[PATCH] iio: add driver for Microchip MCP414X/416X/424X/426X

[PATCH] iio: add driver for Microchip MCP414X/416X/424X/426X

[Slawomir Stepien]

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@poczta.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@poczta.fm>");
+MODULE_DESCRIPTION("MCP41XX digital potentiometer");
+MODULE_LICENSE("GPL v2");
-- 
2.7.3

Re: [PATCH] iio: add driver for Microchip MCP414X/416X/424X/426X

[Peter Meerwald-Stadler]

On Wed, 16 Mar 2016, Slawomir Stepien wrote:

> 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

the driver naming is a mess: the subject says MCP414X, the file name is 
mcp41xx, the DT compatible string says mcp4113x -- this does not match

plenty of the private API, some of which seems to be debug only?
what is really needed to interact with a poti?

comments below
 
> Signed-off-by: Slawomir Stepien <sst@poczta.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

this is already described in sysfs-bus-iio

> +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;

devid is not set/used

> +	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)

should trans really be int, not u8?

> +{
> +	int err;
> +	struct spi_device *spi = data->spi;
> +
> +	/* Two bytes are needed for the response */
> +	if (n != 2)
> +		return -EINVAL;

why pass n if it is always 2?

> +
> +	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);

\n missing

> +		return err;
> +	}
> +
> +	dev_info(&spi->dev, "Registered %s", indio_dev->name);

\n

> +
> +	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@poczta.fm>");
> +MODULE_DESCRIPTION("MCP41XX digital potentiometer");
> +MODULE_LICENSE("GPL v2");
> 

-- 

Peter Meerwald-Stadler
+43-664-2444418 (mobile)

Re: [PATCH] iio: add driver for Microchip MCP414X/416X/424X/426X

[Slawomir Stepien]

On Mar 16, 2016 13:30, Peter Meerwald-Stadler wrote:
> On Wed, 16 Mar 2016, Slawomir Stepien wrote:
> 
> > 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

Thank you for all your comments.

> the driver naming is a mess: the subject says MCP414X, the file name is 
> mcp41xx, the DT compatible string says mcp4113x -- this does not match

OK. I will change that to mcp414x in version 2.

> plenty of the private API, some of which seems to be debug only?
> what is really needed to interact with a poti?

I wanted to export both the non volatile and volatile memory addresses for wiper
position access. That is bare minimum for the poti to operate.

But I also wanted to export additional features of this chip. That is way there
is increase and decrease API, and STATUS and TCON register access.

The memory_map API is a way to access all the not used by chip memory addresses.
This API I think could be deleted. But I still think that some people might find
it useful.

> comments below
>  
> > +File:	/sys/bus/iio/devices/../out_resistanceN_raw
> 
> this is already described in sysfs-bus-iio

Should I leave it and add reference to sysfs-bus-iio or delete it completely?

> > +struct mcp41xx_cfg {
> > +	unsigned long int devid;
> 
> devid is not set/used

That's true. Will fix it in v2.

> > +static int mcp41xx_exec(struct mcp41xx_data *data,
> > +		u8 addr, u8 cmd,
> > +		int *trans, size_t n)
> 
> should trans really be int, not u8?

There is a need for 9 bit value write/read. I used int just for my convenience.
However there is one piece of code missing now I see. I should check the value
of tans[0] to see if it's > 256 or lower then 0. Will add it in v2.

Using u8 will force additional bit operations. I could try using u16 to still
have the option of parsing user input as 9 bit value (eg. 256 position).

> > +{
> > +	int err;
> > +	struct spi_device *spi = data->spi;
> > +
> > +	/* Two bytes are needed for the response */
> > +	if (n != 2)
> > +		return -EINVAL;
> 
> why pass n if it is always 2?

Will fix in v2.

> > +	err = devm_iio_device_register(&spi->dev, indio_dev);
> > +	if (err) {
> > +		dev_info(&spi->dev, "Unable to register %s", indio_dev->name);
> 
> \n missing
> 
> > +		return err;
> > +	}
> > +
> > +	dev_info(&spi->dev, "Registered %s", indio_dev->name);
> 
> \n
> 
> > +
> > +	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);

Also \n is missing here. Will fix in v2.

-- 
Slawomir Stepien

Re: [PATCH] iio: add driver for Microchip MCP414X/416X/424X/426X

[Lars-Peter Clausen]

On 03/16/2016 05:25 PM, Slawomir Stepien wrote:
> On Mar 16, 2016 13:30, Peter Meerwald-Stadler wrote:
[...]
>> plenty of the private API, some of which seems to be debug only?
>> what is really needed to interact with a poti?
> 
> I wanted to export both the non volatile and volatile memory addresses for wiper
> position access. That is bare minimum for the poti to operate.
> 
> But I also wanted to export additional features of this chip. That is way there
> is increase and decrease API, and STATUS and TCON register access.
> 

The important part about a framework and the associated device drivers
is to expose the features of a device using a standardized interface so
you can write generic applications/libraries and share infrastructure.
If an application requires device specific knowledge to access the
features of a device you may as well write a userspace driver using i2cdev.

So when you are introducing new ABI it should at least follow the
standard naming scheme. And also try to think whether this is a feature
that is present in other similar devices and come up with a device
independent way to expose this functionality.

Let's start with the simple stuff, I don't really see the advantage of
having separate inc/dec controls. This can be handled through the
standard raw attribute. If the newly written value is one off from the
previous one use inc/dec otherwise write it directly. And even then it
might make sense to just ignore that and always write the raw value.

> The memory_map API is a way to access all the not used by chip memory addresses.
> This API I think could be deleted. But I still think that some people might find
> it useful.

This sounds more like it should maybe be exposed as a standard EEPROM
device.

Re: [PATCH] iio: add driver for Microchip MCP414X/416X/424X/426X

[Daniel Baluta]

On Wed, Mar 16, 2016 at 6:25 PM, Slawomir Stepien <sst@poczta.fm> wrote:
> On Mar 16, 2016 13:30, Peter Meerwald-Stadler wrote:
>> On Wed, 16 Mar 2016, Slawomir Stepien wrote:
>>
>> > 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
>
> Thank you for all your comments.
>
>> the driver naming is a mess: the subject says MCP414X, the file name is
>> mcp41xx, the DT compatible string says mcp4113x -- this does not match
>
> OK. I will change that to mcp414x in version 2.

Filename shouldn't be generic (e.g ending with xx). It should be a
specific chip name
(a good candidate is the first in alphabetical order), because there
could be chips falling
in the same name category but with a different driver.

>
>> plenty of the private API, some of which seems to be debug only?
>> what is really needed to interact with a poti?
>
> I wanted to export both the non volatile and volatile memory addresses for wiper
> position access. That is bare minimum for the poti to operate.
>
> But I also wanted to export additional features of this chip. That is way there
> is increase and decrease API, and STATUS and TCON register access.
>
> The memory_map API is a way to access all the not used by chip memory addresses.
> This API I think could be deleted. But I still think that some people might find
> it useful.
>
>> comments below
>>
>> > +File:      /sys/bus/iio/devices/../out_resistanceN_raw
>>
>> this is already described in sysfs-bus-iio
>
> Should I leave it and add reference to sysfs-bus-iio or delete it completely?
>
>> > +struct mcp41xx_cfg {
>> > +   unsigned long int devid;
>>
>> devid is not set/used
>
> That's true. Will fix it in v2.
>
>> > +static int mcp41xx_exec(struct mcp41xx_data *data,
>> > +           u8 addr, u8 cmd,
>> > +           int *trans, size_t n)
>>
>> should trans really be int, not u8?
>
> There is a need for 9 bit value write/read. I used int just for my convenience.
> However there is one piece of code missing now I see. I should check the value
> of tans[0] to see if it's > 256 or lower then 0. Will add it in v2.
>
> Using u8 will force additional bit operations. I could try using u16 to still
> have the option of parsing user input as 9 bit value (eg. 256 position).
>
>> > +{
>> > +   int err;
>> > +   struct spi_device *spi = data->spi;
>> > +
>> > +   /* Two bytes are needed for the response */
>> > +   if (n != 2)
>> > +           return -EINVAL;
>>
>> why pass n if it is always 2?
>
> Will fix in v2.
>
>> > +   err = devm_iio_device_register(&spi->dev, indio_dev);
>> > +   if (err) {
>> > +           dev_info(&spi->dev, "Unable to register %s", indio_dev->name);
>>
>> \n missing
>>
>> > +           return err;
>> > +   }
>> > +
>> > +   dev_info(&spi->dev, "Registered %s", indio_dev->name);
>>
>> \n
>>
>> > +
>> > +   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);
>
> Also \n is missing here. Will fix in v2.
>
> --
> Slawomir Stepien
> --
> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] iio: add driver for Microchip MCP414X/416X/424X/426X

[Slawomir Stepien]

On Mar 16, 2016 19:24, Lars-Peter Clausen wrote:
> On 03/16/2016 05:25 PM, Slawomir Stepien wrote:
> > On Mar 16, 2016 13:30, Peter Meerwald-Stadler wrote:
> [...]
> >> plenty of the private API, some of which seems to be debug only?
> >> what is really needed to interact with a poti?
> > 
> > I wanted to export both the non volatile and volatile memory addresses for wiper
> > position access. That is bare minimum for the poti to operate.
> > 
> > But I also wanted to export additional features of this chip. That is way there
> > is increase and decrease API, and STATUS and TCON register access.
> > 
> 
> The important part about a framework and the associated device drivers
> is to expose the features of a device using a standardized interface so
> you can write generic applications/libraries and share infrastructure.
> If an application requires device specific knowledge to access the
> features of a device you may as well write a userspace driver using i2cdev.
> 
> So when you are introducing new ABI it should at least follow the
> standard naming scheme. And also try to think whether this is a feature
> that is present in other similar devices and come up with a device
> independent way to expose this functionality.
> 
> Let's start with the simple stuff, I don't really see the advantage of
> having separate inc/dec controls. This can be handled through the
> standard raw attribute. If the newly written value is one off from the
> previous one use inc/dec otherwise write it directly. And even then it
> might make sense to just ignore that and always write the raw value.

I've got your point. The version 2 will use only the IIO facilities. Then I will
try to build more based on that.

> > The memory_map API is a way to access all the not used by chip memory addresses.
> > This API I think could be deleted. But I still think that some people might find
> > it useful.
> 
> This sounds more like it should maybe be exposed as a standard EEPROM
> device.

Not quite familiar with this, but will look into that.

Once more thank you for comments.

-- 
Slawomir Stepien

Re: [PATCH] iio: add driver for Microchip MCP414X/416X/424X/426X

[Slawomir Stepien]

On Mar 16, 2016 20:28, Daniel Baluta wrote:
> On Wed, Mar 16, 2016 at 6:25 PM, Slawomir Stepien <sst@poczta.fm> wrote:
> > On Mar 16, 2016 13:30, Peter Meerwald-Stadler wrote:
> >> On Wed, 16 Mar 2016, Slawomir Stepien wrote:
> >>
> >> > 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
> >
> > Thank you for all your comments.
> >
> >> the driver naming is a mess: the subject says MCP414X, the file name is
> >> mcp41xx, the DT compatible string says mcp4113x -- this does not match
> >
> > OK. I will change that to mcp414x in version 2.
> 
> Filename shouldn't be generic (e.g ending with xx). It should be a
> specific chip name
> (a good candidate is the first in alphabetical order), because there
> could be chips falling
> in the same name category but with a different driver.

OK got it. Please wait for the version 2.

-- 
Slawomir Stepien