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 <michael.hennerich@analog.com>
Signed-off-by: Chris Verges <chrisv@cyberswitching.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 738 insertions, 0 deletions

diff --git a/Documentation/misc-devices/ad525x_dpot.txt b/Documentation/misc-devices/ad525x_dpot.txt
new file mode 100644
index 000000000000..0c9413b1cbf3
--- /dev/null
+++ b/Documentation/misc-devices/ad525x_dpot.txt
@@ -0,0 +1,57 @@
+---------------------------------
+  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
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 2c16ca6501d5..0c7f4c5dd07f 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -13,6 +13,20 @@ menuconfig MISC_DEVICES
 
 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
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 906a0edcea40..18c8418a5132 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -4,6 +4,7 @@
 
 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
diff --git a/drivers/misc/ad525x_dpot.c b/drivers/misc/ad525x_dpot.c
new file mode 100644
index 000000000000..30a59f2bacd2
--- /dev/null
+++ b/drivers/misc/ad525x_dpot.c
@@ -0,0 +1,666 @@
+/*
+ * ad525x_dpot: Driver for the Analog Devices AD525x digital potentiometers
+ * Copyright (c) 2009 Analog Devices, Inc.
+ * Author: Michael Hennerich <hennerich@blackfin.uclinux.org>
+ *
+ * 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 <chrisv@cyberswitching.com>
+ *
+ * derived from ad5252.c
+ * Copyright (c) 2006 Michael Hennerich <hennerich@blackfin.uclinux.org>
+ *
+ * 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 <chrisv@cyberswitching.com>, "
+              "Michael Hennerich <hennerich@blackfin.uclinux.org>, ");
+MODULE_DESCRIPTION("AD5258/9 digital potentiometer driver");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(DRIVER_VERSION);