(buf, 2, &trans[0]);
+	if (err)
+		return -EINVAL;
+
+	err = mcp41xx_exec(data,
+			MCP41XX_TCON_ADDR, MCP41XX_WRITE,
+			trans, ARRAY_SIZE(trans));
+	if (err)
+		return -EINVAL;
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR(tcon_register, S_IRUGO | S_IWUSR,
+		mcp41xx_show_tcon_register,
+		mcp41xx_store_tcon_register,
+		0);
+
+/* All available attributes that can be created */
+static struct iio_dev_attr *mcp41xx_all_attrs[] = {
+	&iio_dev_attr_memory_map,
+	&iio_dev_attr_nv_wiper0,
+	&iio_dev_attr_nv_wiper1,
+	&iio_dev_attr_incr_wiper0,
+	&iio_dev_attr_incr_wiper1,
+	&iio_dev_attr_decr_wiper0,
+	&iio_dev_attr_decr_wiper1,
+	&iio_dev_attr_status_register,
+	&iio_dev_attr_tcon_register,
+};
+
+/* This will be filled dynamically in probe() */
+static struct attribute **mcp41xx_attributes;
+static struct attribute_group mcp41xx_attribute_group;
+
+static int mcp41xx_read_raw(struct iio_dev *indio_dev,
+		struct iio_chan_spec const *chan,
+		int *val, int *val2, long mask)
+{
+	int err;
+	int trans[2];
+	struct mcp41xx_data *data = iio_priv(indio_dev);
+	int address = chan->channel;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		err = mcp41xx_exec(data,
+				address, MCP41XX_READ,
+				trans, ARRAY_SIZE(trans));
+		if (err)
+			return err;
+
+		*val = MCP41XX_FULL_SCALE(trans);
+
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+		*val = 1000 * mcp41xx_cfg[data->devid].kohms;
+		*val2 = mcp41xx_cfg[data->devid].num_pos;
+
+		return IIO_VAL_FRACTIONAL;
+	}
+
+	return -EINVAL;
+}
+
+static int mcp41xx_write_raw(struct iio_dev *indio_dev,
+		struct iio_chan_spec const *chan,
+		int val, int val2, long mask)
+{
+	int trans[2];
+	struct mcp41xx_data *data = iio_priv(indio_dev);
+	int address = chan->channel;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		trans[0] = val;
+
+		return mcp41xx_exec(data,
+				address, MCP41XX_WRITE,
+				trans, ARRAY_SIZE(trans));
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info mcp41xx_info = {
+	.attrs = &mcp41xx_attribute_group,
+	.read_raw = mcp41xx_read_raw,
+	.write_raw = mcp41xx_write_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static int mcp41xx_probe(struct spi_device *spi)
+{
+	int l, i, addr;
+	int err;
+	size_t attrs_count;
+	struct iio_dev *indio_dev;
+	struct mcp41xx_data *data;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	data->spi = spi;
+	data->devid = spi_get_device_id(spi)->driver_data;
+	spi_set_drvdata(spi, indio_dev);
+
+	data->xfer.tx_buf = data->tx;
+	data->xfer.rx_buf = data->rx;
+
+	mutex_init(&data->lock);
+
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->info = &mcp41xx_info;
+	indio_dev->channels = mcp41xx_channels;
+	indio_dev->num_channels = mcp41xx_cfg[data->devid].wipers;
+	indio_dev->name = spi_get_device_id(spi)->name;
+
+	/* Dynamic attributes */
+	attrs_count = ARRAY_SIZE(mcp41xx_all_attrs);
+	mcp41xx_attributes = kzalloc(
+			sizeof(struct attribute *) * (attrs_count + 1),
+			GFP_KERNEL);
+	if (mcp41xx_attributes == NULL)
+		return -ENOMEM;
+
+	i = 0;
+	for (l = 0; l < attrs_count; l++) {
+		/* Attrs with address == 0 or address == wipers are added */
+		addr = mcp41xx_all_attrs[l]->address;
+		if (addr == 0 || addr == indio_dev->num_channels - 1) {
+			mcp41xx_attributes[i] =
+				&mcp41xx_all_attrs[l]->dev_attr.attr;
+			i++;
+		}
+	}
+	mcp41xx_attribute_group.attrs = mcp41xx_attributes;
+
+	err = devm_iio_device_register(&spi->dev, indio_dev);
+	if (err) {
+		dev_info(&spi->dev, "Unable to register %s", indio_dev->name);
+		return err;
+	}
+
+	dev_info(&spi->dev, "Registered %s", indio_dev->name);
+
+	return 0;
+}
+
+static int mcp41xx_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct mcp41xx_data *data = iio_priv(indio_dev);
+
+	mutex_destroy(&data->lock);
+	devm_iio_device_unregister(&spi->dev, indio_dev);
+	kfree(mcp41xx_attributes);
+
+	dev_info(&spi->dev, "Unregistered %s", indio_dev->name);
+
+	return 0;
+}
+
+#if defined CONFIG_OF
+static const struct of_device_id mcp41xx_dt_ids[] = {
+	{ .compatible = "microchip,mcp4113x-502",
+		.data = &mcp41xx_cfg[MCP413x_502] },
+	{ .compatible = "microchip,mcp4113x-103",
+		.data = &mcp41xx_cfg[MCP413x_103] },
+	{ .compatible = "microchip,mcp4113x-503",
+		.data = &mcp41xx_cfg[MCP413x_503] },
+	{ .compatible = "microchip,mcp4113x-104",
+		.data = &mcp41xx_cfg[MCP413x_104] },
+	{ .compatible = "microchip,mcp4114x-502",
+		.data = &mcp41xx_cfg[MCP414x_502] },
+	{ .compatible = "microchip,mcp4114x-103",
+		.data = &mcp41xx_cfg[MCP414x_103] },
+	{ .compatible = "microchip,mcp4114x-503",
+		.data = &mcp41xx_cfg[MCP414x_503] },
+	{ .compatible = "microchip,mcp4114x-104",
+		.data = &mcp41xx_cfg[MCP414x_104] },
+	{ .compatible = "microchip,mcp4115x-502",
+		.data = &mcp41xx_cfg[MCP415x_502] },
+	{ .compatible = "microchip,mcp4115x-103",
+		.data = &mcp41xx_cfg[MCP415x_103] },
+	{ .compatible = "microchip,mcp4115x-503",
+		.data = &mcp41xx_cfg[MCP415x_503] },
+	{ .compatible = "microchip,mcp4115x-104",
+		.data = &mcp41xx_cfg[MCP415x_104] },
+	{ .compatible = "microchip,mcp4116x-502",
+		.data = &mcp41xx_cfg[MCP416x_502] },
+	{ .compatible = "microchip,mcp4116x-103",
+		.data = &mcp41xx_cfg[MCP416x_103] },
+	{ .compatible = "microchip,mcp4116x-503",
+		.data = &mcp41xx_cfg[MCP416x_503] },
+	{ .compatible = "microchip,mcp4116x-104",
+		.data = &mcp41xx_cfg[MCP416x_104] },
+	{ .compatible = "microchip,mcp4123x-502",
+		.data = &mcp41xx_cfg[MCP423x_502] },
+	{ .compatible = "microchip,mcp4123x-103",
+		.data = &mcp41xx_cfg[MCP423x_103] },
+	{ .compatible = "microchip,mcp4123x-503",
+		.data = &mcp41xx_cfg[MCP423x_503] },
+	{ .compatible = "microchip,mcp4123x-104",
+		.data = &mcp41xx_cfg[MCP423x_104] },
+	{ .compatible = "microchip,mcp4124x-502",
+		.data = &mcp41xx_cfg[MCP424x_502] },
+	{ .compatible = "microchip,mcp4124x-103",
+		.data = &mcp41xx_cfg[MCP424x_103] },
+	{ .compatible = "microchip,mcp4124x-503",
+		.data = &mcp41xx_cfg[MCP424x_503] },
+	{ .compatible = "microchip,mcp4124x-104",
+		.data = &mcp41xx_cfg[MCP424x_104] },
+	{ .compatible = "microchip,mcp4125x-502",
+		.data = &mcp41xx_cfg[MCP425x_502] },
+	{ .compatible = "microchip,mcp4125x-103",
+		.data = &mcp41xx_cfg[MCP425x_103] },
+	{ .compatible = "microchip,mcp4125x-503",
+		.data = &mcp41xx_cfg[MCP425x_503] },
+	{ .compatible = "microchip,mcp4125x-104",
+		.data = &mcp41xx_cfg[MCP425x_104] },
+	{ .compatible = "microchip,mcp4126x-502",
+		.data = &mcp41xx_cfg[MCP426x_502] },
+	{ .compatible = "microchip,mcp4126x-103",
+		.data = &mcp41xx_cfg[MCP426x_103] },
+	{ .compatible = "microchip,mcp4126x-503",
+		.data = &mcp41xx_cfg[MCP426x_503] },
+	{ .compatible = "microchip,mcp4126x-104",
+		.data = &mcp41xx_cfg[MCP426x_104] },
+	{}
+};
+MODULE_DEVICE_TABLE(of, mcp41xx_dt_ids);
+#endif
+
+static const struct spi_device_id mcp41xx_id[] = {
+	{ "mcp413x-502", MCP413x_502 },
+	{ "mcp413x-103", MCP413x_103 },
+	{ "mcp413x-503", MCP413x_503 },
+	{ "mcp413x-104", MCP413x_104 },
+	{ "mcp414x-502", MCP414x_502 },
+	{ "mcp414x-103", MCP414x_103 },
+	{ "mcp414x-503", MCP414x_503 },
+	{ "mcp414x-104", MCP414x_104 },
+	{ "mcp415x-502", MCP415x_502 },
+	{ "mcp415x-103", MCP415x_103 },
+	{ "mcp415x-503", MCP415x_503 },
+	{ "mcp415x-104", MCP415x_104 },
+	{ "mcp416x-502", MCP416x_502 },
+	{ "mcp416x-103", MCP416x_103 },
+	{ "mcp416x-503", MCP416x_503 },
+	{ "mcp416x-104", MCP416x_104 },
+	{ "mcp423x-502", MCP423x_502 },
+	{ "mcp423x-103", MCP423x_103 },
+	{ "mcp423x-503", MCP423x_503 },
+	{ "mcp423x-104", MCP423x_104 },
+	{ "mcp424x-502", MCP424x_502 },
+	{ "mcp424x-103", MCP424x_103 },
+	{ "mcp424x-503", MCP424x_503 },
+	{ "mcp424x-104", MCP424x_104 },
+	{ "mcp425x-502", MCP425x_502 },
+	{ "mcp425x-103", MCP425x_103 },
+	{ "mcp425x-503", MCP425x_503 },
+	{ "mcp425x-104", MCP425x_104 },
+	{ "mcp426x-502", MCP426x_502 },
+	{ "mcp426x-103", MCP426x_103 },
+	{ "mcp426x-503", MCP426x_503 },
+	{ "mcp426x-104", MCP426x_104 },
+	{}
+};
+MODULE_DEVICE_TABLE(spi, mcp41xx_id);
+
+static struct spi_driver mcp41xx_driver = {
+	.driver = {
+		.name		= "mcp41xx",
+		.of_match_table = of_match_ptr(mcp41xx_dt_ids),
+	},
+	.probe		= mcp41xx_probe,
+	.remove		= mcp41xx_remove,
+	.id_table	= mcp41xx_id,
+};
+
+module_spi_driver(mcp41xx_driver);
+
+MODULE_AUTHOR("Slawomir Stepien <sst@...zta.fm>");
+MODULE_DESCRIPTION("MCP41XX digital potentiometer");
+MODULE_LICENSE("GPL v2");
-- 
2.7.3

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