ad525x_dpot: new driver for AD525x digital potentiometers

This driver supports the non-volatile digital potentiometers via I2C:
AD5258, AD5259, AD5251, AD5252, AD5253, AD5254, and AD5255

It provides a sysfs interface to each device for reading/writing which
is documented in Documentation/misc-devices/ad525x_dpot.txt.

Signed-off-by: Michael Hennerich <[e-mail]>
Signed-off-by: Chris Verges <[e-mail]>
Signed-off-by: Mike Frysinger <[e-mail]>
Cc: Jean Delvare <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/misc-devices/ad525x_dpot.txt

···
+---------------------------------
+  AD525x Digital Potentiometers
+---------------------------------
+
+The ad525x_dpot driver exports a simple sysfs interface.  This allows you to
+work with the immediate resistance settings as well as update the saved startup
+settings.  Access to the factory programmed tolerance is also provided, but
+interpretation of this settings is required by the end application according to
+the specific part in use.
+
+---------
+  Files
+---------
+
+Each dpot device will have a set of eeprom, rdac, and tolerance files.  How
+many depends on the actual part you have, as will the range of allowed values.
+
+The eeprom files are used to program the startup value of the device.
+
+The rdac files are used to program the immediate value of the device.
+
+The tolerance files are the read-only factory programmed tolerance settings
+and may vary greatly on a part-by-part basis.  For exact interpretation of
+this field, please consult the datasheet for your part.  This is presented
+as a hex file for easier parsing.
+
+-----------
+  Example
+-----------
+
+Locate the device in your sysfs tree.  This is probably easiest by going into
+the common i2c directory and locating the device by the i2c slave address.
+
+	# ls /sys/bus/i2c/devices/
+	0-0022  0-0027  0-002f
+
+So assuming the device in question is on the first i2c bus and has the slave
+address of 0x2f, we descend (unrelated sysfs entries have been trimmed).
+
+	# ls /sys/bus/i2c/devices/0-002f/
+	eeprom0 rdac0 tolerance0
+
+You can use simple reads/writes to access these files:
+
+	# cd /sys/bus/i2c/devices/0-002f/
+
+	# cat eeprom0
+	0
+	# echo 10 > eeprom0
+	# cat eeprom0
+	10
+
+	# cat rdac0
+	5
+	# echo 3 > rdac0
+	# cat rdac0
+	3

drivers/misc/Kconfig

···
 
 if MISC_DEVICES
 
+config AD525X_DPOT
+	tristate "Analog Devices AD525x Digital Potentiometers"
+	depends on I2C && SYSFS
+	help
+	  If you say yes here, you get support for the Analog Devices
+	  AD5258, AD5259, AD5251, AD5252, AD5253, AD5254 and AD5255
+	  digital potentiometer chips.
+
+	  See Documentation/misc-devices/ad525x_dpot.txt for the
+	  userspace interface.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called ad525x_dpot.
+
 config ATMEL_PWM
 	tristate "Atmel AT32/AT91 PWM support"
 	depends on AVR32 || ARCH_AT91SAM9263 || ARCH_AT91SAM9RL || ARCH_AT91CAP9

drivers/misc/Makefile

···
 
 obj-$(CONFIG_IBM_ASM)		+= ibmasm/
 obj-$(CONFIG_HDPU_FEATURES)	+= hdpuftrs/
+obj-$(CONFIG_AD525X_DPOT)	+= ad525x_dpot.o
 obj-$(CONFIG_ATMEL_PWM)		+= atmel_pwm.o
 obj-$(CONFIG_ATMEL_SSC)		+= atmel-ssc.o
 obj-$(CONFIG_ATMEL_TCLIB)	+= atmel_tclib.o

drivers/misc/ad525x_dpot.c

···
+/*
+ * ad525x_dpot: Driver for the Analog Devices AD525x digital potentiometers
+ * Copyright (c) 2009 Analog Devices, Inc.
+ * Author: Michael Hennerich <[e-mail]>
+ *
+ * DEVID		#Wipers		#Positions 	Resistor Options (kOhm)
+ * AD5258		1		64		1, 10, 50, 100
+ * AD5259		1		256		5, 10, 50, 100
+ * AD5251		2		64		1, 10, 50, 100
+ * AD5252		2		256		1, 10, 50, 100
+ * AD5255		3		512		25, 250
+ * AD5253		4		64		1, 10, 50, 100
+ * AD5254		4		256		1, 10, 50, 100
+ *
+ * See Documentation/misc-devices/ad525x_dpot.txt for more info.
+ *
+ * derived from ad5258.c
+ * Copyright (c) 2009 Cyber Switching, Inc.
+ * Author: Chris Verges <[e-mail]>
+ *
+ * derived from ad5252.c
+ * Copyright (c) 2006 Michael Hennerich <[e-mail]>
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/delay.h>
+
+#define DRIVER_NAME			"ad525x_dpot"
+#define DRIVER_VERSION			"0.1"
+
+enum dpot_devid {
+	AD5258_ID,
+	AD5259_ID,
+	AD5251_ID,
+	AD5252_ID,
+	AD5253_ID,
+	AD5254_ID,
+	AD5255_ID,
+};
+
+#define AD5258_MAX_POSITION		64
+#define AD5259_MAX_POSITION		256
+#define AD5251_MAX_POSITION		64
+#define AD5252_MAX_POSITION		256
+#define AD5253_MAX_POSITION		64
+#define AD5254_MAX_POSITION		256
+#define AD5255_MAX_POSITION		512
+
+#define AD525X_RDAC0		0
+#define AD525X_RDAC1		1
+#define AD525X_RDAC2		2
+#define AD525X_RDAC3		3
+
+#define AD525X_REG_TOL		0x18
+#define AD525X_TOL_RDAC0	(AD525X_REG_TOL | AD525X_RDAC0)
+#define AD525X_TOL_RDAC1	(AD525X_REG_TOL | AD525X_RDAC1)
+#define AD525X_TOL_RDAC2	(AD525X_REG_TOL | AD525X_RDAC2)
+#define AD525X_TOL_RDAC3	(AD525X_REG_TOL | AD525X_RDAC3)
+
+/* RDAC-to-EEPROM Interface Commands */
+#define AD525X_I2C_RDAC		(0x00 << 5)
+#define AD525X_I2C_EEPROM	(0x01 << 5)
+#define AD525X_I2C_CMD		(0x80)
+
+#define AD525X_DEC_ALL_6DB	(AD525X_I2C_CMD | (0x4 << 3))
+#define AD525X_INC_ALL_6DB	(AD525X_I2C_CMD | (0x9 << 3))
+#define AD525X_DEC_ALL		(AD525X_I2C_CMD | (0x6 << 3))
+#define AD525X_INC_ALL		(AD525X_I2C_CMD | (0xB << 3))
+
+static s32 ad525x_read(struct i2c_client *client, u8 reg);
+static s32 ad525x_write(struct i2c_client *client, u8 reg, u8 value);
+
+/*
+ * Client data (each client gets its own)
+ */
+
+struct dpot_data {
+	struct mutex update_lock;
+	unsigned rdac_mask;
+	unsigned max_pos;
+	unsigned devid;
+};
+
+/* sysfs functions */
+
+static ssize_t sysfs_show_reg(struct device *dev,
+			      struct device_attribute *attr, char *buf, u32 reg)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct dpot_data *data = i2c_get_clientdata(client);
+	s32 value;
+
+	mutex_lock(&data->update_lock);
+	value = ad525x_read(client, reg);
+	mutex_unlock(&data->update_lock);
+
+	if (value < 0)
+		return -EINVAL;
+	/*
+	 * Let someone else deal with converting this ...
+	 * the tolerance is a two-byte value where the MSB
+	 * is a sign + integer value, and the LSB is a
+	 * decimal value.  See page 18 of the AD5258
+	 * datasheet (Rev. A) for more details.
+	 */
+
+	if (reg & AD525X_REG_TOL)
+		return sprintf(buf, "0x%04x\n", value & 0xFFFF);
+	else
+		return sprintf(buf, "%u\n", value & data->rdac_mask);
+}
+
+static ssize_t sysfs_set_reg(struct device *dev,
+			     struct device_attribute *attr,
+			     const char *buf, size_t count, u32 reg)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct dpot_data *data = i2c_get_clientdata(client);
+	unsigned long value;
+	int err;
+
+	err = strict_strtoul(buf, 10, &value);
+	if (err)
+		return err;
+
+	if (value > data->rdac_mask)
+		value = data->rdac_mask;
+
+	mutex_lock(&data->update_lock);
+	ad525x_write(client, reg, value);
+	if (reg & AD525X_I2C_EEPROM)
+		msleep(26);	/* Sleep while the EEPROM updates */
+	mutex_unlock(&data->update_lock);
+
+	return count;
+}
+
+static ssize_t sysfs_do_cmd(struct device *dev,
+			    struct device_attribute *attr,
+			    const char *buf, size_t count, u32 reg)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct dpot_data *data = i2c_get_clientdata(client);
+
+	mutex_lock(&data->update_lock);
+	ad525x_write(client, reg, 0);
+	mutex_unlock(&data->update_lock);
+
+	return count;
+}
+
+/* ------------------------------------------------------------------------- */
+
+static ssize_t show_rdac0(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	return sysfs_show_reg(dev, attr, buf, AD525X_I2C_RDAC | AD525X_RDAC0);
+}
+
+static ssize_t set_rdac0(struct device *dev,
+			 struct device_attribute *attr,
+			 const char *buf, size_t count)
+{
+	return sysfs_set_reg(dev, attr, buf, count,
+			     AD525X_I2C_RDAC | AD525X_RDAC0);
+}
+
+static DEVICE_ATTR(rdac0, S_IWUSR | S_IRUGO, show_rdac0, set_rdac0);
+
+static ssize_t show_eeprom0(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	return sysfs_show_reg(dev, attr, buf, AD525X_I2C_EEPROM | AD525X_RDAC0);
+}
+
+static ssize_t set_eeprom0(struct device *dev,
+			   struct device_attribute *attr,
+			   const char *buf, size_t count)
+{
+	return sysfs_set_reg(dev, attr, buf, count,
+			     AD525X_I2C_EEPROM | AD525X_RDAC0);
+}
+
+static DEVICE_ATTR(eeprom0, S_IWUSR | S_IRUGO, show_eeprom0, set_eeprom0);
+
+static ssize_t show_tolerance0(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	return sysfs_show_reg(dev, attr, buf,
+			      AD525X_I2C_EEPROM | AD525X_TOL_RDAC0);
+}
+
+static DEVICE_ATTR(tolerance0, S_IRUGO, show_tolerance0, NULL);
+
+/* ------------------------------------------------------------------------- */
+
+static ssize_t show_rdac1(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	return sysfs_show_reg(dev, attr, buf, AD525X_I2C_RDAC | AD525X_RDAC1);
+}
+
+static ssize_t set_rdac1(struct device *dev,
+			 struct device_attribute *attr,
+			 const char *buf, size_t count)
+{
+	return sysfs_set_reg(dev, attr, buf, count,
+			     AD525X_I2C_RDAC | AD525X_RDAC1);
+}
+
+static DEVICE_ATTR(rdac1, S_IWUSR | S_IRUGO, show_rdac1, set_rdac1);
+
+static ssize_t show_eeprom1(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	return sysfs_show_reg(dev, attr, buf, AD525X_I2C_EEPROM | AD525X_RDAC1);
+}
+
+static ssize_t set_eeprom1(struct device *dev,
+			   struct device_attribute *attr,
+			   const char *buf, size_t count)
+{
+	return sysfs_set_reg(dev, attr, buf, count,
+			     AD525X_I2C_EEPROM | AD525X_RDAC1);
+}
+
+static DEVICE_ATTR(eeprom1, S_IWUSR | S_IRUGO, show_eeprom1, set_eeprom1);
+
+static ssize_t show_tolerance1(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	return sysfs_show_reg(dev, attr, buf,
+			      AD525X_I2C_EEPROM | AD525X_TOL_RDAC1);
+}
+
+static DEVICE_ATTR(tolerance1, S_IRUGO, show_tolerance1, NULL);
+
+/* ------------------------------------------------------------------------- */
+
+static ssize_t show_rdac2(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	return sysfs_show_reg(dev, attr, buf, AD525X_I2C_RDAC | AD525X_RDAC2);
+}
+
+static ssize_t set_rdac2(struct device *dev,
+			 struct device_attribute *attr,
+			 const char *buf, size_t count)
+{
+	return sysfs_set_reg(dev, attr, buf, count,
+			     AD525X_I2C_RDAC | AD525X_RDAC2);
+}
+
+static DEVICE_ATTR(rdac2, S_IWUSR | S_IRUGO, show_rdac2, set_rdac2);
+
+static ssize_t show_eeprom2(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	return sysfs_show_reg(dev, attr, buf, AD525X_I2C_EEPROM | AD525X_RDAC2);
+}
+
+static ssize_t set_eeprom2(struct device *dev,
+			   struct device_attribute *attr,
+			   const char *buf, size_t count)
+{
+	return sysfs_set_reg(dev, attr, buf, count,
+			     AD525X_I2C_EEPROM | AD525X_RDAC2);
+}
+
+static DEVICE_ATTR(eeprom2, S_IWUSR | S_IRUGO, show_eeprom2, set_eeprom2);
+
+static ssize_t show_tolerance2(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	return sysfs_show_reg(dev, attr, buf,
+			      AD525X_I2C_EEPROM | AD525X_TOL_RDAC2);
+}
+
+static DEVICE_ATTR(tolerance2, S_IRUGO, show_tolerance2, NULL);
+
+/* ------------------------------------------------------------------------- */
+
+static ssize_t show_rdac3(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	return sysfs_show_reg(dev, attr, buf, AD525X_I2C_RDAC | AD525X_RDAC3);
+}
+
+static ssize_t set_rdac3(struct device *dev,
+			 struct device_attribute *attr,
+			 const char *buf, size_t count)
+{
+	return sysfs_set_reg(dev, attr, buf, count,
+			     AD525X_I2C_RDAC | AD525X_RDAC3);
+}
+
+static DEVICE_ATTR(rdac3, S_IWUSR | S_IRUGO, show_rdac3, set_rdac3);
+
+static ssize_t show_eeprom3(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	return sysfs_show_reg(dev, attr, buf, AD525X_I2C_EEPROM | AD525X_RDAC3);
+}
+
+static ssize_t set_eeprom3(struct device *dev,
+			   struct device_attribute *attr,
+			   const char *buf, size_t count)
+{
+	return sysfs_set_reg(dev, attr, buf, count,
+			     AD525X_I2C_EEPROM | AD525X_RDAC3);
+}
+
+static DEVICE_ATTR(eeprom3, S_IWUSR | S_IRUGO, show_eeprom3, set_eeprom3);
+
+static ssize_t show_tolerance3(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	return sysfs_show_reg(dev, attr, buf,
+			      AD525X_I2C_EEPROM | AD525X_TOL_RDAC3);
+}
+
+static DEVICE_ATTR(tolerance3, S_IRUGO, show_tolerance3, NULL);
+
+static struct attribute *ad525x_attributes_wipers[4][4] = {
+	{
+		&dev_attr_rdac0.attr,
+		&dev_attr_eeprom0.attr,
+		&dev_attr_tolerance0.attr,
+		NULL
+	}, {
+		&dev_attr_rdac1.attr,
+		&dev_attr_eeprom1.attr,
+		&dev_attr_tolerance1.attr,
+		NULL
+	}, {
+		&dev_attr_rdac2.attr,
+		&dev_attr_eeprom2.attr,
+		&dev_attr_tolerance2.attr,
+		NULL
+	}, {
+		&dev_attr_rdac3.attr,
+		&dev_attr_eeprom3.attr,
+		&dev_attr_tolerance3.attr,
+		NULL
+	}
+};
+
+static const struct attribute_group ad525x_group_wipers[] = {
+	{.attrs = ad525x_attributes_wipers[AD525X_RDAC0]},
+	{.attrs = ad525x_attributes_wipers[AD525X_RDAC1]},
+	{.attrs = ad525x_attributes_wipers[AD525X_RDAC2]},
+	{.attrs = ad525x_attributes_wipers[AD525X_RDAC3]},
+};
+
+/* ------------------------------------------------------------------------- */
+
+static ssize_t set_inc_all(struct device *dev,
+			   struct device_attribute *attr,
+			   const char *buf, size_t count)
+{
+	return sysfs_do_cmd(dev, attr, buf, count, AD525X_INC_ALL);
+}
+
+static DEVICE_ATTR(inc_all, S_IWUSR, NULL, set_inc_all);
+
+static ssize_t set_dec_all(struct device *dev,
+			   struct device_attribute *attr,
+			   const char *buf, size_t count)
+{
+	return sysfs_do_cmd(dev, attr, buf, count, AD525X_DEC_ALL);
+}
+
+static DEVICE_ATTR(dec_all, S_IWUSR, NULL, set_dec_all);
+
+static ssize_t set_inc_all_6db(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf, size_t count)
+{
+	return sysfs_do_cmd(dev, attr, buf, count, AD525X_INC_ALL_6DB);
+}
+
+static DEVICE_ATTR(inc_all_6db, S_IWUSR, NULL, set_inc_all_6db);
+
+static ssize_t set_dec_all_6db(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf, size_t count)
+{
+	return sysfs_do_cmd(dev, attr, buf, count, AD525X_DEC_ALL_6DB);
+}
+
+static DEVICE_ATTR(dec_all_6db, S_IWUSR, NULL, set_dec_all_6db);
+
+static struct attribute *ad525x_attributes_commands[] = {
+	&dev_attr_inc_all.attr,
+	&dev_attr_dec_all.attr,
+	&dev_attr_inc_all_6db.attr,
+	&dev_attr_dec_all_6db.attr,
+	NULL
+};
+
+static const struct attribute_group ad525x_group_commands = {
+	.attrs = ad525x_attributes_commands,
+};
+
+/* ------------------------------------------------------------------------- */
+
+/* i2c device functions */
+
+/**
+ * ad525x_read - return the value contained in the specified register
+ * on the AD5258 device.
+ * @client: value returned from i2c_new_device()
+ * @reg: the register to read
+ *
+ * If the tolerance register is specified, 2 bytes are returned.
+ * Otherwise, 1 byte is returned.  A negative value indicates an error
+ * occurred while reading the register.
+ */
+static s32 ad525x_read(struct i2c_client *client, u8 reg)
+{
+	struct dpot_data *data = i2c_get_clientdata(client);
+
+	if ((reg & AD525X_REG_TOL) || (data->max_pos > 256))
+		return i2c_smbus_read_word_data(client, (reg & 0xF8) |
+						((reg & 0x7) << 1));
+	else
+		return i2c_smbus_read_byte_data(client, reg);
+}
+
+/**
+ * ad525x_write - store the given value in the specified register on
+ * the AD5258 device.
+ * @client: value returned from i2c_new_device()
+ * @reg: the register to write
+ * @value: the byte to store in the register
+ *
+ * For certain instructions that do not require a data byte, "NULL"
+ * should be specified for the "value" parameter.  These instructions
+ * include NOP, RESTORE_FROM_EEPROM, and STORE_TO_EEPROM.
+ *
+ * A negative return value indicates an error occurred while reading
+ * the register.
+ */
+static s32 ad525x_write(struct i2c_client *client, u8 reg, u8 value)
+{
+	struct dpot_data *data = i2c_get_clientdata(client);
+
+	/* Only write the instruction byte for certain commands */
+	if (reg & AD525X_I2C_CMD)
+		return i2c_smbus_write_byte(client, reg);
+
+	if (data->max_pos > 256)
+		return i2c_smbus_write_word_data(client, (reg & 0xF8) |
+						((reg & 0x7) << 1), value);
+	else
+		/* All other registers require instruction + data bytes */
+		return i2c_smbus_write_byte_data(client, reg, value);
+}
+
+static int ad525x_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct dpot_data *data;
+	int err = 0;
+
+	dev_dbg(dev, "%s\n", __func__);
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE)) {
+		dev_err(dev, "missing I2C functionality for this driver\n");
+		goto exit;
+	}
+
+	data = kzalloc(sizeof(struct dpot_data), GFP_KERNEL);
+	if (!data) {
+		err = -ENOMEM;
+		goto exit;
+	}
+
+	i2c_set_clientdata(client, data);
+	mutex_init(&data->update_lock);
+
+	switch (id->driver_data) {
+	case AD5258_ID:
+		data->max_pos = AD5258_MAX_POSITION;
+		err = sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC0]);
+		break;
+	case AD5259_ID:
+		data->max_pos = AD5259_MAX_POSITION;
+		err = sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC0]);
+		break;
+	case AD5251_ID:
+		data->max_pos = AD5251_MAX_POSITION;
+		err = sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC1]);
+		err |= sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC3]);
+		err |= sysfs_create_group(&dev->kobj, &ad525x_group_commands);
+		break;
+	case AD5252_ID:
+		data->max_pos = AD5252_MAX_POSITION;
+		err = sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC1]);
+		err |= sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC3]);
+		err |= sysfs_create_group(&dev->kobj, &ad525x_group_commands);
+		break;
+	case AD5253_ID:
+		data->max_pos = AD5253_MAX_POSITION;
+		err = sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC0]);
+		err |= sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC1]);
+		err |= sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC2]);
+		err |= sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC3]);
+		err |= sysfs_create_group(&dev->kobj, &ad525x_group_commands);
+		break;
+	case AD5254_ID:
+		data->max_pos = AD5254_MAX_POSITION;
+		err = sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC0]);
+		err |= sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC1]);
+		err |= sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC2]);
+		err |= sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC3]);
+		err |= sysfs_create_group(&dev->kobj, &ad525x_group_commands);
+		break;
+	case AD5255_ID:
+		data->max_pos = AD5255_MAX_POSITION;
+		err = sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC0]);
+		err |= sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC1]);
+		err |= sysfs_create_group(&dev->kobj,
+				       &ad525x_group_wipers[AD525X_RDAC2]);
+		err |= sysfs_create_group(&dev->kobj, &ad525x_group_commands);
+		break;
+	default:
+		err = -ENODEV;
+		goto exit_free;
+	}
+
+	if (err) {
+		dev_err(dev, "failed to register sysfs hooks\n");
+		goto exit_free;
+	}
+
+	data->devid = id->driver_data;
+	data->rdac_mask = data->max_pos - 1;
+
+	dev_info(dev, "%s %d-Position Digital Potentiometer registered\n",
+		 id->name, data->max_pos);
+
+	return 0;
+
+exit_free:
+	kfree(data);
+	i2c_set_clientdata(client, NULL);
+exit:
+	dev_err(dev, "failed to create client\n");
+	return err;
+}
+
+static int __devexit ad525x_remove(struct i2c_client *client)
+{
+	struct dpot_data *data = i2c_get_clientdata(client);
+	struct device *dev = &client->dev;
+
+	switch (data->devid) {
+	case AD5258_ID:
+	case AD5259_ID:
+		sysfs_remove_group(&dev->kobj,
+				   &ad525x_group_wipers[AD525X_RDAC0]);
+		break;
+	case AD5251_ID:
+	case AD5252_ID:
+		sysfs_remove_group(&dev->kobj,
+				   &ad525x_group_wipers[AD525X_RDAC1]);
+		sysfs_remove_group(&dev->kobj,
+				   &ad525x_group_wipers[AD525X_RDAC3]);
+		sysfs_remove_group(&dev->kobj, &ad525x_group_commands);
+		break;
+	case AD5253_ID:
+	case AD5254_ID:
+		sysfs_remove_group(&dev->kobj,
+				   &ad525x_group_wipers[AD525X_RDAC0]);
+		sysfs_remove_group(&dev->kobj,
+				   &ad525x_group_wipers[AD525X_RDAC1]);
+		sysfs_remove_group(&dev->kobj,
+				   &ad525x_group_wipers[AD525X_RDAC2]);
+		sysfs_remove_group(&dev->kobj,
+				   &ad525x_group_wipers[AD525X_RDAC3]);
+		sysfs_remove_group(&dev->kobj, &ad525x_group_commands);
+		break;
+	case AD5255_ID:
+		sysfs_remove_group(&dev->kobj,
+				   &ad525x_group_wipers[AD525X_RDAC0]);
+		sysfs_remove_group(&dev->kobj,
+				   &ad525x_group_wipers[AD525X_RDAC1]);
+		sysfs_remove_group(&dev->kobj,
+				   &ad525x_group_wipers[AD525X_RDAC2]);
+		sysfs_remove_group(&dev->kobj, &ad525x_group_commands);
+		break;
+	}
+
+	i2c_set_clientdata(client, NULL);
+	kfree(data);
+
+	return 0;
+}
+
+static const struct i2c_device_id ad525x_idtable[] = {
+	{"ad5258", AD5258_ID},
+	{"ad5259", AD5259_ID},
+	{"ad5251", AD5251_ID},
+	{"ad5252", AD5252_ID},
+	{"ad5253", AD5253_ID},
+	{"ad5254", AD5254_ID},
+	{"ad5255", AD5255_ID},
+	{}
+};
+
+MODULE_DEVICE_TABLE(i2c, ad525x_idtable);
+
+static struct i2c_driver ad525x_driver = {
+	.driver = {
+		   .owner = THIS_MODULE,
+		   .name = DRIVER_NAME,
+		   },
+	.id_table = ad525x_idtable,
+	.probe = ad525x_probe,
+	.remove = __devexit_p(ad525x_remove),
+};
+
+static int __init ad525x_init(void)
+{
+	return i2c_add_driver(&ad525x_driver);
+}
+
+module_init(ad525x_init);
+
+static void __exit ad525x_exit(void)
+{
+	i2c_del_driver(&ad525x_driver);
+}
+
+module_exit(ad525x_exit);
+
+MODULE_AUTHOR("Chris Verges <[e-mail]>, "
+	      "Michael Hennerich <[e-mail]>, ");
+MODULE_DESCRIPTION("AD5258/9 digital potentiometer driver");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(DRIVER_VERSION);