diff --git a/drivers/hwmon/pcf8591.c b/drivers/hwmon/pcf8591.c
new file mode 100644
index 0000000..1d7ffeb
--- /dev/null
+++ b/drivers/hwmon/pcf8591.c
@@ -0,0 +1,325 @@
+/*
+    Copyright (C) 2001-2004 Aurelien Jarno <aurelien@aurel32.net>
+    Ported to Linux 2.6 by Aurelien Jarno <aurelien@aurel32.net> with
+    the help of Jean Delvare <khali@linux-fr.org>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/mutex.h>
+
+/* Addresses to scan */
+static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b, 0x4c,
+					0x4d, 0x4e, 0x4f, I2C_CLIENT_END };
+
+/* Insmod parameters */
+I2C_CLIENT_INSMOD_1(pcf8591);
+
+static int input_mode;
+module_param(input_mode, int, 0);
+MODULE_PARM_DESC(input_mode,
+	"Analog input mode:\n"
+	" 0 = four single ended inputs\n"
+	" 1 = three differential inputs\n"
+	" 2 = single ended and differential mixed\n"
+	" 3 = two differential inputs\n");
+
+/* The PCF8591 control byte
+      7    6    5    4    3    2    1    0
+   |  0 |AOEF|   AIP   |  0 |AINC|  AICH   | */
+
+/* Analog Output Enable Flag (analog output active if 1) */
+#define PCF8591_CONTROL_AOEF		0x40
+
+/* Analog Input Programming
+   0x00 = four single ended inputs
+   0x10 = three differential inputs
+   0x20 = single ended and differential mixed
+   0x30 = two differential inputs */
+#define PCF8591_CONTROL_AIP_MASK	0x30
+
+/* Autoincrement Flag (switch on if 1) */
+#define PCF8591_CONTROL_AINC		0x04
+
+/* Channel selection
+   0x00 = channel 0
+   0x01 = channel 1
+   0x02 = channel 2
+   0x03 = channel 3 */
+#define PCF8591_CONTROL_AICH_MASK	0x03
+
+/* Initial values */
+#define PCF8591_INIT_CONTROL	((input_mode << 4) | PCF8591_CONTROL_AOEF)
+#define PCF8591_INIT_AOUT	0	/* DAC out = 0 */
+
+/* Conversions */
+#define REG_TO_SIGNED(reg)	(((reg) & 0x80)?((reg) - 256):(reg))
+
+struct pcf8591_data {
+	struct mutex update_lock;
+
+	u8 control;
+	u8 aout;
+};
+
+static void pcf8591_init_client(struct i2c_client *client);
+static int pcf8591_read_channel(struct device *dev, int channel);
+
+/* following are the sysfs callback functions */
+#define show_in_channel(channel)					\
+static ssize_t show_in##channel##_input(struct device *dev, struct device_attribute *attr, char *buf)	\
+{									\
+	return sprintf(buf, "%d\n", pcf8591_read_channel(dev, channel));\
+}									\
+static DEVICE_ATTR(in##channel##_input, S_IRUGO,			\
+		   show_in##channel##_input, NULL);
+
+show_in_channel(0);
+show_in_channel(1);
+show_in_channel(2);
+show_in_channel(3);
+
+static ssize_t show_out0_ouput(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct pcf8591_data *data = i2c_get_clientdata(to_i2c_client(dev));
+	return sprintf(buf, "%d\n", data->aout * 10);
+}
+
+static ssize_t set_out0_output(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
+{
+	unsigned int value;
+	struct i2c_client *client = to_i2c_client(dev);
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+	if ((value = (simple_strtoul(buf, NULL, 10) + 5) / 10) <= 255) {
+		data->aout = value;
+		i2c_smbus_write_byte_data(client, data->control, data->aout);
+		return count;
+	}
+	return -EINVAL;
+}
+
+static DEVICE_ATTR(out0_output, S_IWUSR | S_IRUGO,
+		   show_out0_ouput, set_out0_output);
+
+static ssize_t show_out0_enable(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct pcf8591_data *data = i2c_get_clientdata(to_i2c_client(dev));
+	return sprintf(buf, "%u\n", !(!(data->control & PCF8591_CONTROL_AOEF)));
+}
+
+static ssize_t set_out0_enable(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+	unsigned long val = simple_strtoul(buf, NULL, 10);
+
+	mutex_lock(&data->update_lock);
+	if (val)
+		data->control |= PCF8591_CONTROL_AOEF;
+	else
+		data->control &= ~PCF8591_CONTROL_AOEF;
+	i2c_smbus_write_byte(client, data->control);
+	mutex_unlock(&data->update_lock);
+	return count;
+}
+
+static DEVICE_ATTR(out0_enable, S_IWUSR | S_IRUGO,
+		   show_out0_enable, set_out0_enable);
+
+static struct attribute *pcf8591_attributes[] = {
+	&dev_attr_out0_enable.attr,
+	&dev_attr_out0_output.attr,
+	&dev_attr_in0_input.attr,
+	&dev_attr_in1_input.attr,
+	NULL
+};
+
+static const struct attribute_group pcf8591_attr_group = {
+	.attrs = pcf8591_attributes,
+};
+
+static struct attribute *pcf8591_attributes_opt[] = {
+	&dev_attr_in2_input.attr,
+	&dev_attr_in3_input.attr,
+	NULL
+};
+
+static const struct attribute_group pcf8591_attr_group_opt = {
+	.attrs = pcf8591_attributes_opt,
+};
+
+/*
+ * Real code
+ */
+
+/* Return 0 if detection is successful, -ENODEV otherwise */
+static int pcf8591_detect(struct i2c_client *client, int kind,
+			  struct i2c_board_info *info)
+{
+	struct i2c_adapter *adapter = client->adapter;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE
+				     | I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
+		return -ENODEV;
+
+	/* Now, we would do the remaining detection. But the PCF8591 is plainly
+	   impossible to detect! Stupid chip. */
+
+	strlcpy(info->type, "pcf8591", I2C_NAME_SIZE);
+
+	return 0;
+}
+
+static int pcf8591_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct pcf8591_data *data;
+	int err;
+
+	if (!(data = kzalloc(sizeof(struct pcf8591_data), GFP_KERNEL))) {
+		err = -ENOMEM;
+		goto exit;
+	}
+
+	i2c_set_clientdata(client, data);
+	mutex_init(&data->update_lock);
+
+	/* Initialize the PCF8591 chip */
+	pcf8591_init_client(client);
+
+	/* Register sysfs hooks */
+	err = sysfs_create_group(&client->dev.kobj, &pcf8591_attr_group);
+	if (err)
+		goto exit_kfree;
+
+	/* Register input2 if not in "two differential inputs" mode */
+	if (input_mode != 3) {
+		if ((err = device_create_file(&client->dev,
+					      &dev_attr_in2_input)))
+			goto exit_sysfs_remove;
+	}
+
+	/* Register input3 only in "four single ended inputs" mode */
+	if (input_mode == 0) {
+		if ((err = device_create_file(&client->dev,
+					      &dev_attr_in3_input)))
+			goto exit_sysfs_remove;
+	}
+
+	return 0;
+
+exit_sysfs_remove:
+	sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group_opt);
+	sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group);
+exit_kfree:
+	kfree(data);
+exit:
+	return err;
+}
+
+static int pcf8591_remove(struct i2c_client *client)
+{
+	sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group_opt);
+	sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group);
+	kfree(i2c_get_clientdata(client));
+	return 0;
+}
+
+/* Called when we have found a new PCF8591. */
+static void pcf8591_init_client(struct i2c_client *client)
+{
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+	data->control = PCF8591_INIT_CONTROL;
+	data->aout = PCF8591_INIT_AOUT;
+
+	i2c_smbus_write_byte_data(client, data->control, data->aout);
+
+	/* The first byte transmitted contains the conversion code of the
+	   previous read cycle. FLUSH IT! */
+	i2c_smbus_read_byte(client);
+}
+
+static int pcf8591_read_channel(struct device *dev, int channel)
+{
+	u8 value;
+	struct i2c_client *client = to_i2c_client(dev);
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+
+	mutex_lock(&data->update_lock);
+
+	if ((data->control & PCF8591_CONTROL_AICH_MASK) != channel) {
+		data->control = (data->control & ~PCF8591_CONTROL_AICH_MASK)
+			      | channel;
+		i2c_smbus_write_byte(client, data->control);
+
+		/* The first byte transmitted contains the conversion code of
+		   the previous read cycle. FLUSH IT! */
+		i2c_smbus_read_byte(client);
+	}
+	value = i2c_smbus_read_byte(client);
+
+	mutex_unlock(&data->update_lock);
+
+	if ((channel == 2 && input_mode == 2) ||
+	    (channel != 3 && (input_mode == 1 || input_mode == 3)))
+		return (10 * REG_TO_SIGNED(value));
+	else
+		return (10 * value);
+}
+
+static const struct i2c_device_id pcf8591_id[] = {
+	{ "pcf8591", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, pcf8591_id);
+
+static struct i2c_driver pcf8591_driver = {
+	.driver = {
+		.name	= "pcf8591",
+	},
+	.probe		= pcf8591_probe,
+	.remove		= pcf8591_remove,
+	.id_table	= pcf8591_id,
+
+	.class		= I2C_CLASS_HWMON,	/* Nearest choice */
+	.detect		= pcf8591_detect,
+	.address_data	= &addr_data,
+};
+
+static int __init pcf8591_init(void)
+{
+	if (input_mode < 0 || input_mode > 3) {
+		printk(KERN_WARNING "pcf8591: invalid input_mode (%d)\n",
+		       input_mode);
+		input_mode = 0;
+	}
+	return i2c_add_driver(&pcf8591_driver);
+}
+
+static void __exit pcf8591_exit(void)
+{
+	i2c_del_driver(&pcf8591_driver);
+}
+
+MODULE_AUTHOR("Aurelien Jarno <aurelien@aurel32.net>");
+MODULE_DESCRIPTION("PCF8591 driver");
+MODULE_LICENSE("GPL");
+
+module_init(pcf8591_init);
+module_exit(pcf8591_exit);